info on E 85 tune

[crowsnest]

Just wondering if anyone out there has a tune for E-85? I have a flex fuel f-150 and was thinking of getting a gryphon. I would think with the octane level (105 in some cases) being so high that you would get a lot more power out of a tune. Does anyone have a E-85 tune or did you all just get the 87, 91, and 93 tunes? Or does PHP even have a E-85 tune? I PMed groovey chick, but no response yet, probable lost in space. lol

[Jackpine]

They're really snowed under crowsnest. I don't really know if Bill has an E85 tune or not. It actually needs to be different than an E10 tune because in addition to the fact that timing can be advanced due to the higher octane rating, it burns properly at a richer air/fuel ratio than ordinary gas. (I seem to remember something like 9.8:1?) Maybe, the flex fuel vehicles automatically adjust for this, but I don't really know.

I don't have a vehicle that burns E85, so it's kind of a moot point for me.

- Jack

[crowsnest]

Thanks for the response. I was just curious about it. I would think more octane=more POWER. And everybody loves POWER.

[Sburn]

Originally Posted by crowsnest

Thanks for the response. I was just curious about it. I would think more octane=more POWER. And everybody loves POWER.

In general, that's true. But timing needs to be advanced to take advantage of the higher octane and make that extra HP.

[Jackpine]

Originally Posted by Sburn

In general, that's true. But timing needs to be advanced to take advantage of the higher octane and make that extra HP.

I'm going to quibble a bit here, and I'm not trying to put anyone down - just trying to shed some light on what I think can be a common misconception regarding high-octane fuel.

First, high-octane does not really mean "high power", "better fuel" "cleaner burning", "more efficient" or any of that. It is not "a treat for your engine", as I've heard someone say.

Higher octane refers simply to a fuel's resistance to "detonation" - an explosive burning that may be counterproductive. Back in the bad old days, we had really high compression engines, and these would compress the mixture so much that "standard" grade fuel would actually ignite under diesel compression - before the spark even fired (low octane gas is somewhat easier to ignite). So, if the mixture ignited as the piston was on it's way up, well short of Top Dead Center (TDC), the fuel expansion is working against the piston travel and you get "ping", reduced power, stress on the engine, and higher heat.

High octane kept the fuel from igniting until the spark commanded it, which, DOES occur slightly before TDC, but there is not an appreciable amount of expansion until the piston has passed TDC. And then, the burn is more controlled - instead of being too rapid, it expands at a rate that more nearly matches the piston's movement down the cylinder, giving a "controlled push".

We used to get high octane by adding lead compounds to the fuel, which had the added advantage of supplying some lubrication to the moving parts but the disadvantage of giving everyone lead poisoning.

We got rid of leaded fuels, and most engines had their compressions reduced - way, way down. Then, there were some advances that raised the "octane rating" of gas without adding lead (I think Amoco was a leader in this). So, manufacturers started raising the compression a bit in some engines to take advantage of this. (Higher compression DOES give higher power because there is more total expansion in the power stroke).

Now: Our f150 engines are designed to burn 87 octane gas. The spark is commanded to fire at a point where the burn will be controlled and will give an "even push" on the piston. If you put higher octane gas in it and don't adjust the spark, the burn starts too late! Remember, higher octane has a slower flame front advance rate. You would probably lose power if you did nothing but add the expensive gas, exactly as Sburn said!

So, using higher octane, we can advance the spark a bit - about 0.5 degrees for each octane point. The burn starts earlier, and it is expanding most rapidly as the piston is moving most rapidly (in the middle of the power stroke). You DO get more power with this gas now. With a programmer, the amount of fuel delivered (the A/F ratio) can be adjusted for even more power.

But, even though E85 has super high octane (anti detonation) properties, it has much less energy potential compared to ordinary gasoline (it's also highly corrosive). So, we can advance the spark, and even adjust the A/F ratio, but, we're not going to see as much total power output as we had using ordinary gas, so, we're going to see more fuel used for mile driven, simply because there is less energy available per gallon.

This is not to say that you can't design the engine from the ground up to use alcohol instead of gasoline. And if the engine is properly designed, it can outperform a street vehicle. Race cars do this all the time. They also burn a lot of fuel.

Now, I've probably said a few things incorrectly here, and I'm happy to have anyone "clean up" anything I got wrong.

- Jack

[buschris]

I'm curious about this too, since we have E85 for just at a dollar a gallon

[soutthpaw]

Jack,
Ya beat me to it as usual.. but you are correct about octane ratings. it is purely for preventing pre-detonation of the fuel. END OF STORY! it doesn't do anything else. Here is Colorado our regular gas is 85 not 87 octane but can be used as 87 becase when you are a mile or more high in altitude the oxygen in the air is less so that is a natural inhibitor of combustion.. E85 requires about 15 to 20% more fuel to go the same distance or produce the same power. and thus you will see your E85 mpg drop by 15 to 20 % so unless the gas is more than 15% to 20% Less expensive that regular gas you are not saving anything... locally to me its only about 20 to 40 cents a gallon cheaper than regular gas

[Jackpine]

Thank you southpaw - nice addition from you to the octane and E85 story too!

- Jack

[Sburn]

Here's a link for nationwide and state-by-state percentage spread in prices between gas and E85:

http://e85prices.com/


Nationwide, there's an overall 12% difference right now. A few states have as much as a 16% difference and some (AZ, UT), show E85 is more expensive than gas.


I'll save my opinions about E85 for another forum section...

[Jackpine]

Good link, Sburn! I have not noticed E85 for sale here in Tucson at all. I KNOW what my opinion of E85 is (and it's not good - I ranted on it in a couple of other threads, here, and on f150Online).

I'll be interested to see your opinion!

- Jack