May have been wrong all along

[rrauscher at nni.com]

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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