Hey how do ya override the VSS in a 91 Z28 with a 305 TPI with a auto tranny? The tech artical says for a tbi please help.

 

The difference between the TBI & TPI setup is the speed buffer. The TBI ECM has an external speed buffer & the TPI has the speed buffer built into the ECM. You could do 1 of 2 things. The most desirable way to proceed would be to reprogram the PROM to increase the set point of the speed limiter - see the PROM board for details - or purchase an aftermarket PROM with the speed limiter disabled - Fuel Injection Specialties in TX will do one for $100 to $200 - there are a number of companies to choose from. Another thing to try is disconnecting the VSS inputs to the ECM - I don't know how the motor would run, though, and would not make it a permanent mod.

Tim

 

Speed Density TPI needs the VSS sensor to make its calculations, so disabling it will confuse the computer. Your best bet is to get a new chip.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
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