TBI to Port Injection

David Sagers dls2867 at hotmail.com
Wed Aug 4 18:49:48 GMT 1999


I ran into a brick wall with my DIY EFI project this morning.  I'm 
converting a '92 Suburban TBI to a '90 TPI MAP system.  I have about all the 
parts including the TPI system, brackets, cables, etc...

Called this morning to buy the wiring harness and the tech at Painless 
Wiring said that I was headed for a big problem.  The speed sensor in the 
Sub runs the speedometer and something to do with the brakes.  He said the 
problem is that the TPI ECM uses a different speed sensor than the TBI uses. 
  And they are vastly different in the signals they produce, are not 
interchangeable, nor can you run a dual sensor system.

I remember seeing in a Jegs catalogue that Edelbrock sells a multi-port 
system that uses the the TBI computer but requires Edelbrock's chip to make 
this work.  I called Edelbrock and they do not sell this chip separately, 
only with the full EFI set up.

The Edelbrock system was a possibility until; 1) the tech said that his 
system is not big enough to feed the 400 SBC I have ready to go in the 
truck.  The injectors are only 19 lbs/hr;  2)and the tech said that the cam 
I using would require a custom chip anyway.  I may have given him the wrong 
specs on the cam because I bought a mild towing cam for the Suburban; 3) 
I've already paid for all the TPI stuff and really like the long runners on 
the TPI, not sure I can really afford to shell out another $1000 for 
Edelbrock system.

Some where in the box with the TPI stuff is a harness adapter that is 
suppose to convert the TBI injector harness to an eight injector harness for 
the TPI.

But the big question.  Does anyone know of a chip maker that makes a chip 
that will allow my TBI computer run a TPI system?


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