Originally posted by pinky25@May 13 2005, 08:19 AM
I dont know, I'm in the el paso area if it helps. What does elevation have to do with gas octane levels?
Your elevation has a lot to do with octane. The higher the elevation, the lower the octane requirements because the absolute amount of air getting in the engine is less. Less molecules, less temperature rise on compression, lower compressed temperature of the a/f mixture, lower probability of autoignition=fewer problems with detonation, therefore, you can run lower octane than you would need at sea level. El Paso is nearly 4000 feet in elevation (the airport is at 3958 ft), so you can run lower octane fuels without worries. 86 will be fine for your tC.
You will be down on power compared to sea level though. There's no escaping that, ever, even with FI. You are always starting from an input pressure and adding boost at a ratio of pressures, not to an absolute pressure (unless your compressor is so big it is always running in excess of the engine's needs, but that's a different discussion).
So, high altitudes get lower octane fuels than lower altitudes because they don't need higher octane. You are in a place where 86, 88, and 91 are the equivalents of 87, 89, and 92 at sea level. The gasoline companies know this, and formulate fuels to work well at your location. It's also cheaper for them to produce lower octane fuels, but again, that's a different post.
If you are interested in gasoline and would like to read a bit, check out the gasoline FAQ at
this site. It's getting a little old now, but the basics are all there, and you have to start with the basics anyway. After you've read this whole thing, I also have a few links for detonation that are helpful to understand what it is, why it happens, and what it means to you as the engine owner/operator.
