Does anyone have information on using an LT1 computer with a TPI intake.

I have an 86 TPI intake with an aftermarket computer and I want to replace it with a newer GM computer and mass air flow instead of map.

I am aware of the easy rout = 86 to 89 GM computer with a painless wiring harness. Most likely will be going this rout but was hoping to use LT1 computer.

This is what I have so far and I'm trying to find an opti distributor

The real problem is the opti spark distributor and
using all the sensors and parts that the LT1 uses which I'm not sure if
they are the same as the old ones. I guess one can look up the part
numbers and see if they match what you have :

MAF (addable)
MAP (standard?)
IAT (addable)
TPS (addable - part of TB)
IAC (addable - part of TB)
EGR (not needed)
AIR (not needed)
Head Coolant temp sensor (standard?)
Water pump temp sensor
Oil level sensor (can trick?)
Knock sensor (can be tricked)
O2 (addable)
fans (retrofit LT1 fans into car?)
etc

 

The LT1 computer will be near impossible to use without an optispark. The optispark will not understand the pulses from a regular distributor, and some of the LT1 computers require a crank sensor. Looks like you're stuck with your existing computer if you want to stay MAF.

 

86 year models use MAF. 89-92 models used MAP. LT1 models use both MAF & MAP. What do you mean after market. Is it aftermarket or a OEM speed density model?

 

Since I own, work on and use both, I think I can answer this question with a fair amount of authority.

Inside every Optispark is a small flat disk of metal with 2 rings of slots cut into it. The first ring contains 360 tiny slots and the second ring contains 8 larger slots. This flat disk spins inside a device called an "optical pickup" inside the Optispark which has 2 LED's in it and 2 sensors. The inner ring of 8 slots tells the PCM what cylinder the timing is at, and the outer ring of 360 slots tells the PCM what the exact timing is.



Looks like this, sorry about the crappy pic quality, my camera batteries are dying.

SO.. these two optical signals (called High/Low resolution pulses) are REQUIRED to use the LT1 PCM. . . no one I know of has managed to get away from these. So unless you can fake this, the best PCM to use is like a 1998+ 502 big block SEFI PCM..

 

Hey GhoSSt, your picture is a little ghostly. lol

 

The later ECM is timed to the crank and cam. TPI ECM wasn't. Your desire to do the swap will cease long before it is half figured out. Anything is possible though.
J

 

Hey GhoSSt, what exactly does the "distributor" in a '99 454 function as? Is it partially used as a cam sensor?

Matthew

 

Umm.. as a distributor. :lala:



No, all 1996+ Vortech engines have dedicated crank position sensors. Or all the ones I've seen anyhow.

The new distributors use a funky 3 wire connector and a new style ingition module and coil.

 

Yeah, the ZZ4 plastic timing cover w/ provision for them is what they use on 96-02 350's I believe. I just figured it had something else in it.

And they're that nylon / plastic

thanks

 

The 86 originally had a MAF sensor. The TECII you have must work as a speed density system with a MAP sensor. If you can find an early 1989 ECM out of a Corvette with wiring harness and MAF, I believe it will suit your needs. You can retrofit an LT1 intake onto your engine, but an LT1 ECM without an LT1 engine is not logical. [URL=http://www.lt1intake.com]

 

I have raised an issue about the LT1 intake on non LT1 blocks in the TPI forum. Be aware that you may have to modify the intake(weld) where the EGR port is on the cyl. head. I am guessing that the LT1 intake will post at his sight pretty soon. It is not a big deal......but it requires someone to tig weld it up.
Cheers,
J

 

Hey Junk, I asked John about that a few months ago. I am in the process of replacing my TPI with an LT1 intake. When I bought gaskets to begin redrilling the flanges I noticed that the flange on the LT1 intake was not as wide as the opening in the gasket that surrounds the center holes (EGR openings) in my old style heads. He said his hasn't caused a problem. I still wonder. Is that the area you're talking about?

 

Yeah, that's the problem. You can look at it two ways.
1) exhaust pumps into the engine, then into the PCV valve, then into the intake, then into the combustion chamber.....
So the EGR still works (always on though), CA legal though. Just kidding

2) Hot exhaust(unburned gas) is being blown at pushrods (and gas isn't good for bearings). Lots of oil changes.

2 ways to fix.

1) fill the head's EGR port
2) weld a piece of alum. extending the intake.
Don't epoxy (JB weld) it.

Bearing life, lifters, etc. will become a problem down the road.

There are plenty of shops that can weld it (at least around where I am)
J

 

Are you saying these are the consequences if not remedied. Or if I remedy these still exist.

 

Consequences only if not remedied. If you weld it, everything will be fine.
I think John has run that way for at least 5K miles now. I think......I don't want to speak for him though. I would ask him what he knows cause is really the most experienced with this.
My intake isn't on yet. I am having it welded. If it was on, I would take it off and have it fixed. I have too much money into the engine to let a little thing like this mess it up.
Talk to John though. I think he has been using it the longest.
J

 

I can see what your talking about now. My engine didn't have this problem because the TF G2's don't have that large square EGR hole in the head, just a small round hole that is easyly plugged. I will be plugging mine soon.