Converting Engine to Propane...

[Gamingphreek]

My friend and I are converting a 5HP Briggs and Straton Lawnmower engine to run off of propane. The engine, obviously runs with a carbureator which would need adjusting or rebuilding to accomodate the higher octane propane.

In general, is there anything else that I should research or know?

Also what would happen if I merely connected the fuel line to the propane tank? Would the engine merely turn over or would it not work at all?

Any suggestions?

 

[dkozloski]

Gasoline is liquid and propane is gaseous at normal temperatures. You're going to need a pressure regulator and a propane carburetor. Connecting the existing gasoline fuel line to a propane tank will immediately produce an extreme explosion hazard and any propane spraying around will freeze human flesh instantly. Pound for pound, propane has 14 times the explosive power of dynamite. Do a google search for "small engine propane conversion" and you'll get plenty of information. Talk to someone who works on propane fueled lift trucks. What area of the U.S. are you located in? When I see the fireball on the national news I'll know it was you.

 

[Gamingphreek]

Originally posted by: dkozloski
Gasoline is liquid and propane is gaseous at normal temperatures. You're going to need a pressure regulator and a propane carburetor. Connecting the existing gasoline fuel line to a propane tank will immediately produce an extreme explosion hazard and any propane spraying around will freeze human flesh instantly. Pound for pound, propane has 14 times the explosive power of dynamite. Do a google search for "small engine propane conversion" and you'll get plenty of information. Talk to someone who works on propane fueled lift trucks. What area of the U.S. are you located in? When I see the fireball on the national news I'll know it was you.

Thats what we thought would happen if we connected it to the engine directly. We weren't going to try that but someone suggested that the pressure valve might prevent any backfiring.

We read on Howstuffworks and he read on various other sites that you need a Vaporizer. While obviously we would do that....why would the regular carburetor not work. It turns the gasoline into a vapor form (Please correct me if I am wrong) with the little spray head and then adds an amount of air to the mixture which then proceeds through the fuel lines. Is it because the propane is already a vapor below -44F so it would essentially be trying to spray a liquid but end up with a vapor?

We are not going to try it like that, I am just curious as to exactly why it would not work.

We are both engineering students. We aren't just going to go around with flammable materials and start trying to get the engine to work. We are doing extensive research and will only test after we have checked and triple checked our sources.

-Kevin

 

[dkozloski]

There are some jet replacement kits available that allow you to use the original carburetor. A simple Google search for "small engine propane conversion" will give you all needed information. The jet replacement kit will produce a small vacuum at the fuel line that will allow gas vapors to be drawn fom the appropriate regulator on the propane tank. At present the only flow regulation mechanism in the carburetor is a float valve for liquid fuel. If you have liquid propane in the carburetor the next event has all the makings of something spectacular.

 

[noreaga0221]

Find out the stoichometric for propane. I have a buddy who uses it on his turbo car to cool the intake charge and add higher octane to make more power.

 

[pm]

When I was driving around Eastern Europe (Poland, Ukraine, Slovakia) last summer, it seemed like more than half the "gas stations" were actually selling propane gas. And while the number of propane-powered cars on the road was probably much less than half, there were definitely quite a lot of them since you could smell them when walking next to a road. Over there, there were signs all over the place about shops that would do a gasoline to propane conversion.

Not that this has anything to do with the question being asked, but I thought it was unusual coming from the US to find out that propane-powered cars are in wide use in Eastern Europe, and thought that people might be interested to hear it.

 

[gerwen]

Originally posted by: Gamingphreek

We read on Howstuffworks and he read on various other sites that you need a Vaporizer. While obviously we would do that....why would the regular carburetor not work. It turns the gasoline into a vapor form (Please correct me if I am wrong) with the little spray head and then adds an amount of air to the mixture which then proceeds through the fuel lines. Is it because the propane is already a vapor below -44F so it would essentially be trying to spray a liquid but end up with a vapor?

We are not going to try it like that, I am just curious as to exactly why it would not work.

I think the root of the problem is that the gasoline in a carb reservoir is at atmospheric pressure. It uses the low pressure created by the venturi effect in the carb throat to draw gas into the needle valve to be vaporized. Flow is regulated by the flow of air through the carb as it changes the low pressure at the needle.

Straight swapping to propane causes a pressure in the fuel flow system. How much flow you have is dependent on the pressure of the propane source. You could probably find a carb needle valve setting that would allow the engine to run, but finding that setting would be dangerous. The engine also wouldn't respond well to throttle changes, as the pressure changes caused by different air flow past the needle are likely to be insignificant when compared to the pressure of the propane fuel system.

I would imagine swapping to propane would require some sort of flow control system that can respond to changes in throttle or airflow through the carb.

Btw, this is just mho, based on knowledge of how gas engines work, and no experience converting them to propane.

 

[imported_iNGEN]

Google knows all.

Actually, this should be easy to find and do. I use propane and NO2 on my SE-R. The basic setup was pretty easy. I used valving intended for hot-air balloon burners and extra NO2 foggers for the nozzles, but I already have a predictable airflow and pressure upon dispersal. I bet there are commercial parts available for your application, if not a complete kit.