KA100 Fuel

What type is most recommended? I was with a kart buddy the other day and he said just run 93- it burns hotter than 110 sunoco. I thought complete opposite!

Can someone clear this up for me?

93 octane pump gas likely will not pass the fuel meter test.
As far as the hot burning thing goes, lots of people have it backwards, indeed high octane fuel burns cooler than lower octane.

1 Like

Greg is correct, you want the lowest possible octane rating WITHOUT DETONATION to make max power…the without detonation part is the fine line you dance with between performance and possible damage to the engine.

Most groups run 110 Sunoco because it’s easy to control, but for example USPKS has a spec fuel that is 98 octane (VP MS98L) and the KA’s run fine with that. Lead in these 2 fuels also helps fight detonation.

…so I’m not sure I’d run straight 93 unleaded out of the pump. I’m guessing you’d be OK but why guess and risk it. What I have done to keep costs down on test days is run a 50/50 mix of 110 and pump 93 and I’ve found that combo to work quite well. Assuming this was all for practice as most groups have spec fuel for race days and those days you just need to run that fuel or risk DQ


Greg when you say it won’t pass the fuel meter test are you referring to non ethanol or 10% ethanol blend or both? I was led to believe the non ethanol pump gas would always pass.

Since there is typically a spec fuel for the class, they measure the fuel with a digitron which measures for oxidizers in the fuel and make sure there are no additives in the fuel.

I use either VP MS98L or VP C12, as those are typically required by the series we run in. MS98 is supposed to create a little more power than C12 due to the burn temperature.

1 Like

From what I understand, in the US BP’s V-Power is non oxygenated. But they also talk about “Nitro+” which I have no idea how (or if) it affects the digatron reading.

Semantics: Octane and burn temperature are not related when comparing octane of similar fuel types, at least that’s what I’ve read from fuel chemists.

Running the lowest octane that an engine can handle will usually yield the best performance provided the composition of the fuel is still of good quality. On the downside, the lower octane will leave less room for error on your jetting and or engine temps

One advantage of leaded fuels (if you ignore the carcinogenic part) is that the lead content is good lubricant for the insides of the engine.

While many racing fuels are “high” octane, many are not. The sole purpose of racing fuel is to ensure consistency amongst batches. This is where you can get into trouble with pump fuels, you’re not necessarily getting the same composition each time.

Sooooooo back to the KA, if it seems others are running 93 (at a pump you have access to) without issues, it should be OK for practice. Just make sure you’re conservative on jetting and verify the oil % that those people are using.

1 Like

James, since lead is awful from a pollution perspective, is it possible to not use leaded fuel or is necessary?

Absolutely possible. Really US is the only place that uses leaded fuel in racing anymore. In Europe we stopped using it in the 90’s in karting.

I was surprised to see it being used in karts when I moved to the US in ‘06

The lead (Technically TEL Tetra Ethyl Lead) leaves a coating on the internals of a two stroke that helps with lubrication.

1 Like

Unless regulations have changed pump gas can have up to 10% ethanol without a placard stating such.
Not to mention seasonal changes in the formulation to account for changes in the weather. This inconsistency should be avoided, one of the other benefits of true race gas is that it is pretty consistent year round.

1 Like

I should correct myself, since James mentioned it, it’s not burn temperature, but burn consumption. A higher octane gas can have the potential to not burn all of the fuel during ignition, while too low of an octane can burn a lot more, and typically earlier in the stroke, which is what causes the detonation.

But as stated, while I am sure pump gas is safe to run, and as long as it doesn’t have additives, it should be ok. It is the consistency of the fuel with regards to jetting and mixture. If you practice with pump gas, you’ll get good seat time, but your engine tuning may not be the same each time out.

Octane is the measure of a fuel’s ability to resist detonation. Detonation is caused by excessive heat and/or pressure. If you get no detonation with lower octane fuel, I consider it better. The hotter you can get the exhaust temperature, the faster you should go. The more pressure and/or heat you get, the higher the octane you need.

There are qualifiers. A lot of them! You can prevent detonation with a richer fuel mixture. My testing has shown an engine with high compression, can produce more horsepower, with a lower EGT, then an engine with less compression with a higher EGT. An engine with better cooling properties can produce more horsepower than one with less cooling properties even though the compression ratios are identical.

1 Like

V-Power did not pass the F-Series Gear Up sniffer test.

1 Like

Good info to have. Any idea what it read on the digatron?

Arguably this might embolden the point that with pump fuel you can never really be sure what you’re getting. So proceed with caution.

I did not pay too much attention but I believe the tech guy said the VP comes in at about 0 +/- a bit. Maybe he calibrates the gauge to be 0, not sure. The V-Power was either +20 or -20. He said that the difference was huge. He also said he could tell the difference just by the smell. He knew immediately it was pump gas.

I know this is an old topic, but I’m reading through these things as I’m getting a KA in the next couple weeks. My track just runs pump gas, any advice on how to accommodate that?

From what I’m reading, maybe run a little on the richer side and/or pay close attention to the EGT?

For context, I’ll likely just be turning laps, so I’m not too concerned with getting the absolute max performance.

Hi David, we only run pump fuel in Australia in KA. check out the local importers notes on Carby setting KA3 is equivalent to senior over there (i think)

1 Like