Propane for i.c. Engines

[Paulsv]

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.

 

[dreeves]

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

 

[canadianhorsepower]

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.

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

 

[petertha]

I work in the petroleum industry & was wondering if the potential for misunderstanding was tied up in semantics: ‘gas’ vs ‘liquid’ propane… 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 ‘gas’ (meaning liquid gasoline which has now been atomized into a dense gaseous form in the carb) with propane ‘gas’, 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’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)

 

[mu38&Bg#]

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