propane fuel quandary

[Tom Jamboretz]

I have a few model IC engines running on propane. Using a regulator on 1# bottle with a demand regulator. I also reduce the incoming air with a small orifice in a plate over carb intake.---- At present I'm trying to run a Farmboy engine doing the same thing without good results. The hole in the fuel bar is .022".. That is the size Jerry's plans call for when using gasoline. Do I need to enlarge the hole or make it smaller. What about the choke orifice? Thanks for any ideas. TJ

 

[RichD]

I don't claim to know for sure, but my guess is the .022 orifice was for vaporizing/atomizing the gasoline. The propane regulator will drop the pressure to a very low value ~11 inches of WC(water column). There are ~27.6" WC to the pound so for sure the propane will already be in vapor form. I'd suggest some form of small needle valve to adjust the propane and something similar, but larger to adjust the air flow.

To say it more simple. There should be no need for the .022" orifice anymore.

Just a guess.

 

[Tom Jamboretz]

I don't claim to know for sure, but my guess is the .022 orifice was for vaporizing/atomizing the gasoline. The propane regulator will drop the pressure to a very low value ~11 inches of WC(water column). There are ~27.6" WC to the pound so for sure the propane will already be in vapor form. I'd suggest some form of small needle valve to adjust the propane and something similar, but larger to adjust the air flow.

To say it more simple. There should be no need for the .022" orifice anymore.

Just a guess.

I understand what you are saying. The purpose of a fuel bar is to atomize gasoline. As I have no gasoline I don't need it. Thanks. I'll give that idea a go.

 

[maury]

Tom, if you are using a demand regulator the pressure will be atmospheric at the mixer. You will only get gas into the mixer when there is a vaccuum pulled in the mixer on the intake stroke. By the way, this is the safest way I know to use propane on a model. If you do not use a demand regulator there is always pressure when the gas is turned on, and if the engine quits gas will leak out.

Using gas with a demand regulator requires a different thought process and a different mixer from the conventional. Since gas only flows in when there is a vaccuum, you need to create one by having an adjustable choke plate on the air intake. You will not use a needle valve in the mixer. The mixture is adjusted by adjusting the air intake.

If when you get your engine running this way you find there is too little power you can enlarge the gas hole and re-adjust the mixture. .022 sounds a bit small to me, but I don't know the displacement of your engine.

I happen to be using a demand valve for running a pickup truck - propane conversion. It will run many models simultaneously.

hope this helps,
maury

 

[Tom Jamboretz]

Tom, if you are using a demand regulator the pressure will be atmospheric at the mixer. You will only get gas into the mixer when there is a vaccuum pulled in the mixer on the intake stroke. By the way, this is the safest way I know to use propane on a model. If you do not use a demand regulator there is always pressure when the gas is turned on, and if the engine quits gas will leak out.

Using gas with a demand regulator requires a different thought process and a different mixer from the conventional. Since gas only flows in when there is a vaccuum, you need to create one by having an adjustable choke plate on the air intake. You will not use a needle valve in the mixer. The mixture is adjusted by adjusting the air intake.

If when you get your engine running this way you find there is too little power you can enlarge the gas hole and re-adjust the mixture. .022 sounds a bit small to me, but I don't know the displacement of your engine.

I happen to be using a demand valve for running a pickup truck - propane conversion. It will run many models simultaneously.

hope this helps,

maury

Maury and Rich--- You have both given me some good information on using propane. I have been treating it as gasoline when it is really a pressurized gas. The adjusting of air is the answer. I will make a choke so as to adjust air and let the propane run as it may. Thanks for the help. I'll keep you both posted as to results. TJ

 

[Tom Jamboretz]

Maury and Rich--- You have both given me some good information on using propane. I have been treating it as gasoline when it is really a pressurized gas. The adjusting of air is the answer. I will make a choke so as to adjust air and let the propane run as it may. Thanks for the help. I'll keep you both posted as to results. TJ

Well I made up the choke plate and installed it. Started right up and continued to run. It starts easily. It does have a problem of firing twice before going into coast. Which I assume is lack of power. On occasion it will stroke twice before firing. I have the ign. timing a tad after TDC. Any ideas from anyone? I appreciate the help. TJ