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Thread: OT, how to fake a carburetor for a small engine with a jug and some tubing.

  1. #11
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    Wasn't Brian Rupnow experimenting with a vapor carb similar to this for running some of his small engines from a while back?

  2. #12
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    I believe he was, it's a very popular concept among model engine builders and very simple to build.
    Home, down in the valley behind the Red Angus
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  3. #13
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    Quote Originally Posted by 3 Phase Lightbulb View Post
    If it was running too lean I think he would have noticed when he took the head/exhaust temperature. The temps were normal.
    If you watch his IR gun, the temps measured varied widely depending upon exactly where he was pointing it, making those measurements completely useless for any comparison.

    I will give him a HUGE thumbs up for, at the very beginning, stating that if this was a good idea the car manufacturers would have done it long ago.

    Steve

  4. #14
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    He has done dozens of projects using B&S engines. He is very familiar with which part should be about what temperature.

  5. #15
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    " .... about what temperature" is an inadequate level of precision for making a conclusion in this type of experiment.

    Steve

  6. #16
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    I did notice that he had to "fine tune" the vapor/air mixture in order to get it running decently, as a matter of fact he even mention so at the 7:30 mark.
    In his fuel consumption comparison of the carb vs. vapor system, although the vapor system edged out the carb slightly, it would have been interesting to see the results if the carb's jetting would have been fine tuned as well.
    Home, down in the valley behind the Red Angus
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  7. #17
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    It becomes a matter of how much of the fuel can be burnt inside the engine instead of passing through to the exhaust, and how much can be burnt during the time in which the piston is providing the most average torque to the conrod. Fuel is burnt most efficiently when it's well mixed with the air- same as epoxy works best when it's well mixed in the right ratio. This in itself is not rocket science. Providing the fuel as a vapor means the induction doesn't have to do that job- which it might not do very well- and so there's bound to be some increase in efficiency. I think a lot of modern engines do mix the fuel very well- and do come close to delivering the best efficiency possible.

    Where would you think the 'burning power' of a 100 mpg carburetor would come from? Is there really such a waste of power in the present usage of fuel in an engine- could it be true that 2/3 of the fuels power goes out the exhaust, only providing say 33 mpg instead of 100? I think there's a reality here that we should all recognize- short of some kind of nuclear process with the existing fuel, diesel or gasoline, there isn't a gross failure to use the fuel to it's potential.

    I see this invention as a way to provide only vapors, and not a droplet mixture that might not burn completely in the cylinder. It would be a huge gain if compared with the early carburetors, but not so much now that ways have been developed to improve these burnable mixtures.

    One thing I do see from that experiment is that there is not a lot of power potential in the system as shown. I don't think you could suck enough vapors to provide the engine with full power if the driver asked for it with the gas pedal. A more appropriately modern method of providing the sufficient flow of fuel on demand would be to use some of the exhaust heat to vaporize the fuel as required. Not only will this use some of what otherwise would be wasted heat, it would also allow for a larger quantity of the fuel to be vaporized virtually instantly, and thus for some real power capability from the engine.

    I think also that the air/fuel mixing chamber is key to the problem of supplying a fully and efficiently burnable mixture of fuel and air. I applaud this guys efforts to some extent, while realizing that it's old technology and being applied through what- a lawnmower engine? Show me a modern engine that will give 50 mpg instead of 35 mpg using this technology-
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  8. #18

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    Quote Originally Posted by michigan doug View Post
    He has done dozens of projects using B&S engines. He is very familiar with which part should be about what temperature.
    I feel sorry for all his engines. It is a testament to the longevity of Briggs and Stratton engines!

  9. #19
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    A backfire would be exciting
    Andy

  10. #20
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    Quote Originally Posted by darryl View Post
    Where would you think the 'burning power' of a 100 mpg carburetor would come from? Is there really such a waste of power in the present usage of fuel in an engine- could it be true that 2/3 of the fuels power goes out the exhaust, only providing say 33 mpg instead of 100? I think there's a reality here that we should all recognize- short of some kind of nuclear process with the existing fuel, diesel or gasoline, there isn't a gross failure to use the fuel to it's potential.
    surely not 2/3rds - but there is some wiggle room, Lot's of energy not only goes out the exhaust but also heats the air that's surrounding the engine and trying to cool it, (be it a radiator or forced air cooling fins) which is counterproductive in efficiency but needed so the engine does not have an internal "meltdown",,, you could even run a small cat on the exhaust of that briggs and get it to glow red hot due to all the unburnt hydrocarbons being tossed back out into the atmosphere - so yeah there is always room for improvement - maybe just not "practical improvement" and there are limits due to the carnot theory...


    I think also that the air/fuel mixing chamber is key to the problem of supplying a fully and efficiently burnable mixture of fuel and air. I applaud this guys efforts to some extent, while realizing that it's old technology and being applied through what- a lawnmower engine? Show me a modern engine that will give 50 mpg instead of 35 mpg using this technology-
    While I have taken a car that was rated @ 33mpg and achieved 50mpg with it much of it was due to driving habits but also "tweaking the mixture" so it's not a fair example - But I will give you an example although it would not be considered "modern"

    Smokey Yunick built "hot vapor" adiabatic engines way back when,,, and he had three stages - first stage was fair improvement with just regular internal parts - second stage was more radical with using ceramic internal components and a radiator the size of a heater core, third stage for goes the cooling system entirely and lets the internal components "bake"

    he achieved great efficiency results, and far surpassed an engine that was rated at 35mpg's getting over 50mpg's

    it's true we toss allot of "raw" energy back out - even just cats sitting there glowing red hot is testimony to that - you could run a small steam engine off of them, let alone all the heat transfer into our cooling systems... ALL waste heat that is being dispersed including the inevitable parasitic drag of mechanical friction is a direct reduction in efficiencies...

    Andy you beat me to it - that guy actually built a bomb as he's got a pretty good ratio of gas and air linked to the intake system and one backfire would be all it took - that's one of the reasons I said "fire fire fire" yesterday without even having to watch the vid lol but I did watch it this morning - it is pretty amazing how smooth he got things to run,,, I personally would not try this at home, at least not in the way he's doing it - I might allow a carb jet to leak fuel on an air filters foam side before the intake system, then you have tons of surface area for the atomization without building an enclosed vapor bomb lol

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