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Old 05-01-2008, 07:32 PM   #16 (permalink)
LostCause
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Join Date: Feb 2008
Location: California
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Thunderbird - '96 Ford Thunderbird
90 day: 27.75 mpg (US)
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By comparing the two scenarios you posted, you would only be able to determine pumping losses caused by the throttle body...still useful, but I'm not sure what your motives are. You already know that the engine braking you are describing can be removed via the clutch, so what is to be gained beyond a numerical value?

How are you going to determine the actual pumping loss force? The only thing I can come up with is a force diagram that plots and compares all the forces acting on the vehicle between the different scenarios. Whatever your method, feel free to post how you determined your value. I wouldn't mind brushing up on my physics/logic.

Quote:
Originally Posted by JohnnyGrey View Post
Racers use vacuum on their crankcases not to decrease pumping losses, but to cut down on the amount of air that must be moved between the backs of the pistons. For a big-block V8 at 6K rpm, this is significant. For us, it's not.
Interesting. So the vacuum was used to lower the mass of air that needed to be accelerated/deccelerated during a stroke? I'm assuming this is the equivalent of lowering the reciprocating mass of the engine...

Was vacuum maintained constantly by a pump or did it hold for a significant period of time? The energy to drive a pump would almost certainly kill the benefit in a fuel economy application, but substituting helium (or another light, inert gas) for the vacuum seems doable. I wonder how quickly the gas would be contaminated or lost, though...

- LostCause

Last edited by LostCause; 05-01-2008 at 07:44 PM..
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