Fuel Mixture Pre-Heated Fuel

Discussion in '2-Stroke Engines' started by GeckoRider, Jul 23, 2014.

  1. GeckoRider

    GeckoRider New Member

    Hello everyone, today I came across an interesting "mod" for cars called pre-heated fuel. (this May be common knowledge but not for me haha)

    This involves bypassing the fuel line with a copper pipe that then wraps around the Cooling system in a car and then returns the fuel to the fuel line "pre- heated".

    from what I've read about this process it improves fuel efficiency quite a bit (Example; a car that had 26 miles to the gallon gain 10 mpg with this mod) by helping the oxygen mix with fuel easier (much like sugar dissolves quicker in hot water),

    also because the fuel is heated the molecules in the fuel are further apart and moving more, which means it requires far less energy from the spark to result in stronger combustion.
    (I'm not a scientist this is what I've read, please correct me if I'm wrong :) )

    so my question is has anyone tried this with a two stroke engine?
    I was thinking about trying it with mine by adding a copper tube to the fuel line after the filter then having it wrap around the engine and return to the carburettor.

    thank you

  2. jaguar

    jaguar Well-Known Member

    Sounds like a good experiment to see what difference it makes.
    With the car the fuel stays heated well because it just goes to injectors.
    With our engines the fuel would go to the carburetor which would dissipate the heat through its metal.
    So either we have to let some exhaust gases blow onto the float bowl to heat up the carb and the fuel inside it, or run a hot copper tubing through the float (although I doubt there is room).
    One problem with this idea though is that the coldness of the fuel is used to cool down the engine. Heating the fuel means there will be less engine cooling. But then you can ceramic coat the head and the piston top to absorb less heat from combustion.
  3. GeckoRider

    GeckoRider New Member

    I thought about that but if the copper tube was making a good connection to the engine I assume the fresh non-heated fuel going through the copper would draw away the heat from the engine (hence the fuel being heated haha).

    As for the carb cooling the fuel again, hopefully after running for awhile it would heat up enough to keep the fuel at a reasonable temperature. Maybe the carb could also be insulated as well.

    Maybe the carb could be modified to regulate the temp so some heat is dispersed into the air while still keeping the fuel warm enough to have some effect.

    I guess you never know until you try :) .
  4. jaguar

    jaguar Well-Known Member

    If the heat is from the cylinder or head then it would take a while before they get hot.
    Best to get the heat from the exhaust.
    Just run a tube from a hole in the header to the float bowl.
  5. butre

    butre Well-Known Member

    maybe in conjunction with a water cooling mod. I don't see it being significant enough to be worth doing as anything more than an experiment
  6. HeadSmess

    HeadSmess Well-Known Member

    its a great modification to make :)

    its called "vapor lock"

    the carb heats up to the point that the fuel boils, and then...you have to sit there for ten minutes waiting for it to cool down before you can start again...

    the 0.00000005 watts gained by reducing the evaporative losses is rather fruitless.

    at the opposite end of the scale you get carb icing....due to the heat lost in vaporizing any type of fluid. if youre flying a plane at 10000 feet and the temperature is around -51....yep. carb heating is a mandate for staying at 10000 feet... so a bit of heat in the fuel wont hurt noone...

    oh, they do use the effect in hot air balloons too. thats what those coils around the burners are, fuel preheaters. in this case, the fuel is already a gas. its partially to increase heat produced...but mostly to increase pressure!

    ill be using the idea in my next incarnation of my foundry furnace, get some pipe wrapped into a coil and set it in the refractory. mostly to preheat the AIR, as air heated to say, 500 degrees allows for hotter temps than blasting room air temp in... is the only way to get steel to melt without resorting to oxygen and acetylene!

    whats really needed, in an engine at least, is a way to COOL the incoming air down. well known fact that engines run better when its cold outside. the whole idea behind "cold air intakes" and intercoolers.

    just, if you try doing any thing...remember petrol vapor is explosive. increasing the fuels temperature lowers its flash point. dont want to hear any reports of people getting blown up!

    theres plenty of other, safer options to increase power.
  7. GeckoRider

    GeckoRider New Member

    Haha thanks for the advice and concern, I don't plan on blowing myself up anytime soon (then again I don't think most people do).

    firstly I don't plan on boiling the petrol (95oC), just heat it slightly to see if there is any gain or loss.

    An experiment I am planning on running is placing just 200ml of fuel into the system at room tempriture and running the engine at WOT(with rear wheel lifted) And timing it to see how long 200ml runs for at room temp.

    then repeating the test with fuel heated at 30oC then again at 60oC,
    just to see if there is any gain/loss at all.

    also I should add each test I will heat the engine then run it dry before adding the fuel and let it cool and repeat for each test.

    if you see me on the news in the burns ward feel free to say I told you so :) .
  8. OCCStingray

    OCCStingray Member

    May have some very good benefits in N/A high performance fuel injected engines but anything with a carby will lead to peculation and vapor lock in my experience.

    FWIW fuel, as with all liquids, has a lower boiling point in a vacuum, this is one of the reasons engines cruise so well at speed with the throttle just cracked open, the combination of high vacuum and low pressure behind the throttle blade makes for great atomization of the fuel.
    Food for thought.
  9. hellbound212

    hellbound212 New Member

    On my 1600cc dualport vw engine, the intake connects to exhaust via little flanges that line up, they are called preheat tubes, so im sure it will work if you try it.
  10. OCCStingray

    OCCStingray Member

    Intake ports are pre heated to supposedly help with emissions, something you will find on alot of cars from around the 70's 80's etc, something you will very rarely or never see on a high performance or race/track car.