The question is in the title. I wasn't sure if this belonged in the F/I forums but it does have to do with boost so....
What Is Brake Boost?
Hitokiri
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Theres the brake booster... is that what you mean?
What that is is that it uses vacuum in the intake to assist the brakes... basically it amplifies your foot's force on the pedal, so its not so hard to stop. Its the main thing that makes power brakes happen.
What that is is that it uses vacuum in the intake to assist the brakes... basically it amplifies your foot's force on the pedal, so its not so hard to stop. Its the main thing that makes power brakes happen.
hehe, its not the same as boost in the sense of forced induction. this thread will probably get moved unless youre specifically concerned with the effect positive manifold pressure is having on your brake booster.
basically the brake booster uses manifold vac to help 'boost' the amount of force applied to the brake master cylinder, and ultimately pistons, through the pedal. with fi this can cause an interruption in your ability to brake while under boost.
basically the brake booster uses manifold vac to help 'boost' the amount of force applied to the brake master cylinder, and ultimately pistons, through the pedal. with fi this can cause an interruption in your ability to brake while under boost.
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I think what he's talking about when people do "roll ons" they "brake boost"...I know this isn't supposed to talk about street racing and all, but what it's referring to is when a boosted car is in a gear and it's low in rpm's people rev up and dump the clutch while moving to get a "better jump" on the opponent....
feel free to lock this, i'm not encouraging anything, i'm just telling the guy what he wants to know : )
feel free to lock this, i'm not encouraging anything, i'm just telling the guy what he wants to know : )
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2,998 Posts
^^^^ What I was looking for thanks! Sorry if I broke the "no street racing" talk but my friend was talking for a while about this and I had no clue what he was talking about. As he said you can lock this or erase this if you want.d.bluefocus21 said:
ah, well in that case, its sorta different with turbo cars because boost is a function of load. instead of reving up and dropping the clutch like you might do with an na or sc car you use the brakes and throttle simultaneously to increase the load on the engine and build boost with the turbo.
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423 Posts
Power braking to build boost while rolling works very well in my ATX.
And that's all I have to say about that.
And that's all I have to say about that.
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yeah.. WRONGd.bluefocus21 said:
like the other guy said, you hold the brake down while giving i more gas to increase the load on the motor and thereby rasiing the boost so it doesnt lag
if youve got a well matched engine and turbo then it wont produce as dramatic a result. lets say you have a huge turbo that doesnt come on till say 3700 in 3rd and youre cruising below that. you can brake and load up the turbo while maintaining a constant speed. then when you mash it youre not waiting for the turbo to spool, itll hop up and go cause youve had it chomping at the bit practically.
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see....I don't understand that.....if you are braking, slowing yourself down, how does that help you out? I don't see how that would benefit any.....the guys that i know that do that......just rev up to a higher rpm to give themselves that extra jump....just like you all said...if you don't really spool until a higher rpm...what's braking or slowing your car down going to do? I understand if you are at a light, you have a automatic, holding the brake down to get some rpm....but for a manual car, slowing yourself down to initially get a jump on somebody doesn't make sense........
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423 Posts
Turbo's are load sensitive (more load=more boost) not like a supercharger (more rpm=more boost).
Applying the brakes and gas at the same time raises the load on the engine=spooling up the turbo!
The trick is, to not slow the car down while you are doing this. And it helps if both hands are in plain sight!
Applying the brakes and gas at the same time raises the load on the engine=spooling up the turbo!
The trick is, to not slow the car down while you are doing this. And it helps if both hands are in plain sight!
I seem to recall some joker who said he'd left-foot-brake for his entire autocross run so that he could keep the turbo spooled. I wonder how long his brake pads lasted. :lol:
In theory, this would be a great strategy. But in practice, I doubt it's worth the trouble for all but a handful of drivers. Even at only 6psi of boost, I find that it can be hard to control the car when I let off the brakes with the engine at maximum torque.
It is fun, though. :evilgrin:
In theory, this would be a great strategy. But in practice, I doubt it's worth the trouble for all but a handful of drivers. Even at only 6psi of boost, I find that it can be hard to control the car when I let off the brakes with the engine at maximum torque.
It is fun, though. :evilgrin:
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