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RE: [turbobike] Compression Ratio

NOVA Digital Services (Info@NOVADS.com)
Fri, 5 Nov 1999 22:05:39 -0500

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Because 2 valve heads (combustion chambers) are not as efficient as 4 valve
heads, a lower compression ration is generally required for a 2 valve setup.
8.5 or 9 should be pretty safe for the GPZ turbo setup. 10:1 is is a "safe,
streetable" CR for a 4 valve setup. RE: Valves, for a turbo application
larger exhaust valves would show a benefit through better exhaust flow
to/through the turbo but because the turbo is pressurizing the intake side,
larger intake valves are generally not required.
  -----Original Message-----
  From: owner-turbobike@natvideo.com [mailto:owner-turbobike@natvideo.com]On
Behalf Of Steve Leonard
  Sent: Friday, November 05, 1999 2:20 PM
  To: turbobike@natvideo.com
  Subject: [turbobike] Compression Ratio



  I am building a 1983 GPZ1100, with a MoTeC M4 engine management system and
a IHI-RHB5 turbocharger.....

  Since this a 2-valve motor and I want it to be some what streetable
(preferabably pump gas), what compression do you recemmend, (1260cc), to
reduce detonation I can retard the timing as boost increases with the MoTec
software.
   Also will any great benefit be obtained with 1mm over-size stainless
intake and exhaust valves?
   Is there any advantage to having the combustion chamber and pistons
"coated" with the thermal barrier compounds that are available?( I live
about 10miles from a place that does it)

  regards
  Steve

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Because 2 valve heads (combustion = chambers) are=20 not as efficient as 4 valve heads, a lower compression ration is = generally=20 required for a 2 valve setup. 8.5 or 9 should be pretty safe for = the GPZ=20 turbo setup. 10:1 is is a "safe, streetable" CR for a 4 valve = setup.=20 RE: Valves, for a turbo application larger exhaust valves would show a = benefit=20 through better exhaust flow to/through the turbo but because the turbo = is=20 pressurizing the intake side, larger intake valves are generally = not=20 required.   
-----Original Message-----
From: = owner-turbobike@natvideo.com=20 [mailto:owner-turbobike@natvideo.com]On Behalf Of Steve=20 Leonard
Sent: Friday, November 05, 1999 2:20 = PM
To:=20 turbobike@natvideo.com
Subject: [turbobike] Compression=20 Ratio

 
I am building a 1983 GPZ1100, with a MoTeC M4 = engine=20 management system and a IHI-RHB5 turbocharger.....
 
Since this a 2-valve motor and I want it=20 to be some what streetable (preferabably pump gas), what = compression=20 do you recemmend, (1260cc), to=20 reduce detonation I can retard the timing as boost increases = with=20 the MoTec software.
 Also will any great benefit be obtained with = 1mm=20 over-size stainless intake and exhaust valves?
 Is there any advantage to having the = combustion=20 chamber and pistons "coated" with the thermal barrier compounds that = are=20 available?( I live about 10miles from a place that does = it)
 
regards
Steve
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