Two Stroke Motocross
Two Stroke Motocross Forum => General Two Stroke Talk => Topic started by: riffraff on May 24, 2010, 08:53:34 PM
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What fuel do you guys run in your bikes. I use 100LL Avgas. Any thoughts on Avgas.
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I heard it wasn't good for your bike. And I use the highest octane pump gas.
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sonoco 110 leaded, the purple stuff, mixed with rock oil syn2 32:1
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Purple hunh? 110 oct. avgas was purple, the stuff I use is blue
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I run Avgas at 40:1 with Total R.
Plug runs perfect and even the pipe is grey. :)
Can't beat that smell.
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I've read both ways on the AV gas. I think the one's who say no, actually haven't used it. Don't know just always seems that way with fuels, but I do know the anti E85 guys don't know crap about it, before spouting out it sucks. They say how you lose power etc. They are going by the BTU of each product. But the BTU's just tell at a given amount, which has more power. Regular gas has more BTU per ounce of fuel than Ethanol, and Ethanol has more BTU per ounce than Methanol. But Methanol was the chosen fuel for racers for years in drag racing etc. Why, because it burns super fast. So they would use a ton of fuel comparably, but get more HP because of burning so much. I'm working on my CR125 as we speak as a switch over. I believe I can run a higher compression, with E85 and get more HP. I was all set to do the 144cc conversion, but want to test this first before hand. I believe I can gain 20% just by running the fuel and higher compression. As an example, the car guys with turbos have been running this for years. They can blow a ton of fuel and not worry about detonation, compared to pump gas. Some high HP cars out there running it. The biggest issue with E85 is the problem it has to attract moisture. Will have to keep an eye on and not let fuel sit around.
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in UK we only have choice of unleaded or super unleaded.. whats AV gas?
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I don't race, so I just use pump gas.
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Been there , AVgas (aviation gasoline) is not made to make HP it's made to stop planes falling from the sky. When you tune for it unleaded burns much faster and hotter(methanol burns very slow) yielding more HP.
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AV gas is made for engines that turn very low RPM (usually under 4000), and operate in a below freezing environment, not ideal for an MX bike. Also I have no experience with it, but I have heard that E85 is corrosive to engine and carburetor seals - a conversion to materials that will stand up to it could be difficult. I could be wrong on that one though....
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1 gallon of ethanol = 84,400 Btu
1 gallon methanol = 62,800 Btu
1 gallon of gasohol
(10% ethanol, 90% gasoline) = 120,900 Btu
1 gallon of E-85
(85% ethanol, 15% gasoline) = 90,500 Btu
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i blend 110 leaded race fuel with pump fuel @ 1 gallon 110 with two gallon 87. that blend runs better, jets easier and more consistant than straight premium from the pump in my area. pump gas just seems to get worse every year.
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AV gas is made for engines that turn very low RPM (usually under 4000), and operate in a below freezing environment, not ideal for an MX bike. Also I have no experience with it, but I have heard that E85 is corrosive to engine and carburetor seals - a conversion to materials that will stand up to it could be difficult. I could be wrong on that one though....
I'm testing the fuel tank, lines and the carb parts right now. But basically our bikes are made to accept atleast 15% ethanol already. So I don't think the current stuff and the older stuff can really be compared, same as cars from the 80's. We now know that most vehicles will not have any failures like you mentioned, for corrosition like many had believed before. Lot's of misinformation out there on E85. What i find very funny or interesting. However you wanna say it. We can run e85 legally in cars all around america. But it is not permitted in ProAMA racing. But they allow race gas. Go figure.
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Another personal preference question, o.k I run a 50/50 mix of VP's C12 and pump gas with a minumum 92 octane (ethanol free) this works out to be around 100 octane. This mix can hang around in the can for a long time with out spoiling.
;)(You can mess around with the ratios depending on how you are going to ride.Supercross, tight woods and higher elivations I run it closer to 98 octane. Motocross,higher compression, hotter days I will run it closer to 104 octane.
The real devil is detination it MUST be avoided because that horrible noise is the top of your piston starting to glow red and we have all seen piston,connecting rods that look like someone took a cutting torch to UGLY VERY VERY UGLY.....My 2 cents :'(
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I only run my TM on Avgas because they have a massive port time area at low RPM's and the heads are not suited to our crap fuel.
The compression ratio is also very high as the motor is designed as a race motor.
You end up with a incomplete fuel burn at low rpm's. Motor knocks it's head off. :(
I have heard they run fine in the states because of far better fuels.
There is a mod that I might do to lower the compression ratio from 15.5:1 to 12.9:1 that involves machining the head into a full hemi shape and increasing the cc.
At the moment it just runs far better on Avgas then on pump gas.
The marine industry has had major problems with E85 caused by water ingestion and the fuel will seperate if left for too long.You end up with the ethenol sitting in the bottom of the tank.
Should not be a problem if you keep the fuel fresh.
Also fuel lines and seals can get attacked by the fuel and brake up.
Viton seals are a must.
I recomend to all boat's not to use E85 because of the nature of use. Sitting around for too long.
Run E85 in your bike by all means, just tune it properly and dont let it sit around for too long.
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AVgas (aviation gasoline) is not made to make HP it's made to stop planes falling from the sky.
??? ??? ??? ??? ???
No gas is made to make HP and planes don't fall out of the sky :P Main reason I use avgas is because I'm an aircraft mechanic and have a pretty much unlimited supply of it, been using it for 25 years. Avgas also has stricter quality-control standards, is formulated for anti-detonation and has stabilizers added to keep it from going bad.
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I agree whole heartedly that avgas, when used correctly, is an excellent two stroke fuel.
If the compression, pipe arrangement, and jetting is correct, my personal findings are avgas will produce better power than pump.
Furthermore, it's strictly regulated (well...much more so than pump gas), extremely consistent, highly resistant to detonation, and relatively cheap.
It also stores well.
Are there fuels out there that produce more power? Yes.
How much more?
If both set ups are optimized for that fuel correctly...usually not more than 3-4 percent improvement best case.
Disclaimer...some fuels produced by elf, which I have not tested, show an oxygen content that's huge....and in turn may produce much, much more power (at huge prices)
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No gas is made to make HP and planes don't fall out of the sky :P Main reason I use avgas is because I'm an aircraft mechanic and have a pretty much unlimited supply of it, been using it for 25 years. Avgas also has stricter quality-control standards, is formulated for anti-detonation and has stabilizers added to keep it from going bad.
Avgas only has a specific gravity of 0.73 versus 0.78 for our 98 octane ULP. Avgas burns very slowly, ULP burns very fast. Avgas is not 'formulated' it just has lead and an anti-icing agent.The 'strict quality controls' are not that stringent and more to do with batch numbers etc(we had a bad batch here recently and all piston engine aircraft were grounded).
But none of that makes HP it's simply to stop Lycoming engines detonating.
Just because you will run a bigger jet on avgas doesn't mean your making more HP.
We have BP98 pump fuel that we can tune to the limit on, 100% consistent from servo to servo month to month.
Truth is these days avgas is old hat and there are far better fuels to use.
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Truth is these days avgas is old hat and there are far better fuels to use.
It may be old hat but so is my bike, aircooled non-power valved '79 YZ490, so I don't think there is any better fuel to use for my bike... and did I mention that I get it free, how much better can you get ;D
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How did you get a 79 YZ490?
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It would suck to have to buy special fuel rather than just stop at the gas station for a little supreme while on the way to go riding.I guess we must be fortunate here as ethanol isn't an issue-yet.
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Anyone using toluene? I been hearing a lot about it lately. Usually 5 - 10% mixed with premium pump gas.
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:-[ Ooops, meant an '89, that's what I get for early morning posts
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in UK we only have choice of unleaded or super unleaded.. whats AV gas?
I'm in the UK dude and have the choice of almost all race fuels, do a search, you can get VP, ELF, Sunoco etc. BP sell a 102 pump fuel as well.
I have tried to get E85 working but found to many problems, one was the huge jets needed to run it, we even ran our sx125 without a mainjet installed ? We worked out we cold get about 20min's max from a full tank, but we found it caused a whole lot of wear to piston and ring, almost has the feeling of being 'dry' It also eat crankseals !
Avgas was good when we could get it, we ran that 100% mixed with motul800 @25:1 But its getting harder and harder to find the stuff.
Been experimenting with other stuff recently and found some real good additives in the, well lets say 'solvent' family of chemicals. Melted a few slugs along the way, but now I'm happy running my mix in all our 2st's and its ultra reliable. Pump gas in the UK sucks for anyone running decent motors but most guys dont bother with fuel as they just think fuel is 'fuel' and fill up at their local forecourt. (all the better for us ;))