Fuel Temperature 2

[Islander]

Fuel injected 5.9Liter..50 psi fuel pressure.

Fuel rail temp= approximinately 150 degrees.

Installed dual exhaust.
Found stainless fuel line is now 2" from catalactic convertor..
Mechanic says it is fine..shows me a device another car uses to heat it's fuel..said increases mileage.

For performance...would i not want cooler denser fuel?
or would heating it make for better atomization?

Kinda concerned about fuel line too close to exhaust pipe.

 

[Billios996]

I figured the drop in pressure between the fuel rail and the injector would cause a significant drop in fuel temperature as it's atomized and injected into the runner. Has anybody ever looked at a PE diagram for gasoline? Does the gasoline not assume the energy state after the pressure drop of the injector? Does the enthalpy relate at all to the chemical potential energy of the gas? If the gas is well atomized, does it then normalize to the air intake charge temp before being sucked/forced into the combustion chamber?

I would guess the temperature of the gas is more critical to its distribution to avoid vapor lock and minimize dissolved gases in the gasolne rather than its cumbustion qualities.

Random thoughts of an HVAC engineer
Bill

 

[roadwarrrior77]

I've been doing some research myself on practically the same subject. I've found that heating or cooling the fuel in an injected engine really doesn't make much of a difference. If you have a carbureted engine, heating the gasoline vaporizes it, and therefore the unused energy that normally goes into the converter is used instead of wasted. If you have an injected engine, cooler and denser air charge does help with power and performance, but you won't see the mpg gains that you would with vaporized gasoline. Look up Pogue and Tom Ogle. Ogle was able to drive 200+ miles on 2 US gallons of gas. This was verified by mechanics and media in the early seventies. Oh, and by the way, he was driving a Galaxie with a big block.....True story, research it yourself.

 

[PEW]

I have been experimenting with twin SU carbs on my high compression Reliant 850 cc engine, used in a little road sports and off-road trials car (aiming to get up steep muddy hills).

The SUs are fitted to a pair of "experimental" siamesed inlet manifold castings, cast in aluminium, the engine intake ports being in arranged in two adjacent pairs (port configuration is: Ex,In,In,Ex,Ex,In,In,Ex).

The carb end of each inlet manifold has a round port (1.25 inch diameter), to match the SU, this changes to an oval shape mid section, tending towards a figure of eight profile at the cylinder head, where the adjacent intake ports suck at the whole diameter of the small "plenum" this profile gives, there being no dividing wall inside each manifold. The manifold length is about 4 inches from carb face to inlet port face and is about as close to "straight in" as possible, with very little charge turbulence occurring.

The original setup was a single semi-downdraught 1.25 inch SU, sitting on a water heated plenum casting above a 1 into 4 ally manifold. The tortuous path the intake air followed with this has to be seen to be believed, possibly a major restriction on power output, only beaten by the appalling cast iron exhaust manifold and single downpipe. My engine has a 4 into 1 tubular exhaust manifold of increased diameter, to a straight through muffler.

Since fitting the twin carbs it has suffered from poor fuel economy and produced less power than I expected, bearing in mind other mods on the engine. I have found some difficulty in getting the correct mixture. The carbs spit back at mid to high revs, a symptom of weak mixture, despite trying progressively richer needles. The strange thing is, the tailpipe is very sooty and the exhaust blows black smoke but the colour of the plugs tend to show too weak, which ties in with the spitting back.

I suspect that the little intake manifolds are too short and too cold, not allowing efficient vapourisation of the fuel droplets issuing from the jets. This possibly results in large fuel droplets and inefficient combustion, so much of my precious UK fuel is going down the tailpipe as soot.

I am about to change to a single choke downdraught Weber carb on a modified original manifold (discarding the separate heated plenum). This setup has reportedly given very good results on this type of engine, with up to 25% improvement over the single SU claimed by one very reliable exponent. No-one has so far explained why this should happen, but it is possible that the longer path from carb to inlet port gives better fuel vapourisation than my setup. I think that my setup is great for gas flow but poor for fuel atomisation.

I will report the results.

 

[carnage1]

keep the fuel cool in a street car!!!
there is one piece missiong from this idea of cool fuel
gasoline's octane drops over time due to evaporation. more heat equals more evaporation. so all your high octane bits get sucked into the charcoal can and the low octane stuff is what gets left to burn.
so I highly reccommend insulating your fuel line that runs a bit close to the exhaust.
(this is also why you want to make sure your sealed fuel system is truely sealed)