[orange4boy]

My thinking on this is that from a practical ecomooder point of view, it would be a much better idea and give greater returns to heat the air rather than the fuel because:
1. Fuel is already heated passively by proximity to the engine. It moves relatively slowly through thin metal tubes so has lots of time to heat up. Most injectors are practically in the combustion chamber.
2. Being only 1/14 to 1/16 of the mixture makes it less important than the other 13-15 parts.
3. Injectors do a great job of vaporizing the fuel already.
4. The air intake in most cars is not heated whereas all fuel is passively heated.
5. you will have to get that fuel pretty darn hot to beat the existing temperature.

The short version: WAI easy, PHF, hard.

The general idea is good though.

BTW in propane fired glass melting furnaces preheated air is a big savings because the fuel does less work to heat up the air and thus less fuel is required to achieve a given temperature but this is a different application because all you want is heat there is no mechanical conversion of energy required.

The real question to answer here is how much more efficient is a hot bang compared to a cold one?
In other words, can you get more BTU's out of a hot bang or a cold one?

Has this already been answered here?