94 LT1 PCM in a TPI car

[63LT1Vette]

Has anyone ever considered converting a TPI style setup to use the 94/95 LT1 PCM? If you use the small cap distributor and external coil, modify the harness from the LT1 change to LT1 sensors???
this car is a drag/street racer, it has a 406ci engine and built 700r, it was a TPI car but is now a modified tunnel ram style intake, and many other mods. I'm also looking at turbocharging soon.


I just think it would be a lot easier to tune using the flash type ecm.

[Buzz]

Rather than converting your TPI to an LT1 controller, consider converting to an LSx controller - especially considering the possible future forced induction setup (turbo).

To use the semi-famous 0411 LSx controller, you would need to run a distributor from an L31 Vortec (5.7L) - which should be a drop in conversion. Then a 4x CKP (crankshaft position sensor) would need to be added - a little more work, but not a huge deal in the grander scheme of things.

[EagleMark]

^^ X2 ^^

The LT1 has no provision or upgrade to boost. It was also never used with a distributor of conventional means, just the OptiSpark which is complicated. Although we have talked about the LT1 PCM being used in projects, re-writing code for use without the OptiSpark distributor just put's the project on the shelf.

[dave w]

I would not recommend using the LT1 PCM. I decided on the 0411 PCM with a fabricated harmonic balancer mounted trigger wheel. I was all out lazy, I did not want to disassemble the front of the engine to install a crank trigger, so the bolt on crank trigger system is what I came up with.

dave w

[63LT1Vette]

I have everything I need to program OBD1, My understanding is it is expensive to program OBD2 stuff. EagleMark, I checked the distributor plugs and they are identical on the LT1. I have even used the LT1 coil with a small cap distributor before and that engine is still running today, also I have seen an LT1 with a distributor before. the guy said he got tired of having so much trouble with the opti so he drilled his intake and installed a distributor. Now I do not know what other mods were done as this was before I started using efi but I remember that the wiring looked stock.

[RobertISaar]

the variable angle slots used for the optispark's 4X signal are able to allow the PCM to determine engine speed and provide a cam sensor function at the same time in that it will allow for the firing cylinder to be determined from a single signal. kind of neat, but a pain to look at the code for if you're not aware of it.

boost could be accounted for via patching, though the MAF doesn't care about pressure, only mass flowrate. that portion of the calibration/code is fine, it is the speed-density portion that would need some patching to emulate the 1BAR sensor for all but boost related functions. how the 4L60E trans code reacts.... not sure.



i...... wouldn't go the route, but it is possible to do.

[dave w]

I see your point on the OBDII prices.

I think this link has a write up of what your wanting to do.

http://www.popularhotrodding.com/tec...onversion_ls1/

I'm thinking getting the intake modified with a distributor hole will be a challenge ... I can't find a link for a shop / business doing the LT1 intake distributor hole drilling.

dave w

[dave w]

Here is a link that might help?

http://www.eecis.udel.edu/~davis/z28...n/swapping.htm

dave w

[lionelhutz]

Ummm, he doesn't want to use the LT1 engine or the LT1 intake.

You'd have to swap the Opti onto the front of your engine. You don't have to use it for the spark/ignition part but you need the two reference pulse signals from it. The actual spark could probably be passed through any distributor with locked out vacuum and mechanical advance or you could get the coil per plug conversion kit (can't recall the name but it costs as much as OBDII tuning software so why bother?).

I believe you are right that the coil and ignition module is the same, but that has nothing to do with the PCM receiving the pulses to know when to fire the injectors and plugs. The signals required for the PCM to time everything don't come from the ignition module like most of the GM OBDI TBI and TPI systems.

Drilling an LT1 for a distributor is done to convert it to a different PCM (TPI most likely) instead of the LT1 PCM.

[EagleMark]

I have everything I need to program OBD1, My understanding is it is expensive to program OBD2 stuff. EagleMark, I checked the distributor plugs and they are identical on the LT1. I have even used the LT1 coil with a small cap distributor before and that engine is still running today, also I have seen an LT1 with a distributor before. the guy said he got tired of having so much trouble with the opti so he drilled his intake and installed a distributor. Now I do not know what other mods were done as this was before I started using efi but I remember that the wiring looked stock.

Even if he did get it to work? Was it correct? Just because the plug fits means nothing to the PCM code that is looking for signals to run and they aren't there... so it runs in backup or LHM...

If you want to avoid OBDII software costs and still run boost correctly I'd say use this!
http://www.gearhead-efi.com/Fuel-Inj...information-58

Still no flash but it will run and tune correctly.

[dave w]

Maybe a Large Cap HEI distributor could be modified to hold the LT1 optical disk and module? Then the LT1 computer would be happy!

dave w

[lionelhutz]

Mark, if the LT1 had a normal distributor instead of the opti then it wasn't running a LT1 PCM.

Can't you convert the '7749 to use a flash chip? Maybe not as convenient as you need access to the PCM but it could probably be programmed just as quickly.

[EagleMark]

Maybe a Large Cap HEI distributor could be modified to hold the LT1 optical disk and module? Then the LT1 computer would be happy!

dave w

I may still have a Opti apart that I was looking into that project with but lost intrest. To much $$ fornot enough return on PCM. But if someone was itrested and it's still on shelf they can have it.

Mark, if the LT1 had a normal distributor instead of the opti then it wasn't running a LT1 PCM.

Can't you convert the '7749 to use a flash chip? Maybe not as convenient as you need access to the PCM but it could probably be programmed just as quickly.

Moates has a NVSRAM for the 7730... don't know if it could be done. There is also code/patch work involved but it was Open Source project and available.

[EagleMark]

But if you went with the 1227749 and Mask $58-$59 you could use a permanent mount Ostrich and be done?

[63LT1Vette]

Didn't I read somewhere that someone offered a Opti-spark eliminator. I remember something on this back when LT1s were the hot engine for GM (early 90s). LOL so in the early evolution of this project one of the first modifications I made was to adapt a LT1 intake to the L98 TPI. I built a jig that held the intake in position and milled the distributor opening. I then had to build a pad for the distributor to set on and also the hold down point. I drilled the head bolt pattern and had to run a external thermostat housing. It worked well and was a major improvement over the TPIs small runners. that was quite some time ago. I am just looking at all options before I go and buy a F.A.S.T. or Accel or something like that. I need to be able to make a change at the track from one run to the next. so I need to be able to flash a tune in between rounds as well as be able to data log each run.

Thanks to all of you for the discussion.