HELP octane!

[mikesbikes09]

What octane should i run on a 04 450r with 13:1 and hrc cam?

[whiteboycustom]

110

[zeus54]

i agree check out sunoco's or vp's website's for different fuel types. i just finished with my rebuild and installed a baldwin 14.1 and their mx cam. the piston is made my wiseco. i run sunoco mo2x 112 it's oxygenated which is supposed to combust easier and cleaner according to sunocothan their cam2 110

[whiteboycustom]

my past experiance with oxygenated fuels is u let them sit in ur carb and they gum up, its best to drain the carb, or just run sunoco gt plus 104 its a unleaded fuel

[zeus54]

Originally posted by whiteboycustom
my past experiance with oxygenated fuels is u let them sit in ur carb and they gum up, its best to drain the carb, or just run sunoco gt plus 104 its a unleaded fuel


the lead in the fuel helps lubricate your valvetrain and yes it can leave build up in your carb, however it doesn't do it anymore than other leaded fuels. i personally see more horsepower gains out of the mo2x versus the cam2. it is quite a bit more expense however when i redoe the topend i have noticed less deposit build up on the valves and top of the piston. just my 2 cents.

[450R-156]

I run aviation fuel in my 13.1 with a crf hot cam it is exactly 100 octane

[mike nash]

Originally posted by whiteboycustom
my past experiance with oxygenated fuels is u let them sit in ur carb and they gum up, its best to drain the carb, or just run sunoco gt plus 104 its a unleaded fuel

Isn't the 104 oxygenated?I ran it and machine seemed snappier.But the 110 is less maintainence on intake.

[whiteboycustom]

that 100 octane aviation fuel is 100 octane at 30,000 feet not at the ground and yes 104 is oxygenated but its still a unleaded fuel not leaded like the 110, its a great fuel i run it in my 05 and it runs nice and smooth, ive had 109 vp and 110 sunoco in my cr250 and they gummed up my carb real bad, now i run 104 in the bike and no problems yet

[400exrider707]

Originally posted by 450R-156
I run aviation fuel in my 13.1 with a crf hot cam it is exactly 100 octane

The aviation fuel around me is 106-107 octane and yes thats at higher elevation. I was always told aviation is meant for high altitude and low RPM's, the exact opposite of what our wheelers need.

[GPracer2500]

100LL avgas has a minimum octane rating specification of 99.5 MON. Its MON rating is determined the exact same way every other fuel's MON rating is determined.

Remember folks, there are 3 common types of octane rating:

Motor Octane Number (MON): This is the one we want to be using when talking about fuels for powersports applications. MON is determined with more stringent testing that more accurately predicts knock resistence under high load situations. MON will be the best predictor of actual knock resistence in our engines. Many racing fuels only list MON.

Reasearch Octane Number (RON): This octane rating is similar to MON. It's determined through practical testing of actual fuel samples, just like MON. The difference is that the testing standards for RON aren't as stringent. Because of this, for any given fuel sample RON will always be a higher number than MON. Much of the world puts RON on their gas station pumps.

(R+M)/2: This is an average of RON and MON. This is the number we see on the yellow sticker on our gas pumps in the US and Canada.


For most run-of-the-mill gasolines there is about a 10 point spread between MON and RON. That spread is called "senstivity". The larger the spread, the less able the fuel is at handling sudden changes in throttle postion/load.

When talking about performance fuels and octane ratings you've got to use the same scale in your discussions. Otherwise your just throwing around numbers that can't be compared to other numbers. It's like saying, this pole is 10 long. 10 what? Feet? Inches? Meters?

Take Sunoco's Standard Leaded race fuel:
MON = 105
RON = 115
(R+M)/2 = 110

How would you know were it fits into these fuels below without getting everything on the same scale? You wouldn't.

91 octane pump gas = ~86.5 MON
100LL avgas = 99.5 MON
Mo2x = 109 MON
VP C12 = 108 MON
VP 110 = 107 MON
etc
etc

[zeus54]

Hey GP got a question for you seeing how you seem to be very educated about the subject. Does the oxygenated fuel combust easier?, or is Sunoco probably feeding me a line. I understand the ratings however what I don't understand is the dielectric numbers, can you help me with that?

[GPracer2500]

Originally posted by zeus54
....Does the oxygenated fuel combust easier?, or is Sunoco probably feeding me a line. I understand the ratings however what I don't understand is the dielectric numbers, can you help me with that?

Oxygenated gasolines in general combust more effeciently. Since gasoline can't burn all by itself it needs to be mixed with oxygen. The air being sucked in by the engine is where this oxygen supply comes from. But when an oxygenate is added to gasoline, now the fuel has a built-in supply of oxygen to aid combustion. The vast majority of the oxgygen used in combustion is still coming from the intake air, but it helps the fuel to have some oxygen right there.

I've never used MO2X but I'd expect it to perform on par with any other top-shelf, power-adding oxy race fuel.

Dielectric constant is a measure of electrical capacitance. Oxy fuels have higher values since the oxygenates carry a greater ability to "store" electrical charge. If you already know oxygen content, the only reason I'm aware you might also want know the dielectric constant is for fuel testing purposes. In some racing organizations they use dialectric testers to test a competitors fuel for illegal additive content.

[doc-bones]

100 octane is plenty.