Does anyone know the stock vacuum or PSI for a supercharged or non-charged 1grfe engine? From what I understand, correct me if I'm wrong, the intake manifold pressure is measured in HG vacuum unless a supercharger is installed then it is measured in PSI (assuming the charger boost is greater than vacuum).. I'm trying to find the base, I know it varies by elevation/BP/etc, vacuum or PSI for either a charged or non-charged 1grfe engine. Thanks, Bob.
Manifold pressure at idle should be the same for either vehicle, with or with out supercharger... It should also be the same under any condition where the supercharger is not building boost, IE cruising or low throttle ...
When you would not be at 0 in hg in a NA car, the supercharger should have it's bypass valve open, and the manifold pressure should be identical on the same engine with or with out a supercharger. When you open the throttle and manifold pressure goes to 0psi/0inhg the bypass valve closes and you start building boost.
Most map sensors are self-normalizing, so your vacuum at any elevation, per the gauge, should read the same. It resets 0 to actual atmosphere. Which is why an aftermarket electronic gauge like an auto meter needs voltage that survives crank, because if it resets during crank it will 0 with slight vacuum. A mechanical gauge will read differently at altitude.
Boost gauges generally show in hg of vacuum on the left, 0 in the middle and then PSI of boost on the right.
The factory computer probably reads it in Kpa. ~100 Kpa = ~14.7 psi, or atmosphere pressure at sea level , 0 kpa is a perfect vacuum... 200 KPA would be ~14.7 psi of boost. It's really like 101.3 kpa for atmosphere or something like that, but you get the idea.
The TRD supercharger is a positive displacement pump, so elevation is largely irrelevant, delta
p should be the same no matter the elevation. If it's "rated" at 6 psi, then at what ever engine RPM they are rating it at the outlet pressure should be about 6 psi higher than the inlet pressure.