Originally Posted by Jeep2Xfire
When I made the comment about the MAPs being useless in a forced induction environment, I stand by that for the simple fact that with a supercharger there isn't a vacuum. There is always pressure greater than one atmosphere within the intake plenum. In a NA environment, vacuum is greatest @ idle (normally 17-22 inHg) and then as the throttle plate opens (stepping on the accelerator) atmospheric pressure is let in equalizing the pressure above and below the throttle plate which is how that specific sensor "measures" air. It really doesn't measure air but extrapolates or makes a guess.
Vacuum will be present in the manifold of a supercharged car for considerable proportions of the engines operation, this is because the throttle restricts air admision. The difference comes when a NA engine is at wide open throttle, at that point the MAP gauge will read close to atmospheric, the charged engine will read boost from the MAP gauge. That reading will be used for fueling, ignition timing and diagnostics.
I think you underestimate the value of a vacuum (or more precisely differential in pressure) in metering fuel, a well set up carb isn't doing any "guessing".
Anyone know if the SRT uses a bypass in the manifold to reduce pumping losses at part throttle? (when there is a vacuum reading in the manifold).