Hello forum, I have an 1984 Corvette and I took off the Cross fire injection, swapped in a 406 and currently am running a 750 Holley Carb and the mileage is no good, and I'd like to run boost soon. ( Remote mount turbo Idea ) and I have a spare TPI unit layin around.

So, just to see if it can work, I have the complete TPI unit, MAF unit, wiring harness, ecm, everything but the ecm controlled distributor. But I do have an HEI Accel Distributor, would I be able to hook up the TPI unit, and start it without an ECM controlled version? Can I somehow put maybe the tach output to one of the wires and make it run? Fool the ECM to thinking its controlling the dist?

As of yet I am not sure the TPI unit runs, so I just want to test it out before I dump money into it, if it does maybe I'll get a TPI dist module that has 7-8 pins instead of 4 so it can run with it but Im not totally sure if thats available or would work.

 

You need a computer controlled distributor. The ECM relies on the signal from the pickup coil to fire the injectors.

Kat

 

You can, but as mentioned you have to supply a signal to the ecm so it can fire the injectors. Other than that, the ecm doesnt know the difference.

 

http://www.jegs.com/cgi-bin/ncommerc...91&prmenbr=361

WOuld that 7 or 8 pin module work to send the signal to the ecm? But then again thats More dough I have to spend just to check and see if the TPI unit can run.

Anyway theirs 4 wires, ones a ground, but the others I dont know how to or where to hook up. I dont want to fry anything trying to guess which one goes where. Thanks for the info.

 

Get yourself a used computer controlled distributor for $50 shipped to your door from www.car-parts.com and find out.

Make sure you match the distributor to the year harness and computer you're using or else you'll be splicing wires.

 

Anyway to rig the tach output to one of the 4 wires on the wiring harness and ground the white/black wire to see if it works? I think I'll just have the intake sitting on the tire, plumb it with fuel and run the tach output to one of the wires and see when it starts leaking fuel. Then I'll know I found the correct wire, if not then I might aswell go down to dorris and pick it up for 50 bucks.

 

Mega Squirt can do that for you, MSII actually. It would be quite simple to do with MSII.

 

I don't see why it couldn't be done with a little creativity. I know that GM ecm's have been hacked to control just timing, and numerous other ecm's can control just fuel (a few even have specific units for just that, like the Haltech F9 my brother runs).

I would imagine that you would have to send a tach signal back to the ECM so that it knows rpm, can work out injector timing… but I’m don’t believe* there is any other feedback coming from the distributor so it may be as simple as just ignoring the timing end of things.

* - I wonder if this is actually correct since the rumor is that if you change the distributor position without disconnecting the timing connector the ECM knows that you made the change and adjusts accordingly. Not that I know of anyone that has actually tested this or have seen any evidence that it is true

 

I'm going through this right now.
Not exactly sure which distibutor you have but I have a MSD. My solution was to lockout the distributor remote 8 pin module and
make a pigtail which would connect the msd pickup coil leads to
the pickup coil terminals on the module.

 

The sad part is that relying on the factory tach to output a signal that was relevant in any way to the actual engine RPM would be nearly impossible. It would be far easier to move a step closer to the distributor amplifier module by breadboarding and installing an array of an externally clockable counter/divider and some OP amps to signal the ECM based on the actual HEI switching rate. A small bnreadboard, a few 15V CMOS DIPs and sockets, and you're flying. Actually, now that I think of it, you wouldn't need the divider. The "standard" HEI distributor already produces a switched signal directly proportional to the engine RPM. All you'd need is an OP AMP (possibly inverted) to isolate the reference pulse signal to the ECM - pretty much like the later HEI modules do.

That begs the question, why couldn't you just install the $20 later HEI switching module and use those outputs to the ECM? Use the output from the 'R' terminal on the HEI module as the ECM trigger - just like on the factory TPI setups. You simply wouldn't have/use the spark retard signal through the module. Hopefully, the wiring harness still has the purple/white wire in the distributor connector to signal the ECM.

If you cannot physically fit the newer HEI module into the Accel distributor, you can try the above method.