Hello all,
A project was tried some time ago (30+ years now!) on a Pontiac Fiero,
which investigated the effects of completely vaporizing the fuel before
combustion.
A heat exchanger was put in the intake system, after fuel mixture, to
create enough heat to completely vaporize the fuel.  Because of pressure
loss due to mixture expansion a turbocharger was used to achieve the
same output power.  My memory is of a 40% improvement in BSFC or 40 %
power improvement depending on turbo pressure.
The work was done by Smokey Unik (sp) of "The Best Damn Garage In Town"
fame, and was reported in either Hot Rod or Car & Driver magazine.  I
saw the vehicle at the GM proving grounds while involved in a college
project in 1978 or '79.
Dan F

"40% improvement in BSFC"

I doubt that.

Paul Lamar

40% improvement would be low.  The volatiles would be more available to
the combustion process, giving up more of their power, possibly to
several hundred percent.  There were a number of experimental fuel
systems which got 100 MPG or more from gasoline, back when cars were all
steel.

The reason this technology never took off was because it makes the
engine a ticking time bomb.  When the volatiles are ingested in the
proper mix, everything is fine, but imagine if a concentration of the
most explosive components were brought into a hot cylinder, and none of
the more stable compounds.  You will get anything from detonation in the
cylinder to initiation in the intake system . . .and imagine the joys of
having your preheater rupture, spraying explosive vapor all through your
engine compartment!

Preheating works well with waste vegetable oil being used in Diesel
engines.  It also worked well with alcohol, when I was experimenting
with that back around 1980.  But gasoline is just too unstable and
dangerous, it's intended to be handled as a cool liquid and broken down
inside the cylinder.

Keith W

I don't believe it. If there was a 40% improvement in BSFC that would be unprecedented
in the history of the ICE and it would have been done years ago.
Engined engineers have been busting there buns to get .1% improvement in BSFC.
Manifold heat is used to this day but it does not improve the BSFC anywhere
near 40%. There are a zillion other factors that affect the BSFC and
not just unburned hydro carbons. The RX8 engine recycles unburned HC.
We have all sorts of charts on heat balance and unburned HC are way down
the list.

Paul Lamar

Gentlemen:

Actually, what I was asking in my initial question about heating gasoline was related to my wing surface radiator design.   If the fuel tanks are inside the wing, with hot engine coolant wraped around the tanks at, let's say, 200+ deg F, how much heat is going to transfer to the fuel during the flight (this can be somewhat controlled with insulation etc.).  The question started with "Do I want any of this heat to transfer to the fuel, or do I want to keep the fuel as cold as possible (ambient temperature at altitude)?  Is there any problem with allowing the fuel to absorb some of the heat, not all of it.  I'm not trying to vaporize the fuel prior to the injectors or intake manifold.  How concerned should I be about fuel being heated to, let's say, 100 deg F in cruise.

I can guess there's not much problem with 100 deg since that's probably a normal ramp temperature on a sunny April day in Houston.  Maybe 150 deg F is a target heated temperature?  Maybe the operative word is "warm", not "hot".  Does the fuel actually absorb extra energy from the pre-heating while remaining in liquid form?  We are assuming the air charge is cooled as much as possible with intercoolers to increase its density and the injectors introduce a warm spray.
Greg Fleming
London, Ontario, Canada

The problem with that is the amount of heat transfered will be a function
of how much fuel is left in the tank.

Paul Lamar