Yup, the alcohol burns slower and cooler yielding more HP as it has a longer burn to push the piston down... Costs you quite a bit in fuel mileage..


Doc

 

I'm sure glad you posted this. I was convinced that one of the two stations near me had consistently higher knock, but thought it must all be in my head.

 

That does not make sense. Quicker burn makes more power because you reach MBT in a shorter period of time with less ignition advance. And alcohol does not burn slower than reg gas. Maybe slower than some VP import or some other designer race fuel, that's made to burn as quickly as possible.

 

I may be wrong, but this is the way it was described to me years ago when we ran Sprint cars. The alcohol burns slower and cooler... Cooler allowed us to run small radiators and no cooling fans.. made sense to me... Slower burn created more HP as it actually pushed the piston down the cylinder for a longer period of time creating more HP than gasoline, similar to a diesel engine...

I will check more into this. I had lunch last month with a Racing Fuel salesman and I'd swear he pretty much said the same thing.

Now yesterday, I put a load of Racing Fuel in my MotorCycle which calls for 93 octane from the factory. I should have thought to check oil temp to see if there was a difference but by leg thermostat, it seemed a bit cooler. But some of the diffs that were noticeable.... Smoother running, quieter exhaust tone and seemed to have a little more power along with there looking like a fuel mileage increase.

The quieter exhaust... maybe a mellower sound would describe it but definitely didn't "pound" as much..could actually hear the Stereo better... and I seem to have less backfire on decel.

But, at $2.00 more per gallon, is it worth it on a Street Bike?

Doc

 

The higher the octane number the slower the burn. The slower burn allows you to advance timing increasing MBT. When you advance timing you increase the pressure in the cylinder sooner causing more force on the piston creating more TQ.

 

E85 definitely does not love gobbs of timing though. My way of reconciling the high octane number of E85 is that I now think of octane number as resistance to detonation and not necessarily speed of burn.

 

for e85 what should your closed loop afr be? still 14.7? on wot what should my afr be during spool up and later? considering im using a gasoline wideband.

 

A Mobil engineer I talked to said that the higher the octane, the slower the burn..


Doc

 

I would really like to get one of those ethanol content meters so that i could determine the quality from one pump to the next. I just cant justify spending a few hundred for the gm sensor, then another couple hundred for a display... Might have to wait for a big commission check later this year....

 

I agree. I have about 5 more degrees of timing (cannot specify the RPM range) with E-85 than I did with 91 octane. From what I've read you can run more with C16. However, I much prefer to pay $3.49/gal vs ~$10/gal.

 

"higher octane burns slower" argument may be true between 87 and 100 octane regular fuels. But that's not a good thing. Race fuels are made to burn faster in order to make more power. The reason for that is that a faster burn requires less timing. There is only one goal when it comes to making cylinder pressure - achieve it around 14* ATDC. That is all. The highest pressure is when the burn is complete, that's what pushes the piston -- high cylinder pressure, not the slow burn....
And the lesser timing advance you need to get the complete burn as close as possible to that sweet spot - the smaller the chance to have detonation. And with less timing advance you also reduce the time that the piston spends fighting the expanding mixture on its compression stroke, wasting energy.

Pretty simple concept.

 

I'm moving to PA soon and thanks to the information listed on these forums I found out there will be an E85 station near me. I would love to configure my X to use that kind of fuel but I can't seem to find any others that have done so. Do you guys know if any X's have already been sucessfully converted? Or anyone who is familiar very familiar tuning cars for this conversion?

 

Tuning for E85 on the X should not be that difficult. The hard part is finding injectors/fuel pump that will work properly...

 

Just filled up for the 2nd time since converting to the dark side--10.66 mpg! Boost > *

 

just finished a 599 mile trip. Averaged 17.4mpg. Had to take 24 gallons with me as i wasnt sure i was going to find the crack juice on the trip.