propane use in a moderate to high hp truck

mikmaze

mikmaze

New member
Kicked around the idea a few years ago to go with a propane injection system to help me get a little further on a tank of fuel. I travel often pretty far, and hate getting stuck buying fuel up in no mans land, at stupid prices. I know a spot that I can get to often enough to make it convenient that sells propane pretty cheap, 50 cents a pound when filling bbq sized bottles, price might come down if filling a few larger bottles. What I am not sure of is using the system on a truck like mine, its got a fair amount of power, just don't want to mess things up in a short amount of time just to net a couple mpg. Yes I know the systems are not exactly cheap, but with this new source of inexpensive propane, it may be worth it. Thinking of 40 lb bottles, getting a few, and filling when needed. I know bully dog has a setup, any others worth considering? A DIY build is not out of the question, provided I get some damn good instructions/ parts list.
 
I personally think that you probably would never be able to save enough money to actually pay for the original install... but I am by no means an expert on this, somebody with more knowledge may chime in. Personally I would just put in a titan tank and keep on with good ole #2
 
thought about them too, but a grand for a big piece of plastic...... tough to get my noggin around that concept.
 
I'm installing one of these kits on my '91.5 Cummins:

Diesel Propane Injection Kit Cummins Powerstroke Duramax Up to 100 HP New | eBay

It uses a negative pressure regulator for the injection amount control. I plumbed my coolant to flow through it to ensure the propane is completely vaporized. I can't give you any real world results yet though.

You may run into problems using the BBQ style containers. You're supposed to run a DOT approved tank...however, the main legality here is actually getting someone to fill a non-DOT tank. I snagged a 120 lb DOT tank by Manchester on Craigslist for $25.

It's always a shot in the dark tuning without in-cylinder pressure. The high octane propane won't increase timing (combustion phasing), but it does raise cylinder pressure substantially when it burns. In order to stay under reasonable max pressure limits, I think you're going to have to back timing down slightly with your UDC.

--Eric
 
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Not such a good Idea if you live in a climate prone to extreme changes. I heard but not certain, that LPG is not a clean fuel.
 
With my kit I'm installing a switch to turn a solenoid on/off...and only have it on when the engine is up to temperature (i.e. when the coolant is warm enough to ensure all LP is vaporized well).
 
read it all, and still thinking. probably never happen, I just get too many ideas to do them all.
 
Its fine for a travel extender. Don't expect to ever save any money or get better efficiency from your vehicle, you will still be consuming the same BTU/horsepower to maintain highway speed no matter the fuel.

The money would be better/safer spent on a larger main tank or second bed-mounted tank. No risk of detonation damaging the engine from too much propane and you won't need a second stop to fill the second fuel type.
 
so on a btu basis, 140k per gallon number 2, at about 4 dollars a gallon. propane at 21.5k btu per lb works out to $3.25 per gallon of diesel equivalent. No big savings, and sounds like risk.
 
so on a btu basis, 140k per gallon number 2, at about 4 dollars a gallon. propane at 21.5k btu per lb works out to $3.25 per gallon of diesel equivalent. No big savings, and sounds like risk.
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That's true if you're comparing burning the two fuels in singularity, and assume there is no mutual benefit of combining them. There is a push right now in the R&D automotive world looking at RCCI combustion, or reactivity controlled compression ignition. Essentially, it uses a diesel engine with direct injected diesel along with intake fumigation of a high octane fuel (gasoline/ethanol/etc). It's not too different from introducing propane pre-turbo in our Cummins.

It seems as if there is an efficiency benefit to combining a highly reactive fuel with a low reactivity fuel, moreso than can be seen by looking at the heating values/energy density/etc of the fuels. Looking at a pressure trace vs crank angle, it has to do with maximizing the area under the curve, i.e. maximizing the amount of heat energy you can impart to the piston. The low reactivity fuel (propane) increases cylinder pressure later in the cycle, hence the need to retard timing some to stay under peak pressure limits.

Again, without having an instrumented engine, it's a shot in the dark for tuning. My gut says some have hit it pretty well, and actually do see a decent increase in economy, while others have pushed too close to the edge and see the effects of too much cylinder pressure.

--Eric
 
I bought a 2001 Ford F350 Highboy with 44 inch tires, 4x4, big lift and a 7.3. On the trip back to wis. If i turned propane off I got about 7-10 mpg and had to use ALOT of throttle to maintain 75 mph.
With propane on I got 14-17 mpg and very little throttle to maintain speed. fyi
5 years later the motor went boom, but the idiot that bought it stacked programmers on top of the propane, so i wouldnt blame propane for that.
 
My truck gains 2-3mph and up to 6mpg when the propane is turned on. A BBQ cylinder lasts me 350-400 miles. And the kit cost me about $70
 
matty169 said:
If i turned propane off I got about 7-10 mpg and had to use ALOT of throttle to maintain 75 mph.
With propane on I got 14-17 mpg and very little throttle to maintain speed.
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My truck gains 2-3mph and up to 6mpg when the propane is turned on. A BBQ cylinder lasts me 350-400 miles. And the kit cost me about $70
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Thats called fuel substitution. You're using less throttle because the secondary fuel is being introduced outside the control of the injection pump and the throttle has no connection to it. You're still getting the same 7-10mpg diesel-equivalent efficiency, you're just not including the propane consumption in your math.
 
that is about $7 for a btu to btu equivelent in diesel. So unless you are paying over 7 bux a gal from a strictly btu standpoint, you're better off with straight diesel.
 
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