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Author Topic: Just a question about compression.  (Read 2155 times)

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CVO2FIXUP

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Just a question about compression.
« on: April 23, 2012, 03:45:45 PM »
  My bud just ripped apart his top end to post the heads and change rings etc. ( 60,000.  miles on a 96 )   What I noticed was a very thick coat of carbon on the top of the piston, and all over the dome of the head. It seemed like this coat of carbon was at least 1mm thick, and hard like steel.  So I was wondering will this increase the compression dew to less volume? And if you re tune the bike with all this carbon ( if it has more campression dew to this ) will it make more power, Will it start to ping? What do you think. Cheers.
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JohnCA58

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Re: Just a question about compression.
« Reply #1 on: April 25, 2012, 01:43:34 PM »
ever so slight that c.r. will be increase, but not noticable,  now if running a .030 HG, you could have issue with carbon making contact with the head as it gets thicker, and you will hear it.
« Last Edit: April 25, 2012, 01:45:26 PM by JohnCA58 »
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grc

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Re: Just a question about compression.
« Reply #2 on: April 25, 2012, 02:10:55 PM »
Quote from: CVO2RIDE on April 23, 2012, 03:45:45 PM
  My bud just ripped apart his top end to post the heads and change rings etc. ( 60,000.  miles on a 96 )   What I noticed was a very thick coat of carbon on the top of the piston, and all over the dome of the head. It seemed like this coat of carbon was at least 1mm thick, and hard like steel.  So I was wondering will this increase the compression dew to less volume? And if you re tune the bike with all this carbon ( if it has more campression dew to this ) will it make more power, Will it start to ping? What do you think. Cheers.

Yes, a heavy buildup of carbon will increase the compression ratio slightly.  It will also affect heat transfer, probably lead to preignition and then detonation, and is not something you really want.  If you want to increase compression, do it the right way as a part of a coordinated build.


Jerry
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HILLSIDECYCLE.COM

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Re: Just a question about compression.
« Reply #3 on: April 26, 2012, 07:03:21 AM »
What Jerry said. :2vrolijk_21:
I will add that with the use of a .030" gasket, the combustion chamber is more turbulent, and where the squish band is, the piston will usually be void of any carbon deposits, albeit a flat top piston, or when 20*, or 30* squish shelves are being used, via cylinder head machining. :)
Scott
 
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