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Brad Cox’s home brew race gas: Disclaimer: This is an interview only and is meant just for informational purposes. Please don’t attempt this if you don’t know what you are doing:
HONDAPITSTOP: What kind of gas do you use to race in your Honda Civic HB turbo?
BRAD: I've had great success with Toluene. Sometimes you can find it in 5
gallon cans for like $3 - $4 a gallon. Typically though, you can find it at any paint store in 1 gallon cans for about $8. I mix mine in a 1:4 ratio with 93 unleaded. If I recall, the octane rating
for Toluene is around 114, so the 1:4 ratio gives me about 97 octane. I like Toluene better than Xylene because I don't have to worry about adding some sort of lubricant to it. I dump it in a 2 gallon gas
can that's partly full of 93 octane gas, then shake it up and let it sit over night to mix thoroughly. If you just dump it in the gas tank, it may not mix well.
HONDAPITSTOP: What do you mean by partly full 2 gallon can of gas? Can you be more specific?
BRAD: At this point it doesn't really matter how much gas is in the can with the toluene (btw, I think the proper spelling is BOTH tolulene and toluene :\ ). The goal at this point is just to get the toluene in "solution" with some gas. That way it's guaranteed to mix well with the remaining gas in your tank when you dump it into the car. What I'm shooting for is 1 part toluene to 4 parts gasoline. I like to run my tank fairly close to empty during competition, so I'm guessing there is about 1 gallon in there prior to adding the gas can with the toluene. The gas can contains a half gallon of toluene and 1 to 1.5 gallons of gas. That gives me a fairly rough 1:4 ratio with 2 - 2.5 gallons total fuel in my tank. Enough to eliminate fuel starvation problems and get me through the event. 2.5 gallons probably wouldn't get Kevin's Muscle-stang through one run... had to get a poke in there somewhere. ;-) Since my primary goal is just detonation resistance and not max power, I don't have to be super careful. My car already does fine on 93 octane, but I like the extra insurance when I'm spending a lot of time in rev limiter territory.
HONDAPITSTOP: Do you use your home brew on the streets?
BRAD: I use it exclusively at autocross events, and primarily for increased detonation resistance. Plus, it's hard to describe, but my motor is really "happy" with it. I wouldn't say it's specifically stronger though. It's weird...
HONDAPITSTOP: Is Toluene lead free?
BRAD: Yep. It burns very clean and it won't mess up your o2 sensor... at least not at the ratio I'm running. I have no idea what would happen if you tried a 50/50 mix or something. I guessing most cars would run like crap in those circumstances, but the burn would be so slow it would probably make your EGT's skyrocket. Then you might actually burn up the o2 sensor I suppose...
HONDAPITSTOP: When you go to an autocross event do you drain your gas tank before you fill it up with your home brew or do you just try to run the tank low before an event?
BRAD: I like to run my tank down to about 2 gallons, then dump in the appropriate amount of "brew" to get the octane up a decent bit. Honestly, I'm not too worried about getting it exact because anything between 94 and 98 will pretty much be fine. But I like to get it in the neighborhood of 97. For most cars, fuel starvation determines how much gas they can run in a tank. Dan's old Talon was the worst. Run less than 3/4 tank and somehow the fuel intake would suck in air. My Honda is fantastic about it. I can run right on the red mark without problems.
HONDAPITSTOP: Would you use your mixture in a NA car?
BRAD: For a NA motor I wouldn't bother. In fact, it's hard to even make a case for using 93 octane on your
average NA motor. Other than maybe an ITR or something, most Honda motors just aren't tuned for it. So, higher octane fuel usually ends up hurting power and not just your wallet. ;-) However, boosted
motors love it. Bring on the octane!
HONDAPITSTOP: How about on a H22A N/A
engine with adjustable cam gears. Would you say there might be a benefit to using 93 pump gas or race gas if it was dyno tuned to the higher octane?
BRAD: It's dependant on so many factors... compression ratio, cam timing, ignition timing, valve grind, combustion chamber size/shape, etc. With the adjustable cam gears, you could run more aggressive timing with higher octane. It would make for an interesting experiment though. Carry some toluene to your next dyno session and dump it in after several baseline pulls then tune from there to see if you can get an increase. That would make for some good info!
End of interview.
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