LPG should i go for it? [Archive] - Land Rover UK Forums

Revs

10th Nov 2005, 18:46

Hi, cant afford to keep spending this much on petrol so im thinking LPG is the answer....

My 4.0 SE has covered 114,000 miles but is running sweet and has a FSH. Is this too high a mileage to convert or should i be ok?

would i be better off buying a lower mileage range or disco to convert or would i be stupid to sell a car which i know and trust?

can anyone recommend a company?

cheers for any help :) :rolleyes:

jjsaul

10th Nov 2005, 23:48

convert it !

fisha

11th Nov 2005, 10:39

yup

ty_bach

11th Nov 2005, 11:21

I used to have a 1990 3.9 Vogue which I had converted to LPG using twin 40 (useable) litre tanks under the sills so as not to compromise the loading area capacity. It did mean however, that on long journeys, I had to plan where the next lpg station was in order to keep fuel costs down and optimise the savings. It was great. The slight loss of power was negligable especially when you are talking of this size of engine! The engine ran smoother and the good feel factor of using a more environmentally friendly fuel. Also when going to an MOT, the emission readings were nearly zero. If you go abroad it is cheaper than UK.

If you decide to get a specialist to fit it, make sure you go to an LPGA approved fitter. I did'nt, and had problems with the fitting 'specialist' who frankly gave me the runaroud when I had problems.

Hope this helps

ChrisKaye

11th Nov 2005, 16:16

Hi Revs (no pun intended !)
Just done it to my 4.6 HSE around 50K miles
On my second tank of lpg now
Too early to tell if any engine problems, none so far ! (fingers crossed)
SRS Airbag light is permanently lit up now, neverhappened b4, checked under seat to see if a loose connection but all looks ok. Fitter must have moved or dislodged a cable or so .....anyone any ideas ?
Pleased with the conversion and now do 220miles on £30 of lpg or 13.6p per mile whereas before it was around 26p/mile

I wish I had done mine when I first got it now, so I would say yes go for it, but I would see what others say taking into account your mileage

I used www.Greenfuel.org.uk (http://www.Greenfuel.org.uk) they are in Bath

Revs

11th Nov 2005, 17:09

thx for the comments...

i phoned up rpi and the guy said the 4.0 engine will virtually run forever if its been well maintained, which mine has (cam change at some time tho).

thats great BUT i want the car i LPG to last me the next 3 or 4 years. i've seen loaded series II disco's with 70k on the clock go for under £7000 at auction, would i be more sensible to buy one of these to lpg? what would you do?

cheers again

geoff

12th Nov 2005, 23:28

hi

It will be worth it if you do enough miles to recover the cost of the conversion. I got a sequential kit fitted in Jan, it cost about £1900. I do about 25-30,000 miles a year so it's almost paid for itself. You really need to work out if it will work for you. find out if you have a morrisons near you that sell LPG, they are the cheapest i've found at 32.9 per litre.

cheers
Geoff

shadyadie

13th Nov 2005, 02:36

todays prices 93.9 - 42.9 = 51p (1 gallon = 4.546 09 litres)

.51 X 4.546= 2.31 saving per gallon

Landrover V8 about 18 miles per gallon

2.31 / 18 = 0.128 per mile saving

£2000 / .128 = 15625miles

15625 X 10% = 1562.5 + 15625 = 17188

This is a quick calculation of the realistic miles you will have to do to recoup your £2000 thats 2 years driving for me.
Don't forget you will have the cost of servicing the gas conversion on top of this and you will still have to start on petrol. and IMHO you run a greater risk (risk not certainty) of engine damage.
The 10% is the fact most cars do not do as many miles per gallon on gas as they do petrol.
Also based on the assumtion that tax does not go up on gas.

I had a gassed rangie and decided never again, as no matter what people tell me I have never found gas to be as performing as petrol and in my case I lost bootspace.

The only way I would have an LPG again is if the engine was specifically designed for it.

If you disagree with the MPG for a V8 and say yours will go further then it will take even longer to get your money back.

I also agreewith caber that if not set up right you use a lot of air filters

This is my opinion 114,000 miles is a bit high to convert and gassed motors have a higher risk of blowing a head gasket....

geoff

13th Nov 2005, 07:24

Hi

There is a plus with the sequential injection kit, you do not get blow backs so don't wreck air filter boxes or head gaskets.

geoff

Revs

13th Nov 2005, 10:10

This is my opinion 114,000 miles is a bit high to convert and gassed motors have a higher risk of blowing a head gasket....
hmm this is what i've been wondering, i definately dont want to be going down this route. was your conversion sequential or an older style thing?

if i decide against lpg it'll be TD5 time which im not too keen on as i love the V8. with those figures i will almost certainly recoup the costs cos im planning on keeping the car for a few years.

maybe the safest route would be to buy a lower mileage car to convert but then again i've ironed out all the problems on the car and its running sweet so im reluctant to do this. i know from experience that when buying a p38/disco its almost a certainty to be spending a fortune on fixes the minute after

dilemma

thx again for the comments :)

jjsaul

14th Nov 2005, 00:05

ive never heard of any issues with blown head gaskets unless your engine is ******ed to start with

LPG round here is 32ppl

and no you dont have to start on petrol

shadyadie

14th Nov 2005, 22:06

ive never heard of any issues with blown head gaskets unless your engine is ******ed to start with

Generally gas burns hotter than petrol which puts more strain on seals (ie head gaskets).
plus gas does not have the lubrication properties that petrol does. plus gas can be very prone to backfire.

my gas set up regularly blew the air filter apart..
I think that some V8's have some sort of air flow regulator and gas can also blow this.

Some petrol engines as in jjsaul's case run perfectly well on gas, and usually have a proffesional and expensive conversion on them (don't know what jj has got).

But if gas conversions are so good how come it is not offered as an optional extra on the new range rovers and land rovers

jjsaul

15th Nov 2005, 00:10

Some petrol engines as in jjsaul's case run perfectly well on gas, and usually have a proffesional and expensive conversion on them (don't know what jj has got).

But if gas conversions are so good how come it is not offered as an optional extra on the new range rovers and land rovers

Our conversion was done by 'professionals' before we picked up the vehicle. I think carbs generally are easier to set up with LPG than EFi unless you start meddling with ECU settings.
Having said that i'm intending to LPG convert our rangie myself.

As for optional new extra, they dont do petrol defenders, and i reckon they assume if you can afford £50k for a range rover, you wont worry about fuel cost.....

shadyadie

15th Nov 2005, 18:48

Our conversion was done by 'professionals' before we picked up the vehicle. I think carbs generally are easier to set up with LPG than EFi unless you start meddling with ECU settings.
Having said that i'm intending to LPG convert our rangie myself.
....

I was being complementary. :)

Our one and only gas conversion was done by a "proffesional" before we bought our V8 rangie. it was a "less expensive" conversion that let the gas straight in to the air intake all I will say is never again as not only did it blow the head gasket it also damaged the engine block and according to the garage it was purely down to the extra temperature and pressure.
whilst we had it we had extreme difficulty getting garages to do anything on the rangie that involved going anywhere near the gas set up.
All our local Landrover garages and workshops all advise against gas set ups on V8's.

I do believe that there is a set up that goes straight in to the injectors and includes a lubrication system. Maybe this is better??

geoff

15th Nov 2005, 19:34

Hi

I have a sequential injection system fitted to my car, there is no blowbacks with this system. The inlet manifild is drilled and tapped and a second set of injectors is fitted for the LPG. There is no extra lubrication though, i don't think there is a system that has one.

Geoff

jjsaul

16th Nov 2005, 00:15

i think you can buy the extra flappy thing which stops blowbacks.

geoff

16th Nov 2005, 07:37

Revs

16th Nov 2005, 12:01

Theres an LPGA approved converter near to me who will do a fully sequential system for £1750 + VAT.

I'm pretty sure i want to go for it now, my only concern is still whether its sensible to convert a car with this mileage. Surely putting extra pressure on an engine with this many miles on the clock isnt sensible?

The conversion companies say they've done cars with higher mileages than this but then they want my money so i cant be sure they are un-biased

zxzach

16th Nov 2005, 13:43

yup, had my p38 gassed up 4 weeks ago, 157,000 miles, runs sweet as a nut on gas, my LSE was on gas at 110,000 miles no problems (apart from the occasional blowback - but that was an old single point system, no such problem with this sequential system). drive about 500-600 miles a week and with LPG at 32.9p per litre should recoup the costs by April and then cheap cheap cheap.

fisha

16th Nov 2005, 14:01

As long as the engine is in good shape, then it shouldn't matter what mileage a conversion is done at. I have a friend who had his done at 150k miles.

My P38 was converted at 105k miles although the engine is only 30k miles old ( one of the principle reasons of me keeping the car )

The RRC i have is at 150k miles, but i rebuilt the engine and then converted it.

Not 100% sure about the issues of lubrication . . . where do you need it? The general oil flow routes of the V8 should be enough to cover all the moving parts. You certainly dont want too much petrol as it causes bore wash.

Blow backs, not something i personally have experienced. My P38 has sequential and the RRC has carbs. My guess is that the common blowback issues are most likely attributable to the large plenum and how it holds a air/fuel mix when it normally wouldn't when on petrol. The carb setups have a much smaller volume of air bewteen the mixer and the cylinder compared to a plenum setup, so there is far less build up to cause blow back.

I would still say go for it.

jjsaul

16th Nov 2005, 14:29

Hi James

I had one of those flaps on my rangie, it wont stop a blowback, it just lets the pressure escape from the air filter box to stop it blowing the box into a thousand pieces. When i had a big blowback the clips on my box gave up and it just parted. I'd go for a sequential system now. there are no problems with it. How much is LPG at that place you told me about, just off J12.

Geoff

Last time we were there it was 29ppl, but i've now found somewhere else in wolverhampton that does it at 32ppl, but is much much nearer and i can get there in lunchtime.

jasper110

16th Nov 2005, 14:38

hope you're sitting down

48.9p a litre for LPG where i live. next lpg filling station 40 miles away, 42.9p

thieving b*$^a"@s!!

Revs

16th Nov 2005, 15:02

LPG 42.9p Petrol 90.7p my local prices

great about living on the edge on london is that i've got 4 lpg stations within walking distance!

Roger Whittle

21st Nov 2005, 20:00

I do believe that there is a set up that goes straight in to the injectors and includes a lubrication system. Maybe this is better??

There is. My mate's 4.6 HSE has a conversion like that, although I'm not sure about lubrication. Each of the injectors has a little twagger, probably a solenoid valve, all plumbed and wired in series apparently. You can hear and feel them ticking when the engine changes over to gas. On his conversion the system reverts to petrol on switch off and therefore starts on it too. It changes over automatically at a preset temperature. He reckons the engine runs more smoothly, quietly and cleanly on gas. LPG is about 42p down here and most BP garages do it.

fisha

22nd Nov 2005, 11:10

Bmhor

22nd Nov 2005, 12:28

With sequential systems the gas ecu does not normally turm on the injectors until the temp reaches about 40deg to stop icing.

My RRC was converted at 95K and has now done 240k with no problems.
Starts on petrol and then switches over as the revs drop below 1500 for the first time.

Huey

22nd Nov 2005, 17:41

If your converting the 4.0 or the 4.6 you need to have a sequential system put in. the early conversions on those engines didn't work ours was converted end of July has just covered 10,000 mile in that time and is costing around 12p a mile in fuel. Its mixed running, dual carrageway, town and hills (Scotland) it also pulls the 2 horses effortlesly. We can get around 210 miles out of the tank 95 ltr. In the spare wheel well. The system is Nicholson Mclaren AG2 it has an injector for each cylinder drilled into the inlet manifold. It will have paid for itself in another 12 months. I always think its better to stick with the Landy you know they all have problems.

Jon v8

22nd Nov 2005, 22:01

I see lots of Lp v8 Range rovers with lpg,and with hugely varying levels of sucess.Wether they run Gems(94-99) or Bosch (99 on ) injection,no "cooker ring" or mixer system is able to run the engine properly- long term.This leaves the inlet port injected systems,these can work very well,if installed and maintained properly.This of course relys on the engine being in good nick to start with.The main issue I have with them is that under heavy load/acceleration they are unable to supply enough gas,quickly enough to avoid a very lean mixture. This is where the head gasket/porus block problem gets worse -quickly.When you read the codes out of the engine ecu's it is rare not to see faults to do with oxygen sensor switching etc.If you go ahead with this,find an installer who is willing to connect a 2 channel scope to your oxy sensors so you can watch them switching whilst driving.Before the conversion on petrol,and then after on both fuels Get them to explain what should happen.If they cant/wont-go elsewhere!

Roger Whittle

23rd Nov 2005, 00:53

Roger,

youre describing a sequential injection system there (SGI). Its what i have fitted to mine.

There are a few ways of implementing the injection, but the basic principle is that the liquid state gas goes through a general reducer/vapouriser which turns it into pressured gas. The pressured gas then is fed to the injector banks.

Thanks Fisha, it was beginning to dawn on me that that's what the difference was. It's nice to have it confirmed. There is a little addition to the story of my mate's gas HSE, although neither he nor I are certain that its relevant to this thread. He only does a low mileage and a lot of that will be around town where we live (SW London). Not long after the conversion, he began to suffer major performance degredation on both fuels and it eventually died on him. A very large bill later and he found out that BOTH catalytic convertors had collapsed internally. That was nearly £1000. His Rangie had done about 80k miles and from what others on this thread have said about higher combustion - and therefore exhaust - temperatures, it's possible that the conversion precipitated the failure.

Revs

23rd Nov 2005, 09:02

you can get new cats off the internet for £350 and they arent difficult to fit, shouldnt be a £1k job

fisha

23rd Nov 2005, 09:12

Bmhor - Yes, they normally have to reach a predetermined temp before switching to gas. mine is set as low as reaonsably possible apparently ( i think its 20degC )

Heuy:
You and me both. I squeeze about 220 from a tank in the boot well too and drive the same types of roads ( also with a horse trailer as well :) )

JonV8
If someone is installing a system that cant supply enough gas then its a bad installation. There is no reason to not be able to supply enough gas at higher revs. My tank to vapouriser pipe on the SGI system is 8mm pipe instead of the normal 6mm . . . partly for this reason. A possible common restriction is the pipes where they have been cut. Its important to chamfer the ends again to return them to their original inner diameter as most pipe cutters close in the inner bore after the cut.

Roger:
I would hazard a guess that the cat failure could be more attributable to the short journeys themselves. The cats normally need a good amount of time to fully warm up. If your doing a lot of short journeys then i would suggest that the constant expansion / contraction from heating up and cooling down may have lead to premature failure of the cat.

Jon v8

23rd Nov 2005, 12:46

Like I said, some systems don't supply enough gas- and for various reasons.The main one is because of poor fitting-as you say,not using big enough pipe and not reaming out cut ends etc.It seems to help having an extra filter up close to the vaporiser-this acts as an extra reserve of gas when you crack the throttle open,ensuring there is no loss of pressure at the injectors.I don't fit gas systems, (too much to do as it is!) I see them when they have problems.Either rough running or Mot time etc.The other issue I have with some systems is that the programmes to set them up are just not clever enough to work with gems or worst still bosch motronic (99-on).I stand by what I said earlier about using a scope on both oxygen sensors to monitor the fuel mixture.I only know one person who does this.I won't mention the company name because I know he is snowed under already.It really is the only way to see whats going on in real time,and the only way to make your engine last as long as it can.

Huey

23rd Nov 2005, 17:04

JonV8, I will check with my installer on that point but the performance difference is miniscule or so it feels, The noticable difference is on take off from standing but if your say doing 30 and go for the overtake kick down and let it have full throttle there is no difference that you can tell, Also the gas ECU talks and learns from the Rangey's ECU what I don't know not party to the conversation. Time will tell. personally I love it. But enjoying the discussion.:rolleyes:

fisha

23rd Nov 2005, 22:07

Huey,

do you find that if your at standstill and immediately plant the throttle hard, the engine seems to half-stall, then pickup and pull away fine?

Mine seems to do this on gas, but not on petrol. Its not a big issue, but just wondering if thats what you mean from standstill.

As a general comment on differences in power, i feel its not so much a case of there simply being less power in total, its more a case of the pedal movement being shifted a little bit further down, but that the action is the same after that.

Its almost like the LPG ECU needs to see about 0.5 to 1cm more pedal travel to work than the petrol does.

As far as i understand ( and i dont know if it applies to all SGI ) some of SGI systems work by principally looking at / intercepting the pulses the normal engine ECU is sending to the petrol injectors. Then from there, based on the manifold / gas pressures, it triggers the lpg injectors to supply the appropriate amount of fuel.

That way, monitoring of the lambda sensors, throttle position, air flow etc etc is all handled by the cars ECU. It would also explain how the LPG ECU learns from the engine ECU. I.e. The LPG ECU will perhaps vary the supply a little bit and wait to see what the engine ECU will do to try and counter that change through a change in the petrol injector pulse. The LPG ECU will then learn what actions to expect from the engine when it supplies certain amounts of fuel on each pulse.

This may get repeated on a constant basis and so the LPG ECU is learning ( or more like adapting ) to the engine ECU all the time.

This then may explain why I see a slight difference in the required pedal travel . . . but thats a lot of speculation on my part.

Jon v8

24th Nov 2005, 09:26

Fisha, if your v8 hesitates-at all,then it isn't set up properly.Its not getting enough gas.Starving a rover v8 of fuel is the ultimate insult-I think it even says so in the bible !! Seriously tho you are quite right when you say about the gas ecu piggybacking the engine ecu,trouble is the software often isnt clever enough to be 100%.They are supposed to be self learn but only within the limits of the base settings put in by laptop on instillation.One manufacturer's progamme I saw has 4 settings,idle ,part throttle,mid range and wide open-the poor gas ecu hasnt got a chance.The other problem is the slight time lag - the gas ecu's outputs will always lag behind the petrol one,this often has no effect.But I have seem them where they end up running up and down and eventually stopping. The only way we could stop it was to enforce a slightly rich idle mixture on gas.The worst design I have seem is one where the gas ecu took the output from one of the oxy sensors to use it,but it then fed a constant lambda waveform into the engine ecu.In a real situation the sensors should flatline rich under aaceleration and flatline lean when the injectors shut off on over run.They only should switch rich/lean constantly when at constant rpm.The poor engine ecu was totally confused ! I went out to a 99my RR yesterday to do an airbag light,Switched it onto gas - it ran like a grey fergie on tvo !! I had just come back from a gas "specialist" who were supposed to sort it.The engine ecu had 13 faults relating to mixture adaptions and "catalyist damaging misfires. One fault had ocurred 255 times.Thinking some could be old faults,I cleared them.In less than 2 mins most had come back (Engine idling-I didnt even drive it.) I'm not against Lpg conversions,I just wish that they were better sorted.

fisha

24th Nov 2005, 19:21

i dont disagree that there are some bad installations out there.

in terms of the hesitation - i was thinking about it today. i actually think that the hesitation is from going too rich. it only happens when your stopped and you put the foot down hard and fast. I suspect the engine ECU thinks " kickdown " scenario and throws petrol at the engine initially and then adjusts for the lambda reading afterwards. If it temporarily goes too rich on petrol, then it doesn't really matter too much - what can get burnt gets burnt and the rest thrown out the exhaust.

but, if the LPG ECU is piggy backing, then it'll read the big petrol injector pulse and throw in a similarly large amount of gas. as i understand it, trouble with an over rich lpg mixture is that it stiffles the engine way more than petrol causing the hesitation but it immediately rectifies itself once the lambda readings loop back through the system

And it only happens with a fast push on the accelerator. If i do a smooth press down to floor from standstill, there is no hesitation.

Only way i would know for sure is to fit an O2 guage on the dash.

Jon v8

24th Nov 2005, 19:49

Sorry, it doesnt work that way,when you crack open the throttle the ecu will give pretty much all it can-this is to satisfy "driver demand",to maybe get you out of trouble-overtaking etc.This is why even on new cars (petrol) you sometimes see a puff of black smoke when they are being booted-its fuel that the engine cant burn fully.Your gas just doesnt respond quickly enough,thats why it is ok on petrol.Just try driving around it till you get it sorted.Remember the 2 knock sensors will also be retarding the ignition,(limiting engine output) while this situation is happening.

Huey

24th Nov 2005, 20:11

Fisha, From a standing start it did seem to pause and when it did it was as if the choke was out, it has just had a full service and the gas pressure upped as the diaphram had streched, it was down to about 700 (is it psi) but now back just over a 1000 and the throttle response is immediate. From my limited under standing of how it works I don't think its possible to get the same response as petrol from standing, on tickover the diaphram is closed and gas goes past a tick over screw then when more is required the diadpram comes into play and more gas can be demanded. and if you have a small throttle opening say 1100 rpm then there is no pause however slight. (if thats all wrong feel free to tell me)
Jon V8, I understand what a wasted spark is and on gas my system employes it is it just to get rid of unburnt gas on exhaust?
Out of intrest the 90 on LPG puts the gas into the manifold where the pipe from the filter box is joined to the Inlet manifold and has a vacuum opener on the air meter and it waits for no man on take off (grin factor avery time) .

Jon v8

24th Nov 2005, 20:34

Sorry, not quite sure what you mean.The idea of a wasted spark system is that there is 1 ignition coil feeding 2 cyl's-so 4 coils on your 4.6.Each time the coil is triggered the plugs both fire,but only the piston close to the top of it's compression stroke will actually ignite.The other spark is wasted-hence the name.Any fuel not fully burnt in the combustion chamber will hopefully burn going out through cat.This is why it is very satisfying to watch an exhaust gas analyzer on a cat equipped engine,when its all working properly.Virtually zero hydrocarbons !

TEMPL4R

24th Nov 2005, 21:55

Another problem you get with wasted spark is, lose one plug and the other won't work.

The old Citreon 2CV used the principle, they advised changing the plugs over every so often. Had problems with the earlier Jap bikes.

Chris

Huey

25th Nov 2005, 17:11

I'm in the garage tomorrow for gas so will ask about the wasted spark. When the computer was plugged in to the gas it fires twice as many times as when on petrol.

Jon v8

25th Nov 2005, 19:14

Can you explain further please ? Computer plugged into which ecu- gas or petrol ?

Huey

25th Nov 2005, 19:58

JonV8 It was the gas ecu, I'll be in for a fill and a coffee in the morning same place that fitted the gas so will find out properly and get back to you otherwise I'll be guessing. Should get Richard to get on the forum he likes talking LPG.

Huey

26th Nov 2005, 17:00

On gas it does fire on compression and exhaust strokes he was unsure if there was any benefit, the answer was thats how the program was written, its only possible because its multi point injection. The only thing that came to my mind is the coil is doing twice as much work.
I do know I couldn't afford to run it on petrol though.

Jon v8

26th Nov 2005, 18:31

I think your gas place is a bit confused,the engine ecu controls triggering of the ignition coils- on gas or petrol.There is a spark every 2nd stroke of each piston-but only 1 does the business,the other is wasted.Its not like a distributor system where there is a single spark at or near the top of the compression stroke.Know what you mean about the cost of fuel.Just sold My 93 3.9 vogue se this afternoon-shame,it is a lovely car - like sitting in an armchair at Chatsworth !!!! Did'nt half enjoy it's unleaded tho !

fisha

26th Nov 2005, 19:03

wasted spark is as already said, a single coil firing into 2 cylinders, each on their compression strokes.

1 cylinder will be compressing the fuel mix ready to be burned, the other will be compressing the already burnt mix pushing it out of the exhaust valve. The coil fires into both at the same time.

but the majority of the energy from the coil automatically goes across the spark plug gap in the cylinder which is compressing the fuel mix, and a much lower percentage of the energy goes across the spark plug on the exhaust stroke.

reason for that is to do with the dielectics and ions in each of the cylinders. Its much harder to generate a spark in the exhaust stroke cylinder ( nothing to burn, ions and things prevent the spark ) where as its much easier for the spark to jump across the plug in the fuel mix cylinder which is ready for it.

The split is something along the lines of 80/20 %.