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Re: TBI vs Port Injected
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Date: Tue, 21 Mar 2000 07:11:20 -0500
From: "nacelp" <nacelp@bright.net>
Subject: Re: TBI vs Port Injected
> For a relatively mild street engine is a port fuel injected motor going
to
> produce more horsepower than the same motor with TBI?
Getting a good flowing TPI is usually$$$, or lots of fabing on a single
plane.
Is this an dry air
> flow versus wet air flow difference or really more related to intake
> manifold design?
The two go hand in hand
> Bruce's crossfire setup is an example of an optimized TBI with a good
> manifold, but would this motor have performed better if it were port
fuel
> injected?
The engine was first optimized using single, and dual plane manifolds.
What single plane were you using?
I
doubt the is a EFI manifold that outflows a Weiand 7525 (both in stock
form). The times/trap speeds were a wash, it was too close to call. The
TBI had all the best manners in the world. I know carbs really well so
when
I say optimized I'm including idle circuit, transistion, acclerator pump,
secondary air valve, secondary needles, and hangers, air cleaners, etc.
They were both tweaked as far as a *normal* person would go.
> The following is the background for this preceding questions. I am now
> slowly gathering the parts for a "new" 4.3 for my truck(94 m5 s10).
Mild
=
> 96+ 4.3 heads 2.02/1.60 ported polished and coated, GM performance
marine
> cam in a non balance shaft block, compression ration is TBD, coated
> Edlebrock headers and catback exhaust. Currently it uses a 16184738 VCM
> (VCMs control both the powertrain and the ABS plus generate the signal
for
> the speedometer and possibly other gauges). My options are;
> Retain the current fuel system and improve or replace the intake
manifold.
Can you get a second one?.
What I did was gather several manifolds, and then step by step ground on
one, and alternated back and forth progressively getting wilder, then when
I
went too far, backed up to the last manifold design, and then knew it was
nailed.
This is a very interesting concept, which I will probably try. My only
question is that, if I do this with a stock 4.3 TBI manifold am I starting
with a sows ear? My guess is that I am. This manifold is a single plane
manifold with virtually no runners to the center cylinders and long
convoluted runners to the front and back cylinders. The most compelling
reason for converting to CPI may be to get a decent staring point for
manifold design.
> Swap the ABS system to a stand alone unit and use a auto tranny
calibrated
> 16156647 on a CPI fuel system.
> Find a 1995 16193495 VCM and harness and use SCPI fuel system. This is
what
> I was planning on doing, but I am currently having difficulty finding
parts.
> This VCM was calibrated for a M5 and utilized the earlier CPI
injection
> system.
> Use the 16184738 VCM to control a Sy/Ty fuel system. Probably the least
> practical solution.
"Practical" whatz that?
Grumpy
>
-
----------------------------------------------------------------------------
--------------------------
Date: Tue, 21 Mar 2000 07:57:10 EST
From: Chipsbyal@aol.com
Subject: Re: TBI vs Port Injected
Another option is to use the Chevy 1992 CPI ECM. It won't do your ABS, but
it
isn't looking for a 4L60-E trans either. This ECM only controlled the TCC
on
auto applications. There probably also had manual units. Keep the factory
VCM
for the ABS.
I think this ECM is the 16156647. Howell and TPIS specialties both offered
to provide me a wirning harness to do this. I haven't done it so far,
because I have not been able to find a manual trans bin yet and I don't want
to have two ECUs for sake of passing a visual underhood inspection during an
emissions test.
Rich V.
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