How Much Octane?
Street-legal racers are always looking
for better performance; 100-octane
gasoline is one answer
By Tim Wusz
Reprinted with WITHOUT permission from National Dragster
February 7, 1997
When thinking of octane numbers, most automotive enthusiasts subscribe to “More’s Law,” which is: “If some’s good, more’s better.” This is frequently the case high-octane race fuel for street legal drag racing cars. So, what is octane, why is it needed, and how can it help a street machine make an occasional great pass?
The engines in many street-legal cars have been modified to improve performance. These modifications, which include aftermarket headers, carb/intake manifold, camshaft, rockers, fuel-injection system, higher compression, and modified cylinder heads with big valves, can lead to increased horsepower as a result of getting a greater amount of the proper air/fuel mixture into the engine. When more of the proper air/fuel mixture is in the combustion chamber, the cylinder pressure is greater than it would be in an unmodified engine. This increased cylinder pressure needs more octane. If the octane number of the gasoline is not high enough, it can result in detonation and destruction of the engine.
Even some unmodified engines may benefit from higher octane gasoline. As under-hood temperatures increase, the engine needs a higher octane gasoline. In a dry climate like much of the Southwest, the lower humidty also contriubtes to increased demand for octane. On a low-humidity, 100-degree day with the air conditioner on, an engine's octane appetite can increase by three to four numbers.
76 Unleaded Racing Gasoline is legal for street use and will not harm catalytic converters or oxygen sensors. It provides street engines that require high octane the opportunity to operate at maximum output with no damage from detonation. This gasoline can be used in 1960s muscle cars as well as current performance cars and has been used successfully in four-inch bore engines with aluminum heads and compression ratios up to 12.5:1. Bigger bore engines may need to use lower compression ratios.
Is this AUTHOR WRONG??