Propane Conversions

[MossMan]

Around here the State has many vehicles; mostly Jeep Cherokees, that are setup to run on natural gas. I wonder: what, if any, of those mods were done to those engines; where could you fill those up; and lastly if there are any for sale. If a person could get one of those it may be a worthy platform to start with.

 

[Photog]

Natural Gas as an automotive fuel is actually Liquid Natural Gas (LNG). You see this displayed on many city transit busses. The fuel is not the same as that which you get at home. The natural gas you get at home is vapor, not liquid (bummer). Also, LNG is not consistent in its burning properties. LNG has a wide tolerance on the mixtures that make the fuel. The engine would have to be tuned for the "worst case" fuel. It would be like setting up a gas engine for 70 octane fuel, and burning anything from 70 - 96 octane. It isn't the optimum way to get power or economy.

The fuel is stored in special tanks, at the city bus depot, not scattered around town (also a bummer).

LNG does burn cleaner than gasoline, that is why the cities use it. It also reduces engine wear, and repair expenses.

 

[Martinjmpr]

Does anyone on here know if that applies to our domestic expeditions as well as the average farmer or carnival operator? If we could get off-highway diesel for expedition travel, that would save about $.385 in tax in the state of Texas.

I have seen off-road fuel sold at gas pumps in rural areas of Colorado and Kansas. If you trailered your rig to where you were driving it and did not drive it on public roads, you should be fine. However, what is a "public road?" Does a Forest Service jeep trail count as a public road? My gut feeling is that it would, as would any county road, BLM road, or any other road where a licensed vehicle can legally drive. Obviously a racetrack or a dedicated off-road park would not be a "public road" since there is very restricted access to it.

To add to the confusion, it is very common to see certain types of non-registered farm vehicles driving on public roads in rural parts of the country. I assume these vehicles are probably burning non-taxed, dyed fuel, but if so, how can they legally drive on the paved county roads?

The final issue here is one of enforcement. I imagine that places that sell the non-taxed diesel are under strong "encouragement" to report anything that looks like a violation (like the person who drives his diesel F350 or Dodge Ram up to the off-road diesel pump, fills his tank and then drives away.) But if your rig was on a trailer and you drove it up to the pump to fill it, the gas station might not have anything to say about it. And once you get away from the gas pump, who's going to know? It reminds me of a line from that old Bob Dylan song: "In Jersey everything's legal/As long as you don't get caught."

 

[Martinjmpr]

I think there's some apples-and-oranges discussions going on here.

From what I understand (which isn't much ) there are two ways to convert a gasoline vehicle to use propane. You can either convert it to run propane only, or you can convert it to run propane and gasoline both.

The advantage of the propane only is that it should be considerably more efficient in burning propane than the compromise engine. The advantage of the dual-fuel engine is, duh, the ability to use dual fuels.

So what is more important? The ability to use multiple fuels or the efficiency of propane only? That depends on the user.

And for the gas/propane engines, how does one convert back and forth? Is it as simple as flipping a switch on the dashboard, or does it require you to get under the truck, remove or switch fuel lines, or make other changes to the vehicle?

An additional worry I'd have with propane is how the fuel is stored. BBQ propane is stored in a pressurized cylinder. Where would the pressurized tank be mounted and how would it be prevented from rupturing, which could be catastrophic? Would you have more than one tank?

It may be that as gas gets more expensive, propane will become more viable, but I think answers to the above questions need to be found before we will start seeing propane conversions as a matter of course.

Having said that, a fuel that is cheaper than gasoline, burns cleaner, requires less maintenance, and is locally sourced would be of great interest to me, provided the conversion was not prohibitively expensive and there were enough fuel stations around to make it viable.

I'd probably print out a list of gas stations along with their exact locations, hours of operation and phone numbers before taking off on any long trip, but beyond that I would think it wouldn't be all that difficult. Now, outside the US would probably be a different story.

 

[ntsqd]

My understanding of how older dual fuels are switched is with a pair of solenoid valves. The propane system will have one anyway, so you'd need only add one to the gasoline supply system or turn off it's electric fuel pump.

Late model dual fuels use EFI for the gasoline. I don't know how they handle the propane. I do know that about '98-'00 some considerable effort on the part of many firms & labs went into liquid injection of propane. There were all sorts of battles to be fought. Injector sizing, injector freezing, etc. When I graduated I lost track of the progress so I've no idea how viable those systems became.

Propane is stored at under 300 psi. I think 170 psi is about average, but apparently certain conditions can drive it into the upper 200's somewhere.

FWIW, I think that with a little more than normal care in the design & fab of a fuel tank skidplate that the odds of a rupture will be about equal to a non-pressurized fuel tank. The fellow with the EB I previously mentioned has run one of the Hammers trails and has done a lot of other hard core off roading. I asked him about the potential hazzard and his thinking was "Skidplate!" and it'll be good.

To me the biggest issue is the loss of fuel capacity due to the necessarily round fuel tank(s) shape.

 

[Photog]

Observations from someone with experience is most valuabel. Thank you!

By the way, did you make the proper internal changes to your engine, to make the most of your propane conversion, on your F250 (i.e. cam design with wide lobe separation and medium duration, compression ratio of 11:1, spark timing, etc)? Propane is typically about 107 octane rated.