In a message dated 2/27/01 11:42:04 AM Pacific Standard Time,
DICEMAN469@aol.com writes:
<< ernd, I'm aiming this question at you because you are by far the biggest
tinkerer on this list (I think Will uses the "BLUNT CASH" method). That, and
you like to read, so I'll make this long (lol). I'm having what I feel is a
lean condition at high rpm. I changed the fmu to the vortech adjustable one
finally and I think I have it tuned properly. I've narrowed it down to
outflowing the fuel injectors, a failing inline fuel pump or a clogged cat.
I've decided to fix all of them. I got a high flow 3" waiting to go on (the
old one sounds like it's got a rock in it). I've also got a vortech trex on
order (I figure at the least, I have more capacity, and I can use the
powerdyne fuel pump perhaps for water injection later?? A entirely different
project).
Now for the injectors. The stock 19# injectors I want to give the axe,
and install the 30# ones in their place. Problem being that I'm not willing
to dish out hundreds of bucks just to have the PCM reprogrammed, so I'm
looking for a way around it. At first I was going to run the return line for
the super fmu straight to the tank, and use the fmu to control base line
pressure, then just lower it to compensate. Then I realized if I do that,
it'll screw up the fuel spray pattern and ruin my idle, so i canned that
idea. My idea is to attack the MAP sensor, perhaps finding a value of
resistor that I can use to reduce the injector-open time. With a static
value
the curve in the MAP will be retained, just lower it enough to close the
injector at an acceptable time. I figure I can use the FMU to adjust the
fuel
curve any further. My only goal is to get something in there that isn't
almost at full duty cycle, and I don't want to buy 24# when I got 30's
already in my garage.
Got any interesting ideas on what value we can use?? What about that
dual-potentiometer package you posted awhile back?? Did you ever try that
out?? Lemme know what you got.
-Austin >>
You may not need to reprogram the FMU. I'd first try the 24lb or 30lb
injectors and adjust the FMU. I'd find a dyno with a wideband O2 sensor and
work on the air:fuel ratio. This eliminates the guessing. If your using the
super FMU then you should have a little flexibility. Mechanical FMUs are not
great and getting the fuel curve right,but it will get you close. I'd shoot
for running a little rich to be on the safe side. I've never used a custom
PCM and have had pretty good luck thus far.
Tom
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