Power Brakes and forced induction.

CobraSix

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Just a simple question. I think I know the answer but want to confirm.

Vacuum assisted power brakes will work with forced air so long as I'm not trying to brake while accelerating under boost, correct?

Is there any need to go to a more exotic power brakes set up (electric or hydraboost)?

I guess, I could always add a small vacuum reservoir with a check valve to close under boost to have a few more pedal pumps if I need.
 
I don't know the answer but if needed, older Powerstrokes have an electric vac pump to run the brake booster.
 
Mine work just fine. The one way valve in the booster allows vacuum to build at idle and no boost to create pressure (cancel the vacuum) during a no vacuum situation. If you power brake with boost and the brakes applied, the boost pressure will keep the one way valve shut, but if you deplete the vacuum in the booster and don't let the one way valve to open (returning to a vacuum pressure in the engine manifold), then you will run out of power brakes until you pull a vacuum on the booster again. It really only applies if you were to pump the pedal under boost.

If your one way valve leaks, then you have a problem!
 
ah, would the booster blow seals, or since they are rated to close to 29inHg, would they hold to 15 psi? Otherwise, it seems so long as they hold, allowing the engine to go off boost would recover the brakes.

I'm thinking of installing an additional vacuum reservoir to provide a little back up.

Though maybe I should suck it up and just go with the electric vac pump from the aftermarket. At least that way when my engine grenades itself, I can still stop easily so long as the battery is still there.
 
I'd think if the check valve failed in your booster you won't be able to press the pedal down with the booster pressurized.
 
80broncoman":29bzdqq8 said:
I'd think if the check valve failed in your booster you won't be able to press the pedal down with the booster pressurized.

Exactly.
The check valve does two things:
- allows a vacuum to occur and hold in the booster
- keeps pressure from entering that vacuum area in the booster (atmospheric pressure or under boost pressure)

My booster works as normal on my boosted 300.

I also have my PCV valve hooked up as if it were an N/A engine. The PCV is also a one way and would work just as the check valve in the booster would work.
 
'68falconohio":ku1wjpxz said:
I've read where guys are running late-model Cheby smog pumps for crankcase ventilation on boosted cars.

Hmm...never thought of a pump. A lot of the imports run a catch can to keep any oil from going back into the intake tract, but never thought of a pump. Keep the crankcase pressure down while under boost. I am sure a full 20 psi for over 30 seconds can really build some pressure in the crank case.
 
Here's the thread on turbobuicks I was thinking of. Interesting thread.
Sorry for the slight hi-jack Cobra', it's a vac pump of sorts...right? ;)
 
I used the Ford stock smog pump. Hotrod Mag or somebody similar did the same thing.

Learned a few things, The smog pump is very noisy when pulling vacuum, makes a low rumbling noise.
It will draw the oil vapor out of the crankcase and if it is not plumbed into a catch can it will leave an oily spot under the car.
Don't try to plumb the pump discharge into the exhaust system to quiet the pump, that oil vapor will burn in the exhaust and make pretty colored smoke!

My 215k mile pump gave up not long after trying to use it as a vac pump. Vane pumps make awful noises when they start to fail!

I went back to the standard PCV system.

BTW my brakes are fine. Did work on a turbo Volvo that would loose power brakes when brake boosting.
 
I had an 86 SVO Mustang many years ago. It had a vacuum canister feeding the booster. The canister would hold vacuum while the car was on boost and between it and the reserve in the booster itself there were never any issues.

Come to think of it, my Mazdaspeed Miata and my current CX7 turbo have vacuum assisted brakes and they work fine as well.
 
I am not sure you even need that much. the instant your throttle closes it goes off boost. unless you are all for some WOT braking....

could always drop some coin on a hydroboost setup....
 
I'm trying to keep it simple on the engine. I've thought about hydroboost. Also thought about finding a mid/late 80s Grand National. SOme of those had electric vacuum pumps.
 
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