I've always wondered what happens to vacuum lines on a boosted motor? Like the brake booster, PCV, etc... Don't these lines get pressurized under boost? If so how do you get them to function?

Forgive my noobness.

 

bump for education

 

I'd like to get some feed back on this too. When I was building my Nissan motor for my L6T 280Z I needed a motorized vacuum pump... is this thing still needed? What has every found to be the case?

~Nic

 

oh wow, I never really thought about that. How would the brake booster and such stock vacuum-run/enabled devices take to positive pressure? Does it still do the same thing, or any benefits/problems?

edit, pcv needs to be re-thought i know that much, im running both my vent lines from the crankcase into a baffled can and then into a bung on the exhaust through a check valve.
but how does the brake boosters check valve still work?? I dont understand that.

 

Bump for anti-ignorance

 

Bump for an answer

 

The stock brake booster has a one-way valve in the line so it won't see any boost.

The fuel pressure regulator works fine for boost and continues it's 1:1 pressure rise.

Evap purge is only actuated at certain times which I assume is somewhere in vacuum and low throttle.

The map sensor also can work as long as the voltage output is limited to keep the ecu happy (like in the hack or using a missing link). It's usable to around 11psi.

cruise control. i just know that it still works. It's weird when you fall asleep and the bov wakes you up at the top of a hill....i bet.

 

That's interesting that the cruise control still works.

From my understanding the brake booster will work fine, unless you try breaking with your left foot while at WOT and boosting. Normally you would let off the gas and then brake, therefore the engine and brake booster would be in vacuum.

 

I left foot brake mine while i'm somewhere between 0-5psi. never noticed it feel any different but I'm not exactly romping on the brake either. I think you will have some vac assist at first but then it would taper off (assuming your boosting at the time)

I actually don't have cruise myself but I have done a Z6 and an H22 and they both say it works and is kinda funny on hilly roads.

 

Cool thanks for the info.

 

The brake booster has a bit of a reservoir for vacuum. Ever notice when you remove the booster line it sucks air in for a few seconds.

 

Yeah, it is designed as a saftey feature to give you one.. maybe two good pumps before your brake assits runs out. It is for "emergency" use if the motor dies while driving.

Reading these posts reminded me the vac pump on the Datsun was for the vac controls of the climate control. I gues Honda's are combo electric/mechanical?.?.?...

That cured my woes...

Thankx all.
~N