it may be a stupid question..sorry..where do you get the vacuum for your brake booster and other vacuum related things when you are running boost? won't the vacuum in the intake be gone?

 

Not sure if I understand the question. If you're runing a S/C for boost, then most of the time you are actually running just like a N/A engine. You will be runing under a vacuum. So even though you have a supercharger that's constantly spinning, you are only running boost when you are at WOT and above a certain RPM level. As soon as you get off it, it quickly returns to normal N/A operation.

Edited to add:.. so even on a boosted car, you're only truly running under boost for a few seconds at best. Any other time the extra pressure is being vented off by a bypass or blowoff.

 

The only time you dont have vacume is when youre under boost. How many times do you get into boost, and hit the brakes at the same time?

 

Just T off from the intake to the Fuel pressure regulator.

 

Omg, there's a check valve at the brake booster that keeps any vacuum created by the engine during idle/decell stored in the booster.

 

I don't think he was talking about just the brake booster. I think he was refering to the entire system in general. I also think that he was under the impression that if you're running a "booster" / power adder, you were constantly under boost. Then again, like I said, I'm not sure I fully understand what exactly he was asking or how he thought boost works.

 

your right. i thought when you were not naturally aspirated there was always psi not vacuum. now i know.

 

No problem Many people actually thought the same thing you thought. It would seem normal to think that a supercharger is constantly boosting the engine. Afterall, it's a booster...that's it job! But once you understand how it works it all makes sense. You're really only in boost for short bursts and everything that needs to be isolated from the reverse airflow is protected (PCV, brake booster, etc.)