Aaron-Betta Posted November 19, 2008 Report Share Posted November 19, 2008 It is physically impossible for fuel octane to effect the drivetrain gear ratio. Too true Ira. I didn't factor in the variables. One measurement of speed was done via GPS and referenced to data logging on lappy, on track with different wheel and tire combo. The other is in street trim, on the motorway, measured on dash (maybe my speedo is out ). I will have to give it a go next time i got to the track and test it with just 91 and use the GPS to measure speed. Quote Link to comment Share on other sites More sharing options...
Ira Posted November 20, 2008 Report Share Posted November 20, 2008 Yes and no. Obviously in the extreme cases it is (I remember reading about the Meguiers Ford Focus drag car which ran over 12:1 compression and around 30psi boost!) but there are limits. In a naturally aspirated motor the compression and the cams need to be matched or your wasting your time, and on all but the most extreme big dollar turbo motors a lower CR (somewhere around 8-9:1) will make it safer to run more boost and easier to tune, more of a margin for error. Anything much over mid 11:1 CR for a NA street car running on our crappy gas is pushing it IMO... Turbo motors have dynamic compression. More=better. And you'd just be stupid to not adjust the cams to match a significant change in compression, so it goes without saying. Quote Link to comment Share on other sites More sharing options...
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