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Old 06-08-2013, 10:17 AM
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mew905 mew905 is offline
Motorized Bicycle Elite Member
Join Date: Sep 2012
Location: Moose Jaw
Posts: 647
Default Re: What Octane Do You Use?

Last time I checked my compression, my tester said 90 PSI @ 1811 ft elevation. That was tested with a B&D 18v drill. I did notice however depending on your ports, your pressures vary with speed (higher RPM = higher compression). IF I'm doing my math right that means 13.45 psi atmospheric pressure so 90 PSI from 13.45 PSI = 6.7:1 compression @ around 1500 RPM. Expansion chambers, port timing and altitude will all affect this. Jaguar says he gets ~125 PSI and he's at a higher altitude than I so it could easily be more.

Back to the original question: I run 91 octane Shell Nitrogen enhanced, I have a choice between 87, 89 and 91, so I use the highest I can get, and despite what other people say around here, yes it does help my performance, it feels smoother, doesn't bog as much and I get a higher top speed out of it. Torque isn't enough to feel a difference so I don't know about that. But yes, if you've never tried a higher octane, try it, your ride may be more enjoyable. Sometimes things can be vastly different than what calculations predict
Skyhawk GT-5, Dax RT, RSE Reeds, Jag CDI, Drilled stock exhaust, Puch Hi.
List of HT hardware === Stop four-stroking!
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