Advice on converting petrol car to LPG

franr43

Does anyone have experience of converting their own car to run on LPG?

I've seen second hand and new conversion kits on ebay - can it really be that complicated? I've seen one firm who run a one day course costing £300 teaching you how to do it.

What do other MSE's think?


Thanks Fran

marlot

I'd suggest asking on somewhere like honestjohn.co.uk.

There was an article in Car Mechanics last year - looked easy enough for someone who has done some reasonably serious car DIY. Note that you'll need a professional inspection at the end of the work - your insurance company will demand it.

DavidHM

No experience but a lot of cars will use around 30% more fuel than on petrol.

So:

35 mpg petrol @ 90p/litre = 11.68 ppm

48 mpg diesel @ 92p/litre = 8.71 ppm

27 mpg LPG @ 40p/litre = 6.73 ppm - so there's a saving there certainly

but if a diesel and a petrol car are the same price, it takes 50,000 miles for the LPG car to pay back the conversion cost.

But you say - diesels cost more! Well they do, but LPG will shorten the life of an engine so an LPG car at 120k is likely to be worn out; a diesel car should have plenty of life in the engine itself. Diesel cars will also attract a premium second hand, so if you pay £1k more for the car used, you should get at least £500 back in three years' time, whereas LPG cars are worth the same or less than an ordinary petrol.

All that assumes that the car and the conversion run perfectly and given the risk, especially on a DIY job, that they won't - I would say that although you might save money, there is too much risk and hassle for me to want to go down that route.

balsingh

I would try and drive an already converted car before making the decision. The driving characteristics of the car can change. The most obvious is a tiny hesitation when first moving away or needing slightly more revs to move away (hence the drop in power/economy of about 10-15%).

One good option is to buy an already converted car so you knwo exactly how it will drive rather than getting a surprise.

ooo000ooo

LPG shouldn't lessen the life of a car as it's cleaner burning, oil will be less contaminated and in theory you shouldn't have to service the car as often. On a modern lpg car using multi point injection the driving characteristics are pretty much similar to petrol and driving away doesn't require any more revs. There is a slight reduction in overall power which can be countered by advancing the ignition slightly where possible. I wouldn't do a DIY job as insurance companies tend to want an LPGA certificate to confirm it's been installed correctly plus on an injected car it requires drilling into the inlet manifold to mount the injectors, tapping into the injector wiring to obtain the injector pulse signal to fire the injectors as well as stop the petrol injectors firing then you still have to finetune the system using a pc with an emissions detector. On older carb'd cars you could diy using a plate on the carb to supply the lpg but they were infamous for backfires and setting your car on fire.

veralum

about 5 years ago I converted a 5 cyl fuel injected audi 100 to lpg and rove it for about 2.5 yrs with no problems. I joined an LPG group on https://www.yahoogroups.com and they really helped me a lot to decide which kit and how to do it etc.

the kit was aclosed loop type and was about 500 quid which include having it checked and certified for insurance purposes after I had fitted it.

it took about a day to do and was prettty straightforward, you plug it into alaptop or pc afterward and follow the set up procedure and then away you go.

you could switch between gas or petrol via a switch on the dashboard and when the car was low on gas it just got sluggish so you switched over. my software was set so that it started on petrol then switched over to gas after afew seconds to prevent the fuel system seizing due to lack of use.

I had no trouble and there was no hesitation or the way the car drove, there was a slight loss of power at top speed but (110 instead of 120mph) so you switch to petrol if you want to go faster!

definetely reccomend it! when was the last time you filled a tank for less than 25 quid!

lots of help out there, even a website where you can download all the lpg sites to your pc or sat nav!

on a gas car cos of the way it burns cleaner than petrol the engine oil stays clean so when you check the dipstick after 5k miles the oil looks clean and new!

never heard of ot shortening engine life except on fords who had to have heads with hardened valve seats, they recalled all their factory made lpg focus's I believe

veralum

my fuel injected car had a purpose made thingy which was attached to the inlet manifold, so no drilling required. when it was on gas the injection system was turned off so the car was quieter.