asl
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| posted on 16/10/09 at 12:17 PM |
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LPG or not LPG that is the question.....
Hi all. I'm in the process of looking to buy another road car. I really want an M5 as my last car was an RS4 and I'm after a 4 door with
the same performance.
Now, the thing that puts me off is the running costs as I do 15000 miles a year and the RS4 was expensive enough. A friend of mine has that Porsche 4
wheel drive thing and he has had it LPG converted and he swears by it. I was talking to my dad who works for Honda and he is against LPG as he says it
dries the engine parts out.
My other option would be an oil burning 535d but it really is my second choice. I'm also toying with an EVO X 300SST as although the running
costs are high it is much cheaper to buy....
What are your thoughts on it???
Cheers
Nathan
[Edited on 16/10/09 by asl]
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chrisunwin
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| posted on 16/10/09 at 12:39 PM |
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Nathan
Hi. If you are planning on keeping the car for a couple of years or more, then LPG makes good economic sense. It will save you money in the long
term, but cost in the short them to get it done. Last time I looked into it it was arround £1700 (ish). Depends how much work you are willing to do.
Kits for conversion are cheaper from te Netherlands, as they use it more over there. If you are "Green" then you will be helping the
environment as well. Down side is the loss of boot space for the tank.
Go for the biggest tank you can ger in, Yes you loose boot space, but a small tank means lots of trips to the filling station. You can get flat tanks
now thas sit on the floor of the boot, but their capacity is also small.
There will be no problem with the engine, all modern cars have hardenes valve seats to cope with unleaded petrol, in fact your engine will run much
cleaner on LPG. Fuel consumption will be slightly worse on LPG than Petrol, but it is much cheaper in the first place. I have heard some people
saying that gas in a car is dangerous and can cause an explosion. The gas tanks are MANY TINES STRONGER than standard petrol tanks, and are fitter
with pressure relief valves, It is actually MUCH SAFER than petrol.
Good luck
Chris
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asl
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| posted on 16/10/09 at 12:54 PM |
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That's great Chris, thanks!!
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02GF74
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| posted on 16/10/09 at 01:00 PM |
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performance does not come cheap. you can't afford it, don't buy. 
how ong before there is enough uptake in LPG before the govmt slaps on duty?
I remember when weasel was 1/2 price of petrol, now it is more. Same will happen to LPG, just give it some time.
Many old land rovers and range rovers are converted to LPG - I have not heard of modern ones but then most LR forums are for poor folk running older
cars and engines. Dunno what effect it has on newer engines. or older as it is not my bag, baby.
sit down and do the sums and how long it will take to recoup the cost , resale value, incovneinece etc.
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andkilde
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| posted on 16/10/09 at 01:35 PM |
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Hmmn, I'd need to be educated a bit more about modern propane conversions to make an honest assessment. From experience with conversions on old
carbureted american engines, propane is a good alternative in a commercial fleet operation. It burns very cleanly, stripping a propane engine down is
pretty cool, no nasty buildup on piston tops, not deposits on valve stems, etc.
The conversions I've seen were pretty crude though, roughly the equivalent of strapping a gas barbecue onto the engine in place of the breather
and adding a couple of solenoid operated valves to switch between petrol and LPG from the drivers seat. Fine for a taxi cab or a lunch wagon but I
couldn't imagine doing something like that to a car as complex as an M5.
Cheers, Ted
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britishtrident
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| posted on 16/10/09 at 01:42 PM |
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Consensus is BMWs don't seem to have any problem with valve lubrication when running on LPG, Japanese cars on the other hand are more prone to
valve seat recession on LPG but it can countered by using an upper cylinder lubricant system.
Depending on the cost of LPG in your area and your distance from the cheapest LPG pump you could save over £120 per month but to make economic sense
you will need a big LPG tank 60 litre (48 litre actual) as an absolute minimum. You will also need a top class system and an installer who knows
what he is doing on BMWs.
Unlike systems fitted to older cars with carbs modern systems are multipoint LPG injection which are slaved off the cars original injection system,
the cars own ECU is still in charge of the fueling but the LPG ecu modifies and diverts the signal to the gas injector valves.
As the car still runs closed loop at idle and during cruise this system doesn't cause problem for the emission controls or drivability about
town, but expect a 15 drop in power when running on LPG and expect to use LPG at 10 to 20% worse mpg than petrol.
One problem with sequential gas injection is because the specific volume of gas is much bigger than petrol the injectors have to be physically much
bigger and slower than petrol injectors which can cause problems getting the system setup on cars with a very powerful high revving engines.
On such engines the lpg system has to span a wide set of conditions and the lpg injectors can have trouble keeping up --- this where the expertise
of a really experience LPG fitter is needed to select the right equipment and know the tricks to set it up properly for your car.
I converted my own using a STAG-4 for less than £570 pounds it was very easy (but it took 20 hours) while a relatively simple conversion is well
within most people on this list capability I would hesitate to recommend a first timer takes on a conversion complex engine, getting the component
spec right for a high output engine and dealing with issues such as variable inlet manifolds takes experience.
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britishtrident
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| posted on 16/10/09 at 01:51 PM |
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Previous threads with some good links
http://www.locostbuilders.co.uk/viewthread.php?tid=120736
http://www.locostbuilders.co.uk/viewthread.php?tid=113033
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Front Row Joe
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| posted on 16/10/09 at 02:00 PM |
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EVO magazine converted and ran an Alpina B8 for a while. You could get the back issues to see what their reviews were like. Would seem pretty
similiar to your application. They used a BMW LPG specialist. I no longer have the magazines so can't check for you....
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splitrivet
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| posted on 16/10/09 at 02:01 PM |
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I'd do it like a shot but they wont let you on the Channel Tunnel with an LPG motor however they will let a caravan go over with an LPG bottle
on board, so whats that all about.
Cheers,
Bob
I used to be a Werewolf but I'm alright nowwoooooooooooooo
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adam1985
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| posted on 16/10/09 at 02:39 PM |
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i got mine done worked out that i would get my money back after 2 years if buying at shell at about 52p a litre have now found a few local places that
do it for 38p litre
you dont get quiet the same mpg or performance but it saves alot of money i chose to have the lube system fitted to mine just for extra piece of mind
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asl
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| posted on 16/10/09 at 03:11 PM |
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Interesting stuff guys. Thanks for the links, info and magazine details. Adam what sort of car are you running?
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zilspeed
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| posted on 16/10/09 at 03:37 PM |
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My conversion on the golf I used to have cost me around £600 all in because I did it myself. That was for sequential injection.
If you can't fit a decently big tank and you don't live near an LPG filling station, it's a ball ache.
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zilspeed
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| posted on 16/10/09 at 03:37 PM |
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My conversion on the golf I used to have cost me around £600 all in because I did it myself. That was for sequential injection.
If you can't fit a decently big tank and you don't live near an LPG filling station, it's a ball ache.
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adam1985
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| posted on 16/10/09 at 04:52 PM |
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mines on a 08 civic type r so not in the same league as a m5 or others your thinking of the cars for the misses mainly who does about the same mileage
as you but we didnt fancy a dirty diesil so we now have the best of both worlds
The only problem with it is when it went to the main dealer for some warrenty work to be done they connected everything back up but just said get it
checked over by the lpg garage to make sure everything was fine because they didnt want to get involed in the lpg which i thought was fair enough
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morcus
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| posted on 16/10/09 at 05:22 PM |
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My dad looked into getting a 7 Series with an LPG conversion and found that many local building sites/companies, sold LPG, so it might be easier to
buy than you think (The only garage we knew of that does LPG is in Folkstone).
I've seen quite a few BMW's with 'converted to lpg by ...' stickers.
If your gonna buy from a dealer, make sure you do your research as specialist stuff like this is an area where they will try and rip you off or
confuse you (Or just lie to you and try to sell you something else, A vauxhall dealler told us there had never been a factory LPG astra and tried to
sell us a mondeo, yet we'd just come from another vauxhall dealler who'd just shown us one).
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madteg
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| posted on 16/10/09 at 05:35 PM |
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I run a 4.0L jeep Cherokee on lpg, its as good as my wifes vw passat tdi on fuel costs and will leave most things from the lights. Had lpg on all my
cars for the last 7 years its great. Only thing i would say is get the biggest tank you can or you will find yourself looking for lpg stations
[Edited on 16/10/09 by madteg]
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britishtrident
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| posted on 16/10/09 at 06:24 PM |
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Tank size type & location will always be comprimise ----
Cylinder tanks on big car don't hog too much boot space but they raise the c of g when full, and you loose the option of the rear seat folding
down.
A toroidal tank in the spare wheel well is another option but they tend to be limited on capacity.
As I already said 60 litre tank is the absolute minimum for a largish car ---- 80 or 90 would be a better choice as an 80 litre tank only holds 64
litres of LPG which gives equivalent range to 12.25 gallons of petrol.
[Edited on 16/10/09 by britishtrident]
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mark chandler
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| posted on 16/10/09 at 06:41 PM |
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LPG on my XK8, 300 miles to £35
These are supposed to have soft valves so I got a LPG system that mixes in fuel, I run 85% LPG, 15% petrol which lubricates and cools the valves.
You can also change the ratio, so foot to the floor only petrol or above 3500rpm only petrol, I did this for a while but to be honest could not notice
any change in performance so have left it alone at 85/15 split now.
Its a vogas system BTW, works well, before I ran a range rovers for 200k miles on LPG, one blew a head gasket at ~180k miles, despite 80k miles on LPG
very little valve regression, the reconditioning place refaced the valves and seats, he said nothing worse than a 100% petrol car except that
everything was cleaner.
Regards Mark
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asl
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| posted on 16/10/09 at 07:05 PM |
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Thanks agin guys. I'm lucky with the stations as the shell garage next to my house and the one next to my office both sell LPG.
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morcus
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| posted on 16/10/09 at 07:15 PM |
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If you live right close to an LPG station and work close to another you could probably get away with quite a small tank, you still have the petrol as
well so you can go without LPG at times if you need too.
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britishtrident
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| posted on 17/10/09 at 10:22 AM |
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quote:
Originally posted by mark chandler
LPG on my XK8, 300 miles to £35
These are supposed to have soft valves so I got a LPG system that mixes in fuel, I run 85% LPG, 15% petrol which lubricates and cools the valves.
You can also change the ratio, so foot to the floor only petrol or above 3500rpm only petrol, I did this for a while but to be honest could not notice
any change in performance so have left it alone at 85/15 split now.
Its a vogas system BTW, works well, before I ran a range rovers for 200k miles on LPG, one blew a head gasket at ~180k miles, despite 80k miles on LPG
very little valve regression, the reconditioning place refaced the valves and seats, he said nothing worse than a 100% petrol car except that
everything was cleaner.
Regards Mark
On my car I have it set to switch back to petrol at 5K revs. At full throttle you can feel a slight surge in power when it passes 5k switches back to
petrol.
I have a Crecorder data recorder and have been using it logging journeys. Looking at the logs it is actually quite surprising on how many journeys
the engine dosen't exceed about 3,300 rpm in whole journey. I am now actually considering setting the change over point lower to 4,000 rpm.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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hobbsy
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| posted on 18/10/09 at 04:54 PM |
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Depending on how many miles you're doing and how long you're going to keep it determines whether its worth the hassle.
Small things like how long it takes to fill up annoyed me when I had an LPG car.
Also doing an LPG conversion on a car like an M5 may actually lower its resale value.
Which M5 are you thinking, a late E39 or the newer V10 jobbie?
Me want an M5 too you see but my pockets aren't deep enough for the V10 flavour so thinking a late ish E39...
Considered gas but then changed my mind as TBH I'm only likely to keep it for 2years and the payback time is about that.
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mad4x4
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| posted on 19/10/09 at 05:53 AM |
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I would probably never convert a Car to LPG. Biggest problems are :
1) Getting the Stuff ( esp when the LPG tank only gives about 180miles)
2) The size of the tank
3) Lack of Storage space due to aforementioned tank
However, If you were buying a BIG 4x4 eg a range rover then I would champion it as say go for it it's the best thing.
I had a 4.6 Range rover and it was brilliant on gas getting about equivilent of 30 mpg. by the way it had a donut tank and I lost my spare wheel. but
didn;t loose bootspace.
I think realistically engine size need to be greater that 3.5 Lrts to justifly gas conversion.
Scot's do it better in Kilts.
MK INDY's Don't Self Centre Regardless of MK Setting !
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britishtrident
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| posted on 19/10/09 at 07:28 AM |
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quote:
Originally posted by mad4x4
I would probably never convert a Car to LPG. Biggest problems are :
1) Getting the Stuff ( esp when the LPG tank only gives about 180miles)
2) The size of the tank
3) Lack of Storage space due to aforementioned tank
However, If you were buying a BIG 4x4 eg a range rover then I would champion it as say go for it it's the best thing.
I had a 4.6 Range rover and it was brilliant on gas getting about equivilent of 30 mpg. by the way it had a donut tank and I lost my spare wheel. but
didn;t loose bootspace.
I think realistically engine size need to be greater that 3.5 Lrts to justifly gas conversion.
I get 300 miles to tank and the conversion payed for itself in 5 months on a 1.8 car ---- and have never had a problem getting it as I have 6 lpg
stations within 6 miles.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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asl
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| posted on 19/10/09 at 05:37 PM |
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Hobbsy, I'm thinking about the V10 one probably an 06 or 07 plate. Trouble is I haven't even driven one yet so guess I should do that
first!! I'm also going to have a go in an Evo X and C63 AMG. If none really do it for me I may just buy another RS4 as I really loved that car.
Cheers all for the advice
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