Jdub,
I've been racing for nearly 20 years, and while I've always been able to find a fuel that meets the requirements of my engines and in the correct specific gravity allowed by the racing classes, but I've never really understood all the technical details.
For example, in the drag car, I run VP Import which has a Specific Gravity of .744 @ 60°F, a lead content of 6.0 g/gal, is Oxygenated and has a Motor Octane of over 120+. VP does not provide a Research Octane or an R+M/2 rating for this fuel.
For the street cars, I've always run VP Motorsport 109 which has a Specific Gravity of .722 @ 60°F, is unleaded, is Oxygenated and has a Motor Octane of 101, a Research Octane of 109 resulting in an R+M/2 of 105...
I know in the US we measure fuel at the pump with R+M/2 octane scale. I'm aware that's the Research Octane rating + the Motor Octane rating divided by two.
I guess I'm trying to understand why Research Octane is used at all... And why the R+M/2 value is considered a "standard"?
My understanding (and correct me if I'm wrong) is that the Motor Octane test method is highly accurate and is done under controlled conditions for both intake temperature and fuel temperature and is tested with varying timing and different compression ratios. However Research Octane testing is done with fixed timing and that fuel temp is not controlled with the only variable being the compression ratio. This seems like it would be a fairly non-representative test of how fuel behaves in the real world.
Why would you average the results of two wildy different tests when one of them seems more representative of what a real engine would do and the other is not?
I've been racing for nearly 20 years, and while I've always been able to find a fuel that meets the requirements of my engines and in the correct specific gravity allowed by the racing classes, but I've never really understood all the technical details.
For example, in the drag car, I run VP Import which has a Specific Gravity of .744 @ 60°F, a lead content of 6.0 g/gal, is Oxygenated and has a Motor Octane of over 120+. VP does not provide a Research Octane or an R+M/2 rating for this fuel.
For the street cars, I've always run VP Motorsport 109 which has a Specific Gravity of .722 @ 60°F, is unleaded, is Oxygenated and has a Motor Octane of 101, a Research Octane of 109 resulting in an R+M/2 of 105...
I know in the US we measure fuel at the pump with R+M/2 octane scale. I'm aware that's the Research Octane rating + the Motor Octane rating divided by two.
I guess I'm trying to understand why Research Octane is used at all... And why the R+M/2 value is considered a "standard"?
My understanding (and correct me if I'm wrong) is that the Motor Octane test method is highly accurate and is done under controlled conditions for both intake temperature and fuel temperature and is tested with varying timing and different compression ratios. However Research Octane testing is done with fixed timing and that fuel temp is not controlled with the only variable being the compression ratio. This seems like it would be a fairly non-representative test of how fuel behaves in the real world.
Why would you average the results of two wildy different tests when one of them seems more representative of what a real engine would do and the other is not?