# Propane for i.c. Engines



## Brian Rupnow (Mar 3, 2013)

Now that I am near the end of my build on the Odds and Ends engine, I'm wondering exactly what I would need to run it on propane as opposed to gasoline. I'm sure its more complex than running a hose from my Bernzomatic propane torch up to the carbs air intake!!! What would I need, and where would I buy it, and roughly what does it cost. Any help would be greatly appreciated.---Brian


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## canadianhorsepower (Mar 3, 2013)

Brian Rupnow said:


> Now that I am near the end of my build on the Odds and Ends engine, I'm wondering exactly what I would need to run it on propane as opposed to gasoline. I'm sure its more complex than running a hose from my Bernzomatic propane torch up to the carbs air intake!!! What would I need, and where would I buy it, and roughly what does it cost. Any help would be greatly appreciated.---Brian


 
Brian, 
it's that easy simply use a small propane tank UPSIDE DOWN
and meter the volume like you would do with a small screw. This would
work perfect on a hit and miss, but nothing else.
A vaporizer for propane is like a slide carburator, the more throttle
you give the more fuel goes to your system and air at the same time
like a Mikunie carb
Smaller plug gap and more ignition timing is needed.

THIS IS IN BOLD LETTER FOR ONE REASON IT'S VERY IMPORTANT:fan:
DO NOT TRY TO SPRAY NORMAL GASOLINE WITH A SPRAY BOTTLE TO KEEP YOUR ENGINE RUNNING IF IT WANT'S TO STALL
THIS WILL WORK LIKE A TORCHE MELT YOUR MOTOR YOUR WORK BENCH
AND MAYBE YOUR SHOP.

COMP RATIO ABOVE 8.5


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## stevehuckss396 (Mar 3, 2013)

There were some plans around for a small demand regulator. I'll post them up. I have not built this device but it is supposed to go between the tank and engine. I'm sure someone here will know how to use it. 

View attachment propane_demand_regulator.pdf


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## canadianhorsepower (Mar 3, 2013)

stevehuckss396 said:


> There were some plans around for a small demand regulator. I'll post them up. I have not built this device but it is supposed to go between the tank and engine. I'm sure someone here will know how to use it.


 
Thanks for the posting Steve, I completely forgot to put this in my 
red bold part of the article:wall::wall::wall:

This is not a regulator but a safety switch.
the motor is not running!!!!
not creating vacuum !!!!!!
no propane
NO PROPANE NO EXPLOSION:fan:
 here in Canada we some time bypass this in very cold weather because of pressure lost

Brian, make sure your power plant work 100% before going to propane
and you'll be in business........... other wise you might be in heaven:hDe:
THANKS AGAIN STEVE I HAD TOTALY FORGOT ABOUT THIS SAFETY PARTThm:


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## Brian Rupnow (Mar 3, 2013)

Luc--Why would I turn the bottle upside down?


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## dreeves (Mar 3, 2013)

Brian, I use the demand valve Steve posted to run my Upshur farm engine. I use map gas in the yellow bottle. I had the put a small dia orfice in the air in let of the carb. The engine runs great on the map gas. I will try to put a picture and video of my setup

Dave


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## canadianhorsepower (Mar 3, 2013)

Brian Rupnow said:


> Luc--Why would I turn the bottle upside down?


 
so you would have liquid propane and not gas propane
 they have the same value but liquid is much easier to control


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## canadianhorsepower (Mar 3, 2013)

dreeves said:


> Brian, I use the demand valve Steve posted to run my Upshur farm engine. I use map gas in the yellow bottle. I had the put a small dia orfice in the air in let of the carb. The engine runs great on the map gas. I will try to put a picture and video of my setup
> 
> Dave


 
It's almost word to word what I've said


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## starnovice (Mar 3, 2013)

stevehuckss396 said:


> There were some plans around for a small demand regulator. I'll post them up. I have not built this device but it is supposed to go between the tank and engine. I'm sure someone here will know how to use it.



The guy who designed this is a friend of mine (and several other people on this forum).  I don't believe he gets on this forum very often if ever but if you have any questions I would be glad to give him a call.  He is a very nice guy and is always willing to help.  He, and most of his buddies use this regulator right from the start and never use gas.

Pat


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## canadianhorsepower (Mar 3, 2013)

starnovice said:


> The guy who designed this is a friend of mine (and several other people on this forum). I don't believe he gets on this forum very often if ever but if you have any questions I would be glad to give him a call. He is a very nice guy and is always willing to help. He, and most of his buddies use this regulator right from the start and never use gas.
> 
> Pat


.
 I'm a license lpg togas convertion and propably did 500 of them before you were born. Your freind could be right. but don't make people assume that I'm wrong, specialy when you don't know the answer


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## dreeves (Mar 3, 2013)

There is no reason to get your panties in a bunch because some else has something to say.  This forum is for people to give different ways to get thing done. I for one take things from everyone and come up with a way to get the job done. Just because you are certified to do lp conversions sometime thing on a big scale don't work in scale. I for one love the demand regulator. I would like to see what you use on you model gas engine. I'm always looking for new things to try.

Dave


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## idahoan (Mar 3, 2013)

My buddy and I have also made several regulators each from Richards prints and they work great! I have never herd of anyone using liquid propane to run a model engine but I suppose it is possible.

Nice thing about the demand regulator is that it only pulls fuel when the vacuum of the engine opens the valve.


Dave


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## dreeves (Mar 3, 2013)

Brian,

Here is the demand regulator I made. I made it as a block of 2 so when I get my second gas engine done it will run both.

I hope the video works
http://www.homemodelenginemachinist.com/video/upshur-farm-engine-22.html

DAve


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## Brian Rupnow (Mar 3, 2013)

Dave--Could you please explain a bit about the "smaller orifice in the air inlet" that you had to put into the carburetor. Was that to create either more or less suction to operate the demand valve? Also, what is the difference in map gas and propane. I see that your yellow map gas bottle is laying on its side. Does map gas have a liquid component similar to propane? I was taught long ago to never ever turn a propane bottle on its side or upside down while using it, because there is such a tremendous differential in volume between liquid propane and gaseous propane that the torch flame would grow very large, dangerous, and uncontrolable if liquid propane started to squirt from the nozzle while you were using it. Also, I can not see clearly in the video, but does the line from the demand regulator run to the carb fitting that would normally be the one the gas line attaches to or does it run directly to the air inlet of the carb. Does the carb still use a needle and seat arrangement same as a gasoline type carburetor?


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## dreeves (Mar 3, 2013)

Brian, I believe he the smaller orifice is because it does not need as much air as liquid fuel. It will also increase the suction action on the demand valve. The map gas burns hotter than propane. I have never had a problem with the tank on its side with no difference if upright or on its side. I will check on you if it's safe to have it on its side. Thanks for letting me know of the danger.

I will check the size of the hole in this carb and let you know on Monday. Keep up the good work

Dave


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## canadianhorsepower (Mar 4, 2013)

idahoan said:


> My buddy and I have also made several regulators each from Richards prints and they work great! I have never herd of anyone using liquid propane to run a model engine but I suppose it is possible.
> 
> Nice thing about the demand regulator is that it only pulls fuel when the vacuum of the engine opens the valve.
> 
> ...


 
I'm not saying that his "regulator" is not working what I'm saying it's not a regulator it's a safety switch like the attachement here.

As for using LPG for a model engine I never seen one eather


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## MachineTom (Mar 4, 2013)

Heres some background to build your ideas from. A full scale IC engine on propane begins with liquid propane plumbed a convertor, At less than about 80PSI propane is a vapor, not a liquid. so a convertor regulates the pressure to a much lower amount so that the propane is now a vapor, it then goes to a carbarator of sorts, this device lowers the pressure of the propane, to a bit less than outside air pressure. This is so no fuel will flow unless there is a vacuum between the carb and the engine to draw the propane in. 

You can't feed liquid propane to a gasoline carb, as it will boil off as soon as the pressure is less than 80psi. For a small engine that does not have a changing load, you could come up with a system that dribbles the liquid at the right amount to run an IC engine. 

Beware of liquid propane, it will give you instant frostbite, also careful touching the devise that converts the liquid to gas as it also gets very cold.


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## canadianhorsepower (Mar 4, 2013)

[quoteI have never had a problem with the tank on its side with no difference if upright or on its side. I will check on you if it's safe to have it on its side. Thanks for letting me know of the danger.
][/quote]

Dave, usually your not suppose to use it on it's side.
 but an easy way to check this, simply put the torche attachement on it and slowly turn it upside down
if it's like propane it will sputter and have big flame comming out of it

I didn't get what you men by the small hole you did to your carb


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## mnay (Mar 4, 2013)

I have two friends that have built these demand valves.  They use a small barbeque type regulator on the bottle and the demand valve in between. We stand the bottle upright to avoid any liquid problems.
You typically have to block about 50% of the carburetor opening to get them to run and just feed the propane where the fuel line would normally go.   We a tried it on my small Coles hit and miss and it ran great.  They also run clean, but make sure you supply some lube to the cylinder and valves
Mike


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## Rustkolector (Mar 5, 2013)

Interesting thread! I have two model engines running propane and I consider it the perfect fuel for many types of model engines. To address some of Brians questions, the orfice plate in the carb intake is to get a good vacuum signal at the carb fuel inlet which is needed to get flow from the demand regulator. The orfice plate in the carb inlet is a substitute for a properly sized venturi (not easy) and works just as well. A variable orfice plate is even better. A fuel flow schematic would show gas from the upright bottle going through a bottle mounted pressure regulator (4.0"water column to 0.5 psi) to the demand regulator, and from the demand regulator to the carb fuel inlet fitting. There is only negative pressure from the demand regulator to the carb so light vinyl tubing is fine. I use a Weber Go Anywhere portable gas grill regulator on the fuel bottle. It puts out 4" water column pressure and again, vinyl tubing with barb connections is ok on the pressure side of the demand regulator.

For hit and miss operation a simple fuel mixer with a needle valve is all that is needed. For throttle governed engines, and two jet carb is preferred.

Fueling with liquid propane is not for model engine use, and requires a combination vaporizer/pressure regulator. The phase change of propane from liquid state to vapor absorbs a tremendous amount of heat at the phase change point. If allowed to enter the carb in the liquid state it would quickly freeze it solid. Commercial vaporizers use engine jacket water heat to provide the heat needed for vaporization.

When you build the demand regulator be sure to include the "priming button". This button on the top of the regulator over rides the diaphram spring and allows gas to flow when depressed. Makes starting a cold engine very easy. 

Jeff


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## Paulsv (Mar 5, 2013)

Brian-

You might want to check the plans for sale on Jerry Howell's website:

http://www.model-engine-plans.com/engineplans/bookshelf/demandvalve.htm

He also sells the parts- a needle valve set and a diaphragm.

As I undestand it, you should have both a regulator on the gas bottle and a demand valve in the line.  The demand valve doesn't regulate the pressure- it just blocks flow when there is no vacuum from the engine.

BTW, I have just started on a Webster as my first engine, and am finding your build log very helpful.  My plan is to build it and (hopefully) get it running on a regular carb, and then see if I can convert it to propane with Jerry's plan.


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## dreeves (Mar 5, 2013)

Jerry's plans for the demand regulator look to be the same as posted by Steve. The picture looks the same as my demand valve.

Dave


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## canadianhorsepower (Mar 5, 2013)

Paulsv said:


> Brian-
> 
> You might want to check the plans for sale on Jerry Howell's website:
> 
> ...


 


> The demand valve doesn't regulate the pressure- it just blocks flow when there is no vacuum from the engine.


yes go and look at post 16 that a comercial type ben used for 40 years


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## petertha (Mar 5, 2013)

I work in the petroleum industry & was wondering if the potential for misunderstanding was tied up in semantics: &#8216;gas&#8217; vs &#8216;liquid&#8217; propane&#8230; as in LPG (Liquified Petroleum Gas) or GPL, or LP Gas. Those labels usually referto the typical storage/transport state contained in its pressurized tank as opposed to its lower pressure gaseous form present at a typical burner tip. 

I got wondering how conversions were done on (liquid) gasoline injector engines. A bit of googling showed this alternate fuel technology has many facets as indicated below. But I suspect this model engine application is intending to replacing its &#8216;gas&#8217; (meaning liquid gasoline which has now been atomized into a dense gaseous form in the carb) with propane &#8216;gas&#8217;, no?
http://www.sleegers.ca/solutions/tech/index.php
_There are a wide variety of technologies available from around the world to convert vehicles from gasoline to propane. These technologies are designed to operate on today&#8217;s modern electronicallycontrolled engines. Various technologies are available including:_
_-Mono fuel liquid injection (vehicle starts and runs on propane liquid only)_
_-Mono fuel vapour injection (vehicle starts and runs on propane vapour only)_
_-Dual fuel liquid injection (vehicle starts on gasoline and automatically switches to propane liquid)_
_-Dual fuel vapour injection (vehicle starts on gasoline and automatically switches to propane vapour)_


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## mu38&Bg# (Mar 6, 2013)

The demand valve does regulate pressure - relative to the reference pressure, atmosphere. It will always be slightly below the reference pressure and there is a small pressure drop with flow that must be accounted for in the design. The demand valve can't do a very good job going from 100+PSI to atmospheric in a single stage, so a separate pressure regulator is required for it to function well. The demand valve serves the same function as the float and needle in a float carb or the diaphragm and needle in a diaphragm carb (Walbro). Quite obviously the drawings use a diaphragm and needle, but instead of metering liquid fuel they meter gaseous propane. The design attempts to flow as much fuel as is required by the engine at a known pressure. A Walbro metering diaphragm and needle (demand valve) operate with a ~5psi fuel pressure.

Greg


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