1 reply to this topic

[ozz1]

Whats the ideal CR for an original 649 grind cam (300/300) for use with 97 ron pump fuel? I want to be at the minimum end of the optimum range - if that makes sense - to preserve the ring lands.

 

Engine is 998 + 40'' (with all the bottom end work necessary to be reliable with the cam).

 

Graham Russel pistons. 

 

I'm thinking 11:1 but I've got nothing to back this up.

 

There must be some calculations where stroke/bore, duration/lift and octane are involved to reach an optimum figure?

 

Cheers, 

 

Oscar

Edited by ozz1, 23 January 2017 - 05:19 PM.

[Dusky]

Calculate the dynamic compression ratio. There are easy online calculators for that
You're quite low at approx 7.3:1 ATM.
Would need rod length and exact cam specification to be 100% correct.

Edited by Dusky, 23 January 2017 - 05:47 PM.