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Old 11-06-2020, 08:31 PM   #1 (permalink)
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Fuel Vaporizer

I was on You Tube a couple days ago and saw people who claimed to be running their engines strictly on gas vapors from homemade vaporizers. I was just wondering if anyone here has ever tired this and what their outcome was. I can see where it might work but, some of the homemade systems I was seeing didn't look like they would be very safe and some looked like downright fire hazards.

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Old 11-06-2020, 09:35 PM   #2 (permalink)
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If it worked so well then propane engines should see a dramatic improvement in fuel economy since propanes boiling point it like -40. But they dont.
That's basically a surface carburetor and they were abandoned about 100 years ago.
2 people got burned to death a few years ago when their "vaporizer", which was a 55 gallon drum with a bunch of gasoline in loaded inside a van exploded.
If it worked why not use propane?
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Old 11-06-2020, 11:57 PM   #3 (permalink)
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Don't do it.
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Old 11-07-2020, 12:20 AM   #4 (permalink)
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Besides the fire hazard, since the fuel at the vapour phase would not absorb enough latent heat from the air at the intake, presumably a higher amount of fuel would be required to prevent a knock.
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Old 11-07-2020, 12:01 PM   #5 (permalink)
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you want the fuel and air in the cylinder to me as compact and dense as possible. A gas is less dense than a liquid mist so you could not have as much air in the cylinder and still have an effective fuel air ratio if you use fuel in a gaseous form.

it's the inert nitrogen that does most of the work on the piston absorbing heat and expanding.
pushing and simultaneously preventing the motor from melting. Having less nitrogen and oxygen from the fuel taking up more space means the nitrogen needs to get hotter to do the same work. but there is also less heat available because the fuel and oxygen must match and there is also less oxygen.

the actual ideal fuel air supply would have everything cryogenic.
liquid oxygen
liquid nitrogen
liquid fuel
With room temperature exhaust

I think 50% hydrogen peroxide water with an alcohol injection would be a fun motor to play with and a few steps closer to ideal

Last edited by ASV; 11-07-2020 at 12:12 PM.. Reason: had more to say
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Old 11-07-2020, 02:35 PM   #6 (permalink)
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But, but, but, but...gasoline vaporizes before ignition, even before it gets in to the cylinder...it's the vapor that burns, remainging droplets usually go (mostly) unburnt...the whole point of rough textured intakes - especially for carburated engines - is to create turbulence that helps breaks down/vaporize droplets....half the point of port injection is to spray on to a warm/hot intake port and make it vaporize better and quicker...

About the only way vapor would not be displacing air is in a direct injection engine. Which uses stupid high pressure to make the droplets as fine as possible (and to be able to inject into an already pressurized cylinder) so that they too vaporize ASAP. Especially important considering they don't have nearly as long to do so.

Point being, except for direct injection, gasoline vapor is going to displace air along the way.

And if you want to bring up propane - which is already completely vaporized at any reasonable temperature - YES, it displaces MORE air than gasoline vapor does, because it simply isn't as dense...takes up more than twice the space that gasoline vapor does. Apples and oranges.

The supposed benefit of the whole idea is that you aren't expelling unburnt fuel through the exhaust. Which automatically makes your gas mileage worse than if it was 100% burnt. And has the side benefit of burning cleaner, like propane, assuming it isn't running rich (you could still suck in more vapor than you have air to burn, so a DIY setup probably won't be great).

Fuel vapor displaces air. Droplets don't burn worth crap. Hopefully the rest of your post is accurate...
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Old 11-07-2020, 05:59 PM   #7 (permalink)
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I know most of the people I watched doing this had a ball valve in their vapor supply line so they could control the amount of vapor going into the engine. If I could come up with a way that I thought would be safe I might do some experimenting but, I don't want an open container filled with gasoline vapors sitting under the hood of my car. At the price gasoline is now and driving cars that get 30-55 mpg I wouldn't be doing it so much to save money as I would just to see if I could make it work to improve mileage and cut down on emissions. If someone could come up with a system that was safe and actually worked it seems it should cut pollution considerably.
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Old 11-07-2020, 07:40 PM   #8 (permalink)
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Sounds like you want propane.
You do realize like 1/3 the mass of gasoline won't vaporize at room temperature right?
It takes turbulent flow, engine heat and vacuum to all but fully vaporize gasoline.
Hence the reason why surface carburetors were abandoned over 100 years ago.
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Old 11-09-2020, 01:03 PM   #9 (permalink)
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I have built vapor carburetor systems in the past.

Most everything posted in this thread is spot on, so far.

The expanded gasoline vapors displace air, resulting in less power potential.

Heating the fuel/air mixture results in even more expansion and less mixture density reducing power potential even more.

In low load regimes, you can see fuel economy improvements via less throttling losses, less engine ignition lead time ( as heated fuel mixtures cause increased flame front speeds and knocking ) and the ability to run lean fuel mixtures while maintaining a quality burn.

Then, there is this:

https://www.hotrod.com/articles/hrdp...-vapor-engine/

Smokey used a turbo to bring back some of the power potential. It is amazing he got it to work as he eschewed electronics as a principle.
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Old 12-14-2020, 09:09 PM   #10 (permalink)
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I don't know if this is possible for gasoline vapor, but I read once somewhere on the all-knowing internet that propane (and natural gas) engines can run much leaner than liquid gasoline engines. This also allows for kind of a diesel-like throttling where you can run super lean, keep the throttle valve wide open and adjust throttle by means of introducing more gas (gas as in propane).

On another note, wouldn't the air also have to be very hot to keep the gasoline completely vaporized and dry? Otherwise wouldn't some of the gasoline just condense back into small droplets in the intake charge?

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