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Flexable Fuel?.. I bet this is a new one

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Posted by: NGE---------------------

Here in MN we have some gas stations that offer fuel for "Flexable Fuel Vehicles"... This fuel is 85% Ethanol. It specifically says on the pump and nozzle "For Flexable Fuel Vehicles Only!", I put it in my truck anyways by accident (can't read, LOL). But it works just fine, and costs more than 20% less.

My Questions are these.

Can Flexable Fule be used in a 2-stroke effectively?
Would regular 2-stroke oil mix well with Flexable Fuel?
Does this stuff store well?
Would there be a performance difference?

I can recall, as a kid, running out of gas at a freinds house on my KX125. I lived out in the country so getting home was going to be a long push.

My freinds dad suggested that I take a little fuel oil from his heating tank and run it to get me home.

I tried it and it worked!!... it ran like a dog, but it got me home... and I ran it from there on out whenever I had no fuel and needed the transpo... I didn't bother with the 2-stroke oil, being as it was oil already. But it seemed to do no damage to the motor, and the plugs never even fouled from it.

This makes me think back to high-school, when my small engines teacher taught us that a 2-stroke will run on just about anything. And how it was that the original Dielsel motor ran on vegetable oil.

What are the fuel alternatives for my KDX200?.... I don't mind sacraficing a LITTLE bit of performance if it means I can save money AND help out with the emmisions issues in the world.

Thanks for your input


Posted by: KelvinKDX---------------------

Will this or other fuels work in your KDX - Yes - most likely as long as they will combust in your chamber under spark.  Would i use fuels such as this or other - no.

If a fuel is used that does not burn as efficiently then more of it goes out to atmosphere and to waste.  Power and performance charisteristics to boot.

Do your wallet and the enviroment a favor and use fuesl that are meant to be used in your bike (such as high grade pump).  Using alternatives to get you by so that you are not stranded is not a bad thing.  Realize that you may have a carburator clean-up job an your hands afterwards.

I expect that well hear from Rich on this subject.


Posted by: rv6junkie---------------------

85% Ethanol does cost less, but it contains less BTU's than straight pump gas. It actually cost more to run 85E.

Rich Rohrich is the zen master on fuel. I'm sure he'll chime in soon...


Posted by: Rich Rohrich---------------------

Quote:
Originally posted by NGE
My Questions are these.

Can Flexable Fule be used in a 2-stroke effectively?


Not without major mods to the carb and jetting. The air/fuel ratio of alcohol is dramatically different so you need a much greater volume of fuel for the same amount of air being ingested by the engine. So the fuel passages from the tank to the float bowl usually have to be larger and the jetting has to be MUCH richer across the board.

Quote:
Originally posted by NGE

Would regular 2-stroke oil mix well with Flexable Fuel?


A lot of two-stroke oils have real problems with alcohol so it would require testing the fuel and oil mix in a clear glass container and checking for seperation over a period of time.

Quote:
Originally posted by NGE

Does this stuff store well?


NOPE. Alcohol has the unfortunate habit of drawing moisture from the atmosphere. The more alcohol in the fuel , the more water it will eventually have mixed in.

Quote:
Originally posted by NGE

Would there be a performance difference?


You could actually make more overall power with this fuel if you were willing to make a lot of significant changes to the engine, but you would trade off throttle response and ease of starting for that power. A bad trade off in my book.

It's not a pour and ride type of fuel, and it isn't really the best choice for engines that see big throttle transitions and big rpm swings like dirtbikes do.

I hope this helps.


Posted by: John Harris---------------------

Biggest problem with ethanol in off road fuels is its attraction for water. Water does not burn well in an internal combustion engine. More importantly, oil (as in lubrication in the fuel for a two stroke) does not mix with water, hense you are in great danger of wasting an engine. Do not do this to your off road two stroke!!!


Posted by: NGE---------------------

Quote:
Originally posted by Rich Rohrich
You could actually make more overall power with this fuel if you were willing to make a lot of significant changes to the engine.


Thats what I thought actually. Because a lower octane rating is actually more combustible. All the top fuel dragsters run on alchohol. Doesn't that kind of stand in the face of your comment about it not being good for large throttle changes?

I can certainly see why it wouldn't store well now and, as I suspected, mixing with 2-stroke oil is a questionable endevor.

Thank you for the informative input. It struck me as a viable question and I knew I would get a thoughtfull response here. I am not disappointed in the least (even though I can't be a cheapskate with fuel and act like I'm doing it for the environment... *sigh)


Posted by: rv6junkie---------------------

Quote:
Originally posted by NGE
All the top fuel dragsters run on alchohol. Doesn't that kind of stand in the face of your comment about it not being good for large throttle changes? 


Top Fuel racers use one throttle setting: WOT. A MX rider changes the throttle setting every second or so.n Additionally, our races last a lot longer than 5 seconds.


Posted by: Rich Rohrich---------------------

Quote:
Originally posted by NGE
Thats what I thought actually. Because a lower octane rating is actually more combustible.


The "combustibility" of a fuel and the octane rating has little to no bearing on one another. Octane rating measures a chemistry characteristic that is very different from the basic ability to light the fire. Auto-ignition (ignition from temp and/or pressure) is the basic characteristic that octane represents.

The reason Ethanol is tough to light off has to do with its Volatility. Ethanol has single point of evaporation; where as most standard gasoline is made up of hundreds of different components that evaporate from temperatures well below 90 F to temps above 400F. The tendency of a fuel to evaporate {to change from a liquid to a gas state} is one of the most fundamentally important qualities of fuel in carbureted engines because it has a major influence on the vapor-air ratio in the cylinders at the time of ignition. The greater (higher) the volatility of a fuel the greater the tendency to evaporate. In a normal engine nearly all the fuel needs to be evaporated before ignition. So for any Engine/Air Temperature combination there is a minimum volatility that is required for proper throttle response and high speed running.

Gasoline is normally designed with a specific vaporization curve (or volatility curve) to match the running conditions of the engine that looks something like this:

10% Evaporation 157
50% Evaporation 205
90% Evaporation 217
End point Evaporation 230

The point of all this? 85% of E85 evaporates at the same temperature (172 F), the other 15% of the fuel is there to try and lower the front end vaporization temperatures to help spread the curve out a bit and make it easier to start when cold. What makes ethanol (and methanol) tricky is it's Latent Heat of Vaporization. or the heat absorbed when it changes phase from liquid to vapor. Even though the temperature of 172F doesn't seem all that high the amount of heat required to make that phase change to vapor absorbs an enourmous amount of heat from the surrounding surfaces and cools them down to the point that 172F may be hard to achieve. Causing the some of the ethanol to stay in the liquid form all the way through the combustion cycle. It's not uncommon to see carburated engine running alcohol to freeze oiver form this effect.

All this is part of the value of alcohol as a fuel. This cooling effect lowers intake temps and increases air density to the engine giving the same basic effects as supercharging. It just comes at a cost in terms of dealing with the rather bizzare after effects of all this physics and chemoistry fun.

In a carburated engine it just doesn't work and it leaves a big hole in the distillation curve that makes throttle response non-existent. Tuners call this the "alcohol flat spot"

As long as we've wandered down this road we might as well go all the way and cover one last ethanol related point.

As folks have previously mentioned alcohol attracts water and forms what is called an azeotrope. Once the water and ethanol join in this way you can't isolate ethanol without using some sort of drying agent that can soak up the water.

All the above points hold true for ethanol added to standard pump fuels even when the percentage is lower (in the 10-20% ethanol range), they just occur to a lesser degree.

Just one more reason why a controlled consistent fuel supply like race fuel can pay dividends in terms of response and jetting consistency even in a bone stock engine. You can't burn fuel that you can't evaporate, and with fuel components that need 300F + temps to vaporize you'll routinely find lots of unburned fuel dripping out of your silencer when you have to run pump fuel.

Just a little fuel for thought, so to speak.


Posted by: gwcrim---------------------

Quote:
All the top fuel dragsters run on alchohol.


Sorry. Top Fuel dragsters (T/F) all run nitromethane and a blower. Most TA/D cars run alcohol and a blower. Some run injectors and nitromethane. Nothing like giving up a blower and still being competitive!

And as was said earlier, all dragsters run at idle or WFO. There's only one BIG throttle transition and then the race is over.


Posted by: CMcCarthy---------------------

Quote:
Originally posted by gwcrim


Sorry. Top Fuel dragsters (T/F) all run nitromethane and a blower. Most TA/D cars run alcohol and a blower. Some run injectors and nitromethane. Nothing like giving up a blower and still being competitive!

And as was said earlier, all dragsters run at idle or WFO. There's only one BIG throttle transition and then the race is over.


Agreed. By mentioning TF cars and dirtbikes in the same conversation, you're comparing apples to spaghetti. Sure, you can eat em both, but thats where the similarity stops.

TF cars run 90% nitromethane, and would run over 99% if the rules didn't require the 10% methanol to tone them down. Also, as has been mentioned, the large throttle changes they experience are flooring the gas, and releasing it 4.5 seconds later. Ever notice how they tend to kick all the rods out if you "pedal" the throttle during a run? See Rich's comments for why that happens.


Posted by: boymess---------------------

One other consideration against high levels of ethanol - even though I'm a farmer who loves to see it used in autos - it can have the effect of making main seals brittle and could lead to air leaks. I've experimented with various forms of alcohol fuels in two stroke powered micro-midgets. Pure alcohol will make the little things run like a striped you know what, but consumption goes way up - double. Jetting is done mostly with drill bits!



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