May have been wrong all along

[romans, mark]

Bob:  On the 89 6E code for the 165 ecm, learning is turned
off during decel which prevents the bucking problem.
You might turn off learn when in lean decel to cure the problem.
Mark
----- Original Message -----
From: <rrauscher at nni.com>
To: <gmecm at diy-efi.org>
Sent: Thursday, March 15, 2001 6:55 AM
Subject: Re: May have been wrong all along


>
> The common belief has been that larger injectors won't idle.
> Evidence has been proving otherwise.
>
> And I believe that others have reported the same thing. Going
> to 30's in a TPI setup with no idle or low speed problems
> (with corrected cal). Then there is the Quad4 running I think
> 33's? in a port PnH configuration.
>
> They idle fine. And need that much fuel for the high rpm
> usage. (very little on-time available).
>
> Going to a larger injector will also change when the ecm
> switches between sync & async injection. I have a real dodo
> area in the current setup I'm using. During low speed light
> decel, the car would start to buck to & fro.
>
> Took a long time to track it down to the switching from sync
> inj to async inj. When in async it would lean out causing the
> car to decel faster. Then the INT rises causing the ecm to
> switch back into sync mode. This going richer would cause the
> engine to pick up power again. And the cycle repeats.
>
> First thing I did was to verify the sync-to-async math in
> the ecm. It's correct. Haven't fixed the transition yet. Will
> work on it this summer.
>
> BobR.
>
> p.s. I do hope that Sleepy and Bashful make amends. 747's
> aren't designed for dog-fighting.
>
> >
> >
> >
> >Well, at dinner tonight Sleepy and Bashful got into a heated debate, and
I
>
> >couldn't settle the disbute.
> >The issue was how wrong and yet right GM is in there injector sizing.
> >Lets just look at a 350 v8 say 8D mask.  Bare with me as I just round
> >numbers off.
> >
> >25 times 8  =  about 200#'s per hour, for a 240 HP engine.  That is way
over
>
> >sized.  In the past I just dismissed it as allowing for wear and tear and
> >some PCV levels elevating.
> >
> >I think the rational, is more the ratio of (yes) the mechanical wear and
> >tear of the system but to make the BL alot more corrective in nature.
ie
>
> >as long as you have room on the low side of the injectors operating range
> >you'll be OK.  I see any P+H injector, at it's min linear time will make
for
>
> >an easy to tune and FORGIVING calibration.
> >
> >Also, explains SEFI.   By observation of my GN the 40#/hr injectors with
a
>
> >mild cam was much smoother at idle then the oem ones,  and with the 55s
are
>
> >just as smooth as the 40s.   While I could probably twist it's tail and
run
>
> >550 HP that wasn't my goal, but rather I wanted  a least 450 with a
little
>
> >room for more.  So went with the oversized 55s, but they worked out to be
a
>
> >**nice** size to work with.    Also, reduces the work load on the fuel
> >delivery system.
> >
> >Might again explain some conditions where there is trace detonation when
> >trying to run 350HP which the stock ones should support.
> >
> >In playing with the 355 (cross fire TBI) I had been able to run good
numbers
>
> >with the 85s but it just seemed so much easier to get the numbers with
the
>
> >95s, even though still at the 325 HP level..
> >
> >YMMV
> >Bruce
> >
>
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