Bringing up an old thread, but a good one!...
I was thinking, which steffen707 started to talk about, what if I did a "T" or "Y" bend, so that during engine warm-up, it used warm air, during acceleration or high engine revs (say over 2,000ish RPM), it switched to cold air and at cruising, switched back to warm air. I feel like this would give me the best of both worlds and help increase my FE better than a WAI or CAI alone. How would this be done? It would need some sort of "computer" to know certain variables (engine temp, revs, etc.) in order to switch back and forth appropriately.
Also, somebody mention fuel temp. Would preheating the fuel, in the fuel line before the injectors help with power and/or FE? What about the safety risk? Would there be a higher chance of vapor pre-ignition (e.g. inside the fuel line, well before the engine)? How would this be done? Re-route the fuel line close to the exhaust manifold (again, sounds dangerous)? I can't think of any other ways to preheat the fuel, though.
P.S. I don't have it yet, but I am planning on buying a Ford Escape Hybrid. Don't know if hybrids change the equation or not... Also, the FEH engine at cold start-up, automatically stays on until the engine is at operating temp, so the sooner it gets hot the better, because it will switch to battery sooner.
Soooo many questions!...