When I decided to convert my GC 06 Overland to a dual fuel system, I found little information on the web and it was not always consistent and some claimed that the HEMI could not be converted. Anyway, I wanted to share my experience and impressions but bottom line up front is that the 5.7/6.1 HEMI can be converted with pretty much any Vapor Sequential Injection (VSI) system.
Few in the US will be familiar with LPG but it stands for Liquid Petroleum Gas and is a generic name for a mixture of propane and butane.
I did this conversion for purely economical reasons. I am based in Kosovo and travel frequently to the Former Yugoslav Republic of Macedonia, Serbia, Montenegro, Hungary and Greece. Gasoline is at about $6 /gallon while LPG is between $2.2 and $3.
I had a LPG system on my 96 Cherokee 4.0 and did not experience any mechanical or reliability issues with it. However, that was a carburator conversion and systems for that have been around since the sixties. You loose a lot of power and LPG consumption can be as much as 25% higher when compared to gasoline but it was dirt cheap and I got my investment back in no time.
For the 5.7 HEMI I used a VSI system. In short, you put a tank in the trunk or in lieu of the spare wheel and a fuel line brings the LPG, in its liquid form, to a reducer in which the fuel is warmed and changes to its gas form before being sent to a filter which feeds an LPG injector rail which distributes the LPG to the inlet manifold. There are a bunch a valves and tubing involved as well.
Here's a schematic of the complete system:
The point here is that the LPG is fed to the engine the same way as gasoline and the system has its own fuel mapping ECU which functions in a master-slave configuration with the car's system. In other words its a fully integrated system. This is supposed to ensure that there is no (or at least less) loss of power and that the consumption surplus while on LPG is closer than that of gasoline.
The way it works is that you have a switch to turn the system on and off. For all practical purposes you can leave the system on and never turn it off because the way it works is that the car starts on gasoline and once the engine reaches a certain temperature/cycle it switches automatically to LPG.
That is really about it for the system itself. It took three guys 7 hours to install.
I will eventually time some 0-60 but from a subjective standpoint I did not feel any difference. I took two friends, both car enthusiasts and V8 drivers for a run. We did the first test run on gasoline. I left the car on gasoline but told them that I had switched to LPG for comparison and we did the same run. Both claim to have noticed a slight drop in power. We did the run a third time where I switched to LPG but telling them that I put it back on gasoline. This time they claim to have noticed a slight increase in power.
I burn between 10 and 15 % more LPG than gasoline which brings me at anywhere between 18 – 20 liters (LPG)/ 100 Km depending on route and driving style . The system cost me EUR 1,600 installed and I will be making that money back in under a year.
Some pics now:
The cap next to the trailer hitch is the LPG filling outlet.
The tank. It has a capacity of 73 liters but these tanks cannot be filled over 80% capacity as a security measure so its 58 liters/ 15 gallons effective and that gives me roughly 300 Km/185 miles autonomy.
This would be the system switch. You got to make an effort to see it from the driver seat and its invisible to all passengers. The orange light tells me that the system is on, the green one that the car is on LPG and the red one that the LPG tank is almost empty.
You can see the system's ECO right next to the battery. Most of the components are on the top left (passenger) side of the engine bay.
On this one, you can see the two reducers. The first one at the forefront (with coper screw in middle) and the second one is less visible. Yes, this V-8 system works as a dual 4 cylinder one which is necessary on cars that have this kind of power output.
Here's the LPG injection rail.
And here you can see the LPG tubing feeding directly in the inlet manifold.