Engine upgrade and theft deterrent system

What exactly is your concern about? Do you understand how the VATS works?

Do the upgrades you're considering include a computer that does not use VATS?

My concern is that when I change to the new engine/ECU combination that the resistor key will no longer work due to a difference in resistance in the circuit. Also, I don't know if all L98/LT1/LS1 engine/ECU's use VATS. If not then I will be okay, but if they do, I understand that the resistance value can be different and therefore not work with the current key/ingition switch.

I guess the most simple solution would be to know how to bypass or 'trick' the system into thinking the correct resistance is always present. I am planning to implement an alternatve system that will protect the car from theft.

Thanks,

Dale

Your car should have a VATS module under the dash somewhere, which is designed to work with the particular key you have, and the computer type you have. A computer for a different engine that uses the same VATS scheme should work fine with your VATS module....I'm guessing.

Folks who make harnesses for engine swaps usually have a way to bypas VATS, I think the most common method is to reprogram the PROM so that VATS is turned off. A lot of these engine swaps are done on old cars and the owner doesn't want the anti-theft system.

I swapped a TPI engine into an early Vette using the 90-92 Camaro type computer/harness and the stock PROM, and fooled the comptuer into thinking it had a working VATS module by feeding a 30 Hz square wave signal into the appropriate pin of the comptuter (using a homebrew circuit with a 555 timer chip). All that the VATS module does on these systems is to use the resistor in the key as an element in an oscilator, if it's the right resistance than the signal is the right frequency, and the comptuter turns on the fuel; if the signal is missing or it's the wrong frequency, the computer turns the fuel injectors off.

Jim

Thanks much for your help.

Dale

Jim Forbes: I dug your explanation of the VATS theory of operation. When my resistor key goes bad on my '89 Cam'ro why does the starter not even spin?

Uh......maybe it's not the VATS, but the ignition switch itself, or the lock or rack/pinion? The ignition switch is mounted on the column, behind the dash, and actuated with a rod. The lock itself turns a pinion gear which moves the gear rack at the top of the rod. WHen this stuff gets worn, sometimes it does not pull the rod all the way, and the starter won't engage. But without performing a "laying on of hands", it's pretty hard to diagnose it accurately.

Also, if it's a tilt column, and the column is loose between the upper part and the lower part (you can wiggle the steering wheel back and forth sideways), it could just need the column internal screws tightened...which is a job for someone who knows what they're doing.

Or it could be that the 89 system is different from the 90-92 system that I described?

Could be. I had two ign keys become intermittent, then totally fail. Turning the key would turn on all the electrics, but the VATS module wouldn't recognize the circuit resistance, so it set a vats code in the ECM and disabled the starter relay circuit. It requires 5 min of ign off to cancel the code for a re-try. I simply went to the dealer and got a replacement key each time. Been fine since.