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Propane and Natural Gas Fuel Delivery and Tuning Discussion about the care and feeding of Propane and Natural Gas Engines.

Propane and Natural Gas Fuel Delivery and Tuning

Natural Gas Engines in Cold Weather


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  #41  
Old 10-26-2018, 12:10:21 AM
dkamp dkamp is offline
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Default Re: natural gas engines in cold weather

Well, it depends on the circumstance. Initially (like, when you do the first startup of a new system with a really, really big engine and a long supply pipe), you'll probably need to uncap the drip leg and crack the fuel supply valve and let it flow a little gas through, then cap the drip leg, and push the 'prime' button on the demand regulator (if yours has one), then start it.

If your supply pipe is short, another easy way is to crank the engine, and feed it a shot of something flammable so it'll start, and keep it running that way 'till it draws fuel gas vapors on it's own. An inexpensive propane torch head threaded on a bottle... open the fuel valve just a little, and stuff the head (not lit... juts flowing) into the air inlet will frequently be enough to fire up an engine... just keep it there for a little while, and when the main fuel system finally flows clean fuel gas, the engine will start sounding different.

Which is something that should be noted- most engine guys will listen to a gasoline motor and know when it's sounding 'rich' or 'lean'.

When running a gaseous fuel engine, it acts just the opposite of a liquid fuel engine...
...so when you're 'priming' it with an auxiliary propane bottle, when the engine starts sounding 'lean', pull the propane bottle out. ;-)
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  #42  
Old 10-26-2018, 07:44:27 AM
cjjmw cjjmw is offline
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Default Re: Natural Gas Engines in Cold Weather

Interesting.


All of the "conversion kits" I see online look like they're nothing more than the regulator and just a spacer with a tube in it to feed the fuel. The spacer gets mounted at the inlet of the carburetor. Some are even just a cheesy nozzle that aims down the throat of the carb.

Is there no metering device other than the regulator? They don't even look like a venturi, unless I missed something.

If that's the case, to convert the small 8HP Briggs I have, all I need to do is drill and tap the air filter elbow and connect it to a regulator and I'm done.

That seems way too easy though.
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  #43  
Old 10-26-2018, 09:11:34 AM
cornbinder89 cornbinder89 is offline
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Default Re: Natural Gas Engines in Cold Weather

There is a little more to it than that, but basically you are correct. The fuel inlet to the engine needs a vacuum signal, so either a venturi of its own, or the one on the liquid fuel carb.
The regulator meter fuel from the vacuum signal it gets from the carb.
There are things like fuel lock offs that should be installed as well. The regulator will stop the fuel flow when no vacuum is present, but for safetys sake you want another lock off so no gas can flow when the engine if not in use.
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  #44  
Old 10-26-2018, 09:26:14 AM
Odin Odin is offline
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Default Re: Natural Gas Engines in Cold Weather

The IMPCO system used for LPG forklifts has a demand regulator heated by the jacket water so it won't freeze, and then a venturi in the air pipe that makes the engine suck in the fuel so the demand regulator gets the vacuum signal it needs to operate properly. A simple needle valve is used to trim the mixture to make the engine happy, and can indeed be set by how the engine sounds and feels.

I would think a natural gas system could be implemented in similar fashion, but the jacket water loop enclosing the regulator would not be necessary since it wouldn't be vaporizing a liquid fuel.
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  #45  
Old 10-26-2018, 09:43:46 AM
cornbinder89 cornbinder89 is offline
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Default Re: Natural Gas Engines in Cold Weather

I did dual fuel conversions on manlifts, from little Subaru-Robins, to Ford 300's and they were all done like you say. Easy job.
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  #46  
Old 10-26-2018, 09:44:57 AM
cjjmw cjjmw is offline
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Default Re: Natural Gas Engines in Cold Weather

How critical is the design of the venturi?
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  #47  
Old 10-26-2018, 10:45:12 AM
cornbinder89 cornbinder89 is offline
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Default Re: Natural Gas Engines in Cold Weather

If there was no venturi at all, it may have trouble metering at low power/idle. but in general I'd say not very critical. You just need a vacuum signal to the regulator to "tell it" how much airflow is going thru the throttle plate.
Having said that, if this is going to be a dedicated NG engine, best results will be had with a vapor carb. Dual/triple fuel is always a compromise between being able to burn more than one fuel, and being optimized for any.
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  #48  
Old 10-26-2018, 10:53:37 AM
ronm ronm is offline
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Default Re: Natural Gas Engines in Cold Weather

Quote:
Originally Posted by Odin View Post
The IMPCO system used for LPG forklifts has a demand regulator heated by the jacket water so it won't freeze, and then a venturi in the air pipe that makes the engine suck in the fuel so the demand regulator gets the vacuum signal it needs to operate properly. A simple needle valve is used to trim the mixture to make the engine happy, and can indeed be set by how the engine sounds and feels.

I would think a natural gas system could be implemented in similar fashion, but the jacket water loop enclosing the regulator would not be necessary since it wouldn't be vaporizing a liquid fuel.
That is the same as the OEM systems that used to be on LP farm tractors. The converter was a demand regulator, didn't flow any gas until the engine started. The converter was fed liquid & circulated water to vaporize it. They had a liquid valve & a vapor valve on the tank. You had to start it on vapor & switch to liquid when the water got warm. The engine would not develop full power on vapor.
To somewhat relate to the original subject, imagine that, there was a fad here at one time to bring LP tractors in from Texas where they were common. Dairies & feedlots bought them to be easier starting than Diesels in cold weather...oops...found out that at -20, LP does not flow well at all. They all went back to Diesels after a couple years, at least they would start with a snort of ether if plugged in...
Apologize if this is redundant...I gave up on plowing through all the OT BS about A/C...
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  #49  
Old 10-26-2018, 11:06:18 AM
cjjmw cjjmw is offline
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Default Re: Natural Gas Engines in Cold Weather

Quote:
Originally Posted by cornbinder89 View Post
If there was no venturi at all, it may have trouble metering at low power/idle. but in general I'd say not very critical. You just need a vacuum signal to the regulator to "tell it" how much airflow is going thru the throttle plate.
Having said that, if this is going to be a dedicated NG engine, best results will be had with a vapor carb. Dual/triple fuel is always a compromise between being able to burn more than one fuel, and being optimized for any.
I've been on the fence about it being dual\tri fuel........
Part of me is tired of dealing with gasoline in something that is rarely used, and ethanol just makes it even more fun.

I was thinking two venturis (gasoline carb + the added one) didn't sound optimal.....

I'm guessing if I wanted to make it strictly LPG\NG all I'd need to do is drill out the main jet so a fairly large size and connect directly to that. I highly doubt anyone makes or made an actual vapor carb for a small 8HP B&S engine from 1992.

The two liquid cooled 4 cylinder Hesco units from the 1980s I'm doing for my boss very likely have such a thing, but finding them would be the challenge.
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Old 10-26-2018, 11:11:11 AM
cornbinder89 cornbinder89 is offline
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Default Re: Natural Gas Engines in Cold Weather

I worked on M.A.N. powered city buses that were LP. They were a bear to get running in Chicago's winter. At -23 there just wasn't tank pressure to feed the big M.A.N even when they used multiple tanks. They only used liquid draw, with a pair of heated regulators and a single big mixer.

---------- Post added at 10:11:11 AM ---------- Previous post was at 10:07:51 AM ----------

It's been a while since I went searching for LP stuff, but there used to be a lot of carbs for different sized equipment.
I have a 525 CID Buda I hope someday to convert to LP. Right now it has a BIG 1bbl gas carb.
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