Lean off idle & throttle tip in SOLVED!
I had a serious problem with my car
going lean at initial throttle
tip in and during low speed
initial tip in. It was got to the point
where I could sometimes
not accelerate from a stop sign without
fanning the throttle and
barely moving until I got up to speed.
Several others had the
same experience and I promised I would post
my solution when I
found it.
I am going to include a LOT of information in thispost. I am
posting it on the TwEECer and EEC-Tuner boards as the
problem and
solution is the same for both. My particular testing
was done with
the TwEECer. Without sounding like I am trying to
be a know-it-all
I would recommend saving this post as it is the
first (to my
knowledge) that goes through full detail in
modifying your
accelerator pump settings.
All my testing
was done with a Wide Band Oxygen sensor (DIY-WB) and
datalogging
using the TwEECer RT. I have an A9L processor.
First, there
are 3 keys that can alter your accelerator pump
settings. One is
a scalar value, one is a function, the other is a
table. I have
found that these keys DO NOT WORK like everyone has
been saying.
In fact what you have been told is BACKWARDS from how
they work.
I have 20+ hours including dyno time to backup my
findings so
please at least consider what I am saying.
First: [Accel Pump Multiplier – Global] - This scalar is a
multiplier but not
for desired air/fuel. It has been posted that
you lower this
value to increase fuel (lower values multiplied by
desired
air/fuel would richen the mixture). This is not true. It
works as
a multiplier against the values in the table [Accel
Enrichment
Fuel]. If you lower this number you lower the net value
of the
accelerator pump fuel shot. I have tried values in this
field as
high as 5 and they appear to work. I do not know what the
maximum
value is for this key.
Second: [Accel Enrichment Multiplier vs TP] – This function is again
a multiplier against the values
in the table [Accel Enrichment
Fuel]. The X value is the throttle
position sensor voltage. The Y
value is the multiplier. I have
found no benefit in changing the
values in the last three
positions (2.207 – 4.98). I have found
that increasing the X
value under the Y setting of .977 helps but
not in the following
fields.
Third: [Accel Enrichment Fuel] – I do not know
what the values
represent in this table. I do know the smallest
value available is
0 and the highest is 63. When I first saw this
table I questioned
why the values got smaller with a larger
TP_Rate. The best "guess"
I can come up with is the
TP_Rate refers to your current throttle
position. The higher the
value the further your throttle is already
depressed and the less
fuel you need. My other "guess" is that the
table
reference for the Y values is backwards.
I have found that my
particular application requires MUCH larger
values in the fields
than stock. My table has no value less than 30
and many at the
maximum of 63. I have a theory of why this is. I
am running a
90mm throttle body. A slight change in TPS on my
throttle body
lets a dramatic amount more air in than the stock 55mm
throttle
body. Although the MAF will eventually catch up with the
actual
air flow, your have at least a second where your MAF is still
reading low but you have a large amount of air entering your
intake
manifold. So, the larger your throttle body the larger
these values
need to be.
I am still working on the final
settings but my drivability is
better now than when the car was
stock. I have no hesitation at
throttle tip in and my WB O2
sensor reads a consistent air/fuel at
tip in.
I hope this
helps!