Ideal compression for a 57h

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#21

11-03-2014, 09:22 PM

HD Pilot

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Quote:

Originally Posted by ridedaddy

So what is the ideal cylinder pressure? Where is the line between performance and tuning/reliability/detonation issues?

There is no line! The higher the CCP the better the performance but the more difficult the tune. I think in generally, if you go above about 200 CCP you better make sure there is a great tuner/builder involved.

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#22

11-04-2014, 05:52 AM

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Quote:

Originally Posted by ridedaddy

So what is the ideal cylinder pressure? Where is the line between performance and tuning/reliability/detonation issues?

Just about 200 is our threshold for geared-carbed bikes, and IF a hot-rod injected, then we'd go to as high as 205-210, but that would be a direct conversation with the client prior to that, who it going to tune it, and also would be dependant on his geographical location.
Scott

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#23

11-04-2014, 05:02 PM

UltraNutZ

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Quote:

Originally Posted by djl

I think Gary is coming down on the conservative side. I am 600 feet above sea level in south Texas; summers are hot here. Using my calculator, I would run the .030" head gasket; 10:1 static CR. That would put corrected CR at about 9.3 and CCP about 190psi which is about where you would be assuming 85-86cc chambers and a bit of negative deck height which is typical of the TC motor. If you get a bad tank of gas, the motor would likely ping just as bad at 9.8 static as it would at 10. The tune will also make a difference in the tendency toward detonation. I would not run the 57 at 10.5 static but that's your call as well.

There are plenty of 57 cam installs on this forum; maybe some of those guys will chime in on their setup. I have no first hand experience with the 57 cams but from what I read, I think you would be happy with the cam in either configuration.

djl hit the preverbal nail on the head. I run 10.3:1 and 9.6 corrected with right at 201CCP but that's with 82cc heads from Kirby, .004 and .005 in the hole, and .030 head gasket. Bike runs like a beast, no ping, no knock, no nothing but a smile on your face when you crack the throttle. I will easily walk away from any stock 110, except Roadies.. I don't race with Roadies..

I also agree with the Gary Wallace comment. If I were you, I would contact a reputable builder and ask that same question. I know Gary knows his product better than anyone and I'm not questioning that but the builders know what works in the real-world.

Last edited by UltraNutZ; 11-04-2014 at 05:16 PM.

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