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Old 07-12-2014, 04:03 PM   #29 (permalink)
elhigh
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Location: SE USA - East Tennessee
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Josie - '87 Toyota Pickup
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Depends

Quote:
Originally Posted by figit090 View Post
What about the brake booster when the engine is off?

Also, does an engine with a manual transmission use any fuel if coasting down a hill with 0 throttle, being pulled by gravity above idle RPM?
If yours is a fuel injected engine, the computer might recognize the loading paradigm and provide no fuel while the engine is being driven by the tranny. Certainly a carbureted engine will continue to burn fuel, but only at a slightly above idle rate as the increased vacuum pulls a little extra fuel through the jet.

As for the brake booster, if you're still in gear but letting the car pull the engine, you're getting a strong vacuum into your reservoir the whole time (unless it's a diesel, YMMV). And even if you're coasting in neutral you should still have enough vacuum in your reservoir for a couple of stops.

If not, consider building or buying a supplemental reservoir to tuck into one of the unused spaces of your car, to provide backup.
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