Can someone tell me how superchargers effect engine vacuum?

 

There's positive atmospheric pressure inside the intake, but there's still vaccuum on the intake side of the SC.

 

So what effect does this have on sensors that measure engine manifold pressure, or vacuum, for timing and other adjustments. What about equipment (brake booster, ....) that uses engine vacuum?

I'm just trying to build a better understanding of the effect.

Thanks.

 

I will assume you are talking about the map sensor, it would need to see the boost so that it could add more fuel and take out a little timing. I doubt you will need the brakes very often when you are boosting the engine, except maybe for a burnout. In cars that are factory equipped with superchargers they use check ***** in the vacuum lines so that they can only pull vacuum and not boost. you should have zero vacuum at full throttle, so boost is going to have about the same effect. Hope this helps!

nick

 

aye, and when you're hitting the brakes, the throttle blades are closed and there's no boost, so you've still got the vacuum to run the power brakes.

 

If you look hard enough in the driver side fender well there is a plastic ball. That is a vacuum reservoir connected to the plenum. It has a check valve to hold vacuum for the brakes.
As far as the supercharger, the boost at part throttle should not affect the MAP reading. Remember that at part throttle there is a higher pressure behind the throttle body so there is always some vacuum in the plenum. At WOT the system goes into open loop anyways and the injectors start dumping a lot of fuel in the ports.
I understand some superchargers don't build-up until they get to past 3000 RPM.
On the other hand I might be wrong. I had seen a post by Vader on this subject.

Oz

 

Dont try to hell and toe downshift then! Roots type superchargers inrease vacuum. Have you seen the Carb Vortech system? Carbs run on vacuum, not boost. They had to reverse the whole set up. This is for the idiot who will spend 700 dollars on a carb and reverser, while he could get better performance with efi!