Quote:
Originally Posted by MARTINSR
Maybe the question I should pose is does a motor require a given amount of fuel to provide a given amount of power? If it takes X amount of power to propel the car and X amount of power is proved by Y amount of fuel (with all other factors consistant), does heating it making it less dense help at all when you still need Y amount of fuel which is in the cooled fuel?
I am just trying to understand this, I am not arguing or challenging.
Brian
|
So yeah, X fuel can only provide Y power. You got that part correct.
The problem is that unless you're using 100% throttle, you're not creating all the power you could be making for the fuel you're burning anyway. (Often, even at 100%, you're still not, but that's another story for another time.)
If you're cooling the fuel, your engine then has to input heat to the fuel to vaporize it since the fuel cools the piston tops more. One of the biggest losses in an engine is heat being shed into the combustion chamber rather than used for expansion above the piston. The more heat your fuel/air robs from the parts of the engine, the more heat it has to put back in, in a cyclic fashion.
Using exhaust heat to pre-heat the fuel helps because then the fuel (and air, if you have a WAI) goes into the combustion chamber and is already closer to engine temp, so less energy is required to heat the mix initially, which means that more of the energy released in the burn is able to act upon the piston.
Cooler, denser fuel requires more of the engine's heat stores to become combustible, which makes it less efficient, although able to produce more power overall (not per unit of fuel).