93 AKI fuel will be ~97 RON. A KZ2 will run on it just fine if it’s jetted one jet rich.
I found this RON to AKI conversion blog… interesting stuff.
http://www.pencilgeek.org/2009/05/octane-rating-conversions.html
I’ve got my last pail of VP fuel, then will switch over to Ultra 94 AKI, which meets the ROK’s RON requirements.
Thanks everyone for the informative discussion!
I run a KA100 motor and tried both pump gas and racing fuel. Initially, I ran racing fuel, then switched to a club that allowed pump gas, so I went to pump gas. After running pump gas for 6 or 8 races, my engine builder looked at my motor and he felt that it might be better to run racing gas. It does seem to run better but this all qualitative. The KA100 uses very little fuel per weekend maybe 2 gallons, so the cost is really not that much of the total cost of racing per weekend.
If you’re jetted right on racing gas, and switch to pump gas, you’ll be lean by about 3%. If you’re using American “93” premium, it’s 97-100 RON depending on state and station.
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He seemed to think the motor was running lean and had a touch more wear than usual. I think Charles may have a point about the motor running lean on pump gas, as my motor were dynoed on race fuel. I don’t the needles much at the track, so it might have been lean (although I use an EGT). I could have asked him to dyno the motor on pump gas but then I’d be one of the few out of the many motors that he builds. So, when we looked at what was being spent on fuel, it didn’t seem like it was worth the money pump gas saved vs venturing into the unknown.
Most of the racing fuels used in karting in the US contain lead. It definitely helps reduce wear as it acts as a dry lubricant for bearings, cylinder, piston etc. It’s also a neurotoxin, so there’s that too.
I should add that Sunoco 110 had a formulation change a little over a year ago that resulted in it being no longer recommended for two strokes. That information is buried on Facebook somewhere unfortunately.
What’s the basis of pump fuel vs race fuel jetting difference? Specific gravity or something else?
Energy content per gallon! Ethanol’s is smaller than gasoline. You need more flow for the same power output. On my X30, at the same EGT, the difference is 10-15 minutes on both jets.
So the ethanol is slower or you need more volume for same result as race fuel?
Ah, I’d assumed we’re talking about ethanol free pump blends because ethanol blends are such a can of worms.
Cautionary note for folks: If your track/series/club does not allow oxygenated fuels, you should avoid using pump gas that contains ethanol for racing. Ethanol is an oxygenate and will cause the test meter to read it as so.
Ethanol being faster is kinda complex…. It’s depends how much and if tbe engine is tuned to take advantage of it. Generally most spec packages won’t see an Improvement…. If built to the rules.
You need more volume for the same result as race fuel.
So with pump the usage is, let’s say 15% higher, which cuts down the cost difference a tiny bit. Gas in So Cal is $4/gal, add in the additional volumetric usage, that makes it about $4.50 a gallon. VP is around $75 for a can, which is $15/gallon. Savings is about $20/weekend.
Also running KA. The first half of the season I was mixing 110 race gas with 91 pump gas (highest non ethanol I can locally buy), thinking this averages to about 100. During a practice session I emptied the tank and ran straight 110 and on the clock an by seat of the pants the straight 110 felt faster, crisper and more powerful.
I find this concerning as that is the main fuel used at our track, which is all 2 strokes. Is this information on a Sunoco FB page or an individuals page?
It came up in the enduro road racers group on Facebook as it was the spec fuel at the time. I’ll see if I can find the details.
$20 plus the hour needed to pick up the can of racing fuel compared to just pulling up to the “premium” pump when refueling the tow car on the way to the track.
Ethanol’s improvement on RON is why it’s valuable, in addition to the roughly 1% additional power allowed by oxygenation. RON matters a lot more than MON on high speed engines - the MON test was devised to address problems with detonation in cars climbing steep grades in high gear, back in the days before synchromesh
E00 91 AKI fuel is usually 88 MON, 94 RON.
E10 91 AKI fuel is usually 87 MON, 95+ RON. This meets the X30’s requirement of 95 RON.
E10 93 AKI fuel is usually 87 MON, 100+ RON. This meets the KA100’s requirement of 98 RON.
Sunoco says their Ultra 93 is at least 88 MON, 98 RON, Beyond Octane - Sunoco Race Fuels
Italian engine manufacturers must think Americans like lead poisoning.
I know we have hashed the topic of led in race fuel before, but found this document on octane and lead. Interesting stuff…
You seem to have some experience running fuel with ethanol. I was always advised to not run it as it can gum up the carburetor and it would not pass a fuel test which my track does to check but has indicated it would or could. Assuming the E10 93 is allowed what are you seeing in your experience with carb issues or other issues?
If your track’s fuel requirement is non-oxygenated fuel, then street gas with ethanol will not pass it and you won’t be able to run it. You could of course get the rest of your class on board with getting the lead out of karting and agree to all run 93 E10 to give an identical reading in tech, or change the rule.
I start and idle the engine at the end of the day, disconnect the fuel line from the carburetor, and run it dry, choking the intake and shutting off the ignition when it goes lean and revs up. The only ethanol-related problem I’ve had occurred when I borrowed someone else’s kart who hadn’t done that, and found the jets clogged and the floats fuzzy with green residue. Tillotson gaskets & diaphragms last as long as a piston for me.
My TaGs have been fine on E10 93 - actually, they’ve been a lot less trouble than the engines I ran on racing fuel.
The problem with ethanol is that it’s hydrophilic (binds with water), necessitating the correct gaskets & seals to handle this. Not sure if kart engines are designed for ethanol use or not, but I would assume not unless/until verified by the factory.
On another note, octane is simply a measure of a fuel’s detonation resistance, & not indicative of its potential HP output.