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Old 05-15-2010, 11:02 AM   #11 (permalink)
ShadeTreeMech
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Quote:
Originally Posted by mwebb View Post
..."I admit an increase to compression likely doesn't happen to all cars. ."... ..."" I could see how an increase in compression is possible."...

what ever you may think
(excepting the effects of EGR and variable cam timing)
the engine compression will not change on any car except some SAAB engines
which have variable compression due to a hinge strategically placed in the engine block

the words you seek are
peak Combustion pressure
but do not forget IGN timing will change based on MAP changes and
it is possible that the authors of the article you read were experiencing some of that


..."
A cleaned up air intake can only make a difference when the throttle plate is wide open, "...

i agree with this
but i believe the OP's intent was to fabricate something to pressurize the intake
like RAM AIR on an old Pontiac ...

however i may be INcorrect --
if the OP was referring to the brightly colored garbage with conical filters that ingest hot air from under the hood sold by the alleged "performance outlets".
I found the thread. I finally got desperate and searched through my history till I found it. After rereading the last bit, I found a few important details, especially the bit about this being a turbocharged vehicle. The folks doing the mod also went to extreme lengths to remove any hint of vacuum from the intake system. But using a pressure meter they detected a slight positive pressure where they once had negative pressure; however their setup was like a beefy ram air setup, so no suprise.

I apparently took the example of an extreme setup and applied the logic to a more common setup.

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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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