TwEECing for Newbies
The TwEECer attaches to some Ford computers and allows you to reprogram almost anything. You can remap the MAF, change the fuel and timing curves, even in the case of the A9L turn on a cooling fan that Ford never used. Not all processors (aka EEC,ECM) are supported. Some are grouped into families and have similar tags, are interchangeable and can except tunes from each other. Some Processors are more desirable and better understood and "mapped". Most of the earlier model Mustangs EECs are well understood and are often discussed on the TwEECer BBS. The processor catch code is what most people go by and is located on a sticker just above the connector. Think of it like a personal PC and it's operating software. The PC is the EEC, the software is it's catch code. The software has a changeable database (what you will be monkeying with using the tweecer) that can be swapped between each other in the same family. One of the most famous, well mapped and understood is the A9L. Thats why I used it for my EFI conversion and why most of the information you'll find on this site is about it. Just try a Google search on "A9L EEC" You'll find lots of info. Now thats not to say that the A9L is better, its just what I have chosen to use and document. In fact I've heard good arguments on it not being one of the best. It is however one of the most simple and most often used for this sort of thing. The different families have different strategies and are programmed different. They are computed differently so keep this in mind when you are searching the posts. See EEK vs. EEK THE SHOWDOWN for a better understanding.
One of the sensors Ford uses is an Oxygen sensor it is mounted in the exhaust and measures how much oxygen is left after combustion as to determine how much fuel has been burned. The low cost approach Ford took was to use a "narrow band" sensor. The narrow band sensor can only tell the EEC that it is rich or lean and not how far out it is. The EEC uses this information and bounces between rich and lean by adjusting how much fuel is fed through the injectors. As long as it is 50% between rich/lean, all is well. This works good enough on a stock motor but when you start modifying things it makes it almost impossible to get a proper tune. The way to get around this is datalog using a "Wide Band" sensor. Dataloging can tell you exactly how rich or lean the car is running. We then use this information and apply it to what we know about EEC family we are working with.
Another major, misunderstood sensor is the MAF. The MAF reads how much air the engine using. The maf can be tuned or calibrated with the function called maf transfer . The EEC uses this along with the O2 readings to figure out how long in milliseconds to hold the injectors open (injector slopes)as to supply the right amount of fuel compared to how much air the engine just swallowed( air\fuel ratio).
As you can see from the last two descriptions The EEC needs to know EXACTLY how much fuel it's squirting. The Injectors size, timing, and slopes is important and getting it correct is the first order of business when you start tuning. If the slopes are off, the EEC doesn't know how much fuel it is giving the engine. There are two trains of thought here, manipulating the MAF curve, or the Injectors. Just moving the MAF curve may be easier and a lot of people do it this way. In my opinion, the most accurate way, is to do both starting with the injectors. Although the EEC has a correction factor called KAM, KAM is limited. You need to get the injector slopes correct before you bother doing anything else other than turning off emissions or setting the idle. This is even true on a stock engine. Injectors are different and the tolerances are loose for production. The factory matches them somewhat but doesn't custom tune the eec for the installed injectors. Also, Ford even screwed up in a few cases with this MAF/Injector balance so now that you can with the TwEECer you should get it right. I know of three ways of doing this,1- The "Walt method", 2-use EEC Analyzer,3- ignore the break point and set high and low slope the same(for 19lb injectors use"19") and change the MAF curve. I think the last is the worst although it may work I've never tried it, I haven't tried Walt's method either because I don't have a copy of Excel (I use Open Office it won't do macros) so the only thing I have personal experience with is the EEC Analyzer. Just click on the link, download it, pay the man, and read the help files. Its really cool program. I have an EFI converted 70 Mustang with an Explorer 5.0, Kenne Bell, Lightning MAF. 42lb injectors. Using the EEC analyzer, it purrs like a stocker, gets 18mpg, I drive it to work almost every day and it's getting (according to the analyzer) 415 ponies 580 ft pounds of torque at 3000rpm.
Now you can see that if you have a TwEECer you don't have to match the injectors to the MAF. You can run 30lb injectors with a stock MAF. You don't need or want to use an FMU (adjustable fuel pressure regulator).
As the EECs evolved, and the Government added more strict emissions laws, the strategies for dealing with all of this got more complicated. The EEC still has to deal with varying engine temps, outside air temp, engine load, vehicle speed, ignition timing, transmission, load of accessories, fuel octane, sea level...... well you get the idea. So even with all of this, all of the different EECs involved, the different stock motors combinations, all of the different engine upgrade combinations, and driving styles, one product can allow YOU to tune the car. Understand that if you have a not so well documented EEC your results are limited by what you can figure out. There is no manual, or detailed documentation even on the better known processors. Its really up to you to do the research and ask questions.
OK so this is a lot to ask of one person and almost impossible to document. Thats why we have the TwEECer BBS Yahoo also has a TwEECer BBS, just do a Yahoo search. Don't expect a quick fix to your problems or a downloadable, burn, and run program you can pick off of the Internet. What you can expect is a long learning curve for you to tune your car the way you want it and be able to keep it "streetable". If you need a quick fix or don't want to deal with the learning curve, there are better options for you. It is easy to get started with the most basic features like, turning off smog stuff, changing the idle, and setting the rev limits, and by themselves worth the price of admission. It wasn't but a few years ago that this stuff was impossible through programming and we were limited to tricking the EEC with resistors and fuel pressure regulators.
O.K. so you want to continue with the madness. First thing is first go to the TwEECer web site and download and read the manual. Its a bit scarce, thats why I started this site.
Actually it's MUCH better now!
Next, Log onto and poke around the Yahoo TwEECer site, Acronyms and Hardware may help you understand some terms and gizmo's your not familiar with. I also have a list of the tags for an A9L that may help. The Locals on Yahoo, although very smart and helpful, sometimes get into a tizzy about answering the same darn questions over and over so Refrain from posting Newbie stuff unless you really are stuck and can't find it. Just lurk for a while and search the files and posts on the site. If you want to get a rise out of someone ask if they will post a tune because you just bought a TwEECer and are to lazy to figure out how to do it. Be prepared with Flame-Retardant Underwear if you do.
P.S. all of the articles on this site was written by other people. I have simply saved them and made links where appropriate. Some of them was originally written for the EEC Tuner. The EEC tuner is a different product with different tag names for the same features as the TwEECer but the information still applies. I do not have a cross reference for the different tags and don't have the time or effort to rewrite all of them. I may as time and will allow go through them and change them to reflect the TwEEcers programming. Until then its up to you to figure out what tag to use.
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