VTCS manifold
 

Does anyone know if the butterflies on the vtcs manifold are normally open or closed? I removed my vtcs solenoid when i was n/a, had to change my tune up a bit which i thought was odd, i didnt think speedyefi would retain use so i figured i could just get rid of it. Removed it from a friends car with an me442 and his needed tune changes and drove terribly/barely would accelerate. This got me thinking wether or not mines low speed drivability bucking was an effect of its removal. I know stock kept them closed when coolant was below 165f or 3500rpm and never shut again after that. Just wondering. I might just add it back for the hell of it to see if no one has any thoughts.

The butterfly valves work as you've described, they're closed below 165 and open above 3500rpm with a stock ECU. It's incredibly restrictive and if left closed results in near zero power. The solenoid has nothing to do with it, but the actuator does, that's what has the spring it it to keep it open. Unpowered and with no vacuum, the valves are normally open. I suspect your friend had a little vacuum applied keeping the valves closed.

Thank you!

With an aftermarket ECU throw a square top on and call it a day...