LPG Conversion?

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Currently doing a 50-mile a day commute to work. half dual carriageway, half cross-country backroads. This was in a company provided Mini 1.6 Diesel. This is going back to the employer following a change in job.

Will soon be doing a 70-mile a day commute, and this will be almost all dual-carriageway and it will be in my car - 2002 BMW 540i, which upto now has only ever been a weekend toy. Its not worth a huge amount, but I would rather not change it - I love the car and don't reckon I would get anywhere near the same amount of performance+metal+toys by trading it in.

So.. bearing in mind "I love that car!" and "I don't wanna give up my V8" am I barmy for considering an LPG conversion rather than just selling up and buying a cheapy dag-dag diesel? I won't have the space to keep 2 cars.


Here's my man-maths..

Onboard computer says I'm averaging 22mpg.
So with a 70 litre tank (thats 15 gallons?) costing £80 to fill, and lasting for 330 miles.. so that's going to be 4.5 days fuel??

Taking an average of 200 working days a year.. that means 44 fillups at £80 a time. Or £3540 quid.

A conversion could cost £2000 from a reputable place. I'd never get that back in trade-in, resale or whatever, so its a sunk amount of money.
But I should save 40% in fuel bills? (That £3540 would become £2124)

I figure after a year, it would start paying for the cost of the conversion? And I'd still be wafting about in luxury barge with a stonking motor.
 
That all sounds about right. go for it.

My only advice would to be to get as large of an LPG tank as you possibly can. I had a 60l one and i was filling up every other day.
 
You usually get a bit lower MPG on gas as it has a lower calorific value so your 22mpg may be more like 18mpg on gas, personally i'd do it as it'll be far nicer than a 3k diesel just make sure you get a good quality system installed properly and it'll be fine. Most of the people who don't like LPG tend to only have experience of badly installed, cheap systems.
 
Haven't had a quote yet, but I'd be looking at somewhere like Greenfuel who have been around for years. I know I'll be losing a spare wheel, there will be additional injectors fitted etc.
 
There wont likely be a drop in performance for sure. But my experience of the LPG in my 4.6 Range Rover was that I only got 13.5 mpg (compared to the 17-18 mpg I currently get in my 4.0 V8). So you will lose some fuel economy for switching to LPG.

Also, as said above, absolutely get the biggest tank you can. You can only fill around 70-80% of the tank as a result of gas expansion. I had a 100L tank and could only get around 72L of gas in it. That would only last 200 - 230 miles if I was driving relatively sensible. So you will have to fill up far more regularly.

Make sure you know where you can fill up. I was lucky enough having stations within 5 miles of both my home and work, so it wasn't too bad. If you end up running dry on gas, don't worry about it as I found I was more likely to be on the motorway at this point anyway, so it was the most efficient driving possible on the petrol.

You always have to have at least some petrol in the tank, as the engine will always start on petrol until it gets warm enough to switch. But I once half filled my petrol tank in the Range Rover (100L tank), and it lasted me around 6-8 months quite easily. So you don't use a lot. But there will be a petrol cost anyway.

Injectors are one of the biggest expenses in the conversion, and the fact you will have 8 of them means it shouldn't cost less than £2k for a good conversion. I would expect closer to £2.5k, although you will save a little over the RR conversion as you will unlikely get a 100L tank in the wheel well. And it can take around 5 days to do the conversion, it's not, or shouldn't be, in and out in a day.
 
Injectors are one of the biggest expenses in the conversion, and the fact you will have 8 of them means it shouldn't cost less than £2k for a good conversion. I would expect closer to £2.5k, although you will save a little over the RR conversion as you will unlikely get a 100L tank in the wheel well. And it can take around 5 days to do the conversion, it's not, or shouldn't be, in and out in a day.

The actual parts are not that expensive. top end injectors are only about £20-£25 per cylinder so having 2-4 extra doesn't make a great deal of difference. The front and back end install could probably be done in a day as well but it would take some time to get the management system set up and tuned properly.
 
BRC Injectors, for example, are around £75 each, so having an extra 4 is an extra £300. That would make quite a difference to me. Of course, you could go for the Yellow Keihin injector rails (34-47 BHP per cylinder), I believe these are commonly used in Prins conversions, and they are around £260 for a rail of 4 injectors. So still an extra £260 for the 4 extra cylinders. Not quite the £80-100 you are suggesting for "top end" injectors.

When I was looking around the LPG forum, the general opinion was 3-5 days was typical of a well installed system. And anything where they take less time than this was likely to be of a sub-par quality.

Of course, make your own mind up. I am just conveying the opinions as they were conveyed to me, by people with far more knowledge than myself.

As an example, here is one of the better kits on the market : http://www.lpgshop.co.uk/8cyl-kit-prins-vsi-2-0-with-keihin/

Not sure what all is missing from there, but the tank is for sure, that'll be an extra £100-140 depending on what size you go for. But you're looking at the thick end of £1300 before you start to get someone to fit it for you (assuming it is only the tank that is missing from that kit). If you can fit it yourself though, or know someone who can, then that would be even better.
 
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So.. bearing in mind "I love that car!" and "I don't wanna give up my V8" am I barmy for considering an LPG conversion rather than just selling up and buying a cheapy dag-dag diesel? I won't have the space to keep 2 cars.

......

A conversion could cost £2000 from a reputable place. I'd never get that back in trade-in, resale or whatever, so its a sunk amount of money.
But I should save 40% in fuel bills? (That £3540 would become £2124)

I figure after a year, it would start paying for the cost of the conversion? And I'd still be wafting about in luxury barge with a stonking motor.

Assuming you love the V8 that much, if the car become uneconomical to repair, surely you could buy another V8 and have the kit transferred at a much lesser cost (therefore the kit wouldn't necessarily be a total loss)?
 
You could get an excellent system installed for around £1500. It's no longer necessary to pay the premium for a prins system - the rest of the market has improved massively in the last 3 years.

Hana injectors (£100 ish for a 4cyl rail) are just as durable & accurate as keihin.
 
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