This was a printed doc from the net I've had for a few years. It
was scanned and converted to text in an OCR program so some of the
text is a little screwd. I thought it was worth the trouble and a
FUEL INJECTION FOR BEGINNERS:
Before you leap into the world of fuel-injected high performance, look at what makes the SEFI Ford tick.
By John Hunkins
Fuel injection works on a very simple concept. Fuel is forcibly injected into the path of oncoming air rather than being sucked out into a venturi. Early mechanical fuel-injection systems had elaborate schemes for metering fuel. But they were finicky and expensive compared to carburetors. Later, fuel injection was controlled by a computer that energized a solenoid built into the fuel injector.
These throttle body systems (CFI or TBI) were replaced by port fuel injection (called TPI, SFI, SEFI) in performance applications starting in the mid-1980s. They had the ability to idle cleanly like the throttle bodies, but they had greater power because they delivered more fuel. Engineers put the injectors down at the intake valve (hence the term "port") so fuel could be "shot-gunned" directly into the cylinder for improved performance and economy. Without fuel running through the intake manifold, it could be tuned to deliver more torque.
All 5-liter Mustangs built between 1986 and '95 (and all 5-liter Mercury Capris built in 1986) are equipped with sequential electronic fuel injection, a type of port fuel injection. At the heart of this system is the EEC-IV electronic control assembly (pronounced "eek four"). Often referred to in repair and training literature as the ECA, this shielded metal box (found in the passenger's side kick panel) is the controlling brain of the engine. (In 1994-95 5-liter Mustangs, the EEC-IV also controls the tranny.)
The 60-pin EEC-IV processor uses two large scale integrated circuits that were developed jointly by Ford and Intel. Their operation speed of 15 megahertz means that each instruction can be carried out on average between one and two microseconds-that's just over a millionth of a second. (Information courtesy of Ford Fuel Injection & Electronic Engine Control by Charles o. Probst, SAE, Robert Bentley Publishers, available for $29.95 from Robert Bentley, Inc. in Cambridge, Mass. or through the Ford Motorsport catalog as part No. M frantically?
Think of your EEC-IV as a box with a busy mechanic inside. He's constantly tweaking your engine to make it run its best. And to help him carry out his job, he has both inputs and outputs. In metaphoric terms he has the senses of sight, hearing, smell and touch to help him sense things, and arms, legs, hands and feet to help him do things. Technicians call these inputs and outputs sensors and actuators respectively.
This SEFI 5-liter engine diagram is an excellent map that shows where the various components are located. Note the reverse position of the intake manifold. Many Ford vehicles (besides Mustangs) used the SEFI 5-liter with this alternate assembly; otherwise everything can be found in the same place. Also note that '89-up SEFI 5-liters have a mass air sensor (not shown).
So our EEC-IV "mechanic" rapidly gets information about the status of the engine through its sensors, decides what to do with the information, and then instantly acts on the information with its actuators. Some of the sensors may be familiar to you (partial list):
Mass Air Flow (MAF)* Measures the quantity of air coming into the engine. This sensor (sometimes called a mass air meter) is located on the intake air tube on the passenger's side between the throttle body and the air cleaner. A thin heated wire is cooled by air passing over it. The resulting voltage required to heat the wire is proportional to airflow.
Throttle Position Sensor (TPS)* Measures the angle of the throttle blade corresponding to the driver's accelerator pedal position. The TPS can be found on top of the throttle body.
Profile Ignition Pickup (PIP)* Measures the speed of the engine and the position of the crankshaft. The PIP sensor is inside the distributor and picks up a pulse from a rotating ring with square teeth on it.
Exhaust Gas Oxygen (EGO)* Measures the oxygen content in the exhaust gas. Used by the EEC- IV to detect and [me tune the air/fuel ratio. There are two EGO sensors, one for each bank of cylinders. They are mounted in the exhaust H-pipe near the catalytic converters.
Air Charge Temperature Sensor (ACT) Measures the temperature of air coming into the engine. The EEC- IV will enrich the fuel and increase idle speed when cold. The ACT is located in the top of the intake manifold in one of the front intake runners.
Engine Coolant Temperature Sensor (ECT) Measures the temperature of the engine coolant. The EEC-IV will enrich the fuel and idle speed when cold. The ECT is located on top of the intake manifold and is embedded in one of the coolant passages.
Manifold Absolute Pressure Sensor (MAP) Measures the air pressure in the intake manifold. The MAP sensor (found on the firewall) is used to detect engine load in 1986-88 cars* (1986-87 California). From 1989 to 1995, the MAP sensor (called a barometric pressure or BP sensor thereafter) is used only to measure atmospheric pressure, and a MAF sensor is used to detect engine load.
EGR Valve Position
Sensor (EVP) Measures the position of the exhaust gas
recirculation valve (an emissions-control device). The EGR valve and
the EVP sensor are located on the back of the throttle body/EGR
The EEC-IV carries out its management decisions through actuators. Again, some of them you'll recognize (partial list) :
Fuel Injectors* There are eight injectors (one for each runner) on the intake manifold. These pulse fuel into each cylinder based on an electrical command from the EEC-IV. Longer pulses deliver more fuel, and shorter ones deliver less. The Mustang's fuel injection is sequential, meaning that not only does each cylinder have its own fuel injector, but that the injector is synchronized to inject with the opening of the cylinder's intake valve. This further improves throttle response and elll1SSlons.
(SPOUT)* This is the spark control that the EEC-IV sends to the
ignition module (TFI) on the side of the distributor (1986-93). This
signal determines the amount of ignition retard or advance that the
next spark plug in the firing order will receive. The SPOUT signal
wire has a plug near the distributor that can be removed to
interrupt the signal. (It's located on the passenger's-side inner
fender on 1994-95 models.)
This causes the distributor to revert to the PIP for its ignition signal and is used to check and set the base ignition timing.
Idle Speed Control (ISC) This cylindrical unit is attached to the throttle body and allows the EECIV to vary airflow around the throttle body to control idle engine speed (such as when the NC kicks on). It also acts as a dashpot during starting and deceleration.
Thermactor Air Bypass (TAB) This solenoid (electrical switch) feeds engine vacuum to a valve that switches the flow air (the "smog" pump) to either the emission system or to the atmosphere. This is an emission-control device.
Thermactor Air Diverter (TAD) A companion solenoid to the TAB, the TAD applies engine vacuum to a valve that diverts thermactor air either to the exhaust port in the cylinder head or to the catalytic converter. This is an emissions control device that (along with the TAB and air pump) reduces the production of carbon monoxide and hydrocarbons.
Exhaust Gas Recirculation (EGRC & EGRV) These solenoids apply and vent engine vacuum to the exhaust gas recirculation valve (EGR) on the back of the EGR spacer (between the throttle body and intake manifold). This opens and closes the EGR valve to admit exhaust gas back into the engine. These are emissions-control devices that limit the production of oxides of nitrogen.
Canister Purge Solenoid (CANP) This solenoid opens an engine vacuum line to a charcoal canister that stores residual fuel vapor from the fuel tank. Once open, the fumes are pulled from the canister into the engine for burning. This is an emissions control device that reduces evaporative hydrocarbon emissions from the fuel tank.
Thick Film Ignition
Module (TFI)* Though not a sensor or an actuator, it is a key
element in the SEFI system. The TFI module is responsible for
relaying the PIP signal from the distributor to the EEC-IV and for
controlling the flow of electricity *a key device for the SEFI
Don't let all these fancy acronyms throw you; it's not as difficult as it seems. The ECA has everything under control so there's rarely anything that has to be adjusted. In fact, that's one of the beautiful things about the Ford EEC- IV; it can adapt its operation as the engine gets older. (More on this later.)
Many of the sensors and actuators are on the 5-liter engine for the sole purpose of emissions control. It may even seem that the maze of emissions-related wiring and plumbing would turn your bucking bronco into a wheezing whinny, but it just isn't true. Although the emission equipment on your 5.0 certainly adds to the complexity of the system, it doesn't hurt performance one bit.
You know that old saw about which came first, the chicken or the egg? Well, that sort of logic is called closed loop. And it's a concept central to fuel injection. Closed loop refers to the control of fuel injectors and the feedback of air/fuel ratio via the oxygen sensors. It's called a loop because the computer adjusts the length of the injector pulse (also called duty cycle, which controls the amount of fuel delivered), waits for the A!F ratio from the EGO sensors, and adjusts the injector pulse in an attempt to reach the perfect air/fuel ratio. This loop goes on continuously, tuning your steed from moment to moment.
The opposite condition of closed loop is called open loop. That's when the loop described above is broken. (Information returning from the EGO sensors is ignored.) More like a straight line than a loop, the EECIV adjusts the injector pulse strictly from information obtained from your foot (the TPS sensor), the engine speed (PIP sensor) and other values stored in the computer.
Your 5-liter will alternate from closed-loop to open-loop operation often through the driving cycle. Open loop usually occurs most during cranking, warm up and wide open throttle (WOT). Closed loop occurs most normally during warm cruise.
Backfield in motion
Before you yank off your smog gear or disable it, consider this: There are plenty of fast Mustangs pounding the streets with all or most of their smog gear intact. They're able to do this because of a split in the EEC-IV computer programming called Foreground and Background Processing.
Simply put, Foreground Processing are those calculations that take precedence, and Background Processing are those calculations that don't. This way, the EEC- IV can respond to external events quickly to maintain top engine performance (like a jab of the throttle) and still perform housekeeping duties to keep your engine running clean.
Foreground and Background Processing instructions divide the EEC-IV's workload into two separate piles. These piles are managed by a Foreground Manager and a Background Manager. And within them is a hierarchy that decides which things are most urgent. (For instance, crunching SPOUT numbers and injector pulses has priority over the non-critical function of EGR control.)
Here's food for thought: If you plan on modifying your 5.0, the majority of aftermarket hardware will interface with your emissions equipment (street-legal certified or not). Once you add your parts, just put all your emissions equipment back. You'll end up chasing fewer problems than if you pull the stuff off. Even if you don't modify your car much, don't try to remove the smog gear. If 10-second cars don't need it off, why should 14second cars'?
Use an adapter
An important function of the Background Manager is to coordinate the EEC-IV's adaptive strategy. As we indicated earlier, the EEC-IV has the unique ability to compensate for the engine's age. The adaptive strategy looks at sensor inputs over time and decides how close engine parameters correspond to the prepro grammed model.
Example: You get a batch of bad gas that partially clogs your fuel injectors. As a result, fuel delivery is reduced, creating a lean condition. This condition is sensed by the EGO sensors and is relayed to the EEC-IV. For a while, the computer hunts for a better air/fuel ratio out of the immediate need to satisfy its closed-loop AlP ratio goal. Later, the EEC- IV learns that the injectors always seem to need more duration time than the model stored in memory. Background processing then stores a correction factor in a table so that the correct amount of fuel goes to the engine without hunting.
In fact, your 5-liter is always measuring and comparing. One of the EEC-IV's most important functions is to check on how well a job it's doing. Are its sensors and actuators working within their parameters? And there's a special place the EEC-IV puts everything it's learned; it's called Keep Alive Memory (KAM).
No two engines and no two sensors are the same. Not only are they all slightly different when new, but they change even more as they grow old. The EEC- IV tracks these differences and compensates for them so that vehicle operation stays at peak performance without constant tuning and repair.
But sometimes sensors and actuators reach a failure mode when the EEC- IV can no longer compensate. That's when your Check Engine light comes on. This light really doesn't mean check your engine; it means check your computer for stored trouble codes. That's another great thing about EEC- IV: The computer can tell you exactly what's wrong without you having to turn a wrench!
Beyond the practical reasons for employing an adaptive strategy, it also gives the EEC- IV flexibility for enhanced performance. Improved breathing (i.e., heads, intake, cam, blower) can push sensor parameters out of their normal expected range. The adaptive strategy will pick up on these changes when they are consistent. Once these differences are noticed and written into the KAM tables, even a highly modified EEC- IV car will run like normal.
Speed density VS. mass air
If you own a 49-state 1989-95 (or California '88 model) 5-liter Mustang, your EEC-IV will determine engine load from the measure of air drawn into the engine (mass air). If your 5.0 was built between 1986 and 1988, then engine load is determined by manifold absolute pressure (speed density). For a mostly stock Mustang, there will be little difference in the operation of either engine. (Stock speed density cars are generally quicker in the quarter-mile than mass air cars. The ET difference can
Mass air cars may be highly modified without any adverse effect to driveability. But if a speed density 5 liter is modified much beyond exhaust, throttle body and intake manifold, severe driveability problems will arise (lean backfire and a hunting idle).
Speed density computers are programmed with a mathematical model of the engine's volumetric efficiency (breathing ability). As long as operating parameters don't exceed what engineers anticipate, the EEC- IV can compensate. If the volumetric efficiency of the actual engine improves much beyond the stored model of that engine, then driveability problems occur.
For this reason, Ford Motorsport offers a mass air conversion kit (part No. M-9000-A51 for 5-speed, M 9000-B50 for auto) for Mustangs built between 1986 and 1988. It is highly recommended for those wanting to modify their early fuel-injected 5-liters.
Feeding the beast
With all this talk about computers, you'd think electrons powered the 5-liter Mustang. Gasoline, however, is the fuel of choice. The SEFI Mustang has a high-pressure (30-40 psi) feedback fuel system. This means the fuel not used by the injectors is returned to the fuel tank. Low-pressure carbureted systems are different in that they do not return any fuel to the tank.
The SEFI 5-liters employ an electric pump mounted in the tank that pushes fuel to the engine through small diameter lines at high pressure and speed. (Carbureted engines suck fuel through large lines via a mechanical pump mounted on the engine.) As engine load and demand for fuel increase, fuel pressure is increased via a fuel pressure regulator in the return line. The regulator closes off return flow to the tank, thus forcing fuel pressure up. The closing off of the return line is regulated by manifold vacuum, which acts on a diaphragm within the regulator. So as manifold vacuum goes down, fuel pressure goes up-without any computer intervention whatsoever.
Fuel injectors on stock 5-liter Mustangs deliver approximately 19 1bs. of fuel in an hour when opened continuously and supplied with 39 1bs. of fuel! pressure. This is how they get their 19-1b./hr. rating. (1993-95 Cobra Mustangs use larger 24-1b./hr. injectors.) Keep in mind, this is only a rating system; actual fuel delivery will vary with line pressure and duty cycle.
The factory fuel pump, injectors, fuel line and regulator are properly matched to maximize power from the stock engine. The 5-liter SEFI Mustang engine is calibrated to run on Premium unleaded fuel (91 octane minimum). The use of a lower-grade fuel can cause a degradation of performance and possible engine damage. High-octane race fuel (over 1 00 octane) will not improve performance (without additional modification) and may damage emissions-control equipment.
Next time we'll talk about the EEC-IV's driving force: strategies and goals. We'll also talk about free and low cost 5-liter hop-ups, setting your ignition timing and tips that are duds.
Special thanks to John Clark of Ford's Customer Service Division (Service Training Department) for his invaluable help with this article.
FUEL INJECTION FOR BEGINNERS:
Strategic air command
Sensors provide information on engine operation to the EEC-IV processor. The EEC-IV then continuously modifies fuel delivery and ignition timing (along with controlling emissions devices) for best performance, economy and emissions. A variety of conditions are defined by the EEC-IV, including cranking, warm-up, idle, warm cruise, light throttle and wide open throttle. The EEC deduces these conditions from its sensors, but before it acts, it consults a table of strategy goals.
These goals are the bible of EEC-IV operation and represent the single greatest difference between the EEC and all other aftermarket fuel-injection systems. They define exactly what the EEC wants to achieve through its manipulation, and they represent those priorities programmed in at the factory. They can range (in the most general terms) from minimizing emissions output to maximizing horsepower to ensuring the engine lives through its warranty period.
Naturally, the strategy of the EEC-IV will change dynamically as conditions change. One moment the goal might be to clean tailpipe emissions during cruise on the open highway. The next moment the EEC-IV might detect a sharp rise in throttle angle from the TPS while the engine load signal from the mass air meter rises. For safety and performance considerations, the EEC- IV then redefines its strategy goal to make maximum engine power instead of minimum emissions.
The primary means the EEC-IV has for monitoring its success in meeting strategy goals is a pair of heated exhaust gas oxygen sensors. They relay air/fuel ratio measurements to the EEC-IV. In a matter of microseconds, the EEC-IV will alter the output to its actuators (fuel injectors, spark output, and emissions control devices) until the oxygen sensors tell the computer the strategy goal has been met.
Parts and parcels
In Part 1, we explained how fuel injection operates, with the primary focus on injectors, computer, software and sensors. But there are still many unanswered questions concerning the hardware of the fuel-injected 5-liter engine. Why are injected intake manifolds so different from carbureted ones'? Why are there two pieces instead of one'? What is a throttle body and how is it different from a carburetor? What is an EGR spacer and what does it do?
The 5-liter intake manifold is comprised of two halves: an upper intake and a lower intake. The lower intake closely resembles a carbureted engine's single-piece intake (it's a similar size and shape). But it also houses the injectors, injector rails, fuel pressure regulator, coolant passages, engine coolant sensor, air charge temp sensor, and positive crankcase ventilation (PCV) valve. In the S-liter's case, the individual cylinder intake runners are lined up longitudinally (in line with the crankshaft) rather than converging at a central location (as in a carburetor manifold ).
Carbureted engines require that the carb be fairly close (that is, it's saturated with fuel) and can't travel long distances or turn around comers without adversely affecting fuel distribution or atomization. As such, the short intake runners of a carbureted engine are a compromise for many street -driven cars because they can't be tuned for best torque (more on this later).
By injecting the fuel at the port, the intake runners can be lengthened and turned to conform within the allowable space underhood. This is where the upper intake comes into play. It extends the runners further and contains a large common plenum, or airbox. So what we have are eight long individual runners that terminate in a large common plenum chamber.
And here's where things become drastically different from a carb engine. As the intake valve closes and opens, the column of air in the intake runner stops and starts. As a result, the column of air bounces back and forth between the valve and the plenum, which sets up a standing wave. The frequency of the wave depends largely on the length of the intake runner, so the engineers tune the runner's length to improve performance where they want it. This way, the air can bounce back to the valve, being timed to ram into the cylinder just as the valve opens again. So, longer runners improve low-rpm performance and shorter ones improve high-rpm performance. And keep in mind that all of this is possible due to port fuel injection.
Check the throttle plate with the inlet air tube removed to see if it opens all the way under full throttle. Have a friend push the gas pedal down with the engine off; the throttle blade should look like this but without help from our friend, Mr. Hand.
Heading even farther up the induction path we find the throttle body and EGR spacer. The throttle body is essentially a carburetor without the fuel delivery function. The throttle linkage from the gas pedal attaches to a lever on the throttle body that opens a large trap door (called a throttle plate). On the axis of the throttle plate is the throttle position sensor, which tells the EEC-IV how far open the throttle is.
The exhaust gas recirculation (EGR) spacer is sandwiched between the throttle body and upper intake manifold. This 2-inch-thick piece of cast aluminum passes the air from the throttle body to the intake manifold, but its primary purpose is to mix spent exhaust gas into the incoming air to reduce the production of certain pollutants. Exhaust gas is fed from the cylinder heads up through a channel in the intake manifold into the EGR spacer.
(The pollutants in question are oxides of nitrogen. High levels of these in the atmosphere contribute significantly to smog and acid rain. They are formed at extremely high temperature in the combustion chamber when atmospheric nitrogen, a normally stable element, combines with oxygen. By introducing inert exhaust fumes into the process, combustion temperatures are reduced and nitrogen doesn't bond with oxygen. Under WOT, the computer stops the flow of exhaust gas into the combustion process for reasons of safety and performance. Therefore, it is not necessary to disable the EGR function for best performance.)
A valve on the side of the EGR spacer opens and closes to control the flow of exhaust into the intake. As the exhaust gas can add much heat to the intake manifold and incoming air, it is plumbed for engine coolant circulation. (A line on the front of the spacer feeds coolant to the spacer and a line on the back takes coolant away.) The EEC-IV turns on exhaust flow during normal warm operation (for emissions compliance) and shuts it off under full throttle and when the engine is cold.
Time to pump up
Over the years" we've found several free and cheap ways to improve a fuel-injected Mustang's performance. Some of them can be implemented on the street and some are good only at the drag strip. It should be noted that to take maximum advantage of these tuning tips at the track, racing slicks should be used with a healthy burnout. Driving skill will also greatly influence the ET outcome. Powershifting, proper burnout and staging, and shift rpm experimentation will yield the best results. fuel-injected Mustangs and will put the least amount of strain on your wallet:
1) Advance the base ignition timing. Most 5-liters come with 100 or less initial timing from the factory. In most cases, the timing may be advanced substantially for a dramatic improvement in ET. Most 5-liters can take at least 140 but we've seen as much as 180 in a stock 5-liter using good pump gas (93 or 94 octane). When advanced from 100 initial, you can expect a quarter-second improvement in ET. To increase the timing, obtain an accurate inductive timing light (around $50). Before starting, jack up the front end of the car (use jack stands for safety) and examine the damper on the front of the engine. Look for the timing marks stamped into the damper (you may have to bump the starter over a few times) and mark the spot you want to set the timing at with a white paint marker or other suitable marker. With the car back on the ground, locate the spark output (SPOUT) plug attached to the wiring harness next to the distributor. (1994-95 models have SPOUT connectors in front of the passenger's-side shock tower.) Pull out the SPOUT connector. (It's like disconnecting the vacuum advance on a carb car. This forces the TFI module to pick up its timing signal from the profile ignition pickup in the distributor [i.e., base timing]. When the SPOUT is connected, the TFI module runs off the constantly changing timing signal from the EEC-IV.) Loosen the distributor hold-down with a 112-inch distributor wrench and crank the engine. Connect the timing light and aim it at the damper, rotating the distributor clockwise until the pointer indicates the timing mark you made earlier. Tighten the distributor hold-down with the engine running and recheck the timing. If the timing still reads where you put it, pop the SPOUT connector back in and go racing.
2) Bypass the power steering and smog pump with a short accessory belt (around $25). With the stock belt on, take a long piece of string and wrap it along the pulley path that bypasses both the smog pump pulley and the power steering pulley. Measure the length of string and purchase a 6-rib serpentine belt closest to this length. Install the belt at the track (you can use a pry bar to hold the belt tensioner back) or whenever you want peak power. Note that the installation of this belt will eliminate your power steering and render your smog pump inoperative, so use it sparingly. This reduces parasitic drag on the engine and provides another 5 horsepower to the rear wheels. Hardcore racers can remove the belt entirely for a brief blast down the quarter-mile. This is even cheaper and provides around 10 horsepower but should only be removed just before the burnout (by a friend with the engine off) and reinstalled on the return road. Hint: Remember that this will eliminate your alternator and water pump, so make sure your battery is charged and your coolant temp is low beforehand. Underdrive pulleys can also reduce parasitic drag to a lesser extent, yet can be used on the street for maximum benefit.
3) Install higher-ratio rear end gears. Most 5-liter Mustangs came factory-equipped with 2.73: 1 gears; however, 3.08:1 gears were optional and are fairly common. For fuel economy, both gears are great and can pull down as much as 30 mpg on the highway on an unmodified 5-liter. But for maximum acceleration a numerically higher gear is preferable. If all-out straight line performance is the paramount concern, a 4.10:1 gear is the ticket (for a near-stock engine) but will provide performance at the expense of fuel economy. For street/strip duty, most Mustang aficionados turn to 3.55 or 3.73 gears. Both are a good compromise between economy and performance, with the 3.55 being more economy-minded and the 3.73 being more performance oriented. This is definitely not a do-it yourself item for the first-time Mustang owner. Special tools and skills are required, so choose your mechanic wisely. Parts (gears, speedo gear) and labor will cost between $300 and $500. This change by itself will produce the greatest seat-of-the-pants improvement of all the low-buck tips.
4) Check the throttle blade opening at full throttle. Due to manufacturing tolerances, some stock 5-liters may not get full throttle opening when the accelerator is fully depressed. This can limit performance. To check throttle opening (which should be done without the engine with a flathead screwdriver. Have a friend push down on the gas pedal ( off1) while you look into the throttle body. The throttle plate should be completely open. If it isn't, pop off the throttle linkage with a screwdriver (it's under the throttle body on the throttle lever) and shim the throttle cable with enough plastic washers (one or two should do it) to open the throttle all the way with the pedal down. This can improve your ET by as much as a half-second.
The EGR spacer's function is to inject exhaust gas back into the combustion process. This can heat the intake, so the factory plumbed the EGR spacer with engine coolant. Don't bypass this coolant (as shown) unless you're at the track or have the exhaust riser blocked off in the intake manifold.
5) Adjust the throttle position sensor for optimum voltage. The TPS (located atop the throttle body) is the only means of communication between the throttle body and the EEC-IV computer. If the voltage off this sensor doesn't equate to how far your foot is m the throttle, then performance can suffer. To check TPS voltage, you'll need a digital voltmeter (about $30) and a pair of piercing leads (safety pms will do m a pmch).
Locate the TPS on top of the throttle body and pierce the black and green leads commg out of the sensor. Set the voltmeter accuracy to one-thousandth of a volt (.001 V). Turn the key on (but not the engme) and read the voltage with the throttle totally closed. It will probably read m the. 600- to .800-volt range. For best performance, it should read between .970 and .990. To mcrease the voltage, loosen the screws that hold the TPS to the throttle body and rotate the sensor until the voltage is approximately .980. It may be necessary to ream out the holes m the sensor with a drill to rotate the sensor far enough. Tighten the screws and recheck the voltage.
6) Remove the intake air silencer. All fuel-injected 5-liter Mustangs ('86-95) have a restrictive intake air silencer designed to quiet engine noise for federal drive-by noise standards. Removing this silencer will not only wake up your pony with another 5-10 horsepower, but it will sound meaner too. The silencer is located inside the passenger's-side fender in front of the tire. It can't be seen by raising the hood, but it's just opposite the air filter box on the wheel side of the inner fender.
To remove this conch-shell-shaped piece" remove the air fliter and airbox assembly. Loosen the three bolts holding the silencer to the fenderwell and let the silencer fall inside the fenderwell. Put the front of the car up on jack stands for clearance and fmesse the silencer out of the small passage between the front valence and the fenderwell. The passage may seem too small, but just keep twisting and turning the silencer until it squeezes out. Drop the car off the jack stands and reinstall the airbox on the fenderwell. Pop a free-flowing K&N, Vortech or ACCEL air filter (around $30) in the airbox and pick up another 3-5 horsepower.
7) Replace regular engine oil with synthetic. Synthetic engine oil costs $3-$4 a quart more than conventional oil" but it reduces friction substantially. By swapping to a synthetic" you'll gain another 5-10 horsepower. Not only will you feel more power, but you can go longer between oil changes and rebuilds. Use only 100 percent synthetics like Mobil 1, Castro 1 Syntec, Pennzoil Performax or Redline for maximum benefit.
8) Ice down the intake manifold before racing. Of course, this trick is only for at the track, but it is worth another tenth or two in the quarter-mile. Before heading to the track, drop by a convenience store with a large cooler and pick up two or three bags of ice (on hotter days you may need more). At least 30 minutes before racing, put a bag of ice on the intake manifold. Do not run the engine during this time, and push your Mustang through the staging lanes to avoid heating the engine unduly. The cool manifold will keep the incoming intake charge at its densest for best performance.
9) Remove unnecessary weight. At the track, remove any items from inside the car that can slow you down. Remember, weight equals horsepower. A good place to along with any other flotsam sliding around in the back. (If you're not running slicks, the loss of rear weight balance can make performance even worse, so use a sticky tire when taking weight out of the rear.) Large speakers and amps should be pulled out if possible (you can wire them with quick disconnect plugs for such an occasion). Clean out the cockpit and remove the rear seats. If you plan ahead, you can remove much of the sound insulation hidden under the carpet and in the body (road and engine noise however will be increased permanently). You'll pick up a tenth in ET for every 100 lbs. shed.
It's a dud
As regular 5-liter racers, we've had plenty of time to try different speed tricks, and we've found a bunch of 'em that don't work. Here's a few of the more common duds to stay away from:
1) Don't disconnect any sensors, especially the oxygen sensors. We don't see this too often any more, but when fuel-injected performance engines first became popular, the philosophy of tricking or defeating the EEC-IV was common. Properly operating sensors actually improve performance, so don't disconnect any sensors unless the goal is to run like a lame duck.
2) Don't bypass the EGR coolant flow when running your car on the street. The EGR spacer needs coolant flow because hot exhaust gases heat the intake manifold, EGR spacer and throttle body. At the track, it's OK to bypass the EGR coolant flow if the intake, EGR spacer, and throttle body have been cooled with ice. If your engine's exhaust flow has been blocked offby a plenum spacer or an aftermarket cylinder head, it's preferable to bypass the EGR coolant.
3) Don't rev or idle your engine in the staging lanes. No matter how cool your exhaust sounds, don't put unneeded heat into your engine and intake; it'll only slow down your Stang. Cool your intake with ice at least 30 minutes prior to racing and push your car through staging until it's burnout time. Leave the throttle blipping to the Camaro guys. Race cars are another matter; they may actually need engine heat to get the oil temperature up to operating range.
4) Don't go crazy adjusting fuel pressure on a stock 5liter. If you're following just the tips we've mentioned, you haven't begun to max out the fuel delivering capability of the stock fuel system. Without any change in injector size, fuel pump, fuel pressure or fuel line size, the stock 5-liter fuel system can deliver enough fuel in a naturally aspirated combination to make 280-290 horsepower safely. The factory pre-adjusts fuel delivery to be about 10 percent rich at wide open throttle on a stock 5-liter. Raising the pressure can actually hurt performance. Save your money for a regulator and gauge and buy slicks and gears.
By lowering parasitic drag from the engine's accessories, more power goes to the rear tires. Several ways to accomplish this are with a short accessory belt (bypassing the steering and smog pump), no belt at aU (drag strip only), or underdrive pulleys (shown).
5) Don't use a 160° thermostat on a street engine. Your engine relies on a properly functioning coolant system for maximum power and efficiency. A super-cold 160° thermostat stays open basically all the time (like a flow restrictor) and never keeps the coolant in the radiator long enough to cool down. Most cars, however, can benefit from a mild 180° thermostat (the stock one is 190°). The 180° unit will allow the stock radiator to pull the maximum heat out of the engine while providing a slight fuel enrichment under cooler ambient temperatures. A bottle ofRedIine Water Wetter is a good way to reduce coolant temperature without changing thermostats.
6) Ifusing off-road pipes at the track, hook up the converters for the street. On a bone-stock engine, you'll appreciate the crisp low-end throttle response with catalytic converters. Though converters do increase backpressure and rob horsepower, this is only the case at higher rpm. Off-road pipes on a stock engine hurt 10wend punch. Many street 5-liter owners are disappointed by their performance on the street after being told that they'll gain another 15-20 hp. When the extra power comes at the top end and all the torque falls out at the bottom, it doesn't feel as great as it sounds.
Next month, we'll get into more serious bolt-ons like heads, intakes, camshaft, exhaust, nitrous and other power adders. We'll tell you about all the other extras (and responsibilities) that come with it and what you can expect from your EEC-IV computer.
FUEL INJECTION FOR BEGINNERS:
It's time to get serious with some real bolt-ons, but you better do your homework first
By John Hunkins
Editor's Note: The EEC-IV engine management system is very flexible and friendly to the modern hot rodder, and as a result there are a plethora of aftermarket (and street-legal) parts just waiting to be bolted on. But before you jump into Part 3, we suggest that you look back on Pl!!j~ and P3X!~, as this will save you time and trouble in the long rull.
It's time to graduate, in a manner of speaking. You've bumped up the ignition timing to 15°, there's synthetic oil in the crankcase, a high-flow air filter now replaces the asthmatic stock piece, and you're packing a healthy set of 3.73 gears out back. But as the saying goes, more is never enough.
Whether you're about to step up to some serious hardware or you've already started, there are some key concepts to keep in mind when putting together your fuel-injected 5-liter. As a reader of:MM&FF, you will be wooed by some 125 pages of advertising. You'll have to make many choices ranging from air fIlters to cylinder heads; the possible combination of parts is seemingly endless.
But the purpose of this article isn't to tell you which parts to buy. We've seen races won with all of 'em, so any recommendation would be misplaced. Enigmatically, there is still a right way and a wrong way to build a 5 liter Mustang. It has less to do with parts and everything to do with mind set. The good news is that there are many "right ways" to build your fuel-injected Mustang. The key is finding one of them.
The SVO GT-40 intake manifold is one of the most popular street intakes around. Its long runners promote excellent low range and midrange power, and they are a great choice for street-driven naturally aspirated5-liters.
The big picture
Reduced to its simplest model, your injected 5-liter is nothing more than a combustion chamber with two tubes. One tube leads to the combustion chamber and one leads away from it. So there are three basic ways to improve engine performance: Make it easier for air and fuel to get into the combustion chamber, increase the working potential of the combustion chamber, or make it easier for the exhaust to leave the combustion chamber.
Let's discuss them one at a time.
Intake. In practical terms, we can reduce the amount of effort needed to draw air into the engine. All parts of the EFI 5-liter induction tract can be scrutinized to reduce induction pumping losses. The fuel-injected 5-liter inlet tract consists of the intake air silencer, air filter, mass air meter, air inlet tube, throttle body, EGR spacer, upper intake manifold, lower intake manifold, cylinder head intake port, intake valve bowl and intake valve. Because the camshaft profIle also dictates how much air is admitted into the combustion chamber, we'll include the intake camshaft lobe and attendant hardware in this category.
A "big picture" mentality is helpful here. Think of the induction tract as a chain with many links. A chain is only as strong as its weakest link, so you'll want to strengthen the weak links first. On the EPI Mustang, remove the intake air silencer and replace the air filter, the mass air meter, throttle body and EGR spacer with high-flow pieces (essentially in that order). Once you have increased the airflow capability of these areas, the intake manifold and cylinder head/camshaft should be addressed.
Yet buying and installing the parts needed to create a larger-diameter inlet tract isn't the whole picture. A mismatch in diameter between components, such as a larger throttle body/EGR spacer bolted to a stock intake manifold" can cause a disruption of airflow. Pay attention to critical junctions where cross-sectional area can change drastically (intake-to-cylinder head and throttle body/EGR-to-intake). Cross-sectional area should neither increase nor decrease abruptly, with the exception of expansion into the intake plenum chamber and expansion into the combustion chamber.
In cases where a mismatch in area is likely to occur, a gentle blending is appropriate and even advantageous. The previous example in which a larger throttle body/EGR spacer is matched to a stock intake manifold illustrates this point well. Here, the EGR spacer should be mocked up with the intake" and the opening should be scribed on the intake mounting surface. The sharp step should be ground or machined down to the scribed line so that the transition provides a gradual choke into the manifold. Only then will the full potential of the new throttle body be realized.
When selecting a performance intake manifold, it is important to take into consideration its usage. Naturally aspirated engines (especially those that see significant street duty) should use an intake manifold with longstyle runners, such as the GT-40, production Cobra, Edelbrock Performer 5.0 or Vortech/Saleen unit. The long runner will promote power (through ram tuning) in a streetable powerband, whereas a short-runner boxstyle unit will elevate the powerband into the competition stratosphere (over 6500 rpm).
Some supercharged and turbocharged engines may be well-served by a short-runner box intake ifit is desirable to kill an over-abundance of low-end and midrange. Most street Mustangs with blowers or turbos, however, will feel at their best with a long-runner manifold even if it means cutting peak power by a modest amount.
Increasing the working potential of the combustion chamber might sound vague, but that's because there are so many ways to accomplish this goal. All of them involve putting more air and fuel into the combustion chamber.
Increasing the swept volume of the cylinder will draw in more air charge. This is done by boring and/or stroking the engine. Straker engines are extremely effective at producing increased power with minimal impact on driveability, care and maintenance.
Then there's turbocharging. In this case, more air and fuel are forced into the cylinder by means 0 f an exhaustdriven compressor. The cylinders are filled beyond their natural capacity and thus act like larger cylinders. Pros and cons: Very high levels of power may be produced with modest engine displacement, but the complexity of most available EFI turbo systems deters many first-time Mustang enthusiasts.
Similar ill concept to turbo charging is supercharging. Supercharging also forces more air and fuel into the cylinder, but the compressor element is mechanically driven off the crankshaft (via a belt) rather than by exhaust pressure. Pros and cons: Supercharger systems are in line cost-wise with turbocharger systems, but they are favored over turbos because of their comparative ease of installation. Tuning, however, can provide an 0 bstacle to the full potential 0 f supercharging, and as a result one can anticipate a fairly long learning curve before best results are achieved.
Perhaps the easiest way to increase combustion down.uorce on the cylinder is to use nitrous oxide. Nitrous oxide is an oxidant (it serves the same purpose as oxygen in the combustion process), which is injected in liquid form into the intake manifold along with additional fuel. Pros and cons: In dense, cool liquid form, nitrous fills the cylinder well beyond its natural limit to provide a sumptuous increase in cylinder pressure. Despite its low cost and ease of installation, nitrous requires frequent bottle fills and can become cost pro hibitive if used frequently.
Nitrous kits are by far the least expensive way to add power. This adjustable 50-125-hp kit from The Nitrous Works can be installed in just hours.
After the spent fumes of combustion depart the combustion chamber, all is not fmished. Exhaust backpressure is an impediment to power because the engine must expend energy to pump the exhaust out against the pressure built up in the exhaust. system. A larger-diameter exhaust will thus reduce backpressure and increase horsepower. The importance of a good exhaust system is borne out by the fact that a 50-percent increase in engine power output results in a 200 percent increase in exhaust backpressure given the same exhaust system.
Most parts of the fuel-injected 5-1iter exhaust system can be addressed with ill1D1mal pain to the pocketbook. Of particular concern is the restriction in the factory tubular header and catalytic converter H-pipe. Many manufacturers offer direct replacements for the factory pieces that are much less restrictive, yet smog-legal.
But when it comes to headers, bigger isn't always better. There is an important relationship between the diameter and length of a header primary tube and the power output of an engine. Ideally, an exhaust pulse traveling down a header pipe is followed by an area of vacuum. The stronger the vacuum behind the pulse, the more effectively it pulls the exhaust out of the combustion chamber. 'fhis effect, called scavenging, increases the power output of an engine by reducing engine pumping losses.
For most street-driven 5-liter Mustangs, a 1 5/8-inch diameter header is optimal. It is a good compromise between minimal backpressure and maximum scavenging. Equal-length long-tube headers will make slightly more power output due to their long-runner tuning effect, but shorty headers are more common (for the street) because theY're easier to install and are smoglegal (they can bolt to' the factory catalytic converters). Equal-length shorty headers bridge the power gap between unequal-length shortys and long-tubes because they have some of the mcreased scaven~g effect of long- tubes but are easier to install.
A high-flow converter H-pipe will not only keep emissions down to a legal level" but reduce backpressure significantly. The more capable an engine is at producing power, the more pronounced the effect of a free-flowing H-pipe becomes. A muffler swap will also help reduce back pressure, but the maximum gain will come only when the H -pipe that precedes it is opened up.
The headers, H-pipe and mufflers are key choke points in the exhaust system of a fuel-injected 5-liter and should be addressed f1fst. Next come the flow tubes and tailpipes. Most companies offer 2 I/2-inch pipes (the stock tailpipes are 2 1/4 inches), but some companies 0 ffer pipes up to 3 inches in diameter.
Getting back to our original engine model (intake tract, combustion, exhaust tract), we realize that many, maybe even roo st readers won't modify the entire system in one shot. Some choose to start at the front and work their way back, and others start at the rear and work to the front. Still others pick up parts in random order. All of these ways are fine, as long as you've got a master plan before you start.
We've deliberately skirted the issue 0 f cylinder heads until now for one reason: They represent the single most important part you can buy for your fuelie 5. O. They also are a key stumbling block for many newcomers because they represent a significant cash outlay and require a large investment of time (or money) to install.
It helps to think of a cylinder head as an intersection with a traffic light. Y au have air and fuel coming in ( east/west traffic), and exhaust gas going out (north! south traffic). If there is only one lane in each direction, traffic builds up in long lines at rush hour (that's the throttle opening up). !fyau build a larger intersection with many lanes, you can move more traffic through (air/fuel and exhaust). That's exactly what better cylinder heads do. So regardless of the other induction and exhaust goodies you've installed, if there's a traffic tie-up in the cylinder head area, your power will inherently be limited.
With so much emphasis on which box-stock head is best, an important issue is often overlooked. None of the box stock cylinder heads we've ever dyno tested have been anywhere clo se to their full power potential. A multi angle valve job, bowl blending and port matching improve overall performance tremendously for a minimal cash outlay. A pair of complete cylinder heads costing $1 ,000 can pick up another I 0 percent of flow with a 3 angle valve job and a simple clean-up when done by an experienced shop ($300-$500). Since Ford Windsor cylinder heads are exhaust limited, they benefit the most from exhaust work. Home porting is not advised for the novice, but if you choose to do it yourself, remember that less is always better.
A word about camshafts
We've recently covered camshafts in the printed editon of Muscle Mustangs (see "Roll With It" July, '96):1 so we won't go into great depth here, but a few pointers are in order. The fuel-injected 5-liter uses a hydraulic roller camshaft that offers an excellent compromise between performance and economy. Its rapid opening pro fIle can quickly put both intake and exhaust valves in a region of high flow without sacrificing engine vacuum and cylinder pressure.
The factory camshaft has proven sufficient to put most modified 5-liters into the .12s naturally aspirated, and into the 11 s when aided by a power adder. A larger aftermarket camshaft can improve performance more, but ifduration and overlap become too great, performance can easily be degraded from stock. With the modest 9:1 compression ratio of the EFI 5.0, it is best to limit duration below 2200 (at. 050 inch lift) and to keep the lobe separation angle (LCA) over 114°. If stock pistons are to be used with larger aftermarket valves, try to limit valve lift to .480 inch. If compression is increased to 10: 1 or higher, a longer duration camshaft with more overlap (such as an SVO B303) will produce the best results. Nitrous, blown and turbocharged engines have specific needs that are best addressed by custom camshaft proflles. For these applications, consult your engine builder or camshaft manufacturer for a recommendation.
Think about the future
As a 5-liter hobbyist, you've made the decision to spend some (or all) of your disposable income and time on your car. It would be a waste/ then/ to embark down one road of modification, only to discover that. you would've gotten more enjoyment from going down another. Many times I've ta1ked to guys who have modified their 5-liters for one purpose only to change their minds after spending incredible sums of money and time.
The key is to get maximum enjoyment for the least amount of trouble. First, decide what you want out of your car'7 not what parts you want to buy. Visualize what your Mustang will do and how you will use it in two, three, five years.
If you suspect you'll be running a blower in a year but you're buying heads now, don't get small-chambered pieces. Even though large-chambered heads (over 64cc) will kill some power now, you'll be sitting pretty come bo 0 st time. If you're buying bo x-sto ck heads now and think you fll have them ported later, a more expensive set 0 f aluminum heads might offset the difference in porting labor down the road. You'll get the added heat rejection, lighter weight and higher compression tolerance of aluminum as a bonus.
Don't reinvent the wheel
No matter how hard we try to layout the hardware scenario with test after dyno test., there are always a few folks who just won't get it. As the saying goes, 'fA little knowledge can be a dangerous thing," and nowhere is this more true than with these few. There is always one guy in the staging lane with this street car: .It has a shortrunner box intake, a stock bottom end/ 2.73 gears/ a new set of heads, a B303 cam and no compression, and it wheezes through the traps with 15s all day long. He spends his time in the pits chasing imaginary grem1ins like fuel pressure and ignition timing, not realizing his pro blem is of far greater magnitude.
Being a regular reader 0 f MM&FF and countless other magazines, how could he possibly end up with this nonsensical combination'? The answer is simple:
1) He's got no long-term game plan;
2) he doesn't make an attempt to learn from successful racers and tuners;
3) when he does ask around~ he reads his own meaning into the words and discounts what he doesn't agree with; and
4) he buys for price, appearance and sound as much as for function.
The irony is that all 0 f the parts on his car are great performers, but just not on his car.
Make some friends
Beside the obvious advantage of enjoying a trip to the track or local speed shop with others who share a common interest, making new friends can be helpful to your ET.
More experienced racers and tuners have wa1ked down the same path you are on, and they've learned a 101* .If you haven't sought out the experience of others already, begin now. Y our local drag strip or road course is a good place to start. Speed shops, car clubs, the Internet and even local cruise hang-outs are excellent forums for information exchange.
And don't put all your eggs in one basket. If all your contacts are expert with carburetors and nitrous oxide, they may not have a lot of valid advice if you've got a fuel-injected Mustang with a new blower. Seek out many opinions, especially those of successful racers and tuners who -deal regularly with hardware similar to yours.
Price isn't everything
So you've got a game plan, you're looking at the big picture, and you're planning for the future. Y outre thumbing through the pages of ads looking for a specific group of parts, listing price, place and availability of each item meticulously on paper. Outfit A has the best price on an intake manmo Id and rocker arms, and outfit B has the best price on the heads you want. You call in your orders, give your credit card number, and the parts show up a few days later. You put them on, go to the track, and uh oh, it doesn't run well at all.
Furious, you call back Company A. "What's wrong with the stuff you sold me'? It sucks!"
The guy says, "It sounds like you're getting valve float. Company B always sells heads with inferior valve springs. " So you call Company B. "'The guy at outfit A says your heads are no good and that's why I'm having trouble.
Now I'm stuck with a bad bunch of valve springs!"
By now you're lucky if the guy at outfit B gives you the wrong time of day. He says, "They're full of baloney. We've got plenty of racers running our heads and they work great. Have you checked your rocker arms'? They don't sound like they're adjusted right."
Now you've got a car that runs like junk, a huge phone bill, a huge credit card bill, and two guys who won't give you the sweat off their backs. But at least you saved $50 on parts, right?
A set of freeflowing headers should be ODe of the first bolt-ODS to any EFI 5-liter. These 1 5/8inch shortys from SVO provide a good compromise between less backpressure and good cylinder scavenging.
Let's turn back the clock. Instead of shopping for parts, you shop for parts and service and a shared philosophy with the dealer. You end up with the same parts as before, the same performance as before, and the same problem as before.
Since you decided to buy most or all your parts from him (perhaps at a slightly higher price), he's likely to have the time and inclination to help you. (That's the service part.) And when you decided to purchase the parts from him originally, you did so partly because he took an interest in what you were doing. (That's the philosophical connection.) You not only put food on his table, you became his friend. As a result, he's got a sympathetic ear, some useful advice and a real desire to help you.
With an open dialog, you work through the problem with the dealer. Perhaps he knows exactly what your problem is because of his own personal experience with the part in question. Or maybe the problem is never reso lved, in which case he might give you credit for the original part. Perhaps he warns you ofa potential pro blem before you even buy the part. Whatever the case, his common philosophy and desire to serve you will be the ultimate cure for your problem.
An ongoing relationship with the same dealer can also come in handy. As the dealer becomes familiar with your car, your needs and your budget, he can better anticipate what you need. And as time goes on", you'll begin to trust what he says. An experienced dealer or installation shop will have a repertoire of successful combinations from which to draw based on prior customers. If possible, seek out these fellow customers and get their opinion also.
If you want to raise the performance of your car from point A to point B, you first have to decide where point B actually is. (That's called having a game plan.) Once you know what point B is, then you need the right road map to get you there. (You can't use a map of Chicago to get around Detroit.) Obtain the best information you can about the products in question by reading the articles referenced in this story and by seeking the opinion 0 f successful tuners and racers. 1nink of your EFI engine as an integrated system rather than a collection of loss-leader parts. Great gains are to be had independently in induction, combustion and exhaust. Just imagine what they can do when they work to gether. A naturally aspirated EFI 302 with a stock short -block and the right choice of parts can produce upward of370 horsepower, while those with power adders have been known to hit 600 hp.
Next month, we'll wrap up our series with the care and feeding of your EFI Mustang. We'll get down and dirty with advice on fuel systems, ignition, advanced engine management and tuning tips.
FUEL INJECTION FOR BEGINNERS: PART 4
The proper care and feeding of your modified 5-liter is the key to long and carefree performance.
By John Hunkins
In our Fuel Injection For Beginners series, we introduced you to the different components ofthe fuel injected 5-liter engine and its attendant electronics in PAU__l. We covered free and cheap modifications and progressed to more serious hardware in PQ~2. With much of the focus in MM&FF on the nuts-and-bolts hardware, we shed some light on the bigger picture by explaining a systems approach to induction, combustion and exhaust in r~_rt2. Here in Part 4, we address special considerations for modified 5-liters, including fuel, ignition, engine management, compression and cooling.
Building a hot Mustang has been made easier over the last five years. There are so many ways and so many parts that the possibilities may seem endless. When it comes to horsepower, there is a veritable smorgasbord of choices ranging from nitrous and blowers to strokers and turbos. In the final analysis, though, they all do the same thing by pushing down harder on the piston.
When the power level increases, the capability of the engine outpaces many of the engine's important support systems. Fueling, cooling, engine management and ignition are the most critical areas that need attention. For most cars, there is enough margin built into these systems at the factory to easily support between 300 and 350 hp. A cylinder head, camshaft, intake and exhaust swap generally aren't enough to get you into trouble with cooling, ignition, engine management, or in some cases fuel, but there certainly won't be any margin left, as is the case with a stock engine. Beyond 350 hp, however, you're setting yourself to be responsible for much more than just air and exhaust flow. Every step taken in the performance direction puts you one more step away from the factory's safety and durability measures. At some point, you will have to basically re-engineer your Mustang to maintain its reliability.
But this doesn't have to be difficult or expensive. As a first-time Stang Banger, the basics ofEFI care and feeding are well within your grasp, regardless of how the power is being produced.
Fuel trouble of some kind is likely to be one of the first problem areas you encounter as engine modifications become more intense. It's a direct result of putting more air into the engine. Since air and fuel are combined in a specific ratio of 14.7:1 (called stoichiometric), more fuel must necessarily match the increase in airflow. When fuel delivery doesn't keep pace with airflow, engine damage and power loss can result.
The damaging action, called detonation, results when the air/fuel ratio goes too high (also called a lean condition). Sometimes heard as a pinging or rattling sound, detonation occurs most frequently at maximum cylinder pressure, which corresponds with the engine's peak torque rpm. The fuel-starved lean mixture causes elevated combustion temperature and uneven burning, and the result is that maximum cylinder pressure occurs before the cylinder reaches top dead center. Damage can be a blown head gasket, a burned piston or rings, or a melted spark plug electrode.
Detonation is often unheard, but another phenomenon called pre-ignition is more obvious. Pre-ignition is related to detonation, only it's worse. Pre-ignition occurs across much of the powerband under load and sounds like a wheeze or a coffee can full of marbles. During preignition, the combustion chamber is so hot that an electric spark is not even needed to light the air/fuel mixture. Combustion is out of control regardless of ignition event timing.
Both detonation and pre-ignition are symptoms of fuel may improve these conditions significantly. As a rule, it takes about a half-pound of fuel each hour to support one horsepower. This number, called brake specific fuel consumption, can be used to calculate whether you're getting enough fuel.
From this, if an engine capable of making 400 horsepower uses 200 lbs. of fuel per hour, then each injector must deliver about 25 lbs. of fuel, or 25 lbs./br. Because an injector can't hang open around the clock, we have to give it time to rest between pulses in order to cool down. Most injectors can operate well with a minimum of 20 percent close time, so to deliver 25 lbs./br. we need an injector rated at just over 31 lbs./br.
Injectors for 5-liter EFI engines are available in 19-, 24-, 30- and 36-lb./br. varieties. (Larger injectors are available but may not be compatible with the EEC-IV electronic driver circuits.) So for a 400-hp engine, a 30lb./hr. injector would be the best match. A slight increase in fuel pressure will bring the 3D-lb./hr. injector up to the 31- 32-lb./br. delivery that the engine needs.
Of course, the fuel pump must be capable of delivering enough pressure and volume to satisfy engine demand. The same BSFC rule applies. A 400-hp engine needs 200 lbs. of fuel per hour, only fuel pumps are rated in liters per hour. Multiply 200 lbs./br. by the conversion factor.6 to get 120 liters per hour. Add a 20-percent margin to this for safety (24 liters per hour) and you get a fuel pump rated at l44lph. Any fuel pump larger than 144 lph will work fine for a 400-hp EFI car, provided the pressure rating of the pump is at-or above-what it will be used at (50 psi is a safe minimum).
A cockpit-mounted fuel pressure gauge will be a lifesaver when it comes time to tune your 5-liter. A companion air/fuel ratio meter, exhaust gas temperature gauge and boost gauge (for blown and turbo cars) will also be indispensable in making fuel pressure adjustments.
As an aid to those who want to calculate fuel injector size, fuel pressure and pump size, [\,,1$.1) has produced a pamphlet called MSD Fuel Management (document No. FRM141 10), which contains several helpful formulas, graphs and product descriptions. MSD also offers injection selection computer software (part No. 2000) for customers with an IBM-based computer and 265K RAM. We also covered the mathematics of electronic fuel injection in "Mustang Math" (May '94).
Many times detonation and pre-ignition are problems long after larger injectors, pumps, fuel lines and fuelrails have been installed. The reason is that ordinary pump gas-even premium-quality gas-lacks the resistance to light -off needed in many power-adder engines.
Nitrous, blown, turbo and high-compression engines have much higher cylinder pressures than stock 5-liter engines. In these engines, detonation can be the result of quite a different cause. Here the air/fuel charge is ignited by the spark, expands across the chamber, and elevates cylinder pressure and temperature just as with a stock engine. But these engines have a denser air/fuel charge, which elevates temperature and pressure to a much higher level than normal. Note that we're not saying at a much faster rate. Burn rate is a function of air/fuel ratio, not octane rating. Slow burn rates result from lean and rich mixtures (everything else, including combustion chamber design, being equal) and quick burn rates result from near stoichiometric air/fuel ratios. Detonation is caused in this case by the auto-ignition of the end gases, the last 20 percent or so of the unburned air/fuel charge. The premature spike in cylinder pressure damages the engine in the same way as an over-lean air/fuel charge, i.e., peak cylinder pressure occurs before TDC.
Elevated inlet air temperature in boosted cars also helps the detonation condition. Generally, every 150 F of extra inlet air temperature over 1800 F requires an extra point of fuel octane to keep detonation at the same knock threshold.
What is needed in this case is a greater resistance to detonation. An increase in octane raises the temperature required for light-off and prevents the end gases from auto-igniting. With a higher octane, the flame front can proceed across the chamber in an orderly fashion, cylinder pressure can build predictably, and expensive damage can be avoided.
The EFI 5-liter ignition is comprised of the coil, thick film ignition module, distributor, rotor, ignition wires and spark plugs. Depending on the level of modification, some of these parts may need to be upgraded to provide Virtually all l2.0-second and slower cars with factory compression are completely satisfied to run with a 100percent stock ignition system. And in many cases performance and reliability can be hurt by introducing high-performance ignition components. Owners of these cars will gain little or no ET by swapping coils, ignition boxes and wires.
Fuel-injected cars with greater performance capability, however, will need some improvement in the ignition department to run at their peak. The factory ignition frequently becomes inadequate on cars with turbos, blowers, nitrous or high compression. As the density of the air/fuel charge increases, so does the amount of electrical energy needed to jump the electrode gap and satisfactorily ignite the charge.
When the load placed on the OEM ignition system by these cars increases, the deficiencies in the system can show up in many areas.
In some cases, the air/fuel charge is too dense and the spark will not cross. It is desirable to narrow the plug gap to reduce the dielectric resistance and fire the plug, but without a stronger ignition, a narrowed gap results in less spark energy, an incomplete burn of the charge and less power. In other cases, the spark does not jump because there is a path of less resistance elsewhere on the secondary circuit, such as from a crack in the distributor or a wire shorting to a header pipe. Induction crossfire between wires (usually cylinders 5 and 6) can also cause a misfire.
A new distributor and better wires can help, but even in the best scenario, very high loads are placed on the coil and charging circuit as they try to do much more work than they are designed to. Ideally, more spark energy is needed to light the heavy air/fuel charge (which can in some cases be two or three times as dense as in a stock 5-liter).
This problem can be addressed by an aftermarket ignition system such as one made by jyl£l!'(9l5/8575200), Crane (904/252-1151), Jacobs (800/627-8800) or Electromotive (703/378-2444). These systems are designed to work together with a companion coil (or coils) and in some cases are offered with matching wires. The integrated nature of these systems is helpful in that they take away much of the guesswork-the reengineering factor we earlier spoke of-out of ignition upgrades.
In the case of power adders, the inadequacy of an ignition may show up only under the most aggressive driving. Cranking, idle, cruise and light throttle are often picture perfect, but when the hammer comes down, sputtering, surging and shuddering can result. Many drivers incorrectly assume that the blower, turbo or nitrous system is to blame, but the real cause is the sudden increase in air/fuel charge density. The factory ignition system that was the model of perfection one moment is instantly besieged by too much work. The only solution is a better ignition system.
Besides boosting the spark energy to the intake charge, many aftermarket ignition systems can perform additional tasks important to performance cars, such as rev limiting and ignition retard. Rev limiting can protect an engine from accidental over-revving and valve float and can improve (in the case of a 2-step limiter) launch consistency in the quarter-mile. An ignition retard device can protect (within reason) against detonation in supercharged, turbocharged and nitrous applications. The amount of ignition retard can be dynamically controlled by the quantity of boost via a manifoldmounted pressure sensor (centrifugal blower or turbo) or be switched on at a static level by a throttle-activated micro-switch (nitrous) or a pressure-sensitive Hobbs switch (screw-type blowers).
The simplest and least expensive components of the ignition system, the spark plugs, are often to blame for ignition trouble. Power-adder cars almost always require a colder-range spark plug and less plug gap. The colder plug will prevent heat buildup on the plug tip from initiating detonation, and the smaller gap will allow the spark to jump through and light the denser fuel charge. Blower, turbo and nitrous EFI Mustangs should try incrementally smaller plug gaps (stock gap is .044 inch, '87-93) ifmisfire is a problem. Gap should be no smaller than .030 inch or fouling and stalling may result.
As we pointed out in~, the factory EEC-IV engine management can compensate for a large improvement in volumetric efficiency without any ill effects. When more air is introduced into the engine or when exhaust flow Even Cam swaps are handled well by mass-air-equipped Mustangs. The latitude built into the EEC-IV is robust enough to manage most 5-liters deep into the 11 s or even into 10-second territory.
But as performance improves, the OE spark and fuel maps in the EEC- IV begin to tax the engine unnecessarily. It is advantageous (but not required) around 400-500 hp to employ some engine management tool to gain maximum performance and added reliability.
Depending on the device, add-on engine management can have the power to remap the fuel curve, extend engine rpm, and recurve the spark advance tables. In the best case, power can be improved by 50 hp or more without any changes in engine hardware, and engine longevity can be extended by fine-tuning the full-throttle fuel enrichment and spark timing.
In the worst case, add-on engine management can destroy an engine with detonation, cause poor driveability, and make a car unreliable. Programmable engine management is clearly a double-edged sword and requires some thought. By using such a device, you are setting yourself up to be responsible for some (or all) of the functions provided by the EEC-IV, and that takes patience and a desire to experiment.
If you want to take advantage of programmable engine management but don't have the time it takes to learn the ropes, consider using one of the experienced tuners that install and tune them on a regular basis. Most of these shops have an arsenal of tuning tools at their disposal (air/fuel ratio monitors, chassis dynos, engine dynos, data loggers) as well as experience to guide them Lets look at some of the available systems.
SVO Extender (part No. M-12650-A50, '86-'93; part No. M-12650-A51, '94-95; $589.95). The simplest of the engine management tools to master, the SVO Extender is a staple of fast 5liters everywhere because of its two-dial configuration. One roo b extends the engine rpm limit (from 6500 to 13,000 rpm) and the other sets WOT air/fuel ratio (adjustable from 10.25:1 to 14.0:1). The Extender is a piggyback unit that plugs between the wiring harness and the EEC-IV, and can be hooked up and running within an hour. Jimmy LaRocca of LaRocca's Performance (908/723-1111) is probably the most well-known Extender tuner.
Programmable Management System (part No. EFPMS; $725). Formerly known as the Crane Interceptor II, the PMS is sold for Ford 5-liter applications solely through Anderson Ford Motorsport (800/234-3106). Via a handheld programmer, PMS allows complete programming capability of the EEC-lV's fuel and spark tables. Multiple programs can be recalled, and rev limit, boost-indexed ignition retard, and external control of nitrous can also be programmed. InterACQ data-logging software is optional (part No. EFINTER, $249) but must be used with an ffiMcompatible laptop computer. Like the Extender, PMS piggybacks between the car's harness and the EEC- IV computer but offers an additional measure of tuning flexibility. Anderson Ford offers custom setup and tuning to speed the way to quicker ETs.
ACCEL Digital Fuel Injection EEC-IV Power Processor (part No. 75400; I-bar, 75401; 2-bar, approx. $950, release time fall '96). The DFI Power Processor is more user-friendly than its stand-alone DFI predecessors because it uses the factory wiring harness, sensors and EEC-IV computer. It piggybacks between the wiring harness and EEC-IV module and affords control of fuel enrichment, spark and mass air function. The most unique feature of the Power Processor is that setup has been made easier because startup, cruise and part-throttle functions are still performed by the EEC-IV. At roughly 70 percent throttle, the DFI unit takes control of fuel and spark. The Power Processor can recurve mass air meter output and uses a manifold absolute pressure sensor to determine fuel and spark. A control output for nitrous and low-impedance peak-and-hold injector driver circuits (for injectors over 36lbs./hr.) are also included. An IBM-type laptop computer is required for programming. The DFI system may be installed and tuned at any of the ACCEL/EMIC dealers across the country. To find the ACCEL/EMIC near you, call Mr. Gasket at 216/398-8300, ext. 488.
Electromotive TEC-II ($1,799). The engine management system
with an integral ignition system. An IBM-type laptop computer is
required to program the P AFZ or optional Super*B1end software, but
fuel setup is made easy by adjusting a pair of variables
corresponding to a carburetor's main jet and idle jet size. Multiple
ignition coils it 1a modular 4.6 provide excellent coil saturation
and spark energy at high engine rpm, while a programmable
pressure-referenced spark table allows power tuning. Data-logging
software is included with both software packages. Installation
requires mounting a 60-tooth trigger wheel on the balancer and
complete wiring of the injector, sensor, and ignition harnesses. For
more information, call Electromotive at 703/331-0100.
The factory 5-liter compression ratio of9.0:1 is an excellent compromise that considers available fuel octane, power and emissions. Naturally aspirated 5liters, even some highly modified engines, do well with this compression ratio. However, if a camshaft swap is made or a power adder is installed, it may be advantageous to raise or lower compression.
Longer-duration cams trap less air and fuel than the stock camshaft, so even though the swept volume and the combustion chamber volume are still the same, there is less cylinder pressure. Since the object is to trap more air and fuel in the chamber and not less, a larger camshaft may not be the best thing for a stock compression engine. An increase in compression ratio can restore some of this lost power and take advantage of the cam's greater breathing potential. This can be done with a piston swap or more easily by milling the cylinder head surface. (Somewhere between 10: 1 and 10.5:1 is best for pump gas and cams like the B303.) Hint: For most heads a .006-inch cylinder head cut will reduce chamber volume by 1cc.
Power-adder 5-liters with a turbo or supercharger run best with less compression, because more air and fuel are compressed in the combustion chamber than it would ordinarily hold, thus increasing trapped volume and actual compression. When boost levels exceed 7-8 psi on blown engines and 10-12 psi on intercoo1ed turbo engines, a reduction in mechanical compression ratio is highly advised, or repeated head gasket failure can result. Reducing the compression ratio to the 8.0:1-8.5: 1 range will restore much of the detonation margin to the engine without compromising driveability or emissions. This can be done by swapping in low-compression pistons or by working up the chamber volumes by hand.
Because nitrous has the tendency to cool the intake charge, making it denser and taking up less space, a slight increase in compression ratio may be desirable for best performance on pump gas (9.5:1-10:1). This is especially true when a larger nitrous cam (which favors exhaust) is in place.
With more power comes more heat, which must be carried away by your cooling system. When heat builds up, detonation, excessive engine wear and power loss often result. Since drag cars are least likely to be affected by an inadequate cooling system, we'll focus on street cars.
A high ratio of antifreeze to water will protect your car from freezing in the winter and boiling over in the summer, but it will also reduce the heat transfer function of the coolant. A 50/50 mix of antifreeze and water has roughly half the heat transfer capacity of pure water. Try using a 20/80 mix with Red Line Water Wetter (800/624- 7958). This will still provide excellent freeze/boil-over protection and corrosion prevention, and the Red Line will enhance heat transfer.
A larger radiator will increase the cooling capability of your cooling system if steady cruise reveals an excessively high temperature. Many manufacturers such as Be Cool (517/895-9699), BBK (909/735-8880) and Griffm (803/287-4898) offer larger radiators for Mustang-specific applications. If it's time to replace your water pump, Ede1brock offers a high-volume unit (part No. 8840; 310/781-2222) for severe-duty applications. In some cases, water pump volume is adversely effected by a larger underdrive pulley (which is great on slightly modified cars but may cause cooling problems on quicker cars). A smaller pulley, such as the '93 Cobra unit, will increase coolant circulation with minimum hassle. In older cars, silicate from the antifreeze will plate out on the aluminum parts of the cooling system, reducing the heat transfer capability. A pressurized power flush of the system will remove this plating and restore cooling efficiency.
A supplemental electric cooling fan may be a good idea. Several are manufactured by Flex-A-Lite (800/8511510), Perma-Cool (818/967-2777), ~1I-,_(IiJ:.$_k~1 (216/398-8300) and TCI (601/224-8972). For street cars, an electric fan should be used only in addition to a properly shrouded mechanical fan. (Race cars are fine with a single electric fan and no mechanical fan.) This is because an electric fan (or even two of them) are no match for the stock fan and shroud. Always use a shroud for maximum pulling power and safety. Both drag and street cars may also use a flex fan for an increased airflow and reduced parasitic drag.
This is the end of the line for the Fuel Injection For Beginners series. Our goal was to put EFI performance modifications in perspective for you, showing you not only the whats but the hows and the whys. We hope we've cleared the air enough to make modifying your car a more enjoyable affair. After all, what's the point if it isn't any fun'?
From Mustangs and Fast Fords magazine