VT Gas conversion

[Fitty]

I know the argument about LPG conversion has been done to death. I've looked through all the threads, but I can't find a list of parts.

I've got a VT wagon and I'm going for a straight gas conversion. I want the filler to replace the petrol filler under the cap, and I want to use the stock guage rather than having one of those flashing-light indicators. I would prefer not to have a gas tank just behind the rear seats, so I'd like to replace the petrol tank with one.

As for parts, I've had Impco recommended to me because they have designed their products with Holdens in mind, and because everyone I've spoken to with their products has been more than happy with their performance. As I understand it, the parts required are:

Mixer (what are the issues with traction control here?)
Base plate
Converter
Tank
Filler
Level sensors
Lines

So what I'm after is a specific list of parts, manufacturer recommendations, servicing requirements after installation, things to look out for when getting it installed (such as getting it tuned lean to get "better" mileage)... and for anyone who wants to tell me not to do it to go jump - I'm not interested in hearing what you have to say, I've read it all before in the other threads on this topic.

 

[Cheap6]

The simplest way to ensure that you get everything is to buy the Holden approved kit .

In theory, you will need an LPG installers licence to buy LPG parts new and by asking what you are asking you don't have one. Used may be a different story. If buying used, forget the lines and hoses (used) other than to provide models for where everything needs to go; they have to be replaced when swapping a system across.

To add to your parts list, you will also need a closed loop fuel controller and one or two fuel control valves (two work better but you can get by with one). You will also need two LPG lock off valves, one at the tank and one at the converter. Both need to be switched on only with the engine running. There are black boxes available to do that or a vacuum switch can be used instead. Some installers wire into the fuel pump relay and use the PCM.

It's not a requirement but using the LPG capable PCM will give you an LPG ignition curve.

Straight gas will be more difficult than dual fuel because petrol is normally added during starting. There are work arounds eg. Impco does a solenoid that bleeds converter primary pressure LPG into the mixer while cranking. You also lose the valve saver mode which is mentioned in the other threads.

You could leave the injectors in place to plug the holes in the manifold but it would be neater and not cost much to knock in welch plugs for that.

The kit will come with a bracket for the filler neck which will be designed to cater for both petrol and LPG fillers so you will have to make your own or live with an offset filler.

APA has a list of tanks and their dimensions on their site. That would be a good place to start looking for a suitable tank. If you want to mount the LPG tank in place of the petrol tank, you will need brackets for that and there are requirements in the LPG fitting standard (AS1425.2003) for tank mounting that need to be met. The straight LPG Falcon tank might be a good place to start.

The Holden kit uses an impco 225 mixer and (I think) an 'E' converter. An 'L' converter will also work. The mixer needs to have a feedback type diaphram to work with the closed loop controller.

The closed loop control is a legal requirement and makes leaning the fuel mixtures difficult without disconnecting it. Of course what you do after it is installed is up to you. If the closed loop control is disconnected, a non feedback diaphram may be better. There is limited scope to vary the fuel mixtures across the load range with the Impco carbs. because the LPG flow is airflow based rather than load based. You just get to make global changes. Stoichiometric makes best power and is what is required to make the cat. work for emissions anyway.

LPG spark plugs need to be changed every 20000km. => + ~$15 per year.

Traction contol can't work with an LPG mixer system - it will be switched off if using an LPG PCM and the LPG 'on' terminal is triggered (I think that means it is not powered, if that makes sense). If not using the LPG PCM, you would probably have to sort something else out to switch the TC off.

 

[Holdens Rule]

If he was to run straight gas would he be better off with an injection system rather than a mixer system? My preference is dual fuel for a holden unless you rebuild the motor for straight gas but thats my preference. Was wondering the other day why no one has developed a gas tank that replaces the fuel tank so it is around the same size but also has a smaller petrol tank (say 10 liters) integrated into it. If it was possible I reckon it would be great cause there is really no need for 60 liters of petrol when you run gas and also you wouldn't loose half your boot

 

[Fitty]

Thanks Cheap96... best roundup I've read.

 

[Cheap6]

If he was to run straight gas would he be better off with an injection system rather than a mixer system?

Good suggestion. The economics of SVI vs mixer have been discussed in the other (big) VT gas thread but if one was really determined to fit dedicated gas then SVI might beat stuffing around sorting out mods. to make an otherwise effective dual fuel conversion work with straight LPG. Although, they often (possibly all of them?) start on petrol too.

My preference is dual fuel for a holden unless you rebuild the motor for straight gas but thats my preference.

Mine too, but I can understand why someone with a wagon would want to avoid putting a tank in the cargo area.

Was wondering the other day why no one has developed a gas tank that replaces the fuel tank so it is around the same size but also has a smaller petrol tank (say 10 liters) integrated into it. If it was possible I reckon it would be great cause there is really no need for 60 liters of petrol when you run gas and also you wouldn't loose half your boot

Something like that was done for VS Series II wagon but I'm not sure whether the same is so for VT.

 

[Fitty]

I just spoke to a bloke named David at Lakeside AutoGas who told me that you can't get tanks to suit VT Commodores anymore. Does anyone know anything more about this or have any tips?

 

[Holdens Rule]

I got mine a little while ago and there was a bit of a wait for it but I can't see it being impossible to get one. There is a lot of people getting cars converted and only a few companies making tanks in Australia so I'm told and there is quite a bit of a back log at the moment. The other option is a imported tank but I've been told to stay away from them they're not as good as aussie ones and the fittings are a bit dodgy too.

If you can't get a tank for a VT then the other option is to get a second hand one and get it tested. I did it to my other car and it worked out cheaper then a new tank and had new fittings put on it when getting tested and also a fresh coat of paint so in the end it looked new and had ten years on it just like a new one.

 

[executive_driven]

stay with petrol lol

 

[skipzor]

Im getting gas fitted to my VT next week. all up its going to cost me $100 after $2000 government rebate, thats with a second hand tank which has been tested and repainted. couldnt knock it back.