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Old 09-25-2005, 05:51 AM   #1
Hossamk
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Default Compression Ratio in the Normally Aspirated

Dear All
the air pressure over the sea is 14.7 PSI or 1 bar. in a normally aspirated engine with a compression ratio of 10:1 does this mean that the engine is running on .1 bar or 1.4 PSI is this true?

if this is true, what kind of boost i can run on this engine with the internal cylinders and heads unchanged and with fuel octane 92? i read that using turbo compresses more are in the cylinder which heats it more and the fuel can burn before the Sparks works and the engine will be knocking?
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Old 09-25-2005, 06:54 AM   #2
Jesse00
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first of all, you might want to goto the forced induction forum instead. this is a Natural Aspirate, not the turbocharging forum you wanted. And the maximum safe level you can put into the ej25 engine is around 6psi. However, I remembered someone that put 9psi into theirs, but i think he put alot of money into making it happen. In short, dont turbocharge your 2.5rs, isnt worth the money you spend on it.

If you have a 2.2t engine, then disregard my post (but then again, your in the wrong forum)
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Old 09-25-2005, 08:17 AM   #3
Patrick Olsen
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Quote:
Originally Posted by Hossamk
in a normally aspirated engine with a compression ratio of 10:1 does this mean that the engine is running on .1 bar or 1.4 PSI is this true?
Ummm, no. Those piston things going up and down inside the engine (well, actually back and forth in our engines) compress the air. That's why it's called "compression ratio". So the 14.7psia is compressed to 147psi in a 10:1 engine. Depending on cam timing, the dynamic CR may be higher, so you may see more than 147psi during a compression test.

http://auto.howstuffworks.com/

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Old 09-25-2005, 01:14 PM   #4
Hayes
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Any compression ratio is a STATIC measurement of the combustion chamber. The ratio running is can be lower or higher due to intake and exhaust valve overlap and pumping losses in the intake and exhause system. .
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Old 07-06-2008, 05:21 PM   #5
Suby2.5i
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dont turbo charge your rs's
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Old 07-06-2008, 06:25 PM   #6
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Originally Posted by Suby2.5i View Post
dont turbo charge your rs's
YEAH SAVE IT FOR THE 2.5I LOL
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Old 07-06-2008, 09:25 PM   #7
Patrick Olsen
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Quote:
Originally Posted by Suby2.5i View Post
dont turbo charge your rs's
Thank goodness we bumped a 33-month-old thread for that bit of random advice that had nothing to do with the subject of this thread.

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Old 07-06-2008, 10:02 PM   #8
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