e85 vs avgas + water meth?
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Launching!
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e85 vs avgas + water meth? I have a situation and am looking for a little info. My motor is going to be making 3.8-4.0 hp per cubic inch for long periods of time 30 min. I was planning o running e85 but I am going to run into a problem with fuel tank volume. I have a 65 gal tank and at 1000 hp on e85 I will use 68 gal in 30 min. I am looking at running av gas with water meth injection instead. Thoughts?
Wow. Not what you asked, but you’ll need a pretty hefty cooling system on both the coolant and oil, if it survives. Post stories!
One problem with E85 is the alcohol content consistency. It can typically be 70% at the pump, but vary greatly, so it depends upon if your calibration is fixed or can adapt via a fuel composition sensor.
The 100LL has lead, so if you are running O2 sensors, it will poison them. They may survive 30 minutes, but if you’ll be at full throttle, it won’t be using them anyway.
Have you thought about buying pure ethanol? E98. It is a fixed composition, and has 2% gasoline in it just to keep the drunks out. It is also relatively low cost. This is what I will be using for a high compression blower build.
Most say true race fuel is best though, has the best fast burning combustion characteristics, and proven to make more power over above fuels.
One problem with E85 is the alcohol content consistency. It can typically be 70% at the pump, but vary greatly, so it depends upon if your calibration is fixed or can adapt via a fuel composition sensor.
The 100LL has lead, so if you are running O2 sensors, it will poison them. They may survive 30 minutes, but if you’ll be at full throttle, it won’t be using them anyway.
Have you thought about buying pure ethanol? E98. It is a fixed composition, and has 2% gasoline in it just to keep the drunks out. It is also relatively low cost. This is what I will be using for a high compression blower build.
Most say true race fuel is best though, has the best fast burning combustion characteristics, and proven to make more power over above fuels.
Thread Starter
Launching!
Joined: Aug 2010
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Well that is the problem I am trying address. it will go through 136 gal/hr. Our longest run is 38 min approx so 87 gal. e98 would be worse. my tank is 76 gal. This in a boat so cool water cooling is a non issue. With av it would 51 gal plus 8 of or so of water meth.
Last edited by allblowdup; Feb 6, 2019 at 09:10 AM.
"Av Gas" is 100LL. Low lead really means lots of lead. As long as you don't have an O2 sensor, your engine will run it just fine. But it's also formulated for high altitude. That changes it's vapor point. Great at 10,000'. Not so great at sea level. It won't burn as well as regular pump gas at sea level. Adding methanol injection adds complexity, which decreases reliability and increases maintenance. It also adds weight and takes up space.
Pump E85 is a great fuel for racing, it does have a lot of advantages. But, people think that because it's over 100 octane they can go crazy with compression. But that just isn't true. The 15% gasoline is some of the cheapest dregs from the bottom of the refinery tank. It can cause detonation under the first ring land. Makes the piston look like something out of "Aliens" movie. Been there, done that. E90 race fuel is much better because it's mixed with race fuel, and the formulation is more consistent.
As you've already mentioned, you can't currently carry enough alcohol based fuel. If you need a bigger tank, that will significantly increase your cost, and weight. And you may not have room for a bigger tank. Adding a second tank will once again increase weight, cost, complexity, and maintenance steps. All the things you're trying to avoid in a race boat.
If your engine really needs more than 100 octane, you safest, cheapest, and easiest option is to simply buy racing fuel.
Pump E85 is a great fuel for racing, it does have a lot of advantages. But, people think that because it's over 100 octane they can go crazy with compression. But that just isn't true. The 15% gasoline is some of the cheapest dregs from the bottom of the refinery tank. It can cause detonation under the first ring land. Makes the piston look like something out of "Aliens" movie. Been there, done that. E90 race fuel is much better because it's mixed with race fuel, and the formulation is more consistent.
As you've already mentioned, you can't currently carry enough alcohol based fuel. If you need a bigger tank, that will significantly increase your cost, and weight. And you may not have room for a bigger tank. Adding a second tank will once again increase weight, cost, complexity, and maintenance steps. All the things you're trying to avoid in a race boat.
If your engine really needs more than 100 octane, you safest, cheapest, and easiest option is to simply buy racing fuel.
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Thread Starter
Launching!
Joined: Aug 2010
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I think I have come up with a plan. The e85 I would use is a race blend not from the pump as it is too inconsistent and not available around here. Buying race fuel causes a problem with the exhaust temps increasing vs the e85. I have decided that although I could do it with av and water meth injection, it is another system to fail and does make it more complex once you put in all the safeguards with it. Av gas works fine for our type of racing and is used in many classes already. In the end we only have two legs of our race that I would not have enough fuel for so I think I will build a removable reserve tank that will hold 20 gal or so that I can install for those legs and go with the e85.
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