Lpg the new diesel?

[Trabi601]

SteveSteveson said:

Not sure where the rip off is comparing us to somewhere with much lower cost of living. Really not sure I'd want to be near a DIY fuel system, especially gas. There's a good reason you need qualifications and training to mess about with it in a house.

We paid £1200 for our system, fitted to the Alphard. For a 4 cylinder car, that dropped to £1000.

It's a bit more than going abroad to have it done, but fully UK certified and I can take it back to the installer for servicing and tweaking. I'm dropping it back in next week as I want him to move the switchover point - I think it's still set a little too cold, so get a stutter on cold mornings when cutting over from petrol to gas.

Somehow we also managed to get the float valve stuck, which meant the safety cut off in the filler was triggered... he popped around on a Sunday afternoon and sorted it. You don't get any backup if you have it done in Romania!

I reckon on a pence per mile basis, it's costing less than my BMW 520d.

[ChemicalChaos]

njw1 said:

I ran an lpg converted 540i for a while but just couldn't get on with it, the biggest problem was that as I do a lot of short journeys the engine rarely got warm enough to switch over to lpg so I only used the lpg on longer runs. I probably saved very little in fuel costs in the time I had it. The tank that was fitted was also not the biggest so the range wasn't great, it was also in the spare wheel well so the spare was in the boot but my biggest complaint was that the car just didn't seem to have the same throttle response or as much low down torque as it had on petrol. To be fair it was quite an old system so I would imagine modern systems are better in that respect. I found it about 75% as efficient as petrol in my case and the car also had no cats and had no problem passing emissions tests.

How short were your short journeys? Left idling for 30 seconds from startup, then driven half a mile down the road, my Range Rover will begin to switch over. This is with a modern, multi-point injection Prins system a previous owner had professionally fitted - to a very good standard, unlike a lot of the horror stories out there.
Yes, it is a pain having to either have no spare or no boot space.
Yes, it is a pain having tank size and thus range limited by the wheel well.
Yes, finding stations on a long trip out of area can be a pain.
Yes, if you boot it then you flood the vaporisers and the engine will stutter - you have to be smooth on the power
Yes, it doesn't pull quite as well at high revs.

BUT - doing 12.5mpg on gas (as opposed to 14mpg on petrol, so about 80-85% relative efficiency) means with a gas cost of 47 p/litre at my favoured Liverpool depot (extra gas - they supply the petrol stations so you cut out the middleman and save about 15p/l) then mathematically my car does ~32mpg - more than I'd get from a TD6 with half the power and none of the V8 noise. Oh, and it basically emits flowers from the tailpipes.

However, I sincerely hope LPG doesn't get pushed as the next big thing and remains under the radar - because I can guarantee that if it goes mainstream then it won't bloody well stay at half the price of petrol!!!

Edited by ChemicalChaos on Monday 20th March 20:37

[bearman68]

A few of my customers run it in preference to diesel. The engines seem to like it - all of them seem to have massive miles on, and the oil comes out looking much cleaner than a petrol or especially a diesel. A turbo charged LPG seems a good bet. (I like the extra torque at low revs)

[DaveCWK]

njw1 said:

I ran an lpg converted 540i for a while but just couldn't get on with it, the biggest problem was that as I do a lot of short journeys the engine rarely got warm enough to switch over to lpg so I only used the lpg on longer runs. I probably saved very little in fuel costs in the time I had it. The tank that was fitted was also not the biggest so the range wasn't great, it was also in the spare wheel well so the spare was in the boot but my biggest complaint was that the car just didn't seem to have the same throttle response or as much low down torque as it had on petrol. To be fair it was quite an old system so I would imagine modern systems are better in that respect. I found it about 75% as efficient as petrol in my case and the car also had no cats and had no problem passing emissions tests.

With modern systems you can adjust the coolant temperature at which the LPG switches over - running on petrol for ages while it warms up is a result of a lazy installer not setting it up properly in the first place. My car for example: Cold (overnight) start takes around 20s to switch over at this time of year. Warm (If car has been run within previous 8 hours) starts on petrol & switches within 3 seconds. Hot (If car has been running within ~45minutes) starts on LPG.
You do lose a little torque as the engine timing remains optimised for petrol - to optimise for LPG is sadly a bit more complicated & usually requires an ECU with dual mapping functionality. The degree to which this is detectable depends on the car though - for example you're unlikely to notice in a low compression turbo.
Where the economies of LPG running really come into their own is when cruising at high speeds. At a constant 90mph, a V8 BMW running on LPG likely costs less per mile in fuel than any 2.0 TDi.

LPG will likely remain niche & will never be taxed as much as petrol/diesel.

[Trabi601]

ChemicalChaos said:

(extra gas - they supply the petrol stations so you cut out the middleman and save about 15p/l)

Not quite.

They're a FloGas stockist. FloGas supply the petrol stations, along with AutoGas (Calor). They're only 3p / litre cheaper than most of the AutoGas supplied places around here. Nowhere near 15p.

[ChemicalChaos]

Trabi601 said:

Not quite.

They're a FloGas stockist. FloGas supply the petrol stations, along with AutoGas (Calor). They're only 3p / litre cheaper than most of the AutoGas supplied places around here. Nowhere near 15p.

Obviously it varies by region - for me, Shell and BP stations are 58-65 p/l, wheras EG is 47p

[njw1]

ChemicalChaos said:

How short were your short journeys? Left idling for 30 seconds from startup, then driven half a mile down the road, my Range Rover will begin to switch over. This is with a modern, multi-point injection Prins system a previous owner had professionally fitted.....

Edited by ChemicalChaos on Monday 20th March 20:37

I found that in particularly cold weather the car had to be properly up to temperature otherwise it would cough and splutter, this could take up to ten minutes which happens to be how long it takes me to get to work! The system was an old venturi type single point system which I think was the biggest problem and I wasn't sure how it was plumbed in to the cooling system exactly.

[njw1]

DaveCWK said:

njw1 said:

I ran an lpg converted 540i for a while but just couldn't get on with it, the biggest problem was that as I do a lot of short journeys the engine rarely got warm enough to switch over to lpg so I only used the lpg on longer runs. I probably saved very little in fuel costs in the time I had it. The tank that was fitted was also not the biggest so the range wasn't great, it was also in the spare wheel well so the spare was in the boot but my biggest complaint was that the car just didn't seem to have the same throttle response or as much low down torque as it had on petrol. To be fair it was quite an old system so I would imagine modern systems are better in that respect. I found it about 75% as efficient as petrol in my case and the car also had no cats and had no problem passing emissions tests.

With modern systems you can adjust the coolant temperature at which the LPG switches over - running on petrol for ages while it warms up is a result of a lazy installer not setting it up properly in the first place. My car for example: Cold (overnight) start takes around 20s to switch over at this time of year. Warm (If car has been run within previous 8 hours) starts on petrol & switches within 3 seconds. Hot (If car has been running within ~45minutes) starts on LPG.

LPG will likely remain niche & will never be taxed as much as petrol/diesel.

The system I had had to be switched over manually via a switch in the centre console, as said above it appeared to be quite an old system. I would fully expect a modern multi point system to be much better.

[rswift]

My few pence worth.......I ran my old Jag 4 litre on LPG from 120k miles to 325k miles....ok the water pump failed at some point.

My current Jag, 2003 4.2 V8 X350, converted at 40k, now 7 years later on 160k...no perceivable difference in performance, but significantly cheaper to run than my wife's modern Citroen 2 litre diesel......also had a 200k Range Rover, 175K Jeep. A friend still runs a 400k Saab, and almost unbelievable 300K Range Rover P38...,,,so works for me, would recommend to anyone. If you don't like it, don't buy one....simple. On my first Jag ... about 15 years ago, I seem to remember LPG was 26p/L

[Burnzyb]

Thanks for the reply's guys, I think my mind is made up to be honest now, I'll keep running the s211 for a bit and in the mean time I'll window shop for something lpg that ticks the right boxes

There has been a nice e61 545i on lpg on auto trader that I had my eye on, I've been needing to scratch the v8 itch and I think this is the perfect way to do it

[Burnzyb]

Fastpedeller said:

Unfortunately that doesn't demonstrate anything, as their equipment only has to be calibrated every 6 months.

Unfortunately your point also doesn't demonstrate anything.

[RockyBalboa]

Prins, BRC were the top performers. Other systems (Romano, Stag etc) are often based on the same AEB electronics but you can choose different injectors and reducers. Incidentally, my experience of Romano on anything high powered resulted in the vehicle switching back to petrol at high revs (a properly converted vehicle shouldn't do this unless it is by design).

Lower powered vehicles are pretty easy to convert, anything high powered (in terms of BHP/cylinder or > 270 BHP) require more thinking and certainly in my experience, there aren't that many good convertors but many 'fitters'.

I've run a V8 for nearly 200k miles on LPG. If the conversion is done properly (e.g. drilling and tapping the inlet manifold as close to the existing injectors as possible) with a suited system (suited to the power of the car), you should have few problems (except on cars with soft valves!).

I get about 70-75% of the mileage that I got on petrol. I have easily saved over 20 grand I reckon. Power is on par with petrol (no real discernible difference).

Going forward, with the mass introduction of direct injection, fewer and fewer cars are able to be converted and those that can be converted also require petrol addition which further eats into any savings. In short, I don't currently see much of a future for LPG for post 2006/7 cars.

Edited by RockyBalboa on Wednesday 29th March 23:04

[Alex_225]

I must say that LPG has raised it's head for me as well but I would gladly look at something I'd want to fit LPG to.

For example, I use an E Class diesel for my motorway driving. Mainly because it's relatively quick (3.2 straight six) and returns 45-50mpg so it's actually great for it's size and performance.

But, if I chose to buy something similarly sensible in terms of size but with a V8 engine, I could do the same driving for the same cost. If I bought an E500 or E55 as a long term 'family car', converted to LPG it wouldn't be quite as much of a sting regularly on the wallet as running a V8 normally. From what I'm reading, performance remains similar.

[RockyBalboa]

Alex_225 said:

I must say that LPG has raised it's head for me as well but I would gladly look at something I'd want to fit LPG to.

For example, I use an E Class diesel for my motorway driving. Mainly because it's relatively quick (3.2 straight six) and returns 45-50mpg so it's actually great for it's size and performance.

But, if I chose to buy something similarly sensible in terms of size but with a V8 engine, I could do the same driving for the same cost. If I bought an E500 or E55 as a long term 'family car', converted to LPG it wouldn't be quite as much of a sting regularly on the wallet as running a V8 normally. From what I'm reading, performance remains similar.

I feel it's only worth the initial outlay if you are doing at least 12,000 miles per year - i.e. the greater the mileage, the quicker the pay back.