Converting Cars to LPG

-THERE are a number of greener alternatives to petrol in the pipeline. But there's one that's here right now - LPG, or liquified petroleum gas. Here MARTIN FOSTER looks at the pros and cons to present a balanced picture to help you decide if an LPG conversion is right for you.

BASICS first, then. Liquified Petroleum Gas is obtained when crude oil is refined into products like petrol, diesel, heating and so on, and directly from extraction areas such as the North Sea.

To convert a petrol car to LPG (diesel engines require more extensive modification and so are a less practical proposition) involves external modifications to the engine and an additional pressurised fuel tank. This means the engine can then run on LPG or petrol, at the flick of a switch, so if you aren't near a gas pump (more on that later), you can simply switch over to petrol. Assuming you haven't run that dry too, of course.

That the fuel is pressurised might worry some people, but the pressure at which LPG is held is roughly the same as an aerosol of hairspray. In practical terms, it means that filling up an LPG car is much the same as a petrol car, except that the nozzle from an LPG pump has a more secure, bayonet fixing. The LPG tank is also fitted with an automatic shut-off valve, which stops the filling automatically when the tank is 80 per cent full, leaving a 20 percent space for the normal thermal expansion of the gas.

Although gas-power has been around as long as the internal combustion engine itself, it is a relatively new technology in its current commercial form, so LPG is subject to new, and very high, safety standards.

An LPG conversion includes one-way valves in and out of the tank to ensure the fuel can only flow in the correct direction and the fuel tanks themselves are made from a special high-grade metal and are tested to many times the working pressure of the gas.

In the event of an accident, the tank automatically seals, so there is far less chance of spillage than with a conventional petrol car. And if the car catches fire, another valve will release the gas in a controlled manner and fire-fighters are trained to extinguish the burning car and simply let the gas's blue flame burn out.

In its raw form, LPG has no smell at all, but the same scent as used in domestic household gas is added so a leakage could be identified. And no, you can't be 'gassed' by it.

An average conversion costs around £1,500, although less sophisticated cars can be converted for around £1,000, and owners of cars with more complex, sophisticated engines could face bills of around £2,000.

The installation is no simple job, though, and you can see where the money goes.
Without getting too bogged down in the technicalities, but for those who have some understanding of how a petrol engine works, there are basically two main types of LPG conversion.

The principle is much the same as with a petrol engine - mix the fuel with air to form a vapour and feed that into the combustion chambers. The more basic system uses a mixer unit to feed the air/LP mix into the inlet manifold; the more sophisticated and efficient gas-injection system involves drilling and tapping the inlet manifold so special injectors can be fitted to feed in the gas.

Both systems then require the engine management system (the box of electronic tricks that controls the workings of the engine) to be 'remapped', a time-consuming exercise which uses a laptop computer from the passenger seat on a long testdrive.

And so to that extra fuel tank, the one aspect of the installation that seems to raise so much interest because of its potential impact on the car's practicality. There are three main types of tank, all built to the same high specifications, but different shapes and sizes to fit in different areas of the car - and each with its own pros and cons.

The first, and most simple, is a cylindrical tank which sits on the floor of the boot area. The obvious disadvantage here is that it takes up boot space, so if you need all the available space - even on an occasional basis - this is not the solution for you.

The second type is designed to be mounted under the car's boot floor, but these are only really suitable for 4WD vehicles with ample ground clearance.

The most popular and practical choice is a toroidal, or 'doughnut', tank that drops into the spare wheel space, usually recessed into the floor of the boot. This takes away none of the available luggage area, but it does mean you need to find a new home for the spare wheel (which will then take up storage space anyway), or you can opt for one of the instant repair products.
These fall into two main types. The first is a relatively inexpensive (just a few pounds, in fact) aerosol that you attach to the tyre valve in the event of a flat and which re-inflates the tyre at the same time plugging the puncture.

The second more expensive solution (around £30 per vehicle) is a liquid that is installed in all four tyres before you have a puncture and which actually repairs the puncture immediately it happens - permanently and for the life of the tyre. So as well as freeing up the space normally occupied by the spare, it also means you won't experience a blow-out, or even an inconvenient slow puncture. LPG installation specialists can supply full details of both products.

All types of tank require the fitting of a second filler, which is usually mounted in the opposite rear wing to the original petrol filler.

So that covers the practical installation, safety and use of LPG, but before you can decide if it is right for you, we need to consider the nitty gritty - what it costs and what it will save you, both in terms of emissions and the all-important finances.

There is no doubt that LPG is a cleaner fuel than both petrol and diesel.

The main air quality pollutants of concern in the UK are particulates and oxides of nitrogen (NOx) - in Central London, road traffic causes 93% of all particulate emissions and 58% of all NOx emissions. Department of Health statistics show that particulates are responsible for several thousand advanced deaths each year and many thousands of instances of illness and reduced activity.

Compared with petrol, vehicles running on LPG emit around 12% less CO2 and around 30% less NOx, Hydrocarbons (HC) and carbon monoxide (CO). Compared with diesel there is around 90% less NOx, 1/50th of particulates and only 1/500th of the ultra fine particles.

But how ever much we might like the idea of running a cleaner car, an average conversion cost of around £1,500 means we are looking for a significant reduction in running costs too.

Recognising its environmental advantages, the Government has either frozen or reduced the duty on LPG each year over the last eight years. In the March 2001 Budget, LPG duty was reduced by 40% and frozen in real terms until 2004. This has resulted in a forecourt price for LPG of around half that for petrol and diesel.

On the other side of the scales, you have to take into account that the distance travelled per litre is approximately 20% less than for petrol.

It's worth noting that, if you are in the market for a new car, it is possible to buy one that already runs on LPG (makes include Vauxhall, Volvo, Ford and Rover).

It is a further endorsement of the Government's belief in LPG that grants towards the additional purchase costs of some LPG vehicles or LPG conversions are available through the Energy Saving Trust's (EST) Powershift scheme.

It seems likely that this scheme will be extended in time, but the bad news currently is that the EST will only consider applications for specific vehicles - and they have to be less than five years old. These vehicles are listed in an EST publication called the Powershift Register. The scheme also only recognises certain systems, not all of which are available from all installers, so you will need to shop around. If you do want more information on grants, see our 'Want to know more?' panel for contact details.

It must be said that the quality of service provided by the installers will vary, as they do in all industries, and if you are happy with the company's general attitude and professionalism, we would suggest you ensure they are members of the Liquified Petroleum Gas Association (LPGA - again see the 'Want to know more?' panel for contact and website details), which will ensure you have no problems with insurance (more on that in a moment) and that their staff are fully and properly qualified.

Providing your car has been converted by a qualified/approved fitter and has a LPGA certificate of conformity, insurance premiums should stay the same. And an LPG conversion should actually increase the value of the vehicle - particularly larger cars, which would otherwise be very expensive to run.

Finally, a word of reassurance for those who might worry about availability of LPG fuel. As we go to press there are more than 30 outlets across the county (and they are growing all the time), ranging from specialist suppliers like installation companies, to major outlets, such as supermarket garages, and the facility to switch over to petrol means you should never get caught out.

If environmental concerns are paramount for you, there is no doubt that LPG is currently the most practical alternative to petrol and diesel. And there is money to be saved too. Just how the sums work out for you depends on how long you plan to keep the car and how much mileage you cover.



Want to know more?
For details of LPG conversion grants, and details of LPG outlets in Devon, call the TransportEnergy Hotline on 0845 6021425, or visit the Power Shift website at: www.powershift.org.uk

The LPGA is a non profit-making association founded in 1969 and has approximately 140 full members and 40 affiliate members. It represents all the major LPG companies in the UK and the sales from member companies cover over 98% of the total LPG sales in the UK. Write to the LPGA at Pavilion 16, Headlands Business Park, Salisbury Road, Ringwood,