J N's MiniRam backfire

[JN]

Hi,

    Some answers to your questions.  Car is an 89, 165 ecm $32B.  I have a
chip from fastchip that I have been playing with that has modified MAF
tables for a ported MAF.    I also tried my stock timing map and other
various things.  I have been concentrating on my pump shot.  I called TPIS
and they knew right away what my problem was.  They said I bet your getting
a big backfire through the intake.  They told me to modify the pump shot
tables and that should do it. I increased the pump shot by 45% and that did
nothing.  I plan on increasing the pump shot more and experimenting.  Fuel
pressure is set to 50 psi line off.  If you blip the gas, the pressure
spikes to 50 like it should.  TPIS suggested raising the pressure to 60 psi
and I explained to them that for whatever reason, my multecs seem to start
locking up at pressures over 50.  With that in mind, they suggested going to
a 24 pound injector.  I have a set of 30 pounders that I have been saving
for the 396.  I figured that they were too large for a 350 with ported heads
and a slightly hot cam.

Thanks,
Jason Norris
----- Original Message -----
From: <timsiford at hushmail.com>
To: <gmecm at diy-efi.org>
Sent: Thursday, November 09, 2000 9:14 AM
Subject: J N's MiniRam backfire


> Jason sent me an XLS spreadsheet with data from a scantool that shows a
> backfire happening when he blips the throttle.  Car = 1987 Vette w/
MiniRam.
>  Its pretty interesting.  (Jason, I am posting here because I can't find
> your e-mail, thirdgen appears to be down, and I also want to share this
> info with others here).
>
> The data clearly shows Jason 'blipping' the throttle from off idle.  There
> are 4 data points on the throttle blip and you can clearly see the O2
volts
> going from the switching behavior at idle (TPS=0.53V) to 0mV on a Throttle
> blip.  The data is below.  This appears to be a fueling issue (expecially
> when viewing the SA in relation to the throttle blip and LV8).  Its
undetermined
> as to whether or not it is a PROM fueling issue or a mechanical fueling
> issue.  What do you guys think?
>
> RPMs,TPS, O2, AFR, Knock, SA, LV8
> 875, 0.530, 836, 14.7, 0, 25.4, 57
> 875, 1.630, 712, 11.7, 0,13.8, 189
> 875, 3.310, 292, 11.7, 0,15.9, 177
> 1300, 2.94, 0, 11.8, 0, 28.2, 175
> 1725, 0.90, 13 ,14.7, 0, 45.5, 124
>
> Jason - quick question for you.  The MiniRam has ZERO provisions for EGR.
>  What PROM are you running?  Are you running $6E code, $32B code?  Is your
> PROM image based off an original TPIS image or did you start with the
stock
> image as a base?
>
> A separate issue is that IMHO, knock -should- be detected and isn't.
>
> Tim

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