AV gas

Dont know if anybody is interested but thought Id post this up for anyone that may be thinking about it. I picked up some 100 LL av gas locally and tried it out.

Had read some of the posts about it and came away with the impression that it probably would not make a noticeable performance difference, but maybe the lead would help extend valve life. :lol:

Well all I can say is that there IS a noticeable improvement in performance. My bike runs better, especially when lugging at low rpms. Doesnt stutter near as much at low rpm, pulls ALL the way thru the rpm noticeably better. It always had good throttle response, now just starts pulling harder and at a lower rpm. I didnt measure it, but mixed it one part av gas to two parts high octane pump gas. Not sure what the long term effects of running the av gas mixture but seems worth it.

I used it once... didn't notice any difference. :lol:

Be careful running true aviation fuel. It has anti-freeze agents in it, and other properties required by the FAA. Now high octane gasoline, if you can afford it, get it. There's a station down on chandler Blvd that sells it, but I've been afraid to go by and see what it's elling for lately.

100 or 110LL is good stuff. Your motor will run cleaner and cooler with it. JM02.

Be careful running true aviation fuel. It has anti-freeze agents in it, and other properties required by the FAA. Now high octane gasoline, if you can afford it, get it. There's a station down on chandler Blvd that sells it, but I've been afraid to go by and see what it's elling for lately.

I figure as long as its mixed at a 1 part to 2 parts ratio and the eng actually runs better there should'nt be any problems-but we will see. The high octane unleaded pump gas I always use is from the ampm on the corner and I think it is 91 IIRC. The av gas was $4.70 a gallon self serve.

100 or 110LL is good stuff. Your motor will run cleaner and cooler with it. JM02.

Some of the threads I had read prior to trying it out said it could foul the spark plug, and some said it would cause the eng to run hotter but I dont know. I didnt have to make any jetting changes or adjustments at all.

Dont know if anybody is interested but thought Id post this up for anyone that may be thinking about it. I picked up some 100 LL av gas locally and tried it out.

Had read some of the posts about it and came away with the impression that it probably would not make a noticeable performance difference, but maybe the lead would help extend valve life. :lol:

Well all I can say is that there IS a noticeable improvement in performance. My bike runs better, especially when lugging at low rpms. Doesnt stutter near as much at low rpm, pulls ALL the way thru the rpm noticeably better. It always had good throttle response, now just starts pulling harder and at a lower rpm. I didnt measure it, but mixed it one part av gas to two parts high octane pump gas. Not sure what the long term effects of running the av gas mixture but seems worth it.

I used to tell people all the time that it made a huge differnece in my old four stroke. It is a better fuel than pump gas. It is good for they scooter. It is worth the price difference

Mix your own with Torco additive. Costs $1 per gallon more. Turbo cars running stupid hige levels of boost do it. I did it for years. 2.1 bar of boost on pump gas with 9:1 compresion, 550 hp from 2.0 L motor with a GT30 turbo. With straight 91 I could barley break 350hp with out massive detonation.

I run it in my race gas 2 stroke 144.

I've always heard that AV Gas would make you run too hot, too. I've heard of guys gassing up their boats with it at Lake Powell and blowing motors. All hearsay, though, and could be totally inaccurate. I'd just be cautious.

I ran pure avgas in my silverado for a few months, couldnt tell if it ran cooler or hotter but it did ruin my o2 sensors haha. I think the high octane and lead content will burn up some motors

Higher octane runs richer, so therefor cooler. I ran it straight in my 250r and it actually screwed with the jetting, it was a bit crisper, but it also had a big stutter mid way through the power.

Higher octane runs richer, so therefor cooler. I ran it straight in my 250r and it actually screwed with the jetting, it was a bit crisper, but it also had a big stutter mid way through the power.

I was wondering when this topic was going to pull in some real information- not just opinions. Way to go- :lol:

Octane doesn't actually make it run richer but it acts like it's richer. What it does is slow the burn rate of the fuel. Unless the motor is set up to use the higher octane it's often of no benefit to use it.

Pinging you hear when a motor is detonating is the flame front hitting the piston while it's still on the compression stroke. This causes the forces at work to collide in the motor. If that is happening using a higher octane fuel slows the burn rate of the fuel and prevents the above mentioned collision. In some extreme cases the charge in the cylinder will explode instead of burn.

Other things like compression ratio, ignition timing, and fuel mix also play a part in the burn rate of the fuel compared to the position of the piston in the stroke. Changing one often dictates the need to change the others to balance the effects.

Higher octane runs richer, so therefor cooler. I ran it straight in my 250r and it actually screwed with the jetting, it was a bit crisper, but it also had a big stutter mid way through the power.

I dont think I would run it straight, some of the info that I read said there is just too much lead in it and spark plug fouling and excessive deposits would result.

I was wondering when this topic was going to pull in some real information- not just opinions. Way to go- :lol:

Octane doesn't actually make it run richer but it acts like it's richer. What it does is slow the burn rate of the fuel. Unless the motor is set up to use the higher octane it's often of no benefit to use it.

Pinging you hear when a motor is detonating is the flame front hitting the piston while it's still on the compression stroke. This causes the forces at work to collide in the motor. If that is happening using a higher octane fuel slows the burn rate of the fuel and prevents the above mentioned collision. In some extreme cases the charge in the cylinder will explode instead of burn.

Other things like compression ratio, ignition timing, and fuel mix also play a part in the burn rate of the fuel compared to the position of the piston in the stroke. Changing one often dictates the need to change the others to balance the effects.

Yeah until a comparison is done on a dyno, it will be mostly opinoins, no matter what type of tuning mod your talking about. But sometimes it is obvious using the seat of the pants dyno whether or not there is a performance increase or benefit.

I dont think I would run it straight, some of the info that I read said there is just too much lead in it and spark plug fouling and excessive deposits would result.

I ran straigt AVGAS in my 2000 KX500 for 8 1/2 years with no problems ever. It was jetted properly and i had the higher compression head gasket on it. Never ran hot, never stuttered. Perfect burn on my plug.

I would not run it straight in a 4stroke as it is hard on the valves. I know people that run it 50/50 and no issues.

Here is what I use for race gas instead of race gas. Way cheaper works the same. Sunoco 104 is basicly 93 octane with this stuff mixed in then soild at $10 a gallon. DIY for $1 more per gallon over 91 octane price. Great for hi comp heads and pistons.

I seriously doubt race gas adds power on a stock motor. Race gas allows more compresion or advaning timing significantly without detonation therefore making more power by extractig more energy. Without changing th engine it does not make more power magically on a stock motor. It may feel crisper or "run" better but that is not the same as more power.

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The only advantage I have found in race fuel is that it crisps up the throttle response and at my amatuer level it doesn't make a difference. The lead in AV gas acts as a lubricant as well for valves and was good for cars with soft valve seats but it can build up. Unless you have serious motor work I have found that running the more expensive stuff makes the cash go faster. However, I do mix 25% 110 octane with 93 pump when the track has alot of steep hills, but only because my RM pings going up this Monster hill at 1 of our local tracks. My brother would run AV gas in his 400ex that was punched out to a 480. He never had any problems though. I have also heard good things about the Torco additive.

From a motorcycle and former aircraft mechanic (I make more money and have twicve as much fun with bikes!) Av gas has all the properties previously stated. The additives raise the octane which in turn lowers the volatility (speed of burn in loose terms) and the additives also help the engine to run cooler at high temperatures (one of its main jobs in a aircooled recip engine on a plane). At higher alt. we aircooled guys bikes run hotter due to less air molecules for heat to transfer too. At more normal altitude, the cooling effect of air is greater on an any motor but an aircooled motor really takes a beating. This is where av gas can help a little.

For more initial investment vs. long term cost (mod vs. fuel) it would be cheaper (assuming the bike you ride will be the same for a couple of years and you always use av gas) it would be cheaper to build your motor to run cooler (this is for air cooled guys) by proper jetting, adjusted cam timing, good oil cooler, and fresh quality oils and of course a non worn top-end. oing these things will make the bike run better, produce more torque (which always means more horsepower), more reliably and cheaper over the course of a couple of years.

Therefore- I do not run avgas. If I build a higher compression motor for performance I prefer to use an oxygenated fuel that is unleaded or leaded and with a lower octane number. For my roadrace and supermotos I ran VP Racing U4.2 to fulfill this need. It is readily available ( I sell it!) no mixing needed and relatively cheap if mixed (say in compensation for a thinner head gasket as a lone engine mod). In all temps and altitude I have never had any ping, detonate or seizure issues with jetting properly dialed in.

Avgas is not bad- I just am not sold on it and they don't pay contingency for a good finish!

Good info from everybody. My 250x isnt stock but definetely isnt a race bike and I havent ever tried any kind of race gas but I did like the extra umph that the av gas added. I have a wiseco 13.5 comp piston and stage 1 cam, and different gearing. Any fuel that is reasonably priced, adds power to help keep the rpms down some, and help extend valve life is what I am trying to accomplish.

Good info from everybody. My 250x isnt stock but definetely isnt a race bike and I havent ever tried any kind of race gas but I did like the extra umph that the av gas added. I have a wiseco 13.5 comp piston and stage 1 cam, and different gearing. Any fuel that is reasonably priced, adds power to help keep the rpms down some, and help extend valve life is what I am trying to accomplish.

I am pretty sure that the 250X engine is considered a race engine..even moreso with the hi comp piston and cam. Having said that I did the same set up and I was told by the hi comp piston manufacturer that 91 pump gas was fine for it.

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