Holden's dual-fuel Commodore


Holden's a gas: Commodore wagon is as powerful as petrol one.
Taranaki, stuck out there on the west coast of the North Island, is the centre of New Zealand's energy industry. All the oil, natural gas and associated energy-based products are produced in Taranaki.
That means that everyone from a cook switching on the gas stove in Whangarei, to a tourist luxuriating in gas-heated bath water in Queenstown, are doing so because of the special oil and gas-producing properties of the geology under the little western region. So what has all this got to do with a motoring column? Well, it also means that more than 15,000 motorists all over New Zealand are running around in vehicles powered by another Taranaki energy product – liquefied petroleum gas, or LPG.
Actually, LPG is a lot more important than just for use in vehicles.
Taranaki produces more than 100,000 tonnes of the stuff every year, and it is transported by ship and by road tanker for use for cooking and heating in more than 500,000 households all over the country. It is also the product that we use for our barbecues.
So what is LPG? When natural gas is brought to the surface at the many wells in Taranaki, it is what is known as "wet" because it contains hydrocarbon products such as propane and butane, which are known as LPGs. These are removed from the gas at the production stations. LPGs have the special property of being able to be turned liquid at atmospheric temperature simply by being moderately compressed. When they are in the liquid state they are roughly 250 times as dense as when as they are gas, and this means they are easy to store in bottles until they are needed – and all that has to happen then is for the pressure to be reduced, and they become gas again.
The LPG that we use for general purposes in New Zealand is normally a 60/40 mix of propane and butane, which – this is a motoring column after all – gives it a motor octane number of about 95. So that's all the background. The real point of this article, however, is to take a drive in a car that runs on LPG and see how it goes. So we've got our hands on a fresh-to-you, straight-out-of-Australia, dual-fuel Holden Commodore.
From the outside the car is pure standard VZ Commodore Executive wagon, which means that it must be right up there among the Most Bland Cars in New Zealand. In fact, if this Holden were a human, it would probably wear corduroy shoes, beige cardigans, and rate Coronation Street as entertainment highlight of the week. But underneath that boring exterior is a vehicle that is all high- tech excitement.
It features a newly- developed version of Holden's Alloytech V6 engine that has been modified to run on both petrol and LPG, using new valves and hardened valve seats to cater for the harsher LPG operating conditions.
For the technically-minded, I need to say that the engine features a system called sequential vapour gas injection (SVGI) which injects gas directly into the air intake runner, eliminating excess gas circulating through the air intake system. This system is so efficient it is able to mimic the engine's petrol injection sequence, and that means power and torque figures when on LPG are close to those when on petrol – in other words, there is no performance loss.
No matter whether on petrol or gas, the power remains at 175 kilowatts, and the torque stays at 320 newton metres. The downside is some considerable difference in fuel consumption, however. The LPG economy with the wagon is 14.8 litres per 100 kilometres, while the petrol economy is 11.3. But the big upside is that LPG is almost exactly half the price of 91 octane petrol. At last check, the gas had just gone up to 84.9 cents per litre, while the petrol price was $1.76.
And remember, LPG produces less carbon monxide, nitrous oxides and greenhouse gases than petrol. An interesting thing about the dual-fuel Commodore is that there are only three ways you can notice that it can run on LPG. First, the spare wheel is mounted in the rear loaded area to allow a doughnut-shaped LPG tank to take up the space where the spare used to be.
Advertisement
spac_writeAd("/site=s/area=s.stuff.motoring2/aamsz=300x250/ch=");
Advertisement
Secondly, when you open up the fuel filler cap there are two fuel nozzles there – one for petrol and the other for the LPG. And thirdly, there's a little fuel selector switch on the centre console, just behind the vehicle's electric window controls. This switch has two positions and a fuel operation indicator lamp, which will change colour to indicate which fuel mode the Commodore is running on.
Red tells you its petrol, amber tells you the system is in a transition state while it transfers to the selected fuel. And green tells you it is running on LPG. And that's about all the driver needs to know about driving on petrol or LPG – everything else is taken care of. Probably the only other thing that needs to be taken into consideration is that the traditional fuel gauge on the dashboard is only there for petrol operation, while a series of four lights alongside the changeover switch advises the level of LPG reserves, with four lights advising the tank is full, down to one light flashing and a beeper sounding telling the driver to get back to the petrol. Pretty good system, huh?
Of course, the dual-fuel Commodore costs more than the normal Executive, with the wagon priced at $52,350, while the petrol equivalent retails for $45,200. But if you cover a fair few kilometres every year for your work or leisure, the half-price LPG wouldn't take that long to remove the $7150 price difference. And you'd also be removed from the vagaries of petrol price fluctuations. Nice thought?