Tech Corner

We get a lot of questions about fuel metering changes required for oxygenated fuels... and that is a good thing, because racers should be asking those questions.

Luckily, the answer is not necessarily complicated.

Let’s look at Sunoco EXO2 for instance.  It’s a good fuel to use as an example because it contains 10% (by weight) oxygen.  Without proper fuel enrichment, you won’t find the power you’re hoping for, and in fact the engine may not even run well.

Alcohols like methyl alcohol (methanol) and ethyl alcohol (ethanol) are often used in race fuels.  Sometimes they are a small part of the fuel and sometimes they are a primary component of the fuel.  Methanol is commonly used “straight” – that’s why it’s called racing alcohol by many.  Ethanol can also be used straight, and some racers do, but it’s more common to hear about E85, a blend of about 85% ethanol.

Much has been said about the octane rating of alcohols.  However, technically speaking, the octane ratings of alcohols can not be measured.

All octane test engines, as defined in the octane rating procedures set forth by the American Society for Testing and Materials (ASTM), are carbureted.  Air/fuel ratio adjustments on octane engine carburetors are limited and can not accommodate the extremely different air/fuel ratio requirements of pure alcohols.

Overheard at the local track:

• “High octane fuels burn slower.”
• “My motor doesn’t need all that octane so that fuel won’t do me any good.”
• “I need the highest octane so I can max out my timing.”

Unfortunately, those statements are not always true.  As a matter of fact, those statements only have some merit in the street gas world where 93 octane fuel is king and 87 is used by most.  In the world of racing gasolines where higher octane choices abound, sharp engine builders and racers know they need to look beyond octane to find the right fuel.

Race fuels generally last longer than typical pump gas but often times race fuel is stored for several months between racing seasons.  Here are a few good tips to keep fuel as fresh as possible from one season to the next:

• Keep containers tightly sealed.  This will minimize the loss of certain components in the fuel that tend to evaporate more readily than others.
• Keep fuel tanks and fuel cells as full as possible.  This will reduce the amount of “breathing” since there is less vapor space above the liquid level and thus reduce the amount of moist air seen by the fuel.
• Store fuel where there are minimal temperature swings.  Changes in temperature can make a fuel container or fuel cell breathe more which can degrade fuel quality.
• Store fuel in such a way that it is not exposed to daylight.  UV-proof dark fuel jugs, steel drums, and the like are required for maximum shelf life of the fuel.  Fuels contain components that are sensitive to light; the octane rating of the fuel can drop if the fuel sees too much light.
• Perfectly stored, most race fuels will last more than a year.  If you are not sure you can use the fuel up within 2 years, add a quality fuel stabilizer to the fuel as soon as you purchase it.  Fuel stabilizer can only postpone fuel degradation; it can’t fix fuel that’s already bad.
• Try to avoid putting additives into fuel unless they are needed.  And remember, just because one dose of an additive is good, don’t assume a quadruple dose is better.  Overdosing can trigger other problems such as particle build-up in the fuel and deposit build-up in the engine.

Please note that these points deal with optimizing the “shelf life” of racing gasoline and do not cover safety aspects of handling gasoline.