Not all LP gas systems are designed equal. There are those cheapie conversions (the ones that often leave vehicles bonnet-up at the side of the road), and then there are car manufacturer approved LPG installs. These are the far superior conversions, because if the system is factory approved (and therefore honoured under new car warranty) it has to be relatively well engineered and trouble-free. Not like a Joe's pieced-together universal gas conversion that, for some strange reason, keeps backfiring and blowing the airbox into pieces! In this situation, it's probably not the quality of the individual components that is solely to blame; it's the "custom" installation technique...
To illustrate how far gas installations have come over the past few years (mainly due to car manufacturer intervention) we've followed the factory-approved installation of an Impco gas system onto a brand new Holden Rodeo V6 dual cab. Manufacturer-approved gas installations rarely take place inside the new car dealership. Rather, the job is usually farmed out to an Impco-accredited workshop - such as ABBA Mechanical Repairs in Adelaide. Note that only a trained Impco outlet - qualified to convert your specific vehicle - can fit a system that won't void your new car's engine warranty.
The Factory Approved LP Gas Installation Process...
Kicking off, the number one task is to remove the factory rear section of exhaust pipe. This is necessary to make maximum space for the new rear-mounted 60-litre LPG cylinder. Next, the installer will route the copper-cored gas line from the front of the vehicle to the gas tank area. The gas line is secured to the underbody using a series of high quality screw-in fasteners.
Next comes the installation of the gas tank. Using a hydraulic lift, the bulky cylinder is raised under the body and manoeuvred into its correct position. With the cylinder position finalised, it is secured to the vehicle using extra heavy-duty bolts. Absolutely no cutting or fabrication is required to put the tank to the body.
That hanging LP gas line can now be fitted into the tank. This is done by flaring the end of the gas line and inserting a flare nut to enable it to screw into the tank fitting.
And now we come to the gas filler. The Rodeo's new owner has the choice of having the filler positioned next to the rear license plate, or in the rear quarter panel. In this instance, the rear quarter was the preferred option. Accordingly, our installer used a metal hole-saw to bore a hole through the Holden's brand-spankers side panel - soon followed by a clean up with a file and a final paint seal around the edge.
The supplied plastic filler cap and assembly (those big ugly chrome filler caps are now a thing of the past!) is pushed through the hole and fastened from behind. The fitment of the filler-to-tank gas line completes this stage of the install.
With the gas cylinder bolted into place, it's time to fit the Impco-supplied rear section of exhaust pipe (which extends from the final factory flange back). Passing further out toward the side of the vehicle (and away from the tank), the new pipe requires a section of the rear mud flap to be cut away. This extra clearance is achieved by removing part of the mud flap with a holesaw and a file.
Next comes the first part of the wiring job. Starting in the Rodeo's engine bay, a section of the Impco loom is tapped into the factory fuse box and neatly routed to the back of the vehicle (next to the factory loom and beside the chassis rail). Each part of the Impco loom is tailored to length.
In addition to the use of split convoluted tubing, this metal stone shield protects the short length of wire that passes inside the front inner wheel arch. Note - since the Rodeo's chassis moves separately to the cab - this shield is not mounted hard up against the body.
The gas system wiring loom that runs through the engine bay is virtually undetectable. Connecting to the main ECU connectors, the Impco system feeds into the throttle position sensor, EGO sensor and injector control harness. Notice that the gas loom runs parallel to the factory engine bay wiring and shares the very same mounting locations. Matching earth lugs and plug-straight-in connectors are also part of the deal so that nothing looks out of place.
The Impco kit comes with a metal bracket to mount the gas converter right along side the factory charcoal canister. The canister does not require relocating. Plugging into the converter are wires for tune-up/diagnosis and the gas lock solenoid. Two hoses are then run from the engine coolant system into the converter. These warm the converter so that it can effectively convert the gas from liquid to vapour.
The last hardware component to go into the vehicle is the gas mixer. The Impco 225 unit used in the Rodeo conversion comes with a cast elbow leading into the throttle body and a short length of convoluted pipe to link the other end to the airbox (which remains in its original location). It all slides on elegantly and clearance around the body of the mixer is ample. Two connections are then made to the mixer. The wiring goes onto the vapour lock (which stops gas continuing into the mixer when you switch over to petrol) and a hose runs into the intake manifold (to give the mixer the right vacuum signal so it can determine mixtures).
The still-left-in-the-box Impco loom and electronics can now be wired into the vehicle's cabin. The components that go in are the gas on/off switch and two separate computers for the gas management and for interfacing with the factory ECU (it fools the factory ECU into thinking it's still running the injectors when they're actually switched off). Their adjoining loom - again - features cut-to-length wires and the ready-made brackets that the brain boxes are mounted on are also a nice touch. No tank level gauge was required in this conversion, as the factory fuel gauge is automatically configured to display this when you switch to running gas.
With hardware mounted, it's time to drive down to the servo (on petrol!) and fill the gas tank up. With a belly full of good-stuff, the installer can now set about tuning the gas system for peak performance. This is simply a matter of finding the tune-up/diagnosis connector under the bonnet and plugging in the Impco Fuel System Analyser. Taking measurement from the factory EGO sensor, the analyser displays the (at idle) air/fuel ratio. The tuner aims to get the numerical reading to 50 (which represents lambda) by adjusting a screw on the mixer.
With this done, the last phase of tuning is nothing more than to go for a drive. After tapping into the Impco system's tune-up-diagnosis connector, the gas computer automatically goes into around 24 minutes of self-learn mode. During these 24 minutes, the vehicle is driven under a variety of operating conditions - cruise, on/off throttle and heavy load and rpm.
After being paid to cruise around in a new car for a while, the last job of the installer is to fit a LPG warning tag onto the body. And that's it - after only about one full day, the job is done!
So what are the main differences between this and a cheaper-type gas installation?
As a rule, a factory-approved gas system costs more than a made-to-fit special. However, the difference in engineering is huge...
Each of these factory-approved kits comes with absolutely every conceivable component necessary for the conversion. This means everything from the tank and cast mixer to the tailored wiring loom, the earth lugs and specifically mapped gas computer. In addition to the self-learning tune function, the software automatically delivers petrol-assisted start-up as well as throttle isolation (to prevent crank-over flooding). The EFI fuel pump is also automatically cycled at preset intervals, with fuel passing back through the factory return line. Of course, extensive testing of the completed factory system has got rid of any possible problems such as hoses rubbing together and components mounted too close to the hot exhaust manifold.
To get some inside information on the specifics of this system, we spoke to Paul Nolen - coordinator of the Impco V6 Rodeo Program. He says that their choice of converter (the Model E) was fairly easy to make, as its 325hp rating was more well-suited than the other two common units (the L and J models). No Rodeo-specific modifications were made to this off-the-shelf converter. The 225 mixer, however, did receive a one-off cast elbow on the front of it, and is officially rated at 205hp. This was the most space-efficient and power-suitable mixer out of around 15 Impco models. With around 12 months of development (and countless hours on a chassis dyno), Impco wrote the dedicated software contained in the two black boxes. This data is specific only to the Rodeo V6, and is essential in helping it to pass Australian emission (drive cycle) requirements. Paul also added that on some vehicles - such as the VX Commodore - it's the manufacturer who elects to write the programs.
Of course, the factory-approved system is also covered by a warranty. Impco cover their kit for 3 years/100,000km (2 years/50,000km if installed after the car is sold). Engine and other warranty coverage continue to be warranted by the car manufacturer.
So know you know why you won't see many "proper" gas equipped cars stranded on the side of the road!
Contact:
ABBA Mechanical Repairs
+61 8 8296 6107
www.abbamech.com.au
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