Fuel ?????

[NJD]

Hey what kind of fuel is everyone using? Do you guys get premium from a local gas station or do you buy race fool from the local bike shop? I was thinking of getting Sunoco ultra 94 and then adding octane booster, I was wondring if that would work or if I would encounter any issues. Anyone try this before?

[CorvetteZ06]

good qeustion, if you have a high compression motor, and could not get race gas for some reason, would it be ok to run ultra 94 + octane booster?

[pimpt250r]

Im not a mechanic,
,Im a painter
but I would'nt run any type of octane booster
that is so bad for your engine its not even funny,,
because its not really booster its a chemical that helps the fuel burn better/hotter
if you added it to a 5gallon can your only gonna get maybe 2 more points out of it
not really worth the 6-9 dollars your gonna spend on 1 bottle
go to your little home town airport and run A/V
i think thats around 100 octane 4-5$ a gallon

[ChvyCruzen]

AV gas is also known as 100LL. LL means low lead. Their octane rating system is different than the ones we use at the pump. AV gas is actually about 112 octane if thats what you were to get at the pump. I think its about 4 bucks a gallon, I get it myself but its been a while since I got some.

I wouldnt run octane booster either. I'd run AV gas if you're above 180 psi. It runs a little hotter on AV gas and the lead helps keep stuff clean. My plug doesnt get as brown compared to pump gas but I know its not lean. You'll have to change your jetting for AV gas or race gas if you end up using that.

[GPracer2500]

Here's some facts about 100LL and it's octane rating. If you don't want to read everything, that's fine--the parts in bold are all that really matters:

100LL has a minimum specification of 99.5 MON. This number is determined using the same ASTM D2700 test method that all other gasoline uses to determine MON. Contained within D2700 is a table for converting MON to the "lean mixture rating" that 100LL is badged with. Additionally, 100LL goes through ASTM D909 testing. This is the "rich mixture supercharged rating". That number is irrelevent to us. It means nothing to our engines. Pump gas, race gas, and every other kind of gasoline has a rich mixture rating too but only aviation fuel is actually tested for it.

The old aviation gasolines where named 80/87 and 100/130. Those two numbers in each name correspond to the lean and rich mixture ratings mentioned above. Those fuels are pretty much gone now. 100LL was developed to replace them both and has the same octane ratings as 100/130 but it gets there with less lead (hence the "low lead" label). That's were the 100 in 100LL comes from--its lean mixture rating, low lead.

Pump gasoline is rated by (RON+MON)/2. But 100LL is not normally tested for RON (which is determined with ASTM D2699). So we don't really know what 100LL's octane rating would be if stated in R+M/2. In most cases pump gasolines have about a 10 point spread between MON and RON. That spread is called the fuels "sensitivity" and the lower the number the better. I have seen some testing by Conoco Phillips in which they did test 100LL for RON. It came about in their research on Aviation Grade Ethanol (they tested 100LL for comparison purposes). The result was that 100LL has a RON of 106.5. But RON is not part of the specification standards for 100LL so I wouldn't put too much weight on Conoco's results. All they were trying to show was that 100LL is far less sensitive to tempurature than AGE in both MON and RON testing. Without 100LL actually having a minimum specification for RON I'm not willing to say that without a doubt, all the time, in every case, 100LL has a RON of 106.5.

But taking those results at face value means 100LL has a sensitivity of 7 (which is pretty good) and an R+M/2 rating of 103. But I'm not too concerened with RON or R+M/2. MON is the superior test method and is the most relevent number for our engines.

91 pump fuel = ~ 86 MON
94 pump fuel = ~ 89 MON
100LL = 99.5 MON
Racing fuel = there is so much variation in the types of racing fuels available that it's tough to generalize (e.g. VP 110 = 107 MON, VP C12 = 108 MON, VP U4 = 92 MON). You just have to pay attention to the specs to know what you've got.

[clutch22]

Originally posted by ChvyCruzen
You'll have to change your jetting for AV gas or race gas if you end up using that.

So if i'm using a 170 main jet on premium. what do you think i'd have to go to with Avgas?

[ChvyCruzen]

Originally posted by clutch22
So if i'm using a 170 main jet on premium. what do you think i'd have to go to with Avgas?

I would go up 2 sizes if it were me. Play it safe. Do plug chops. Dont be afraid to go even fatter if you want to. If you have a temp gauge or gun, use it and compare those numbers to previous heat cycles on premium gas.

I have a thing for running rich. Neil also designed my bottom end to handle extra fuel ;)