Fuel mixing

[John Dempsey]

I personally wanted to run 94 octane in my car on cobbs aggressive map, but you can\'t get 93 or 94 at the pump in CA. I spent a while figuring out the math mixing 91 octane with 100 octane and thought I would share it. For 94 octane you need 9.33 gallons 100 and 4.67 gallons 91. For 93 octane you need 3.11 gallons 100 and 10.09 gallons 91.

[DriveHard]

Boy am i happy i can get 93/94 almost anywhere...

That would suck to have to blow 30 to 40 bucks on the 3 or 4 gallons of 100oct JUST to get to 93/94 respectively !!!

jeeze thinking about it.. i went thru 19.3 gallons of fuel at my last Time Trial day ( 147 miles of actual track laps @ a whopping 7.6 MPG !!!!)

it was about 4.10 a gallon for 93 + the full tank to get to the track, and the 3/4 tank to get back ......


why did you just make me calculate what i spent in GAS at the track last time out ... approx $193.00

[John Dempsey]

Haha. My apologies. It is a pain but at least I can run the aggressive maps now and I thought I would save some people the effort on the math side of things.

[chowbox]

Ya I'm very glad i don't live in the peoples republic of Kalifornia. Our smog program was dismantled because after studies it proved it didn't do crap. And to top it off I work for a very large oil company with all the 93 octane I can burn for free as one of my perks.

[Turbolader]

There is a common misconception why the western states don't have 93 octane. While it is true that (all) the ACN formulations were developed with SMOG in mind, the octane level is actually a function of demand.

The western states have a much higher percentage of consumers running cars that require "premium" fuel and thus, to make all of this fuel, they purposely dilute the octane to 91 (to make more of it). In other parts of the US, the refineries can "afford" to provide 93/94 octane because the demand for premium is lower because a higher percentage of consumers use non-premium fuel.

http://www.modified.com/editors/tech...hno/index.html

Make sure you're running unleaded race gas if your making your own 93 octane. Not that I think it is a good ideal with the n54/n55 already shaky fuel system, but some guys mix in some toluene to add octane.

[swaite]

Anybody mix E85 with regular/premium? I've heard of E85 being anywhere from 94-113 octane, with no definite answer. I tried mixing a few gallons with 91 and saw minimal, if any increase in power, but a noticable increase in fuel comsuption.

[Turbolader]

Sorry this is so long....

The true octane rating of E85 is about 95 ((ROM+MON)/2). (See Page 29 in the pdf below)

http://ethanolrfa.3cdn.net/dd9e74ce1..._rbm6bdgh3.pdf

The energy density of E85 is substantially less than that of gasoline:

E10 (What most states burn) - 33.18 MJ/L
E85 - 25.65 MJ/L

This is why the consumption goes up. Aside from the corrosive issues related to E85, there is another problem. The stoich for gasoline (100% -- not sure how much the 10% ethanol changes it) is 14.7. Stoich for pure E85 is right around 9.7. Because of this, and because the ECU thinks you're always running pure gasohol (e10), it's not going to adjust for the difference in stoich, so you will run lean, even though the ECU thinks you're running fine right at gasoline stoich.

(I surmise that your ECU detected lots of pinging because of the lean condition and therefore added some ms to each injection cycle and ran "rich" which would explain your gas mileage decrease. The people that really know the MDS80/81 would know for sure if there is logic to protect for lean condition by running overly rich.)

I know of some people that ran various mixes of e85 not for more power, but for the cleaning ability (both of the fuel system and at tailpipe emissions). I do not know which state you live in, however there is a good chance it is a violation of state law (might even be a federal law because of the EPA?) to mix anything into gasoline (With exception to additives marketed/tested/approved for the use)

If you have a race-only vehicle that is no longer under emission laws, and if you have upgraded your fuel system (injectors & pump) as well as tuned in the new injector constants & lambda values, then yeah I would run E85 all the way...It can make substantially more power for quite a bit cheaper than race gas.

If you have a street car, then I wouldn't run it.