Thread: Octane boost
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Old 04-28-2010, 08:09 PM   #15
Lobo1186
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Join Date: Sep 2009
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Q: Why not simply use racing gasoline or aviation fuel?

A1: Most types of aviation fuel have very high lead content, which would rule out cars equipped with catalytic converters. Most piston engined aircraft burn leaded fuel. Also aviation fuel has a very different hydrocarbon mix to optimize volatility properties at high altitude.

A2: Racing gasoline could be a much more convenient way to run high octane fuel compared to having to constantly mix in toluene with each fill up. There are, however a few caveats:


You don't know for sure if you are really getting what is being advertised. You should find out if the fuel inspectors verify the actual octane of the racing gasoline in addition to ordinary gasoline. If you paid $3/gallon and only got 94 or 95 octane instead of 100 octane you may conclude erroneously that your car does not benefit from octane boosting.

You don't know what octane boosters are used in the racing gasoline. The worst case scenario is buying leaded racing gasoline without knowing it. Unleaded racing gasoline may still contain damaging octane boosters like MMT or methanol. A very high alcohol content will lead to fuel line erosion, accelerated fuel pump wear, very poor fuel economy and possibly lower performance, as alcohols have a less impressive MON rating than aromatics.

It takes smaller quantities of toluene to achieve the same octane boost compared to 100 octane racing gas. I have not seen unleaded racing gas for sale that exceeds the octane rating of toluene.

Since toluene is not officially sold as a fuel, gas taxes do not apply. Also racing gasoline tend to have higher markups being of interest to the performance minded enthusiast and thus is very likely to be more expensive to buy and use long term than toluene, which is typically used in more mundane applications like paint thinner.

Q: Ok, what is the catch?

A: It should be mentioned that in the US, efforts are underway to reduce the aromatic content of gasolines in general as a higher aromatic content leads to higher benzene emissions. Benzene is an extremely toxic substance. However it should also be noted that the proportions that is being discussed in this FAQ is relatively small and in the grand scheme of things is probably insignificant. Moreover, the industrial standard for defining gasoline composition allows plenty of leeway in aromatic content and the proportions present in US gas is already lower than most other countries. I therefore feel that the information provided here is useful to a performance minded car enthusiast while not being significantly detrimental to the environment.

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Since I didn't have any reference point for how much to use, I dumped about a half gallon of this mix into a mostly empty tank (the GT has a 16 gallon tank) and then filled up with Chevron 92 octane.
I didn't get to drive the car until PIR the next morning, (my GF doesn't like the 200; it's too big) but the report was that there was no change for a mile or so, and then all of a sudden, the engine seemed to smooth out and became quite eager to rev and run.
Well, by that calculation, I only managed to bump the octane to just shy of 93, but it seemed to make a big difference. I ran the car hard all day, (for reference, it's got an '87 MC turbo motor, K26, 12psi boost, and currently no intercooler) and even at 12 pounds of boost, I never once felt the ECU backing the timing off. Granted, the ambient temps never got above 50, and my water and oil temps were rock solid. (Oil just pushing above 100C)

The only cars that I had to get out of the way for was an Integra Type R and a couple of race-prepped P-cars. I even managed to lap the NSX once! It was a really good day!

Reference materials:


1. Gasoline FAQ

2. McLaren Honda Turbo - a technical appraisal
Ian Bamsey
ISBN 0-85429-840-1, published 1990

3. Chevron's excellent Motor Gasolines Technical Review

4. Agency for Toxic Substances FAQ on Toluene
In summary:
Use in a well ventilated area, don't drink even a little of it, and
report spills of more than 1000 pounds to the National Response Center

5. Toxic Chemicals in your Environment (Australia) FAQ on Toluene
In summary:
this "Total Environment Center" likes a totally chemical free environment,
and even at that they can't find fault about much more than acute exposure
cases, and they also say not to drink any of it.

6. Exxon Chemical Americas - Toluene, Technical Material Safety Data Sheet

7. Recicladora Temarry de Mexico - Recycling Processor
Recycling information and Material Safety Data Sheets on numerous chemicals including Toluene.

For some reason the link will not work so I bring it to you. read it if you want if not skip over it.
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