E85 versus 100 octane

[Deep Six]

I'm curious about the performance difference in tuning for these two fuels. I would expect the cost of running race gas would be higher at $8 to $9 per gallon but in the overall scheme of things that isn't a lot in comparison to the total for a typical track weekend. E85 is really scarce for me while race gas is available local and at nearly every track as well. Really comes down to whether one has a distinct advantage over the other.

[SmsAlSuwaidi]

E85 has more octane than 100, provides more cooling and is way cheaper.

[G_Ride]

^ What he said. Out of convenience you might just want to stick with 100 octane. You'll also go through E85 faster than you would with 100 octane under similar driving conditions.

[carlossanchez89]

I am running E85 on my Full Blown FR-S and definately go through E85 faster than any other fuel I have ran. I spend less on the fuel but fuel more often thus more money. I get about 180 miles on a full tank. Usually pay 3.14 per gallon. I fill up in Arcadia and in Culver City. That is on 12 pounds of boost.

[Shiv@Openflash]

I've been running our soon-to-be-released e85 maps on our shop FRS (header only) and the improvement (over 100oct) are substantial. Although not as night and day as comparing it to 91oct. Where the extra octane/cooling really helps the engine is above 6000rpm where the engine can't run ideal ignition advance due to octane limitations. Take that away and the engine really does sing another (much happier) tune!

[whitefrs]

Originally Posted by shiv@vishnu

I've been running our soon-to-be-released e85 maps on our shop FRS (header only) and the improvement (over 100oct) are substantial. Although not as night and day as comparing it to 91oct. Where the extra octane/cooling really helps the engine is above 6000rpm where the engine can't run ideal ignition advance due to octane limitations. Take that away and the engine really does sing another (much happier) tune!

are u coming with an e85 FI soon??

[Shiv@Openflash]

Originally Posted by whitefrs

are u coming with an e85 FI soon??

Soon is a relative term I'm afraid. E85 map is essentially done. Our first FI maps are close to being done. I don't have a time frame for an E85 FI map. I suspect other users will beat me to it since it's still some time before we boost our shop car.

Shiv

[StormTrooper]

i am curious as to how 110 low lead would compare and how fast it would ruin an o2 sensor??

[fstlane]

Originally Posted by shiv@vishnu

E85 map is essentially done.

SEMA worthy news! Release the beast and I'll field test it in an autox on Saturday. Thanks for all the (free) updates!

[Dephective]

E85 is like 102-105 octane. Pure ethanol is 113 octane. These also provide a substantial cooling benefit inside the combustion chamber, which means not only greater timing advancement, but a denser fuel mixture.

100 octane is not only stupid expensive, it also lacks the cooling benefit that E85 provides.

[Shiv@Openflash]

Originally Posted by fstlane

SEMA worthy news! Release the beast and I'll field test it in an autox on Saturday. Thanks for all the (free) updates!

http://www.ft86club.com/forums/showthread.php?t=50707

[rice_classic]

Originally Posted by Dephective

E85 is like 102-105 octane. Pure ethanol is 113 octane. These also provide a substantial cooling benefit inside the combustion chamber, which means not only greater timing advancement, but a denser fuel mixture.

100 octane is not only stupid expensive, it also lacks the cooling benefit that E85 provides.

E85 achieves stoich at a much richer AFR than gasoline so you have to pump more fuel into the chamber. Between having a larger molecular oxygen content in the fuel and needing to stuff more into the combustion chamber 2 things occur, you have a cooler charge (that helps resist knock and det) and you've improved the volumetric efficiency of the combustion process.

Is that "better" than 100 or 110 octane? Well, maybe not better as it comes with a cost and that cost is burn rate. You have to consume a larger volume of fuel. So MPG is decreased. A street car that needs to fill up with a pump means the logical answer between 100octane and E85 is going to be E85. 100octane is usually $10/gallon and hard to find while 110 is ~$13-14/gallon.

If you're running an endurance race (like 24 hours of Daytona) in a race car on E85 then you're going to be expelling your load much quicker and will have to stop for fuel more often and in that scenario E85 is the clear loser. That endurance race team would want to be using a fuel that makes roughly the same power but requires them to stop for fuel less often. Cost of fuel is not an issue for these teams.

[Tekamul]

I've seen a few people talking about running E85 with advanced timing. Any concerns about fuel system life? Toyota/Subaru have said that the system isn't even designed to tolerate E15, never mind E85.

[arghx7]

Originally Posted by Tekamul

I've seen a few people talking about running E85 with advanced timing. Any concerns about fuel system life? Toyota/Subaru have said that the system isn't even designed to tolerate E15, never mind E85.

Of course there are concerns about fuel system life. A lot of the vendors promoting their E85 tunes *cough*Visconti*cough* just swept those aside. Lots of people are running E85 at least occasionally with no obvious detrimental effects, but these cars aren't even 2 years old yet. And if you put one tank a month in there, maybe it doesn't matter over the long haul. But nobody can be sure yet.

My position is: if you know there's a risk, maybe even a significant risk, of something going wrong later with the fuel system, go for it. But don't pretend that a risk doesn't exist, and don't try to convince others that a risk doesn't exist.