Av Gas? Anyone run it?

[ray_ray]

The above is totally true. I am adding to this post because I am a licensed FAA Aviation maintenance technician rated in both airframe and powerplants.

Thanks for helping clarify so much here for a layman such as myself... These gas blends (for lack of a better word) are a little confusing to say the least ... Same as engine oils ...

 

[Big Timmy]

A high comp head and avgas is the quick route to 2 stroke power. But, did you know higher octane actually does not make more power by itself. In fact the most power comes from lower octane as long as it is not pinging. Also realize rejetting is probably good when switching over to one to the other.

Keep in mind, Mixing 2 stroke oil in any gasoline will always lower the octane levels in that gasoline by simple mathematical dilution. Too much required 2 stroke oil can also increase wear within that engine and cause it to run hotter by simply increasing friction. Add to that dilution of the octane rating as well having added the increase in oil to that gasoline and you have a recipe for problems in your 2 strokes.

 

[K5PL5]

I use av gas cuz theres no ethanol in it.

 

[Mike-AK]

The above is totally true. I am adding to this post because I am a licensed FAA Aviation maintenance technician rated in both airframe and powerplants.

Although many piston driven airplanes have a low static compression, detonation is a No No in aviation. Many of these piston engines run a supercharging system whether gear driven or Turbo supercharging systems which are exhaust gas driven and these systems simulate sea level conditions for maximum power at take off. The amount of actual boost ( if any) is controlled by an altitude sensing bellows which keeps the boost at these sea level conditions, ( 29.92 inches of Mercury, or about 15lbs of pressure). Unlike automotive turbo charging systems that actually see Boost beyond the naturally aspirated pressure of 15lbs. Airplanes seldom do see actual boost beyond that or ever go beyond "Death Valley, below Sea Level, Mineshaft conditions" . Which is more than 30.00 inches of mercury and would be approaching 16 or so lbs per square inch pressures on the intake charge. The supercharged aircraft piston engine has this system installed so it can get to maximum power at take off period. It can make its 15lbs of pressure even at altitude as well so it can carry it's rated load and take off. Your average naturally aspirated engine in a "putt putt" airplane can't make there rated Horsepower unless they are at sea level. Thats where your Turbocharging comes into play here. It continues to make the rated horsepower at Altitude as well, as horsepower is diminished as altitude goes up. So the loss of horsepower is overcome with the turbocharger or supercharger. Allowing them to fly at higher altitudes.

How many times have you heard the old stories of bush pilots taking people up into the mountains to some lake to go fishing and land on the water and drop off all their gear and supplies. Then a week later try to carry them out with all their gear and fish as well and can't gain enough altitude upon take off to clear the trees. They end up crashing into those trees, Altitude is the culprit. Add to that the fact many of these lighter aircraft are not supercharged to allow maximum power at take off.

The higher levels of Octane in Aviation fuels are there to keep the engine from detonating. Not that it actually needs it but that its for safety reasons to avoid detonation. I believe Avgas has a slower burn rate than automotive fuels and racing gasoline. As most of these engines do not see the RPMs of the modern day motorcycle or car engine for that matter. They are built to have huge connecting rods, large wrist pins and heavy pistons to take the possible abuse of detonation so they don't fall apart and fall out of the sky.

It does smell good, but it will also burn your eyelids when run on the street as I used to mix it with pump gas in my 426 Hemi car. To much blended though with the pump gas would cause the car to load up and it had to be blown out, out on the highway, which is what the idea was anyway. While blowing off a few "Chevies" and putting some money in my pocket.

My opinion, if you need higher octane gas, because you have a detonation problem then run race fuel in your higher RPM applications. Aviation gas is for aviation.

Just remember pinging or "Preignition" is different than Detonation.

Detonation can be caused by Preignition but Preignition cannot be caused by Detonation. 2 distinctly different things here.

View: http://www.youtube.com/watch?v=PCgFKipMsBE

 

[Wolf]

First off...I am so sorry for causing one of those "oil" like discussions
The only reason I had even entertained the thought of running it has nothing to do with power. Our 125 needs race gas or it will make a heck of a racket - that motor is set up for it. The 250 TXC just runs cleaner with at least a 50/50 race gas pump blend. Race gas is just so darn expensive, and considering the amount of hours we rack up I was looking for a cheaper way out. Our premium fuel at the pump here in New England is absolute crap + Ethanol.

 

[Big Timmy]

Dig the cartoons. Don't be sorry for discussing fuels.

A two strokes combustion chamber on the cylinder head can be recut and modified to effectively raise the compression ratio easily 1 to possibly 2 points without any ill effects and still run the same fuel it used to run. Especially on modern water cooled applications. Look at the chamber next time you have it off. Take a look at the domed area of the chamber in the center. It can direct the flame front during the combustion process down to the top of the middle of the piston (which can cause pinging noice) if the shape of the center of the chamber is too vertical where it meets the rest of the outer diameter of the chamber. The head can be shaved, compression raised and the outer edge rechambered to the proper degree of percentage of rise with regard to the slightly domed piston shape and it will direct the flame front out towards the outer diameter of the piston towards the rings and most of your rattling and noisy operation will cease. It's been done a million times by 2 stroke gurus all over the world.

I realize ethanol is damaging to your fuel system and carburetors guys and not having it in your fuels is a good thing. I happen to live in Arizona and I don't think they even change the blend of gasoline here for the climate or seasons. Like they have to do all over the rest of the U.S. I've only seen gas go bad here once in over 25 years. That was in an old welding machine. Yes it was gummed up pump gas.

Aviation creeps forward with technology at a slow pace because everything is "experimental" outside the tried and proven systems they now have for Type Certificated Airplanes. Which are the only airplanes that can be used for revenue. The current technology of the average personally owned light aircraft is Technology right out of the middle of the last century because they (FAA) thinks its failsafe.

The fuel for avaition will still have Tetraethyl lead in it for many more years because its still needed to run these old piston engines. Things like hardened Stellite and Beryllium valve seats have hardly reached the aviation sector. They are going to Low leaded fuels, Yes. Aviation gasolines have always had about 20 times (parts per million) more lead content than automotive fuels ever had. Lead doesn't by itself increase the Octane rating of Aviation gas but it does has an effect on it with regard to helping the engine in resisting detonation.

 

[MorrisBetter]

And the idea that it is designed to only run at high altitude is false. How does the plan get up there? It has to take off at ground level at a point where the motor needs PEAK power to take off.
And I can't believe no one has mentioned, IT SMELLS GREAT!!!

You will not find the word "only" anywhere in what I wrote. It's has to work at at low temperatures and high altitude. It WILL work at low altitude/high temps, but it's a compromise.

This is a much better solution: http://www.torcousa.com/torco_product/un_acce.html

Can't argue about the smell of 100LL.

 

[MorrisBetter]

I should point out that I'm a pilot since 1988. Many years ago I had to drain the tanks of my Cherokee, and I couldn't resist the temptation to put fuel in my Mopar (not a 426). It felt overly rich and idled badly. Pretty much what Big Timmy described.

A blend of avgas is likely better than pump gas, but not the best solution by far. The Torco stuff I mentioned above will raise the California 91 octane pump gas to 102 octane for about two dollars a gallon. Half that if you want 95 octane. 100LL is $6-7/gallon. The 91 I bought yesterday was about $4, so a ~95 octane 50/50 mix will be ~$5.25 or more. So the avgas route is more money, and not really the best regardless of cost.

Another advantage is that you can carry several 32Oz cans in you truck and blend up gas that you buy anywhere. No need to find an airport.

For dual sport in areas that don't sell anything but the cheep stuff (Stovepipe Wells for instance), carry a can with you and turn that water into wine.

 

[Big Timmy]

I should point out that I'm a pilot since 1988. Many years ago I had to drain the tanks of my Cherokee, and I couldn't resist the temptation to put fuel in my Mopar (not a 426). It felt overly rich and idled badly. Pretty much what Big Timmy described.

A blend of avgas is likely better than pump gas, but not the best solution by far. The Torco stuff I mentioned above will raise the California 91 octane pump gas to 102 octane for about two dollars a gallon. Half that if you want 95 octane. 100LL is $6-7/gallon. The 91 I bought yesterday was about $4, so a ~95 octane 50/50 mix will be ~$5.25 or more. So the avgas route is more money, and not really the best regardless of cost.

Another advantage is that you can carry several 32Oz cans in you truck and blend up gas that you buy anywhere. No need to find an airport.

For dual sport in areas that don't sell anything but the cheep stuff (Stovepipe Wells for instance), carry a can with you and turn that water into wine.

I concur. I pour part of a can of Octane booster into all my jugs of pump gas. I've probably used every brand at 1 time or another. I will try the Torco next time I see it my local bike shop. The 426 Hemi would run overly rich and idled rougher then the cam normally would with the Av Gas. I used to refer to it as "blubbering" but thats not something most would understand. My 426 Hemi was no slouch and certainly wasn't known for blubbering. It was built By Rick and George Santos at S&S automotive in San Leandro. Not to far from yourself. I went to school with Rick and Dave Santos. Rick was the "NHRA Top Alcohol World Champion' 3 years in a row back in the late 90s. He knows how to build a Hemi.

 

[Mike-AK]

I might try some of that Torco stuff. It would be easier than mixing from 5-gallon jugs. It would also be handy to carry an 8 oz bottle in your pack when out and about. What is it? If it is just toluene or benzene, it's not worth $20 per quart.

 

[MorrisBetter]

I might try some of that Torco stuff. It would be easier than mixing from 5-gallon jugs. It would also be handy to carry an 8 oz bottle in your pack when out and about. What is it? If it is just toluene or benzene, it's not worth $20 per quart.

All they say on their web site is that it, "...contains some of the same ingredients as their race fuels." That's pretty wide open. If it does what it says, $20/Qt is reasonable. That's better than a ~$70 can of race fuel. Actually, it's been a while since I bought one of those 5 Gal. cans, so that price may be way off.

 

[MorrisBetter]

I concur. I pour part of a can of Octane booster into all my jugs of pump gas. I've probably used every brand at 1 time or another. I will try the Torco next time I see it my local bike shop. The 426 Hemi would run overly rich and idled rougher then the cam normally would with the Av Gas. I used to refer to it as "blubbering" but thats not something most would understand. My 426 Hemi was no slouch and certainly wasn't known for blubbering. It was built By Rick and George Santos at S&S automotive in San Leandro. Not to far from yourself. I went to school with Rick and Dave Santos. Rick was the "NHRA Top Alcohol World Champion' 3 years in a row back in the late 90s. He knows how to build a Hemi.

Hey Big Timmy, that's my neck of the woods. I drove within a mile of there yesterday. I had to go over to Vic Hubbard's. I bet you know that place well.

 

[Mike-AK]

I did some reading online and several sources say the Torco Accelerator uses Methylcyclopentadienyl manganese tricarbonyl (MMT) as it's primary ingredient. This used to be added to unleaded gas when it was first introduced as an anti-knock additive. Supposedly nasty toxic in it's unburned state. Back to Avgas.

 

[Big Timmy]

Hey Big Timmy, that's my neck of the woods. I drove within a mile of there yesterday. I had to go over to Vic Hubbard's. I bet you know that place well.

Oh Yes. I spent a few bucks at the Vic Hubbards,Speed and Marine back in the day when I lived in Castro Valley and moved around up in that area. My 70 Hemi Challenger used to roam the streets up there eventually out to Stockton until I moved to AZ. It got a full tube chassis in my shop here and I built an IndyMaxx 572" Hemi to go into the mid 8 Second zone.

I have spent countless dollars on 55 gallon drums of race gas for the big Hemi and mixing up concoctions of Aviation fuels for my Current 543' Indy Wedge I now run in my 66' Belvedere which is a street car. I had to pay out the "Ying Yang" to buy fuel to run the 572" Aluminum Motor. It was 13.7 to 1 compression ratio. I just never could get decent results blending Avgas to work with any of my combinations including my Dirt Bikes and theres an airport less than a mile from my house. I go by it every day while working to get to the Border fence I maintain.

Added a few pics of my other 4 wheeled toys.

 

[Big Timmy]

I did some reading online and several sources say the Torco Accelerator uses Methylcyclopentadienyl manganese tricarbonyl (MMT) as it's primary ingredient. This used to be added to unleaded gas when it was first introduced as an anti-knock additive. Supposedly nasty toxic in it's unburned state. Back to Avgas.

I know a guy (Butch) who used to drive a tanker truck carrying liquid Tetraethyl lead back in the late 80s. He was walking the catwalk once washing out his tanker trailer and was splashed all over his arms with tetraethyl lead while doing this with a 2" water hose. He slipped and fell off the truck injuring himself. Before he was able to go back to work from the result of his fall injuries he had already died of lead poisoning. It had absorbed into his skin on his arms and it was a grim descent for him as he went kinda crazy from the damage it caused. I used to go visit him at his home and one day he was dead. Lead is sort of deadly also.

So go get that AvGas and more power to you and your bike.

If you need the lead for a top end lubricant on your valve guides and stems perhaps you would consider this. I would buy some small bottles of scented top end lubricant for race gas that we use in our Drag race cars from 'Summit racing or Jegs" and your bike will smell like a "Jolly Rancher candy". Your neighbors will even like it. Mine do.

 

[T.Read]

I tried a few tanks of 110 leaded Renegade racing fuel mixed 50/50 with 93 non ethanol. Couldn't tell much difference in the performance really. But I was also having some issues with how it was running that I think I've fixed finally. Been running 93 non ethanol since then and it's been fine. Piston looked pretty clean when I took the head off to replace the head gasket.

 

[ghte]

I know ducatis in the US are having their plastic tanks swelling due to ethanol. I suspect you are as well but the tank sits on top of the cross member and is not internal to the trellis frame. The Meth is causing the Ducati tanks to crack in some cases.

 

[Wolf]

Re: fuel additives
I used Klotz octane booster one time. While it seemed to work well, it turned my white tank brown....ugly brown....beware....

 

[Planepower]

Avgas is not really a good choice for terrestrial machines. It's formulated for high altitude and cold temperatures. Read-up on Reid Vapor Pressure (RVP). Anybody that has flown light aircraft can attest to the different feel of Avgas on their skin. A pre-flight inspection includes a check for water in the fuel tanks. Eventually you spill 100LL on your hands, and it evaporates very quickly at low altitudes. It feels more like alcohol than gasoline. It's very different from the 91/93 available at the corner station. The short story here is that avgas is intended to work at cold temperatures and low atmospheric pressures in engines that are more like your lawn-mower Briggs & Stratton than your Husky's race motor.

Race gas is a far better choice for motorcycles, and is available almost everywhere. Sunoco and Torco both make great race fuels. Both companies have fuel finders on their web pages. I have a 100 octane pump 15 miles from home in Sunol CA. They also sell 5 gallon cans of 104 through 118 octane that can be mixed down to whatever you need. I bet there's a dealer near most of us. Buy a 55Gal drum and a quality hand pump and you can mix and dispense a custom blend that is exactly what you want/need.

I've only experimented, but have noticed that it's not as crisp on acceleration. Being in the light aircraft biz, I've done some reading on the comparisons and will have to agree with Morrisbetter. AVGAS was designed for big slow engines at altitude ( higher than 10,000ft). Think lower compressions of about 6:1 and rpms of about 2800 - it's designed to be more stable and with a slower burn rate. I usually get the opposite question; can I use auto gas in my aircraft? That usually ends disastrously.
I don't think AVGAS will hurt anything, but for the price you pay, may as well find something that will work better. I've seen skidoo guys buying lots at our pumps, but not sure why. Maybe it's better with turbocharged 2 strokes in the mountains?

 

[Big Timmy]

I know ducatis in the US are having their plastic tanks swelling due to ethanol. I suspect you are as well but the tank sits on top of the cross member and is not internal to the trellis frame. The Meth is causing the Ducati tanks to crack in some cases.

Iv'e heard many times that the modern fuels have so many additives nowadays that motorcyles will all be coming out with Aluminum tanks very soon. Take a look at some of the race teams bike, like James Stewarts Yoshimura Factory Suzuki, they have already done this. The modern fuels of today are able to penetrate clear through the plastic making them gummy and sticky to the touch and they are subject to failure. For the average trail and offroad guys this will happen long before the rest of the bike and parts are worn out.