749 O/L idle help needed

[Dig]

Pardon the ugly formatting... yahoo mail is kinda
lacking for digest...

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Date: Sun, 29 Oct 2000 15:29:37 -0500
From: Barry Tisdale <btisdale at cybersol.com>
Subject: 749 O/L idle help needed.....\

Gentlemen:
Trying to get a *solid* idle in my Sy - 

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The Grail.... ;)

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Oxy sensor set @ 0 time (therefore open loop always)
Timing table set flat in the idle area - this is
working - no timingvariations
A/F closed throttle table set flat in idle region; VE
vs RPM table set flat
in idle area.
Still, the BPWs fluctuate from, say, 1.09ms to 1.25ms.
 IAC shows no more
than 50 +/- 1, timing = no variation, idle speed from
650 to 750 (target is
725).  Idle is best @ 1.25ms here, something trying to
lean it out.
MAT =~ 90F, coolant @ 160F - want steady warm idle
first, will work on cold
later.  Manifold vac steady @ 16" +/- 1/2 (mild cam).
*Something* is causing the BPWs to vary, almost like
its still in C/L.
Any suggestions?  Obviously, I'm overlooking something
here

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I've only seen you mention 2 tables, thus far, closed
throttle and VE vs. RPM.

There are others.... Battery voltage, and Boost Bias,
to name a couple. 

Also, IAC can cause AE events... you might want to
look to see if that's occurring.

Generally, though, it almost sounds like you have
a vaccum leak somewhere. If I run in OL, my idle
smooths right out... likes extra fuel. I have tweaked
the closed throt. AFR vs. temp table, though.

Try adding a couple ticks to the low end of the F94
table...(0x10 or so) bumps low pulse widths up a bit.

You didn't mention if this was 2 bar or 3 bar...
makes a big difference in what indexes you use into
the VE and other tables.

Smaller diameter torque converters can also affect
idle quality. You'll see/hear from a lot of guys 
who went to the TCS 9/11, and had it effect their
idle. A little playing with the IAC parameters can
help quite a bit to smooth things out.


Later,

Dig
turbodig at yahoo.com






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