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Old 05-13-2010, 08:53 PM   #7 (permalink)
ShadeTreeMech
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Quote:
Originally Posted by mwebb View Post
there will be slightly increased pressure on the throttle plate
IF
you install some kind of ducting to direct air into the "intake" under pressure
it will have absolutely NO effect on engine compression
it will have absolutely NO effect on fuel trim .

it may have a slight effect on engine MAP
which is Baro - intake vacuum

and a slight positive effect on suction throttling loss

the overall effect on FE should be a benefit , but it will not be a large benefit
I admit an increase to compression likely doesn't happen to all cars. But i read an article that was linked here (wish I could find it....) where these aussies went to extremes to eliminate all pressure losses from the throttle plate to the intake horn. When it was all said and done, they suceeded but the car began to predetonate with regular octane fuel and they had to switch to premium.

If an engine is engineered assuming restriction in the intake system leading to the throttle plate, I could see how an increase in compression is possible.
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Quote:
Originally Posted by jamesqf View Post
I think you missed the point I was trying to make, which is that it's not rational to do either speed or fuel economy mods for economic reasons. You do it as a form of recreation, for the fun and for the challenge.
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