I haven't been able to find any information on this here, and I'm not sure if/how it would work so I thought I'd ask. First though, let me preface this with a bit of background:

On some older vehicles (e.g. my father's old tractor. lol, farmer) the intake and exhaust manifolds were one piece, in this configuration the heat of the exhaust was used to vaporize the fuel. This principle still exists in FI engines, but the heat of the combustion chamber is what does the trick instead (right? please correct me if I'm wrong).

So here's my question. If the intake manifold were heated by some means (engine heat via hot coolant or otherwise) and the fuel was preheated in the same fashion we should get better vaporization of our fuel, right? If we did it should lead to more horse power/better mpg/etc, correct?

It's just some food for thought. I haven't seen any threads about this and was wondering how it might be done and if the results would be worth the effort. Thoughts?

 

I have a '61 Chevy with a 235 straight 6 that heated the intake manifold with the exhaust heat, I switched over to an aluminum intake manifold to put a 2bbl on it that eliminated the heat exchange and it was a PIA to get warmed up on the super cold days! The exchange only took place at cold temps via a choke like setup with a spring that heated up and closed off a door when the car reached operating temps so this wouldn’t come into play when the engine was warmed up. On the xB there are coolant lines that go into the throttle body and circulate water from the radiator around there. As for the air temps, cold air is denser and will provide more power than warm but on cars now the computers can compensate for almost anything and give you what it feels is maximum efficiency and power in relation to the variables it is dealing with at the moment!

 

Thanks for the input. I am not interested in heating the intake air. I am interested in heating the surface on which the fuel is sprayed and the fuel itself.

I understand that warm air is less dense. That being said I also understand that warm gasoline vaporizes more easily. I'm looking to make sure that the gasoline is as completely vaporized as possible, because I think that it could give a boost in HP or MPG.

I have read in various different places that under "optimum conditions" most FI systems will vaporize 97% of the gasoline. My guess is that "optimum conditions" are rarely reached in any vehicle, and that preheating the gasoline and spraying it onto a hot surface will improve vaporization.

tl;dr I don't want hot air, I want hot gasoline.

 

x2

ive seen a few people dissable the coolant transfer line and have said it runs better.

 

If you are looking for a boost in HP you need cool fuel and cool air they go hand in hand! Take a look at racing applications they routinely use cool boxes where they fill up a container with ice then the fuel line then passes through it in a spiral fashion to provide a consistent cold supply of fuel to the runner. There are also numerous other fin type fuel coolers to mount in the front of the vehicle to help to bring the temps down, water and meth injection is another common way used to control the combustion chamber temperatures, as well as heat shield gaskets to be placed between the throttle body and intake manifold, if you follow the pattern all these methods are trying to LOWER the temp which help in preventing detonation. As you wanted to talk fuel we won’t even discuss the lengths folks go to cool the air charge with CAI or FMIC but you can see where I am going with that..
The vaporization aspect you spoke of is basically the engine lighting off the fuel air charge and the fuel is already being sprayed into a super hot combustion chamber as it just finished expelling the burnt gases from the exhaust stroke prior to the intake valve opening to bring in this new mix which in part will be used to cool down the chamber temp, hot fuel will work against this.

So in summary cold fuel is great!

 

^X2, I think 365Motorwerks has hit it on the head. Heating the fuel anymore is not going to give you anything. In fact, heating the fuel after its sprayed out of the injectors in that fine mist may actually cause it to ignite, which you definitely don't want. If your looking for more power, cooling the fuel & air is the way to go. For those old engines that had the intake & exhaust manifolds as one unit, that was more of a design of the head/combustion chamber that caused that, since it was found inefficient for pretty much anything (power or fuel economy) such designs were discontinued a long time ago.