Originally Posted by MechUT
Believe me!
LOL. I'll tell you why, and you decide.
To put it as simply as possible, higher octane actually makes it harder for combustion to happen in the cylinders of you car engine. This may seem like a bad thing, but it is actually a good thing, because it helps control the timing of when combustion begins.
High performance engines (including and especially turbos) have high compression ratios, that can cause combustion to happen earlier than it should (ie the pressure is so high, the fuel ignites before the spark plug fires). The higher octane in the gasoline prevents this from happening, thus protecting your engine from "knocking" which is very damaging.
In a sense, the higher octane gasoline has nothing to do with providing performance. It's more a mechanism of protecting engines that are designed for high performance with high compression ratios.
Now, something like a 911 turbo (not sure) may actually be designed for 94 octane. In this case, you would get the maximum (advertised) performance by using that gas, and the engine would have to adjust for lower performance if you put in something less (like 89 or even 91 octane).
Definitely, your e90 engine would perform better with 94 octane if you could increase the compression ratio as well, but that you cannot do. Compression ratios are a physical aspect, you can't upgrade them ecu chips, etc.
Sorry for such a long explanation, but let me provide an analogy to help you save money on the premium it costs for 94!
You can run at a certain maximum speed, that is unique to you. With the right running shoes (ie 91 octane gas) you can run at your maximum speed without a problem. Now, if you wear leather dress shoes not designed for running (ie 89 octane gas) you will automatically run slower, because it hurts to run fast with the wrong shoes. In the same way, the engine will do whatever it can to scale back performance on 89 octane, to protect itself.
Now if I give you some highly advanced running shoes, they will not make you run any faster than your maximum speed. The shoes don't make your muscles any strong then they can possibly be, and doesn't make you any faster. This is the same as putting in 94 octane, it can't just increase the power of a car to more than it was designed for. Maybe someone else (Donovan Bailey or the 911 Turbo) needs these better shoes to run faster than anyone else, but you're not him.
|
BMW E92 335i 
