Calibration fuels

Each of our samples were mixed in a ratio equivalent to having added the entire contents of an octane booster bottle to a 15- gal. tank of 91-octane fuel. Each 1-gal. sample was stored in sealed metal containers at room temperature to prevent evaporation or degradation of the fuel or the octane booster. The toluene mix was composed of 12.5 oz of toluene and 3.125 oz of mineral spirits, treating the same 15-gal. fuel tank. As there was too little to make a difference in our 1-gal. test samples, 0.375 oz of transmission fluid (claimed to act as a lubricant) was left out. According to Tim Wusz, the mineral spirits and motor oil would only lower the octane rating if added in sufficient amounts. The results are shown in the tables below.

Since we wanted to determine the efficacy of the home-brew octane booster recipe, we re-verified the toluene results, using an infrared measurement system. Tim Wusz of Rockett Brand Racing Fuel performed the same tests using different equipment. The AKI results of the MMT and ferosene boosters were ignored as they were invalid on this equipment. We re-measured the RON and MON on the base gas and the home-brew mix. Any change was negligible.

Intake manifold; the canisters on the left are for calibration fuels and the bank on the right is for test fuels.

To see how much toluene had to be added to 1 gal. of base fuel to make a significant difference in the AKI, Rockett Brand concocted three different mixtures ranging from volumetric 10- to 30% toluene.

As described by Wusz, there is an optimal window of effectiveness for toluene additives. Beyond that, the increased fuel density begins to have detrimental affects on proper fuel carburetion and also retards combustion.

Toluene-laden fuels burn slower and make less power on high-revving engines. So much in fact that much of the air/fuel mixture is still burning as the charge exits through the exhaust valve. This is a sure way to destroy your emissions-control equipment and not pass smog. For these reasons, true race fuels don't just use toluene or other active ingredients to boost the octane. Instead they use better-refined hydrocarbon chains that raise octane while retaining optimal combustion characteristics.

So there it is, octane boosters tested and explained in a nutshell.
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