What's Involved In an Ethanol Conversion?

May 8, 2008 10:13 PM

What are the differences between vehicles that are ethanol (e85+) compatible and those that are not?

I'm looking for specific materials and design differences in the various fuel system parts. Fuel pump, injector(s), fuel lines, tanks, PCM curves, ect. This is with an eye toward conversions of older fuel injected vehicles.

posted by IronLizard to travel & transportation (14 comments total)

I have not done this conversion, but I've read a little. At the very least, PCM programming is different. Ethanol has a higher octane than regular pump gas and burns cooler and cleaner. You may need to upgrade your fuel pump as you will be comsuming 30% more fuel than usual.

There are some musclecar/tuner enthusiasts converting their cars over and getting instant ~10% horsepower gains as a result. Here's what looks like a reasonable introduction: ls1.com - How to run your LS1 on E85.
posted by zippy at 10:22 PM on May 8, 2008

I know the fuel injector O-rings are from a different quality of plastic that are not eaten away by the more corrosive nature of E85. I don't know about any other parts though. I would assume the fuel lines and anything dealing with fuel delivery would be the same.
posted by SeanMac at 10:24 PM on May 8, 2008

E85 eats through regular rubber hoses and seals so the fuel system would probably need these items replaced. Also because of the increase in fuel consumption you may need larger injectors depending on how close to the limit the stock injectors are running.
posted by Mitheral at 10:29 PM on May 8, 2008

In addition to the corrosive issues, E85 means that it's 85% ethanol, and isn't the octane rating. The octane rating of E85 is around 100-105 according to Wikipedia -- that's a pretty big difference from octane 87.

Successfully converting an engine designed to chew on regular gas into E85 requires at least consideration of the cylinder timing in addition to the fuel injectors, fuel lines, etc.

One thing to consider is that if the engine is supercharged, you may need to adjust the supercharger's boost -- Koenigsegg had to for its monstrosity.
posted by spiderskull at 12:22 AM on May 9, 2008

Sorry, meant fuel injectors, not fuel pump, in my response.
posted by zippy at 12:43 AM on May 9, 2008

There is an extra sensor in the fuel system that tells the ECU how much ethanol is present in the fuel. Without this extra sensor the vehicle would be limited to running E85 exclusively. It would never be able to run on plain gasoline. The resulting air/fuel ratios would be so rish that the engine would possibly not run at all. Even if it did, all that extra gasoline going through the engine and exhaust would pretty quickly cause damage.
posted by eratus at 4:21 AM on May 9, 2008

Wrong, wrong, and wrong. Also, wrong.

The difference between a flexfuel car and one that's not is a sensor within the fuel system that tells the computer to delay timing.

Ethanol is more explosive but contains significantly less power (thus the higher octane but lower performance). Therefore, with ethanol (much like BioDiesel), efficient burning requires retarding the timing by up to 5 degrees. The difference here is that FlexFuel cars running E85 are MORE LIKELY to get BETTER better mileage, and by "better", I mean "about 90-92% as much as on gasoline MAX."

Any car will run E85. The difference is that your car explodes it too fast and therefore loses a great deal of the propulsion generated by the explosion. I.E. you'll get crap mileage, about 75-80% of normal.

Ethanol doesn't eat fuel lines, and fuel lines have been synthetic rubber for a long, long time now anyway. Seriously any car from about 1995 on (more like 1985) will run E85 fine, you'll just get poor mileage.

Also, don't fall victim to E85 hype. When cellulasic ethanol becomes a reality, I'll hop on that train. Currently, US Ethanol is NOT an "alternative green fuel". That's outside the corn argument---most of our ethanol is derived from petroleum. (And ethanol from corn is stupid too. Don't get me started.)
posted by TomMelee at 5:59 AM on May 9, 2008

Ethanol doesn't eat fuel lines, and fuel lines have been synthetic rubber for a long, long time now anyway. Seriously any car from about 1995 on (more like 1985) will run E85 fine, you'll just get poor mileage.

Do you have any documentation to this? The corrosive nature and eating away at my fuel systems is one of the first reasons not to use e85 in a normal car that I've heard from people who seem to know about this stuff.
posted by jmd82 at 6:21 AM on May 9, 2008

When cellulasic ethanol becomes a reality, I'll hop on that train.

Yeah, good luck with that.
posted by electroboy at 6:48 AM on May 9, 2008

TomMelee writes "Wrong, wrong, and wrong. Also, wrong.

"The difference between a flexfuel car and one that's not is a sensor within the fuel system that tells the computer to delay timing."

I'm not sure if this was directed at me and I can't speak to every manufacturer but here are some differences for Chryslers when they first started Flex Fuel Vehicles in 1993 on the Spirit/Acclaim:

• Piston rings were chrome-plated since methanol attacks the molybdenum-based material more commonly used for piston rings.
• Valve stem oil seals were methanol resistant.
• The intake manifold was adapted from the (now discontinued) 2.5 Turbo engine, to use multiple point fuel injection and make the FFV vehicles more powerful and probably more fuel-efficient out of the gate.
• Because of the toxicity of methanol, the filler tube included a spring to prevent siphoning.
• Filler tube to tank grommet.
• The fuel tank was two gallons larger and used high-density polyethylene (instead of steel), fluorinated to minimize evaporation through the tank.
• Fuel pump.
• Fuel level sending unit with external resistor element
• Stainless steel fuel lines.
• Teflon fuel line connectors with braided stainless steel protective covers
• Stainless steel fuel filter housing

But hey, your probably right, all these stainless parts and external fuel sending units and teflon was probably just a big scam to get more money out of fleet operators or something.

Lots of stuff needs to be changed once ethanol content gets over 10% or so.
posted by Mitheral at 7:33 AM on May 9, 2008

Sorry, shouldn't have been so stand-off-ish. First off, like I said---there's no natural rubber in a car made since 95. Ethanol isn't so much corrosive as it is an embrittler, thus non-porous materials are generally the way to go w/ alcohol based fuels.

And you're right, my bad. Running nothing but E85 will potentially require engine modification. However, realistically, in the new FlexFuel vehicles the only *fleet* difference is the chip. There's not a separate trim line or anything.

There are waaay too many people running E50 without engine modification on late model cars. Anyway mithereal, I know you're a car guy because we've talked before. Look at your list and tell me what on it isn't fleet standard since the mid-90's?

Ethanol's not toxic, Methanol is. Ethanol is what you drink. An anti-syphoning mechanism just so people don't drink your fuel is funny. There is, of course, methanol IN lab-grade ethanol/e85, but to say ethanol is toxic is a misnomer.
posted by TomMelee at 9:48 AM on May 9, 2008

Methanol =/= ethanol. The former is much more corrosive, while the latter isn't too much to worry about; at least that's what I've gleaned so far. I think a conversion to methanol would be much more involved.

in the new FlexFuel vehicles the only *fleet* difference is the chip. There's not a separate trim line or anything.
That's because they were engineered beforehand to expect that sort of fuel; naturally, the most simply switching mechanism is through the ECU. With an engine that isn't expecting that type of fuel, you obviously need to make modifications.
posted by spiderskull at 9:54 AM on May 9, 2008

The main difference when running E85 is the air/fuel ratio, not the timing. Normal gasoline is burned at 14.7:1, where E85 will be closer to 10:1, so your fuel economy will be much worse with E85. Some systems have ethanol sensors, others do it in software by what the closed loop fuel trim learns. If your ECM or PCM isn't calibrated for flex fuel, you will probably set a fuel trim code and run lean, because the engine diagnostic software will think that your fuel system has a problem.
posted by rfs at 11:54 AM on May 9, 2008

Also, the fuel in many areas already has 10% ethanol in it, and has had for years. I'm sure the car manufacturers have already made any changes to their materials that were needed.

The difference is, as others have stated, in injector size and computer programming. Both of which cost more, and that's why it's not getting rolled out for what amounts to a tiny market share.

I recently put e85 in my non-flex car, and it ran just fine. Only problem is that I got a check-engine light for "long term fuel trim" because it had to over-adjust itself to get the right air-fuel mixture.
posted by gjc at 11:28 AM on May 10, 2008