“ The 12:1 is not horrid. That's a pretty safe A/F for a turbo car. As I said earlier, safe enough to take into consideration 91 octane fuel and varied temperature changes for the entire North American market. FWIW, I run the Supra at 11.5:1 or so… “ – rrocket
Thank you, rrocket, for the information. Of course 12:1 is not horrid. If anything, you might want it even richer for the sake of engine welfare. But, you are cooling the engine with $1/litre gas. Rather expensive engine coolant. Besides, doing so the engine emits HC and C into the atmosphere. Anyway we are talking about two different things. You are talking about engine performance and I am talking about pollution. Technical discussions are always fun and informative.
BTW, the flat torque curve of the 335i engine is impressive, for which I admire BMW’s engineering skill. Suppose the boost is rather mild 7psi (may be higher in reality), that means the effective compression ratio (not A/F) is more than 15:1, already in the detonation territory, and the engine needs to be cooled like hell. I think its direct-to-cylinder fuel injection helps in this regard. The Supra engine did not have this luxury.