LPG conversion on 840ci sport

Of all the cars I have seen with the LPG conversion, they have always given problems with valve damage and headgasket failures. Nobody will want to carry out any non-routine maintenance on it and its 2nd hand value will plummet. You will be spending good money to save on fuel costs then loose all those savings many fold over as soon as you get problems.
Why do you think the government use LPG? It's politically correct and us tax payers foot the maintenance bills!
I would steer clear.

8Tech.

To simply break even on an install you would have to travel around 25000 miles. And that's assuming that the system works perfectly with no maintenance/breakdown issue directly attributable to the LPG conversion.

Add to that the loss of performance, and the scarcity of LPG stations, you will no doubt end up using the regular petrol tank instead - negating the whole issue.

Unless you plan to run the car into the ground completely over the next decade or so, racking up another 100K or more it probably isnt worth it.

I'd have a Dealer warranted LPG car from new, but not a retro fit onto an old 8.

Can of Worms.....

yes, not very econimical around town, but as you say, with cruise-control on and motorway driving, 30mpg is acheivable. But, don't convert it to LPG, it's not a delivery van!.

Zitat von 8Tech

Of all the cars I have seen with the LPG conversion, they have always given problems with valve damage and headgasket failures. Nobody will want to carry out any non-routine maintenance on it and its 2nd hand value will plummet. You will be spending good money to save on fuel costs then loose all those savings many fold over as soon as you get problems.
Why do you think the government use LPG? It's politically correct and us tax payers foot the maintenance bills!
I would steer clear.

8Tech.

This is nonsense. The only cars that have valve damage (which is actually valve seat recession) are those with poor quality, very marginal heads that are just strong enough to run on unleaded. Very similar to the problems that older cars designed for 4-star had when switching to unleaded. The reason being that propane burns slightly hotter than petrol, but 99% of engines have no problem with this -- one well known exception is the Ford Zetec engine, which Ford have rectified by producing a better quality head for their factory dual-fuel systems, everything else is the same.

If you can explain how running on propane causes head gasket failure then I'm happy to hear it, otherwise I'll just assume that's one of these "a guy down in the pub told me....." statements. I've certainly never heard such a thing, and can't imagine why it would be the case.

You're certainly entitled to an opinion on the benefits and drawbacks of running petrol engines on propane, and what you say may be true as far as doing non-maintenance work goes. But let's stick to the facts. A well-designed and properly installed propane system can actually reduce wear on the engine as it naturally vapourises at operating temperatures, giving a better mix and less bore-wash (as happens with petrol). You also get reduced oil contamination.

Personally I wouldn't pay the £2000 conversion cost as I don't think it's worth the money unless you're doing very high miles, but I don't believe the 8 is a particularly unusual or difficult car compared to any other modern V8.

Why don't you have a look here and contact these guys to ask some questions, at least you should get factually correct answers (although they may well try to swing you towards the purchase):
http://www.go-lpg.co.uk/BMW_840_V8.html

I have no affiliation with these guys at all, and in fact have never even spoken to any of them, so I have no idea if they're trustworthy or reliable, but their work certainly looks of a good quality.

in these days when GWB & Co are doing everything to raise fuel prices all around the globe, looking for another type (cheaper) of fuel is normal thing. Over here in Poland LPG is very popular, price ratio is 3:1 and for last 10 years using this fuel in different cars, engines conclusion is:
LPG conversion pays back for small engines (max 2000cm3) on bigger lumps general worn is so fast it's no cheaper at all (service costs)
when running on LPG you have to use special oil with higher grade,
the same with spark plugs which are also "special" and to change every 5000/8000 km,
More frequent air filter changes, etc.

I know a few e31 examples running on LPG, theirs owners aren't happy people.

Zitat von adamski

in these days when GWB & Co are doing everything to raise fuel prices all around the globe, looking for another type (cheaper) of fuel is normal thing. Over here in Poland LPG is very popular, price ratio is 3:1 and for last 10 years using this fuel in different cars, engines conclusion is:
LPG conversion pays back for small engines (max 2000cm3) on bigger lumps general worn is so fast it's no cheaper at all (service costs)
when running on LPG you have to use special oil with higher grade,
the same with spark plugs which are also "special" and to change every 5000/8000 km,
More frequent air filter changes, etc.

I know a few e31 examples running on LPG, theirs owners aren't happy people.

I'm afraid your logic doesn't make any sense to me. A dual-fuel conversion pays back on a small engine but not a large one? Very strange reasoning, you'll need to cover a much higher mileage in a small engined car to make the same amount of savings due to the lower fuel consumption. This is reflective of the market (at least in the UK) -- do a quick search of Auto Trader or whatever your preferred publication is, and compare how many dual-fuel Ford Fiestas you see for sale compared to large, gas-guzzlers like V8 Land Rovers. The latter will far outnumber the former.

Where is the "special" oil with higher grade? Is Mobil 1 or Castrol RS not up to the task of running a dual-fuel car? This I very much doubt, as mentioned before you actually get less oil contamination when running an engine on propane, this much has been proven as fact. Likewise, "special" spark plugs replaced every 5000 miles? This is nonsense, plain and simple. The truth is that a propane mix is slightly more difficult to ignite than petrol mix, which will show up any ignition weakness more readily. However, any decent modern ignition system, and particularly a coil-per-cylinder arrangement like BMW uses, will have absolutely no problem running on propane with standard spark plugs, replaced at the standard service schedule. Some people choose to reduce the plug gap a little, but personally I doubt even that will be necessary as long as the system is properly set up and your coils are all in good working order.

The final part which I find to be completely nonsensical is about replacing the air filter more frequently. WTF? So if you run your car on propane it makes the air filter get dirty more quickly, even though the fuel never goes near the air filter? I'm sorry but this is just complete rubbish, no other way to describe it. Yes you should be using good quality spark plugs, oil and filters, but you should be using those anyway on a car like this.

If you want to make a reasoned judgement then it's necessary to get the facts, and that posted above is anything but true. I don't know where you get your "facts" from, or what goes on over in Poland with regards to dual-fuel conversions, but it is certainly not reflective of what goes on here in the UK. A converted car is serviced exactly the same as a standard car, with the addition of a short annual service of the propane system to check that everything is still within spec, and adjust if necessary. On some systems there may be a filter to be cleaned, or the vapouriser is drained by releasing a drain screw.

I think your problems that you've heard of are probably down to poor installation and/or poor equipment. A decent quality, and most importantly properly installed, sequential gas injection system will perform much the same as the petrol system, with a small drop in power and similar small drop in economy due to the lower calorific value of propane compared with petrol. Engine wear will be reduced, service schedules are unaffected, and of course your fuel bills will be halved.

As stated previously, personally I don't think it's worth the price of the installation on an 8-series. If you're currently paying 20p per mile for petrol, then that will become around 10p per mile on propane -- a saving of 10p per mile. So if it costs £2000 to install the system, you'll need to do 20,000 miles to break even. That would take me around 4 years, and it's unlikely I'll keep the car that long. Realistically I'd need to do around 30,000 miles to make enough of a saving (£1000) to make the extra hassle worthwhile, which would take 6 years -- not worth it.

So financially it doesn't make sense unless you're doing at least 10,000 miles per year, and preferably close to 20,000. Those are the real reasons I consider it a bad idea, none of the scaremongering crap that seems to do the rounds on the internet . Oh and if anyone can prove the stuff about needing "special" oils, spark plugs, and air filters, then I will publicly apologise and take it all back.

ough aghh, propane gas defender
10 years ago LPG conversions hit the market like a bomb (at least in Pl), during this time this type of fueling improved a lot especially multi injection and that's good. However engines we are interested in M30/60/62/70/73 weren't designed to run on air propane gas mixture at all and faster or later signs of failure will be seen and you're right this later or faster depends if conversion job has been done properly.
Engine isn't the only part affected, fuel injectors and fuel pumps are prone to damage. These parts aren't used when engine burns gas, so very often when fuel pump is working, fuel biulds in lines and stops in injectors making them unusable in some period of time.
Next are:
Much less power,
Fussy engine service (valve seats, gaps to set in shorter intervals)
Decreasing space in the boot by fitting there a gas tank,
Drilled holes in body work from boot to engine bay (where is originality?),
Much weight on car,

Please ask LPG users about condition of theirs cars in 3, 5 years of use

And this smell when you have to follow someone who is running on gas, like eggs out of date

LPG is good but for working horse for special cars like BMW E31 isn't

Zitat von adamski

ough aghh, propane gas defender
10 years ago LPG conversions hit the market like a bomb (at least in Pl), during this time this type of fueling improved a lot especially multi injection and that's good. However engines we are interested in M30/60/62/70/73 weren't designed to run on air propane gas mixture at all

And the thousands of other cars that run on it were designed to run on propane? No, I think you'll find very few cars are designed to run on propane. The reality is that most petrol engines can run on it perfectly well, albeit with reduced efficiency as propane can run with a higher compression ratio due to the significantly higher octane rating (around 110 IIRC).

Zitat

and faster or later signs of failure will be seen and you're right this later or faster depends if conversion job has been done properly.

If you take a look around there are plenty of old 7-series, both V8 and V12, which have been converted and have been running on propane for a long time. A few I've seen had over 250,000 miles on the clock, and still running fine. I think those of you with automatic gearboxes are far more likely to see a failure there before any major engine problems develop due to a properly configured propane conversion.

Zitat

Engine isn't the only part affected, fuel injectors and fuel pumps are prone to damage. These parts aren't used when engine burns gas, so very often when fuel pump is working, fuel biulds in lines and stops in injectors making them unusable in some period of time.

This is why most properly installed systems will run the engine on petrol for a few minutes after starting. Keeps the injectors and fuel pump in use, preventing seizing. I have rarely heard of injectors failing due to this, again it's usually due to poor installation where the car is set to run on propane all the time, and the petrol system doesn't ever get used until a year later when the owner runs out of propane and tries to switch back.

Zitat

Next are:
Much less power,

Nonsense, you'll get a small decrease in power due to the lower calorific value, but on a big V8 it will barely be noticable

Zitat

Fussy engine service (valve seats, gaps to set in shorter intervals)

Again, nonsense. These cars have hydraulic tappets, so if your mechanic is adjusting the gaps then I'd question whether he actually knows what he's doing (or is at least charging you for). Valve seat wear is slightly increased due to the increased combustion temps, but on a well designed engine like this one it's likely that the valve seats will outlast the rest of the engine -- look at all the old 7 series I mentioned, don't hear many valve seat recession problems in them even with inter-galactic mileage.

Zitat

Decreasing space in the boot by fitting there a gas tank,
Drilled holes in body work from boot to engine bay (where is originality?),

This much is true, and is one of the things that would obviously have to be considered.

Zitat

Much weight on car,

About 50Kg, maximum (not counting the weight of a tank full of propane, but that is offset by the fact that you're unlikely to have a tank full of petrol on a dual-fuel car). If 50Kg makes such a huge difference to you in a 1800Kg car, I hope you never carry any passengers.

Zitat

Please ask LPG users about condition of theirs cars in 3, 5 years of use

Yes, please do. I think you'll find few of them have any problems -- provided the system was installed properly in the first place. Particularly those 7-series owners with over 200,000 miles on their cars.

Zitat

And this smell when you have to follow someone who is running on gas, like eggs out of date

That is almost certainly due to poor mixture control. Propane burns very cleanly, producing almost entirely carbon dioxide and water vapour. If you can smell either of those then your nose is somewhat superhuman. You get far less by-products compared with petrol, so it should smell far less. A smell of eggs is usually caused by sulphur, which propane has almost none -- far less than even "ultra-low sulphur" unleaded petrol that is the norm in the UK these days. So you're more likely to get a sulphurous smell when running on petrol.

Zitat

LPG is good but for working horse for special cars like BMW E31 isn't

I think your experience is very much tainted by poor quality installs, probably consisting of the wrong type of equipment which is then incorrectly configured. I have no personal experience of the conversion standard in Poland, but I have heard some horror stories. There are even stories of people travelling from the UK to Poland with their car to have it converted, because even after the cost of travelling it is much cheaper.

For comparison, a car like the 840 would cost around £2000 to be converted here. That is around 11260 in Polish money according to an online converter. What would be a typical price for such a conversion in Poland? I suspect it may be significantly less, and sometimes you do get what you pay for.

I agree that doing such a conversion on an 840 probably doesn't make economical sense. However I'm an advocate of making that decision based on fact and rational judgement, not spurious claims about huge power losses, destroyed engines and smelling of eggs . This sounds like a classic case of FUD marketing (fear, uncertainty and doubt), something Microsoft have mastered to a fine art, at least partly explaining their ability to squeeze out competitors across the board.

Let's stick to the scientific facts, and if you can prove any of the claims about engine damage or other problems (on a properly installed system) then I'm happy to hear it.

Paul, the burning question is ............. (excuse ridiculous pun)

How do you know so much about LPG ???

Makes for an interesting read though

Zitat von TallTony

Paul, the burning question is ............. (excuse ridiculous pun)

How do you know so much about LPG ???

Makes for an interesting read though

My runaround car is a 3.0 Omega MV6, which has a properly-installed, and good quality dual-fuel system installed. It was already on the car when I bought it (about 18 months ago now), and I have a receipt for the work of around £1800 IIRC. It's obviously a bit simpler on this car being a V6, and it's got such a big boot it uses a larger cylindrical tank which is cheaper than the (smaller but fits in the spare wheel well) toroidal type.

It runs much the same on propane as it does on petrol, both at idle and at 6750 RPM (redline). It produces much the same power -- you can switch it over and accelerate hard on either fuel, and I can't tell the difference from the ass dyno (although I'm sure there's a small measurable power loss if you use a dyno or stopwatch). Fuel economy drops a little due to the lower energy density, so I'm getting around 24 MPG average as opposed to 26 or 27 MPG that I got on petrol. Still equates, cost-wise, to around 60 MPG on petrol.

Oh, and this car has 172,000 miles on the clock. It drives at least as well as any other Omega with high mileage, it gets serviced exactly the same as a petrol car would get serviced (although the oil comes out noticeably cleaner after 8-10,000 miles), uses standard Vauxhall spark plugs with standard gap settings, standard air filter, standard oil filter, standard plug leads. There is no smell from the exhaust, less so than on petrol. I recently replaced the valve cover gaskets (they leak oil with age much like the BMW ones) and the camshafts looked brand new. The tappets have never needed adjustment, nor are they noisy.

In short, the only noticeable difference is that it costs £30 to fill up, rather than £70. If it's done right, you won't get any problems with engine wear, nor will you need a special air filter(!). These are the facts of my experience, not some third-party Chinese whispers I read on the internet ;).

I'll state again, I still don't think it's worthwhile due to the initial cost. That car has saved me in fuel costs (compared to the 8 ) almost the price it cost me to buy the whole car so even if the engine were to blow up tomorrow because I didn't use a special LPG-friendly air filter it's already paid for itself. The beauty of dual-fuel cars is that they barely affect resale value, so you can buy a pre-converted runaround for buttons avoiding the conversion cost, yet still make the savings. They're also easier to sell at the lower end of the market, because people want a cheap car that will save them money, yet you can still have nice performance. I may sell this car soon as I don't do so many miles, and judging by the market I'll probably lose only £500-£750 compared to what I paid for it, after 18 months and about 30,000 miles :D.

Hi there,

I recently got LPG G3 into my other car, a 2001 540i touring.
It is a system specifically designed for the 4.4.ltr V8 BMW engines and uses the Motronic electronics from BMW to inject the LPG. This results in a perfectly behaving engine under all conditions. It works even quiter on LPG when idling then on petrol. I drive about 40.000 km a year and I can advise anyone to go for this... it drives like a dream, fuel costs are down from 18 eurocents to 7.2 cents per kilometer The engine oil keeps clean for much longer due to the absence of petrol washing in the cilinder bores :-)) No noticeable lack of power, the tank is a 74 liter that was installed in the sparewheel place under the floor in the back. The filling point is inside of my rear bumper (righthand side) so no holes in the metal bodywork.
I have repeatedly said that people should cook on gas, and not drive on it, but now I am wondering why I did not do this earlier, and how many euro's I would have saved then.....

I also considered installing LPG in my 1998 840CI automtic, but I will not do it because I only drive the car for a few thousand km's a year for fun, and the originality of this beauty with 50.000 km's should remain intact.

Best regards,

Sander

Old Topic re-kindled but my thoughts never change.

Why on earth buy a V8 bm then cry because it isn't fuel efficient

If you need Economy then buy a Diesel Peugot & leave Munichs finest alone

hello everyone----
Thisis my personal opinion on LPG.
I own 850 motorsport---I will never ever convert that car on lpg---thisis future clasic,leave as is. but....
I also own Lincoln Navigator 2005---5.4 engine which does 13miles on galoon----so after 2 trips to east part of Poland( each trip cost me around £650---petrol + ferry),my mate give me the idea about LPG.
I found company LPG autocentre on Notrh circular road(inside power total petrol station)in london.
Cost me £1500,2 years guarantee,very frendly boys & professional work.Tuck them 2 days to do conversion.&&&&&you know what----make my happy any time I go to petrol station----80 litres lpg---£37.

My mate which give that idea---own several cars & all of them have been converted to LPG(mercedes ml 430.bmw 728,mercedes s500)---not problem at all.
I anyone want I can post the photos how the system look on my car(have to take pictures)

its yours choice & yours money mates!!!!
cheers

hello everyone----
Thisis my personal opinion on LPG.
I own 850 motorsport---I will never ever convert that car on lpg---thisis future clasic,leave as is. but....
I also own Lincoln Navigator 2005---5.4 engine which does 13miles on galoon----so after 2 trips to east part of Poland( each trip cost me around £650---petrol + ferry),my mate give me the idea about LPG.
I found company LPG autocentre on Notrh circular road(inside power total petrol station)in london.
Cost me £1500,2 years guarantee,very frendly boys & professional work.Tuck them 2 days to do conversion.&&&&&you know what----make my happy any time I go to petrol station----80 litres lpg---£37.

My mate which give that idea---own several cars & all of them have been converted to LPG(mercedes ml 430.bmw 728,mercedes s500)---not problem at all.
I anyone want I can post the photos how the system look on my car(have to take pictures)

its yours choice & yours money mates!!!!
cheers

Quote: "Why on earth buy a V8 bm then cry because it isn't fuel efficient
If you need Economy then buy a Diesel Peugot & leave Munichs finest alone"Unquote.

I could also buy a M5 or a V12, but I like the practical ultrafast incognito 540i touring a lot more. I even know of a guy's that run their new 7-seriess and Porsche cayenne cars on LPG >> why pay more then nescessary for fuel if you use a car for about 200.000 km and then trade it in for a new one?

It is simple a matter of calculating: 40.000 km with an average milage of 8 km/liter costs about EUR 5000,- per year on petrol in NL.
40.000 km with an average milage of 7 km/liter costs about EUR 3.000,- per year on LPG in NL. The EUR 2.000 I save this way is always welcome, certainly because there is NO WAY you can tell you're running on LPG instead of petrol, except the price and the Prins LPG G3 installation has a 280.000 Km warranty and is service free

It also has to do with the way you value money, I can drive my 840 for free because I save on petrol with my daily driver... I could also go on a winter holliday to the snow for that (free) money

I agree that with a special car like the 8-series it is NOT good for value and originality to hook up LPG, and that's excactly why I won't.

Cheers!