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Posted (edited)

I was wondering about AV gas. Is the octane rating for it less than Race gas, because I can get it from the local airport for $2.90 a gallon versus the $5.00-$7.00 per gallon for race gas? I am buying a NOSS head and am getting 20cc domes so I need to go with higher octane. Plus it isn't that much more expensive than premium pump gas. So, I should be able to run this fuel either 50/50 or straight and be fine, or would there be something that I have to change? Another thing can I run AV gas in my wifes Raptor, and my daughter's Warrior or will this be a problem because they are four strokes? Riding areas are 200', 2400' and then 4000'. Thanks for the info.........

Edited by Animalman294
Posted
I was wondering about AV gas.  Is the octane rating for it less than Race gas, because I can get it from the local airport for $2.90 a gallon versus the $5.00-$7.00 per gallon for race gas?  I am buying a NOSS head and am getting 20cc domes so I need to go with higher octane.  Plus it isn't that much more expensive than premium pump gas.  So, I should be able to run this fuel either 50/50 or straight and be fine, or would there be something that I have to change?  Another thing can I run AV gas in my wifes Raptor, and my daughter's Warrior or will this be a problem because they are four strokes?  Riding areas are 200', 2400' and then 4000'.  Thanks for the info.........

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you should not need av gas with 20 domes .Hope you have a sunoco or other where you can buy 93 or 94 octane.You should be around 150 to 160 compression.high octane does not give more power it just does not detonite as easy,meaning more controlled ignite point.

Posted
you should not need av gas with 20 domes .Hope you have a sunoco  or other where you can buy 93 or 94 octane.You should be around 150 to 160 compression.high octane does not give more power it just does not detonite as easy,meaning more controlled ignite point.

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He's right you should be fine at 94 octane. only time you may wanna pay attention is at the low elevation, but as you go up your compression will go down.

Posted

AV gas is a good fuel. great for borderline between pump and race gas. I run it with 20cc domes +4 timing and a +4 stroker. Only $2.82 a gallon. If evey slight altitude and temp change messed up jetting it wouldnt work well in planes now would it?

Posted

Very good point!

 

 

 

AV gas is a good fuel.  great for borderline between pump and race gas.  I run it with 20cc domes +4 timing and a +4 stroker.  Only $2.82 a gallon.  If evey slight altitude and temp change messed up jetting it wouldnt work well in planes now would it?

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Posted

"Av gas is no good for raceing. The octane is inconsistant and every slight temp and altitude change will screw up your jetting."

If every slight altitude and temp change messed up jetting it wouldnt work well in planes now would it?

335732[/snapback]

good point, that's what i was thinking when I read that. the octane is inconsistent in fuel for airplanes? i highly doubt that, it may be in pump gas but not in AV gas.

Posted
Av gas is no good for raceing.  The octane is inconsistant and every slight temp and altitude change will screw up your jetting.

335637[/snapback]

yes temp and altitude changes can effect your jetting and other things as well but not "octane" alone.

Posted

AV gas is somewhat incosistent. It is allowed to fluctuate like 8 points or something like that. Not sure how crucial it is in bikes, but I don't remember any of the guys at the drag strip using AV gas. I'll see if I can find a write up on it I read awhile ago.

Posted (edited)

I was running a 50/50 mix of 110 and 93 with no problems. Decided to try 100LL AV gas and my bike ran the same but a little hotter than normal.

Edited by kenr74
Posted

I was curious about how AV gas octane rating differed from automotive fuel so I did a little research. The difference is AV gas octane is measured based only on MON (Motor octane) method and auto fuel uses MON and RON to calculate octane.

 

Auto gas is mesured my (RON+MON)/2 (RON = research octane)

 

Here is a quote on how AV gas octane is determined:

 

"The Aviation Rating is determined using the automotive Motor Octane test procedure, and then converted to an Aviation Number using a table in the method. Aviation Numbers below 100 are Octane numbers, while numbers above 100 are Performance numbers. There is usually only 1 - 2 Octane units different to the Motor value up to 100"

 

Here are 2 quotes on how MON compares to RON:

 

"For most hydrocarbon fuels, including those with either lead or oxygenates, the motor octane number (MON) will be lower than the research octane number (RON)"

 

"Modern fuels typically have sensitivities around 10"

This is the difference between RON and MON, RON being typically heigher by 10.

 

The conclusion I got from this article was that if you took an AV gas octane rating (MON) and also had the RON rating, then find the automotive rating using (R+M)/2 it would probably be a fair amount higher octane rating for automotive fuel.

Therefore I would conclude that AV gas rated at 100 octane would better resist detonation than automotive fuel rated at 100, or AV gas octane number is lower than auto gas for the same fuel.

 

I guess av gas is good shit?

 

(Click Here) This is the article that I pulled my info from.

See these sections for the pertinant info:

6.5 What does the Motor Octane rating measure?

6.6 What does the Research Octane rating measure?

6.19 Are aviation gasoline octane numbers comparable?

 

Another good section for those of you mixing 50/50 race/pump fuel

6.15 Can I mix different octane fuel grades?

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