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Old April 16th, 2024, 08:29 PM   #19
Fred659
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Name: Frederic
Location: Quebec City
Join Date: Jan 2020

Motorcycle(s): 08 Race Prepped ZX-10r, 09 Race Prepped Ninja 250 (300 motor). 74 Norton Commando 850 (Project)

Posts: 55
Quote:
Originally Posted by Mohawk View Post
You need to ignore static compression ratios & work out the dynamic compression ratio based on the cams you are running. 95RON is good for 11-11.5/1 dynamic ratio. Most unleaded fuelled bikes run 10.5-11/1 dynamic ratios. If your dynamic ratio is higher then you will need higher octane fuel. There are calculators on the net for this. Wallace Racing do one.
I just calculated the DCR for my engine:

12.6 SCR (from all my measurements) (Stock 10.6; 08 zx-10 = 12.9)
int cam closing at 56° (08 zx-10 = 77°)
Rod Length of 3.770"
10.56 DCR (stock would be 8.912; 08 zx-10 would be 9.028)

From: https://www.omnicalculator.com/every...pression-ratio

could you please tell us where you got the 95RON information and where did you find that most unleaded fuelled bikes run 10.5-11/1 dynamic ratios?

Thank you
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