I noticed this yesterday - When I'm stoped and I pump my brake the engine goes from the 600RPM idle to about 1100RPM. Is this normal? I assume It's just some pump kicking in for the powerbrakes, but I thought I would check.

 

Normal, brakes use engine vaccum for boost. You use vaccum when you pump it and it replenishes from the engine which will increase rpm.

 

yes.

 

Correct

 

OK, so say you're racing with a big turbo, so you have to left-foot brake to keep the revs up. Instead of vacuum, you now have a boost condition in the brake booster. What happens to the assist then???

 

I've always wondered that as well but never remember to try it. When you turn the car off you can still pump the brakes a few times with assist before it gets stiff - my first guess would be it would act the same way while under boost.

 

i think there is a one-way valve somewhere...

t..

 

The brake light switch is hooked to the ECU. That way, it gets advanced waning when your getting on the brakes, and the injector pulse width needs to be increased. To compensate for the added load on the engine...

 

why?

to compensate for the brake lights coming and on loading up the alternator charging system...

thats all.

t..

 

Wrong. If anything pulse width will decrease. When the engine goes into decel. Emission increase. Most cars cut the injector off or down on decel.

There is a check valve in the vaccum hose to prevent boost and keep vaccum in the vaccum booster. When there is no vaccum, you can still brake its just not assisted. Obd1 and earlier cars have an actual check valve in the hose just above the brake booster, obd2 cars have a lump in the hose in the same spot, guess what it is.

Heel/toe manuever can be done with one foot, especially if you have aftermarket pedals.