Does a 10 to 1 compresion ratio engine need to run 92 octane fuel?
Does a 10 to 1 compresion ratio engine need to run 92 octane fuel?
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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That made me LOL.Originally Posted by RobertISaar
The man who says something is impossible, is usually interrupted by the man doing it.
eventually, it runs down to 2 different methods of tuning for octane: the quick way and the thorough way.
quick: just run the best fuel you can get consistently, tune for that.
thorough: get the lowest grade of fuel you would consider running, tune for that, step up a grade, run more advance(since you should be able to), see if it gains any power/economy, if so, step up another grade, repeat. when you get to the point of increasing octane does not allow for more advance(or you're running so much that it hurts power), then you'll know at what point you'll be wasting money.
YEAH BUT THIS IS AN ORAGANAL mOPAR 6 pack engine, darn caps...
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
The real issue is not strictly compression ratio - it is dynamic compression ratio AND combustion chamber design. A modern combustion chamber with a good quench area and some swirl to mix the air/fuel together can run low grade fuel at higher compression than an older design - like say a Hemi. Dynamic compression is mostly a function of cam profile - a 'rough' cam with lots of overlap and long duration effectively lowers the compression pressure in the cylinder.
That said - I never even considered paying for high octane fuel when I was younger and built Chevies with 10:1 to 12:1 with no problems. My cams always had lots of duration and my carbs were set a little rich though. It was pretty easy to hear a chevy knock for some reason. Usually just set the timing by ear for whatever it would take :D
odd things the police have said to me; "you can't drive that on the road", "I like your cow", "I didn't think you would pull over so quick"
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