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Old 11-18-2007, 03:30 PM   #1
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Question Compression ratio questions

Since I am not an engine builder, just wanted to make sure that my calculations are not completely off as I am toying with some ideas.

1) Since shaving the head increases compression (according to Randy from solomiata 10 thousands shave = approximately a 0.25 compression ratio bump), then I assume that either slightly taller pistons (whether from increased compression height pistons or piston coatings) would also bump compression accordingly? But is the effect of a 10 thousands inch head shave = 10 thousands inch increase in compression height assuming all other things are equal?

2) Again, assuming that you have enough clearance to keep the pistons clear of the valves, is the only other major consideration of increased compression dealing with the additional heat and corresponding increased likelihood of detonation or are there other issues? (Assuming that the increased compression is with taller pistons, not a head shave which I know can affect timing.)

3) Within reason, if you can control the heat/detonation, higher compression should produce more power and earlier spool with all other things being equal?
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Old 11-18-2007, 07:39 PM   #2
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not sure about more power, but everything else in #3 looks right.

BTW - dynamic compression:
http://lh5.google.com/jifjif/R0DLrOA...tcompRatio.jpg
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Old 11-18-2007, 08:29 PM   #3
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Quote:
Originally Posted by jif View Post
not sure about more power, but everything else in #3 looks right.

BTW - dynamic compression:
http://lh5.google.com/jifjif/R0DLrOA...tcompRatio.jpg
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Old 11-18-2007, 08:38 PM   #4
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Old 11-19-2007, 04:31 AM   #5
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nice wk y8s ... graph courtesy of Randy @ solomiata.com naturally ...

googling "boostcompratio" gets some interesting results too ...

Last edited by jif; 11-19-2007 at 04:33 AM. Reason: attribution
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Old 11-19-2007, 10:01 AM   #6
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Thanks y8s, I saw that chart. Again, just making sure that heat is the major consideration. So you either run less boost or cool the charge really well a la e-cool/pc-pro (haha)?
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Old 11-19-2007, 10:49 AM   #7
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detonation will occur at any temperature given enough compression (dynamic or otherwise). though usually only in labs. like in a variable compression engine used for determining a fuel's octane rating.
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