Could be a stupid question
Thread Starter
Joined: Sep 2004
Posts: 2,552
Likes: 12
From: Visalia, California
Could be a stupid question Not sure if this has been covered, but didn't see anything about it. When boosting, what happens to the power brakes, since they depend on vacuum? Always wondered about that... Would I be better off running 1 60-1, or the t3/t4 (53lbs/min) in a single combo for a relatively conservative build not seeing more than 7psi?
This is an intersting subject! I have searched & found very little info.
Since I haver an A4 in my car with the vacuum modulator mod, I have wondered about similar things. Like should I get a trans brake for the drag strip so I'm not sucking boost off while I'm power-braking in staging? Or will the s/c mess with my vacuum modulator & thus the tranny shift pressure when I'm into boost?
I'd like to see what 'the experts' think......
Since I haver an A4 in my car with the vacuum modulator mod, I have wondered about similar things. Like should I get a trans brake for the drag strip so I'm not sucking boost off while I'm power-braking in staging? Or will the s/c mess with my vacuum modulator & thus the tranny shift pressure when I'm into boost?
I'd like to see what 'the experts' think......
Thread Starter
Joined: Sep 2004
Posts: 2,552
Likes: 12
From: Visalia, California
Still don't have an answer to this question, any pros have any idea what happens? I know at least one of you guys with a stocker installed boost and can answer... Would love to know what to expect!!!
Well its rare that you are on the brakes and the gas at the same time... So, most of the time, its not an issue.
However, at the track, when you are trying to build boost at the line, as long as you have the brakes pressed before you start pushing the gas you can get some good brake pressure. As soon as you are on boost, don't try to pump the brake or all of the vacuum in the booster will go away and voila, no brakes.
Only time I have run into it, was coming out of the burnout box and went to stop...
Ryan
However, at the track, when you are trying to build boost at the line, as long as you have the brakes pressed before you start pushing the gas you can get some good brake pressure. As soon as you are on boost, don't try to pump the brake or all of the vacuum in the booster will go away and voila, no brakes.
Only time I have run into it, was coming out of the burnout box and went to stop...
Ryan
^~~~ What he said. Why would you need brakes if your going full throttle under boost. Usually you would use line lock or a transbrake when racing.
I think guys with more radical cams should worry more about their brakes working than the turbo guys..
I think guys with more radical cams should worry more about their brakes working than the turbo guys..
Thread Starter
Joined: Sep 2004
Posts: 2,552
Likes: 12
From: Visalia, California
Good point... So with FI, there never is vacuum, so how does the booster get vacuum in the first place? Makes sense what you guys are saying though! Appreciate the responses!
Wrong, just because it is forced induction, doesnt mean it will never get vacuum. It only will not get vaccum under boost.. The vaccum comes from the 1/2" hose going from the booster to the back of the intake manifold, where the MAP sensor is also located..
