Re: 749 O/L idle help needed

[rr <RRauscher@nni.com>]

Ok, here's the equation for bpw:

bpw = bpc * map * ~t * ~afr * ve * bVcor * blm * dfco * de * clt

bpc: injector, displacement constant
map: well, map
~t: inverse coolant
~afr: inverse afr
ve:
bVcor: battery volts correction
blm:
dfco: decel fuel cut off
de: decel enleanment
clt: int & prop term

In open loop, the blm, int & prop terms are steady. You shouldn't be in
dfco or de. Coolant and bpc should be steady. That leaves bVcorrection,
map and afr. In open loop, afr changes with map. Seems like you should
check that your vehicle volts are steady. If so, then your problem is a
fluctuating map. Patch a set value for map into the code, and try it for
idle.

BobR.


Dig wrote:

> Pardon the ugly formatting... yahoo mail is kinda
> lacking for digest...
>
> ----
> Date: Sun, 29 Oct 2000 15:29:37 -0500
> From: Barry Tisdale <btisdale@cybersol.com>
> Subject: 749 O/L idle help needed.....\
>
> Gentlemen:
> Trying to get a *solid* idle in my Sy -
>
> -----------
>
> The Grail.... ;)
>
> -----------
>
> 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
>
> ------------
>
> 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@yahoo.com
>
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