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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