The E85 Mystery

Jordo! · 06-19-2014, 03:45 PM

Quote:

Originally Posted by TopgunZ

Ill admit that the more power your making, in every revolution, the motor weakens. Rods, pistons, rings, everything.

However, you can make that power with less chance of it letting go due to predet. Also you can stretch out the lifetime of that motor if you are running less boost by using more timing, which is safer to do with E.

If quenching hotspots are the only issue, then, yes, that follows.

Also, if E85 has a lower stoichiometric ratio than regular petrol I believe that translates into more potential energy (i.e., combustion pressure) to get out of it, so that could be contributing too.

I have no idea what the actual mechanical tolerances are on a stock VQ37HR longblock, tho...

Are there any confirmed breaks from overpower as opposed to detonation?

Nixlimited · 06-19-2014, 04:38 PM

Quote:

Originally Posted by Jordo!

Also, if E85 has a lower stoichiometric ratio than regular petrol I believe that translates into more potential energy (i.e., combustion pressure) to get out of it, so that could be contributing too.

Ethanol has significantly less potential energy than gasoline. That's why it takes significantly more of it (think huge injectors) to make lots of power. But it's excellent for knock resistance.

Per Wiki: Gasoline has 114K BTU/gal to Ethanol's 76K/gal.

Jordo! · 06-20-2014, 03:31 AM

Quote:

Originally Posted by Nixlimited

Ethanol has significantly less potential energy than gasoline. That's why it takes significantly more of it (think huge injectors) to make lots of power. But it's excellent for knock resistance.

Per Wiki: Gasoline has 114K BTU/gal to Ethanol's 76K/gal.

I think the key value here is latent heat of vaporization vs. amount of fuel needed to achieve peak torque, which is a factor related to stoichiometry -- check out p. 117 on down at this link.

http://martysgarage.info/manuals/bell2ttuning.pdf

It's from A.G. Bell's book on fueling 2-stroke engines, but he has the exact same formulas/rationale in his 4-stroke supercharged tuning book.

Anyway, in theory, less efficient, but more energy ultimately produced as a consequence.

Now, if E85 ends up breaking about even, then it's just less efficient, but has a higher auto ignition threshold and higher octane, in which case never mind my other point

Nixlimited · 06-20-2014, 09:25 AM

Quote:

Originally Posted by Jordo!

I think the key value here is latent heat of vaporization vs. amount of fuel needed to achieve peak torque, which is a factor related to stoichiometry -- check out p. 117 on down at this link.

http://martysgarage.info/manuals/bell2ttuning.pdf

It's from A.G. Bell's book on fueling 2-stroke engines, but he has the exact same formulas/rationale in his 4-stroke supercharged tuning book.

Anyway, in theory, less efficient, but more energy ultimately produced as a consequence.

Now, if E85 ends up breaking about even, then it's just less efficient, but has a higher auto ignition threshold and higher octane, in which case never mind my other point

Those are great books BTW!

djtodd · 06-19-2014, 10:35 PM

Quote:

Originally Posted by Jordo!

Are there any confirmed breaks from overpower as opposed to detonation?

Not that I know of. I'm sure mine will go eventually. I flog the hell out of it at the track pretty regularly. And that's 600+ whp on stock internals. But of course that's one of the main reasons I went with e85.

I'm just treating it as an experiment at the point. How long can I beat on it at these power levels at the track before it fails? We'll see!

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