LPG conversion pros and cons (1 Viewer)

[Susanna]

Hi Everyone! Newbie here.

I'm about to buy my first van conversion and I'm looking at Mercedes Sprinters. There's one in particular on eBay that I've got my eye on. I have questions and maybe some of you more experienced folk can help?

1. The listing says 'Petrol with LPG conversion' would that mean that one must always fill it with LPG, or is it possible to switch between tanks as with biodiesel conversions?

2. Does anyone have a motorhome running on LPG? Would you share with me the pros and cons? For instance, is it hard to find places to fill it?

Thanks in advance!

Susanna

 

[mfw]

You can switch between petrol and LPG normally done because Lpg is less than half the price of petrol per litre

 

[klaatu]

One 'con', which may or may not be relevant to you, is that you can't go on the channel tunnel with a vehicle with an LPG conversion.

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[thebriars]

LPG is getting harder to find. BP have removed it from a nearby garage. Other garages may do the same. I nearly bought a Mitsubishi car which was duel fuel. It was discontinued after a year. Mitsu could not get it to work reliably with both fuels. If a manufacturer like Mitsu who build their own engines can't make it work then there may be an issue there too.

 

[simsy56]

Mine is petrol/LPG. Starts on petrol, changes automatically to LPG after a couple of minutes, you wouldn't know the difference until you come to fill up. LPG 50 odd pence, petrol £1.20 odd pence. Runs the same, very little carbon emissions, and plenty of LPG stations. You cannot use the Chunnel though.

Craig

 

[Suvvi]

LPG is very common in other countries and I've had first hand experience in Poland with lpg conversions lasting to high mileages 250k km +

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[Huw s]

I converted my v6 MGZT to lpg 4 years and 100k miles ago, can't fault it.
Petrol lpg MHO will need to be stirred allong through the gears - even if it has a turbo?

 

[TinaLes]

Whilst I realise that to run on LPG the engine has to be petrol, not diesel, what are the emissions on an LPG engine?, I would imagine much less, but stand to be corrected, why are they never mentioned these days? (I am aware that there are a few still running on LPG)
Please dont tell me that LPG were never commercially "promoted" as it would have been a lose leader for Government Taxation?
Used to see many used large engined petrol cars, Volvo's in particular for sale in the Autotrader, why were they like dinosaurs, when petrol was always expensive, wasn't it?
Look forward to hearing the truth on this, as it was many years ago, and it would explain why LPG stations are so much harder to find these days.
Les

 

[jockaneezer]

Not sure on the exact emissions, but the oil in our lpg powered forklifts at work always looked like it had just come out of the tin whenever I dipped them and when working inside, the exhaust fumes were hardly noticeable.

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[gerry mcg]

LPG powered vehicles are not allowed on the Chanel Tunnel

 

[Boringfrog]

Surprised you can get a petrol Merc Sprinter?

 

[tonyidle]

Whatever hydrocarbon fuel is burned certain emissions are a given: CO2 is a product of combustion and as it only depends on how much fuel is burned the more fuel-efficient the engine the less CO2 is produced. It is discharged in its entirety from the exhaust; NOx is produced as a result of heating atmospheric Nitrogen inside the engine. Engines with higher combustion temperatures (in other words the most efficient engines) produce more NOx; unburned fuel; CO.

"Two-way" converters combine oxygen with carbon monoxide (CO) and unburned hydrocarbons (HC) to produce carbon dioxide (CO2) and water (H2O). In 1981, two-way catalytic converters were rendered obsolete by "three-way" converters that also reduce oxides of nitrogen (NOx);[1] however, two-way converters are still used for lean-burn engines. This is because three-way-converters require either rich or stoichiometric combustion to successfully reduce NOx"

In addition unburned LPG will not dilute or dirty the oil.

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[pappajohn]

LPG will always be less fuel efficient than petrol.
My last LPG powered vehicle used an average 20% more than petrol for the same mileage.... But the savings made it worthwhile.

 

[Huw s]

Yes always they will do less per gallon, but more like 10% less these days.
Good writeup on lean burn and emmissions there. There are many, myself among them that argue the 3 way cat actually produces more emmissions than the lean burn engine - sure there would be more nox, but combatting this is simply injecting water.
Why did lpg not catch on? In practical terms the only downside is less mpg, less filling stns, and it can take longer to fill.
The real reason I believe is because of the naysayers in this country -"it'll burn your engine out, the gment are set to increase taxes, you won't be able to buy it etc"
Four years later and I wonder why I didn't do it years ago...

 

[Spriddler]

Do you have a garage conveniently near with LPG servicing/repair experience? At some point you'll probably need it.

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[Spriddler]

Ooops!

 

[Paul an Jane MK]

I had a 2.5 V6 that I converted to LPG as @pappajohn and others have said LPG does not give the same efficiency as petrol. 20% down as suggested is probably not far off.

So if it does 25 mpg on petrol you get about 20 mpg on LPG but when I had mine LPG was About 79p compared to £1.32 for petrol. So a saving but lower economy does erode savings plus LPG system is also supposed to be be serviced in addition to your normal vehicle servicing so if serviced properly is an additional cost yet further eroding savings.

As said LPG won’t start or run a cold engine so you need to keep some petrol in tank and in winter you use more petrol as it takes time to warm up. I had a modern LPG which you really could not tell when it switched over.

Would I have another LPG fitted, No, on mine the big end bearings went just over 100k, never had big ends go on any engine before but could just have been a coincidence.

I must also say, TBH on a commercial type vehicle I think the torque of a diesel is more suited to that type of vehicle so I would definitely pick a diesel Motorhome over a converted petrol to LPG

 

[TUCANO]

@Susanna,
to the forum. I have the app myLPG.eu which gives you exactly that.

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[Huw s]

Why would I need a service centre for my 2.5v6? I fitted and set up the kit 4 yeras ago, its done 100 and something thousand on it, never had an issue other than the liquid solenoid failed last year ( tight space on these gives little choice on where to fit this, so it went on the nottom of the front bulkhead, in the wet.
The plan for the system was 5 years, 20k a year, it's surpassed the miles allready.
Big end issues can hardly be caused by lpg, since peak torque actually drops slightly compared to petrol.

 

[tonyidle]

Yes always they will do less per gallon, but more like 10% less these days.
Good writeup on lean burn and emmissions there. There are many, myself among them that argue the 3 way cat actually produces more emmissions than the lean burn engine - sure there would be more nox, but combatting this is simply injecting water.
Why did lpg not catch on? In practical terms the only downside is less mpg, less filling stns, and it can take longer to fill.
The real reason I believe is because of the naysayers in this country -"it'll burn your engine out, the gment are set to increase taxes, you won't be able to buy it etc"
Four years later and I wonder why I didn't do it years ago...

It came too early for it's own good. Many engines at the time weren't safe with unleaded petrol never mind LPG. The most popular conversions used a feed arrangement that was a ring of holes around a second venturi ahead of the car. Accurate mixture control occurred at one throttle position only and various bodges existed to improve things. All of that changed with LPG injection and especially with systems piggy-backing the petrol ECU but it's reputation had been set and it has suffered ever since. It didn't go mainstream in the early days because few garages (or owners) fully understood it. Many snake oil salesmen suddenly became LPG experts and did nothing to help the cause. Now it is possible to fit a conversion that is reliable and economical but it still has the reputation it gained in the early days.

 

[pappajohn]

Yes always they will do less per gallon, but more like 10% less these days

Not when it's a 6.8ltrs V10 churning out 365bhp and over 400ftlb dragging 7500kg of RV.
8mpg on gas or 10mpg on unleaded sounds about right...

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[Silver-Fox]

Out of interest, as has been said cars start on petrol the change to gas.

How does it work with a forklift truck then as they don’t have petrol tanks.

 

[mitzimad]

Whilst I realise that to run on LPG the engine has to be petrol, not diesel, what are the emissions on an LPG engine?, I would imagine much less, but stand to be corrected, why are they never mentioned these days? (I am aware that there are a few still running on LPG)
Please dont tell me that LPG were never commercially "promoted" as it would have been a lose leader for Government Taxation?
Used to see many used large engined petrol cars, Volvo's in particular for sale in the Autotrader, why were they like dinosaurs, when petrol was always expensive, wasn't it?
Look forward to hearing the truth on this, as it was many years ago, and it would explain why LPG stations are so much harder to find these days.
Les

when the congestion charge was started in london lpg vehicles were exempt so many companies went out and bought dual fuel vehicles a few years later the removed the exemption so they died a death

 

[tonyidle]

Out of interest, as has been said cars start on petrol the change to gas.

How does it work with a forklift truck then as they don’t have petrol tanks.

It's a myth that cars have to start on petrol: the system is set up that way to force the user to run briefly on petrol so that the petrol system doesn't dry out. It is important to run on petrol for a brief period on a regular basis: it doesn't have to be every time or at start-up but that's the only way to ensure the average user won't forget to do it. It is perfectly possible to set up the system to start on gas if that's what the user wants.

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[Huw s]

Yes that and the fact that early ones couldn't run rich enough when cold, so would backfire into the air filter...

 

[Huw s]

Not when it's a 6.8ltrs V10 churning out 365bhp and over 400ftlb dragging 7500kg of RV.
8mpg on gas or 10mpg on unleaded sounds about right...

Would that fuel injected v8 or carburreted?

 

[simsy56]

Would that fuel injected v8 or carburreted?

Fuel injection, same as mine.

Craig

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[simsy56]

It's a myth that cars have to start on petrol: the system is set up that way to force the user to run briefly on petrol so that the petrol system doesn't dry out. It is important to run on petrol for a brief period on a regular basis: it doesn't have to be every time or at start-up but that's the only way to ensure the average user won't forget to do it. It is perfectly possible to set up the system to start on gas if that's what the user wants.

I have had a couple of RV's that had LPG generators. No petrol was required to fire these up, they just drew LPG from the LPG tank.

Craig