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2 Posts
Discussion Starter #1
My intended use of these LT1 computers is on a 1993 Chevy van running a 350 or a 383 engine all rebuilt as a low RPM torque monster: 193 swirl port heads form a 1990 Caddy Brougham with Keith Black “D” dish pistons and what most call “The Peanut Cam”

One subject I would like to talk about is a 383 with 400 crank and stock 400 rods, as I am looking for MPG will the extra stroke help or hurt my plans??

The plan is to build it to pull strong enough to run below 1500 RPMs in top gear as around 75/80MPH.

I need strong torque so it will not be lugging. (this low RPMs will be done by adding an old BW over drive behind the main 4 speed tranny.)

I was going to piggy back a stock 85+ ECM on top of my Vans ECM with a MAF sensor and running the hidden high way mode when learned that the 94/95 LT1 is both a sequential and operates a L60E tranny.

This seems to be a great set up, I feel that sequential fuel delivery will be much better with my planed on low cruse RPMs. (I am aware it is less a matter with higher cruse RPMs.)

BUT my plans have run into a few problems and questions: and These are becoming a major questions:

1) Can a OBD1 94 LT1 be program in the tables and the setting for High Way Mode into a LT1 ECM??
2) Does a LT1 ECM HAVE to have a Optispark system to run??
3) OR can the FI small distributor work in place of a optispark??
4) Does the LT1 ECM require two O2 to work or can it run off of one??
5) Can I using a correct OBD1 Cable and Tunercat fine tune the settings after I have installed the High Way mode tables?? (assuming you do # 1)
6) Can anyone provide instructions on HOW to correctly time the Optispark if I custom fit it to an older distributor??

So it is beginning to look like getting one for the better sequential fuel delivery may not be worth all the trouble...

I am told I will need to add a Optispark system and run two O2s...

And if I cannot add the Highway mode might not see all the fuel savings I am hoping for.

So using the older ECMs with the Highway mode and less fuss seems to outdo the improvement from sequential fuel delivery.

It only works if I can run both and to be able to fine tune the range of the lean burn to my engine....

The older system can be run off a laptop and adjustments made live on the fly, where the LT1 you have to make a change and THEN flash it in and test drive and if you need another adjustment stop and flash the ECM again and retest...until it is right.

So the $64,000 question will be how much will sequential fuel delivery improve MPG?? I am aware in a normal car very little, but as I am looking at engine speeds in the 1000 to 2000 range a slower breathing engine MIGHT benefit from the tighter system.

And there is a slight claim that the fuel caught behind the intake valve have a little time in a hot head to vaporize a little so that might even a HOT intake manifold...

A decade ago I was just getting into TRYING to get better MPG in my Highway Chevy VAN which was horrible... and one of my searches led me to the 3rdgen site.

I was so excited that I hunted up and bought two complete TPI systems with a number of MAFs and extra that time adjustable Fuel Injection look so good. Then came OBDII....

But work, health and lack of funds slowed me to dead crawl and I have yet to put them on hold and my super engine.

Meanwhile my need for road trips lessened and then I was trying to make more MPG with a company called Dutchman and their HFC Hydrogen system.

And when that proved to be junk (and the company) I still tried to make other HHO systems work, after SO MANY Claimed they do...and as at that point in the late 90s and early 2000s the old OBDI systems were now becoming either Junkers or Collectables which means THEY will not want these systems… So I spent the next decade (when I had time and money) still trying to come up with a big MPG improvement system FOR only OBDII systems...

I have learned a lot and like Edison more of what will NOT work than much that can.

The ONLY one that will work is my 2000 Stock Mercury Grand Marques which gets 27/30 MPG Hyway at 65MPG can get 32/35 MPG again at 65MPH running the leanest it will burn and not misfire at 16.5:1.

BUT I cannot use this setting for normal driving, so it is only shown for testing..I am still looking for someone that can reprogram my 2000 Ford ECM with the Hyway Mode or figure out a way to fake it and have is an automatic system.

So when I build my super toque motor for my van with a 80s TPI I want to use a LTI ECM to control it and I will tune it to match my engine in the van.

This is why I am here..

28 Posts
honestly, i wouldnt recommend ANY of that. youre already into the full custom side of your build. save yourself a lot of grief and go with a LS.

16 Posts
There may be a pnp ecu from other than that go with a 0411.
383 with Scat crank, 5.7 or 6in rods, 9.5:1- vortec heads and TBI.
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