How does vacuum work on a boosted engine?

[North Cali Autocrosser]

How do vacuum operated parts work on a boosted engine? Like the brake booster, cruise control, etc.

[John_D.]

<blockquote>quote:</font><hr>Originally posted by North Cali Autocrosser:
How do vacuum operated parts work on a boosted engine? Like the brake booster, cruise control, etc.<hr></blockquote>


Good question.... That was one of my questions for the ATI beta kit too. No answer yet.

The booster will hold vacuum because of a one-way valve in the vacuum line. That's why you still have power brakes when you first get in the car, before you start it. Also, if you let off the gas before you hit the brakes, the engine will start making vacuum again. So the booster should be ok.

Cruise (especially uphill at interstate speed) is one I'm still curious about. I'm thinking it won't hold.

[North Cali Autocrosser]

Thanks man, I can't wait to get the supercharger on my car, less than two months to go! :D

[nocutt]

<blockquote>quote:</font><hr>Originally posted by North Cali Autocrosser:
How do vacuum operated parts work on a boosted engine? Like the brake booster, cruise control, etc.<hr></blockquote>

One way check valve...the booster should have a built in check valve so should the tranny modulator ( I am assuming the 4L60-e has the vac. signal)and the purge canister...
JohnD is right as soon as you get of the gas, vacuum "should be created" easily...

[Dominic]

The only time you should be under boost is WOT, and nobody brakes @ WOT [img]smile.gif[/img]

[Loochy88]

<blockquote>quote:</font><hr>Originally posted by Dominic:
The only time you should be under boost is WOT, and nobody brakes @ WOT [img]smile.gif[/img] <hr></blockquote>

so hypotheticly, if you were powerbraking on your auto and you smashed the throttle the breaks would give out all together and youd launch forward?

[black98V6]

not really the brake booster mainly assists in applying the brake, I don't think it has much to do with holding it, though one thing I am curious about is doing a heel toe downshift, I guess so long as when you blip the throttle that you don't get into boost it would all be good..

[1BadAzzGT]

Vacuum is the exact opposite of boost. Once you hammer it (if you watch on the boost/vacuum gauge), it actually will go into boost. Under normal conditions, vacuum is normal measured around 17-20" and fluxuates as you increase the throttle.

I hope that helped to explain it for you.

Take care,
Tim