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Old 06-17-2008, 03:08 AM   #97 (permalink)
LostCause
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Location: California
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Thunderbird - '96 Ford Thunderbird
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Quote:
Originally Posted by Yuri4x4 View Post
I disagree with the vacuum boosted brakes comment. If you shut your car completely off, you still have vacuum assist for a few pedal pushes. Those are FREE. In fact, you can also speculate that it MAY be BETTER to use that vacuum before re-starting your engine, possibly reducing resistance inside the engine...
They aren't free because the next time you start your car, the engine will have to create a new vacuum in the brake booster.

If the booster has no vacuum, then the sealed engine condition you describe would be more applicable. Every intake stroke during start-up will be doing the work of creating vacuum. If the booster has vacuum, then the intake stroke will not do work as the booster pressure will stay constant.

We are counting minute fractions of a penny saved here, but engine vacuum will never be free.

- LostCause
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