Hello,

This is regarding a 1994 LS400 (so non-VVTi), but information about other years may be applicable. My question is: is there a sensor (maybe TPS or IACV) that receives signal from the ECM when the throttle is open (i.e. anytime other than idle)?

Let me provide some context: I just finished rebuilding a 1UZ with an Eaton M90 supercharger. The engine is running well for the most part, but I want to utilize the vacuum-activated bypass valve on the supercharger. For those who don't know, Eaton superchargers have a little actuator on the side with a lever that controls a butterfly valve inside the supercharger. The actuator itself has 2 nipples; #1 is connected to the intake before the supercharger rotors but after the throttle body (sees vacuum), and #2 is connected to the intake plenum after the supercharger rotors (sees boost).

On the Buick that this Eaton M90 came out of, there is a VSV in between nipple #2 and the intake planum. When the car is at idle, that VSV is in default position (closed) and no boost can get through. This means that there is only vacuum applied to nipple #1, which activates the actuator and opens the butterfly valve inside the supercharger, allowing air to bypass the rotors and avoid boosting the motor at idle (keeps temps down, reduces wear, etc). When you stepped on the gas in the Buick, the Buick ECM would send signal to the VSV, open it up, and it would apply boost pressure to nipple #2, close the internal butterfly valve, and force all incoming air to pass through the supercharger lobes.

Without some sort of VSV, the bypass valve is either always open (low/no boost) or always closed (constant boost) depending on which of the two nipples I connect vac lines to. Obviously the stock 1UZ ECU isn't supercharged so it isn't programmed with a dedicated pin to control this type of valve. Hence my question: is there some other sensor that receives signal during acceleration that I can piggyback off of to emulate the boost control VSV on the Buick?

Thanks!