Raising compression ratio

Engines, Transmissions & Final Drive questions and answers

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93_Clubman
Speed Racer
Posts: 11983
Joined: Mon Aug 08, 2005 11:35 pm
Vehicle: Clubman
Location: Melbourne

Raising compression ratio

Postby 93_Clubman » Wed Dec 24, 2008 8:00 pm

Haven't done this myself, but hope the following helps:

Keith Tanner in Mazda Miata MX5 Performance Projects says "between 0.010 inch & 0.020 inch (0.25mm to 0.5mm) is a good range".

Norm Garrett in Mazda Miata Performance Handbook says "every 0.065 inch you mill off the head removes about 0.15 cubic inches from the chamber & increases the compression ratio approximately half a compression-ratio point".

Lisa
Learner Driver
Posts: 23
Joined: Wed Jul 02, 2008 12:48 am

Raising compression ratio

Postby Lisa » Sun Jan 04, 2009 8:05 pm

the best way to increase compression is via hi-comp pistons. decking or shaving the head, will only net you a very small gain in compression.
same situation if you were to fit a thinner head gasket.

my b/f adam used wiseco hi comp pistons in his ae86 4age engine and went from 10.5:1 factory, to 12:1 using pistons.


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