Thread: Dual fuel-propane and gasoline

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lamin8r, my Dodge was supposed to be dual fuel but the PO never used the gasoline EFI so it was all clogged up and disconnected. At -40, I had to drive something else, the propane wouldn't flow.
Another thing...with any pressurized gas, you can't use underground parking, and they get all hyper when you drive on a closed ferryboat. They make you shut off the tank valve as soon as you stop. And I've been told, but never looked in to it, that if your garage goes up in flames with a propane vehicle in it, there's no insurance. Which all seems strange when you consider how many little forklifts there are in big warehouses that are running on propane so the monoxide doesn't kill everybody!
BTW, you are talking LPG gas, which is a different animal altogether from propane. Thousands of pounds pressure in the tank instead of less that a hundred with propane. Around here, you need a megabuck compresser to use that stuff. A neighbour had a test setup installed for free, and he still said it didn't pay! He ran all his tractors on LPG, as well as his road vehicles. In busy farming seasons, the compresser couldn't keep up with the demand of all the machines needing fuel every night.
No, thanks, I'll stick with gasoline!

Rereading posts, I think I have mixed up LNG with LPG a few times.

To answer the OP's question about dual fuel systems and TBI, the propane system still requires the use of a mixer to supply propane to the engine. The difference between a propane mixer and a propane carburetor is that the carburetor has throttle valves (usually using the throttle body from a gasoline carburetor) in addition to the mixer. Therefore, a straight (mono-fuel) propane system replaces the gasoline carburetor with a propane carburetor. A dual fuel system adds a mixer (typically upstream) of the gasoline carburetor and solenoid valves on the fuel lines determine which system supplies fuel to the engine. As described by lamin8r, you switch back & forth between fuels with a 3-position switch that energizes the appropriate solenoid valves.

Mixers are used with carburetor and TBI engines. Multiport EFI engines are best converted with injection conversions. That is, rather than having a mixer fumigate propane into the intake manifold, an injection conversion adds a parallel injection system to the engine and has propane injector nozzles installed at the intake ports. Although theoretically possible to have propane port-injection with a gasoline TBI system, there are no commercial systems that do this. Technocarb still makes dual fuel TBI conversions.

On an energy basis, a gallon of propane has about 74% of the energy of gasoline. However, open-loop propane mixer systems typically get more like 75-80% of the vehicle's gasoline economy. Feedback systems generally get better fuel economy than open-loop systems. Because of the lower energy content of propane, propane needs to priced much less than 74% of the price of gasoline to have a reasonable payback on the conversion. The lower price should still make up for the slightly lower fuel economy from the additional weight of the propane tank.

The retail price of propane is usually very high compared to gasoline because there is high margin on small volume sales (like 20# BBQ cylinders). To get a much better price on motor fuel, you would have to get an account with a propane supplier. For example, Ferrell Gas in Buffalo, NY is selling propane for $2.35/gallon (winter price), which is their first quantity break (1000-5000 gallons/year). If you would have locked-in the price last summer when the market was low, your price for this year would have been $1.95/gallon. The taxes on motor fuel in NY state amount to $0.2635/gallon so your total price for propane could have been $2.2135/gallon.

Do NOT use a 100# cylinder in an on-road vehicle. It is illegal and will not pass NPFA 58. Only use ASME motor fuel tanks for on-road applications.

Propane burns marginally hotter than gasoline. It has a different flame speed than gasoline so it is very important to use a propane-specific advance curve. This is a bit more challenging to do with dual fuel systems now that Dual Curve is gone but there are alternatives.

Although you can increase your CR to take advantage of propane's 104 octane rating, it is not necessary. For street engines, a 10:1 CR will work well and you keep high-test gasoline in the tank for dual fuel systems. With a dual fuel system, you would primarily be using gasoline to keep it from becoming stale so the added cost of high test would really be negligible.

If you travel long distances, it is a good idea to plan your trips around fuel stops. Propane is plentiful in the USA, but cheap fuel is what you're after. Check the following sites for alternative fuel locations:

• Alternative Fuel Fill Stations and Prices
• Alternative Fuels and Advanced Vehicles Data Center: Alternative Fueling Station Locator
• Pilot Flying J - Fuel Pricing

As to hoses being ripped of and the vehicle exploding........ any _proper_ installation will have an excess flow valve in the tank outlet which makes this type of issue almost impossible. much less likely than a gas vehicle having a hose ripped loose and the vehicle bursts into a ball of flame.
Only in Hollywood.

Russ

I visited Las Vegas back in the 70's and, IIRC, the taxi driver we rode with mentioned that his taxi was running on Natural Gas. As a matter of fact, he thanked us as Canadians since the gas came from Alberta and he said he was saving a lot of money using it.

Originally Posted by lotsatoys

As to hoses being ripped of and the vehicle exploding........ any _proper_ installation will have an excess flow valve in the tank outlet which makes this type of issue almost impossible. much less likely than a gas vehicle having a hose ripped loose and the vehicle bursts into a ball of flame.
Only in Hollywood.

Russ

I hope you're not calling me a liar!

Originally Posted by NTFDAY

I hope you're not calling me a liar!

absolutly not. sorry if you took it that way. just saying a _proper_ installation makes a propane system very very safe, and nearly impossible to make explode. then again.... anything can and does happen under the right set of cercumstances (no matter what the fuel).

Russ

Well you know it's a cinch nothing has been changed or improved since the original stuff came out!!!!!

Kind of like in the early 1900's when many were sure that automobile thing was just a whim and they'd stick with their horses?????

40 years ago, before the takeover in agricultural self-powered implements with the diesel engines, many, many farmers were running dual fuel LPG and gasoline as a cost savings measure.... worked fine then! And now, some of these "idiots" running diesels are actually trying bio-diesel!!!!! Then we could go back to my original statement and they could just run a really nice team of Strawberry Roan workhorses and life would be much better, right???? Trying new things is both interesting and educational.....and sometimes they actually work out!

Just think,Dave..if ya tried to hitch up a pair of work horses now,there would be some namby pamby action group would probably try to get you into court for exploiting dumb animals...

Originally Posted by lamin8r

Just think,Dave..if ya tried to hitch up a pair of work horses now,there would be some namby pamby action group would probably try to get you into court for exploiting dumb animals...

Probably....

Found some good information here;

Main Page - Raso Enterprises Auto Parts

yeah, and now the by product costs more then the product they're refining for......Never have figured out how that works!!!!!

Dave..I wonder how many "Strawberry Roans" I'd need to pull my 44 foot air seeder? Or 60' of harrow/packer hitch?
I'd have to seed my whole farm to horse feed to keep 'em alive, and what would keep me alive?
Well, at least this year I'd have lots of water for 'em! 200 acres a couple of feet deep!

Originally Posted by R Pope

Dave..I wonder how many "Strawberry Roans" I'd need to pull my 44 foot air seeder? Or 60' of harrow/packer hitch?
I'd have to seed my whole farm to horse feed to keep 'em alive, and what would keep me alive?
Well, at least this year I'd have lots of water for 'em! 200 acres a couple of feet deep!

Wow!!! You guys have some big time flooding again, huh??? Do they offer "no plant" insurance up there? Brother in law farms all his land and mine, sez he'll be out about 160 acres this year from the water.....

Dave... there is a "flooded acres" deal with crop insurance that purports to give you 100 dollars an acre but the last time we got drowned like this, I applied for it and after all the tookage and screwage I got about 500 bucks! I run without that gov't program now. It takes a total failure just to get the premium back.