4 replies to this topic

[Jim Drago]

Several people a year ask me about mixing E85 with pump gas. The questions are always how much power does it make and is it legal. It does make a little power if mixed and tuned correctly but it is just as illegal as running ERC or other non compliant fuels.

 

This started with one of my favorite "Krazy" Texan in 06 or so and has never really went away. Apparently the popularity is again on the rise as the calls of what "others" or "I heard so and so is doing X,Y and Z" are increasing and now coming from areas far outside of Texas. I have heard of competitors mixing E85 with gas in the expected 4:1 or 5:1 blends all the way to 50/50 mixes(crazy).

 

A few facts..

The current fuel rules are listed on page 99 on the September GCR on SCCA.com

 

We are allowed a maximum of 10% ethanol by the rules and a DC of 166 or less.

 

If any mixture of fuel contains over 10% ethanol you are non compliant. You need substantially more ethanol( and proper tuning) to see any gains in HP. If your fuel contains 10.1 % ethanol it is easily detected in the GC test. If your fuel contains 12% ethanol or more, it will fail the DC test ( the normal fuel testing at the track) The HP gain between 10% ethanol or 12% is not detectable.

 

The max allowable DC in the GCR is 166.

The DC in pump gas is about 125, high is about 135. The DC of E85 is 1100. So while mixing of fuels may not be an exact average with regards to the DC. It is very easy to determine the fuel is non compliant as your DC will be well over 166. 4:1 and even 5:1 mixes will fail even track side tests miserably as the DC will be 300+.

 

Many feel that this mixing is legal, it is NOT. Many feel it can be not be detected at the track less a $250 fuel protest, not true! It can easily be protested on DC alone or caught in post race fuel test. A mix of any ethanol and fuel that is more than 12% ethanol will be caught on the most basic fuel tests, consider this fair warning.

I will forward this along to majors committee to insure we do some more fuel testing during the year as this has apparently become an issue in 2013 in SM and SRF, or so I am told and was otherwise unaware. 

[davew]

I 100% agree with what Jim said.

 

I used straight pump gas from the local Mobil station. 89 octane midgrade. No more than 10% ethenaol as stated on the pump.  tested at 158 this spring. May be because we have "winter and summer blends" as mandated by EPA. Same stuff from the Road America Citgo tested at 145 a week later.

 

I played with some exotic fuels this summer on the dyno. Nothing that was close to legal made enough difference to be worth the expense or effort.

 

Tune with pump gas, dyno with pump gas, race with pump gas.

 

Dave

[Todd Tagget]

So we use 91 here on the left coast.. I assume the east coasters are running 93 ?  is there much if any advantage of 87 vs 89 vs 91 or 93 ? Anyone done any dyno work on this / 

[Jim Drago]

So we use 91 here on the left coast.. I assume the east coasters are running 93 ?  is there much if any advantage of 87 vs 89 vs 91 or 93 ? Anyone done any dyno work on this / 

 

 

If you ask 10 different people, you will likely get 10 different answers. 

From all you mentioned above, the difference in HP is probably determined more by which 87,91,93 you have, how fresh it is and whether or not it is 10% ethanol  than the actual octane rating of teh fuel.  Some fuels contain ethanol, some don't, concerntrations vary.  Tuned properly, I doubt you see 1 hp between any of them from top to bottom. 

[davew]

Octane rating has nothing to do with performance ability. It is about anti knock/ping that is common in higher compression engines.

 

Street fuel varies from region to region and month to much accross the country. I get to deal with winter, summer, wisconsin and Illinois versions. Which is why you get 10 different answers that are all correct.

 

This is another of those expenses that a multi car team/shop can amortize over many cars. I dynoed many octanes from many brands. I even brought home Road America fuel to test versus Blackhawk fuel. I then passed that info to all my cars.

 

Dave