chris.olson
Petty Officer 2nd Class
- Joined
- Mar 15, 2009
- Messages
- 173
This is an old thread, which means the mods will likely trash it, or lock it, if anybody posts on it. So I’ll start a new one, even though it’s the same topic and the original poster never got an answer from anybody actually running E85 in a boat engine.
forums.iboats.com
The answer is yes, I have been running my Mercury four-cylinder two-stroke on E85 since late last summer. However, it required some significant engine modifications.
First of all, it does not harm gaskets because there is no gaskets. The cases are sealed with anaerobic sealer. It does not harm the case seals because those are lubricated by oil. When the fuel-oil mix goes into a two-stroke crankcase the gas (or ethanol) evaporates and leaves the oil behind, which is what lubricates bearings and seals. Either gasoline or alcohol is a solvent and it does not lubricate anything. You must, however, use a synthetic oil that is compatible with alcohol. E85/E98, methanol and nitromethane is very common in two-stroke racing engines and there's a lot of different brands you can use, so I'm not going to recommend one here.
The first problem you will run into with E85 is that ethanol requires higher temperatures and pressures to get it to ignite reliably and burn completely. This means higher compression ratios. I had custom Wiseco 13:1 dome pistons made for my engine, it was already .010 overbore. 13:1 is about perfect for E85 in a Hemi chamber. With E98/E100 or pure methanol you can go as high as 14.8:1. Wiseco will make custom forged pistons for anything, and it cost me almost $500 to get a set of pistons built. I was a little worried that the stock starter would not be able to turn it to get it started, but it turns out that it will.
Second issue is ignition timing. Ethanol has a research octane of 108, pump octane of 113, and it burns very slowly compared to either gasoline or diesel fuel. It's going to take more timing advance for ethanol, and a hemi combustion chamber works the best. Only way to tune your timing curve, and get it right, is on a dyno. Combustion chambers that are not true hemi are not going to work all that well and you’ll end up with “corners” in the combustion chamber where the flame front will never get to before the exhaust event.
The third problem is carbs. Modifying your carbs for alcohol is non-trivial. Without a flow bench, if you guess on drilling the passages and jets you'll either end up too rich or too lean, and alcohol is more susceptible to changes in air temp and humidity than gasoline is to get the mixture right. Your fuel system needs to be modified for a 9:1 air/fuel mixture at idle and mid-range, and 7:1 at full throttle. Stoichiometric for gasoline is 14.7:1, for E100 it’s 9:1. 9:1 works good for E85 and gives slight fuel enrichment that will provide at least 50% more than stock power in a high-compression engine.
Contrary to what people think, an engine designed for alcohol will NOT burn more fuel than a comparable gasoline engine. The key is thermal efficiency. A purpose-built alcohol engine, while it runs with a richer mixture is more thermally efficient than a comparable gasoline engine due to a phenomenon called latent heat of evaporation to get a phase change, and the fact that the fuel carries oxygen with it. It requires less throttle opening to get the same power as with gasoline, and at the same throttle opening the engine will make considerably more power on E85 than it can on even the best racing gasoline.Thermal efficiency trumps energy density in liquid-fueled piston engines every time.
I got my engine to run with modified carbs, but it's not quite ideal. It starts hard when cold because the carbs do not have accelerator pumps to "prime" the engine to get it to fire. I'm currently looking at putting some parts together to build a custom dual throttle body electronic fuel injection system for it. EFI has the ability to adjust to ambient conditions better than carbs can. One of the challenges with a marine two-stroke is keeping water out of the O2 sensor so it’s going to require an open-loop system that does not use an O2 sensor and just uses MAP to adjust fuel mixture.
There is several advantages to E85.
- more power - significantly more
- about the same fuel economy as gasoline in an engine designed for it
- cheaper than gasoline (in the midwest)
- water is not an issue - E85 can hold 2% by volume of pure water and it won't affect it in a carb or EFI system.
- Purpose-built alcohol engines have considerably higher combustion and exhaust temperatures than gasoline or diesel engines. They are able to drive turbochargers more efficiently. Yes, alcohol is a cool-burning fuel, but not in a high-compression engine designed for it. If you’re interested in such things, Cummins and John Deere have invested heavitly in E85/E98 diesels for the future.
www.agfax.com
Disclaimer Part:
The reason I did this is because I've been an engine builder, building alcohol engines for tractor and truck pulling, and stock and sprint car racing, for better than 40 years. I had never built a two-stroke alcohol engine, so decided to try it with my old Mercury outboard. I live in the midwest where we have a ready supply of E85 quite cheap (compared to today's gas prices). This is not a project for the average person unless you have access to help from a professional who is familiar with alcohol engines. You can get any old low-compression engine to run on E85, but it won't have the performance you expect and this is the problem with so-called "flex fuel" vehicles that can burn E85. They make them able to run on it, but not as efficiently as a purpose-built alcohol engine can.
anyone running E-85
so what are the drawbacks to running e85 94 octane fuel in the older hi compression motors, other than water absorbsion, and cooler running motor, all fuel line have new hoses
forums.iboats.com
The answer is yes, I have been running my Mercury four-cylinder two-stroke on E85 since late last summer. However, it required some significant engine modifications.
First of all, it does not harm gaskets because there is no gaskets. The cases are sealed with anaerobic sealer. It does not harm the case seals because those are lubricated by oil. When the fuel-oil mix goes into a two-stroke crankcase the gas (or ethanol) evaporates and leaves the oil behind, which is what lubricates bearings and seals. Either gasoline or alcohol is a solvent and it does not lubricate anything. You must, however, use a synthetic oil that is compatible with alcohol. E85/E98, methanol and nitromethane is very common in two-stroke racing engines and there's a lot of different brands you can use, so I'm not going to recommend one here.
The first problem you will run into with E85 is that ethanol requires higher temperatures and pressures to get it to ignite reliably and burn completely. This means higher compression ratios. I had custom Wiseco 13:1 dome pistons made for my engine, it was already .010 overbore. 13:1 is about perfect for E85 in a Hemi chamber. With E98/E100 or pure methanol you can go as high as 14.8:1. Wiseco will make custom forged pistons for anything, and it cost me almost $500 to get a set of pistons built. I was a little worried that the stock starter would not be able to turn it to get it started, but it turns out that it will.
Second issue is ignition timing. Ethanol has a research octane of 108, pump octane of 113, and it burns very slowly compared to either gasoline or diesel fuel. It's going to take more timing advance for ethanol, and a hemi combustion chamber works the best. Only way to tune your timing curve, and get it right, is on a dyno. Combustion chambers that are not true hemi are not going to work all that well and you’ll end up with “corners” in the combustion chamber where the flame front will never get to before the exhaust event.
The third problem is carbs. Modifying your carbs for alcohol is non-trivial. Without a flow bench, if you guess on drilling the passages and jets you'll either end up too rich or too lean, and alcohol is more susceptible to changes in air temp and humidity than gasoline is to get the mixture right. Your fuel system needs to be modified for a 9:1 air/fuel mixture at idle and mid-range, and 7:1 at full throttle. Stoichiometric for gasoline is 14.7:1, for E100 it’s 9:1. 9:1 works good for E85 and gives slight fuel enrichment that will provide at least 50% more than stock power in a high-compression engine.
Contrary to what people think, an engine designed for alcohol will NOT burn more fuel than a comparable gasoline engine. The key is thermal efficiency. A purpose-built alcohol engine, while it runs with a richer mixture is more thermally efficient than a comparable gasoline engine due to a phenomenon called latent heat of evaporation to get a phase change, and the fact that the fuel carries oxygen with it. It requires less throttle opening to get the same power as with gasoline, and at the same throttle opening the engine will make considerably more power on E85 than it can on even the best racing gasoline.Thermal efficiency trumps energy density in liquid-fueled piston engines every time.
I got my engine to run with modified carbs, but it's not quite ideal. It starts hard when cold because the carbs do not have accelerator pumps to "prime" the engine to get it to fire. I'm currently looking at putting some parts together to build a custom dual throttle body electronic fuel injection system for it. EFI has the ability to adjust to ambient conditions better than carbs can. One of the challenges with a marine two-stroke is keeping water out of the O2 sensor so it’s going to require an open-loop system that does not use an O2 sensor and just uses MAP to adjust fuel mixture.
There is several advantages to E85.
- more power - significantly more
- about the same fuel economy as gasoline in an engine designed for it
- cheaper than gasoline (in the midwest)
- water is not an issue - E85 can hold 2% by volume of pure water and it won't affect it in a carb or EFI system.
- Purpose-built alcohol engines have considerably higher combustion and exhaust temperatures than gasoline or diesel engines. They are able to drive turbochargers more efficiently. Yes, alcohol is a cool-burning fuel, but not in a high-compression engine designed for it. If you’re interested in such things, Cummins and John Deere have invested heavitly in E85/E98 diesels for the future.
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Disclaimer Part:
The reason I did this is because I've been an engine builder, building alcohol engines for tractor and truck pulling, and stock and sprint car racing, for better than 40 years. I had never built a two-stroke alcohol engine, so decided to try it with my old Mercury outboard. I live in the midwest where we have a ready supply of E85 quite cheap (compared to today's gas prices). This is not a project for the average person unless you have access to help from a professional who is familiar with alcohol engines. You can get any old low-compression engine to run on E85, but it won't have the performance you expect and this is the problem with so-called "flex fuel" vehicles that can burn E85. They make them able to run on it, but not as efficiently as a purpose-built alcohol engine can.