This is a combinated question and suggestion. If you're already planning on implementing it or if you're planning not to, then this is a question. If you haven't thought about it yet, then it's a suggestion. Anyways. I'm quite an LFS fan, I must admit that already. One thing that differs LFS from other car simulations and games is the way the engine sounds are generated. You might already know this but I'm just going to explain it anyway. In LFS the sound produced by the engines are partly mathematically produced. There are samples involved but it's only a click of a millisecond. This sample then produce a sound (I'm assuming it's based on when the valves open among other things) and this sound varies from different engine layouts and piston amounts and gives the engines there true characteristic sounds. It would be really cool if Outerra would use something like this too rather then pre-recorded samples. I can assure that generating the sounds this way will sound a-lot better.
Examples:
Inline 4:
Inline 5:
Inline 6:
V8:
