May have been wrong all along

[Programmer]

Can you explain this "synch" and "asynch" operation ? (When you have
time...)

Lyndon.
----- Original Message -----
From: <rrauscher at nni.com>
To: <gmecm at diy-efi.org>
Sent: Thursday, March 15, 2001 7:55 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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