hot fuel vs. cold air
 

ive been thinking about this. you can have a hot air intake to heat the fuel up so the gas burns better or cold air because its more dense then hot air.
but the i found out for every 25 dreases you heat the fuel up is one mpg and for cold air its every 11 dreases colder its one mpg if i remember right

so my q is this has anyone tested this?::D

Yes, many ecomodders have tested cold vs hot air intakes and almost all found that the latter is better for fuel economy. CAI gives more power, but at the cost of more fuel*. There are scores of threads about CAI vs WAI. There are also lots of threads on preheating fuel, so no reason to repeat all of their info here.

*) This is true only for gassers. Diesels like cold intakes for both power and FE.

I have found that heating gasoline to 180 deg. F yields about a 10% return improvement in fuel economy. Detonation threshold seems about the same for a given octane value. Greater tendency to vapor lock during hot restart. Most OBII ecu s have the ability to recognize this condition and will keep injectors closed until engine restarts. May take 2 or 3 tries but it will fire up. Heating intake air also improves fuel economy but I have found a greater tendency to go into detonation especially when ambient temps. go above 60 deg F. If you run a dedicated water or water/methanol system you can effectively supress detonation with even the lowest octane fuel.

Diesel or gas?

10% cool :D is there any way that can hurt my truck??? if not sounds like im going to be heating some gas do you use the coolant? to heat it

gas

probably not
 

all systems run most of the time at an
Air to Fuel ratio of 14.64 to 1
1 part fuel
14.64 parts air
by weight

so
1 part of fuel will have much less influence on the temperature of the complete mass entering the combustion chamber than the 14.64 parts of air

and
on systems that have a return line
that extra unused very heated fuel goes back to the fuel tank , heating the fuel in the tank
which causes heavy duty evaporation and pressure build up in the fuel tank much of that pressure and HC
can
be vented
to atmosphere
because most systems are not designed to handle that scenario
fuel vented to atmosphere does not increase FE as it is
wasted

10% improvement .... not very likely

your right!!!!!!!!! but what if we bypass the return line?

That would be bad. Systems with return lines need the flow for cooling and fuel pressure regulating purposes (I think). It probably would not run if you blocked it off, or it would run poorly. New cars do not have return lines, so maybe something could be done there. But I wonder what hot fuel will do to the life of a fuel injector.

I would listen to mwebb - heating fuel will probably have little effect on anything.

Well dang, I never knew that! And here I went to all the trouble of making a hot air intake for MAX (Kubota-powered sports car) thinking that temperature was more significant than density on a compression-fired engine (and that reducing density would be beneficial too, because it reduces pumping effort). Why does cold air intake improve mileage on a diesel?

PS--mine's turbocharged--would that make a difference in optimum air temp for FE?