Jon Ison
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| posted on 1/2/09 at 10:52 PM |
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Stupid Numpty LPG question.
LPG conversions ?
I don't know a lot about these (read zero) but would I be correct in thinking they all still have the capability to run on petrol ?
I don't want to buy one and find I'm limited to the fuel station I cant get to without running out of fuel.
Anyone ever come across a converted vehicle that don't run on both ?
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blakep82
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| posted on 1/2/09 at 10:53 PM |
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my mums runs on both 
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liam.mccaffrey
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| posted on 1/2/09 at 11:05 PM |
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looking into this myself,
yes I think most are dual fuel with some being mixed fuel and intercept the signal to the injectors to switch to gas. there will be a switch on the
dash to change
will be ringing the insurance company tmorrow to get their thoughts on certification and such
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mark chandler
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| posted on 1/2/09 at 11:11 PM |
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Both, you throw out the spare wheel and the gas tank replaces this.
Start on petrol when warm over to gas, I have run a few cars with sequential conversions, no loss in performance.
My current drive, a XK8 does 300 miles to £30.
No need to worry about the extra weight, compressed LPG is half the weight of petrol so it balances itself out.
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zilspeed
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| posted on 1/2/09 at 11:12 PM |
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Main considerations for me involving the practicalities of fueling.
How big will my fuel tank be ?
How far do I have to go to get fuel ?
How will my consumption be compared to petrol ?
In my case.
32litres
12 miles, but the filling station is in a place I don't often go. Regular station is 17 miles away.
75 % as far when compared to petrol.
This gives me an absolute range of around 220 miles on gas. Much as I like running on gas at 46p/litre, the inconvenience is not to be ignored.
My 'effective' mpg as if I were running on petrol would be something like 52 mpg. I get 100lb/ft for my 52mpg. Golf 1.6 petrol.
My workmate burns diesel and gets 172lb/ft for his actual real 52mpg. Golf 1.9 TDI.
Hope that makes at least a little sense.
[Edited on 1/2/09 by zilspeed]
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MikeRJ
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| posted on 1/2/09 at 11:24 PM |
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quote:
Originally posted by mark chandler
Both, you throw out the spare wheel and the gas tank replaces this.
Start on petrol when warm over to gas, I have run a few cars with sequential conversions, no loss in performance.
There's always some loss of performance, it's simply inevitable unless the engine is designed to run only on LPG. However, the sequential
systems are vastly better than the old mixer systems, and you won't usually notice the loss on a decent sized engine.
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mark chandler
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| posted on 1/2/09 at 11:35 PM |
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P38 range rover was actually better on LPG than petrol.
I put this down to worn petrol injectors/efi system not being as efficient as new LPG injectors.
Also with decent LPG systems you map then to the car. But you do need to plan your journeys to maximise the savings.
I believe the theoretical performance loss is around 3%, I have never run LPG on anything less than 4.0ltr engines, I drifted to the dark side and ran
diesels for a few years, but far prefer petrol/LPG.
Regards Mark
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hobbsy
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| posted on 2/2/09 at 12:04 AM |
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Depends on the engine and conversion but TBH one real valid point from the users point of view was made by zilspeed.
You can't argue with the same effective consumption vs performance issue. I've had both a 1.9TDI PD A4 and a 1.8T LPG A4, they both were
roughly the same on fuel but you had to rev the nuts off the petrol A4 whereas the TDI one had monster amounts of torque. So it was a far better
daily drive - by miles.
Overall power was probably about the same once you take the hit for running LPG.
Also I think you either get a performance hit and use about the same amount of gas as petrol, or get a more expensive / better set up conversion and
get more gas in to retain the performance but then you use more gas.
Or course if you advance the ignition to suit whilst on gas you can probably make some of this back and in forced induction setups make more power as
its higher octane.
I'd still like something with an NA V8 or a turbo V6 / straight 6 on gas before pre-2001 cars get too old (I want to avoid paying the ~£400
tax). Ok it'll probably do 15 to 25 mpg on gas but thats 30 to 50mpg (on the outside) equiv on diesel, worse than my current diesel tin top but
then its a V6 or V8.
I've had 3, 4, 5 and 8 cylinder (briefly) cars and I need to fill some of the gaps
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blakep82
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| posted on 2/2/09 at 12:26 AM |
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not sure what system my mums is, but its a nightmare to drive on gas. fine on the move, but pulling away from lights, car parks etc, its awful.
actually, its awful on petrol too. but slightly worse on gas.
either way, i refuse to drive it. the car that is. nothing to do with the LPG, so going a bit off there, but gas is pretty good. don't reckon
you'll notice any difference on the motorway for example
[Edited on 2/2/09 by blakep82]
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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Antnicuk
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| posted on 2/2/09 at 07:54 AM |
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i bought a 540 E39 4.4 v8 BMW and converted it to LPG. Best car i have ever owned!!!
Didnt notice any difference in performance.
600 BHP per ton, Stylus Brought back from the dead! Turbo Rotary Powered!
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britishtrident
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| posted on 2/2/09 at 08:05 AM |
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You will get more info here http://www.lpgforum.co.uk/
You may find this site of interest
http://www.lpg-kits.org.uk/shop/
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hughpinder
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| posted on 2/2/09 at 09:36 AM |
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I have run 2 cars on lpg - a honda civic 1.6 (172000 on lpg) and a 2.5l subaru legacy(90000 moiles on LPG).
All conversiond I know of can switch LPG to petrol(while running - no need to stop car or anything).
The honda has a noticable loss of torque when runing on lpg. The subaru it was not possible to tell the differance. Both use 15/20% more fuel by
volume compared to petrol, but it has been much cheaper. LPG is expensive compared to petrol at the moment. During the 9 years I have used it, you can
usually buy 2.1 to 2.3 l lpg for the same price as 1l diesel, currently 1.8 times the price.
I have driven all over the uk and france and only very occasionally end up using petrol rather than LPG.
It is worth running on petrol for 10 or 15 miles at the end of every tank(I just let the gas run out( loss of power like if you run out of petrol),
switch to petrol then fill up and switch back as soon as possible), as LPG has no lubricants in it and petrol does have.(for the valves).
The tanks that fit in a spare wheel well are usually about 40l, but you always have "air space" above of about 20% of the tanks volume, so
you will get 30-32l in each fill. Cylindrical tanks are available up to 'what'll fit' size. My civic coupe has a 65l tank in the
boot sideways against the back of the rear seats.
Regards
Hugh
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hobbsy
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| posted on 2/2/09 at 12:03 PM |
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quote:
Originally posted by Antnicuk
i bought a 540 E39 4.4 v8 BMW and converted it to LPG. Best car i have ever owned!!!
Didnt notice any difference in performance.
Thats the sort of car I was referring to in my post - i.e. if your considering a smaller engine you might as well go diesel. If you want a 6 or 8
cylinder beast then LPG is a better option.
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zilspeed
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| posted on 2/2/09 at 01:03 PM |
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My performance on gas is as good as on petrol.
I put that down to spending an unhealthy amount of time on mapping the bugger.
What I was saying was that my little Golf makes 100lb.ft on gas or petrol.
If I run a Golf TDI, the bottom of the range 100bhp one that does around 52mpg, I get 177lb.ft of torque.
It has to be a factor of you want to run a genuinely economical car on gas.
When running a 4.0 ish car, it makes it doable, not genuinely cheapskate like me.
That's why the dark side will probably reclaim me once Skud the Skoda eventually dies. (Golf is going, Skud will be my transport for a bit).
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britishtrident
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| posted on 2/2/09 at 01:58 PM |
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When looking at mpg you have to consider the calorific value of the fuel per liquid gallon.
From highest to lowest
Diesel
Petrol
LPG
The because it is closely related to the calorific energy the carbon content is in the same order. Because of this LPG can never match the MPG of
Petrol just as Petrol can never match a good Diesel.
In addition the dual fuel LPG-Petrol converted car will suffer a slight power and fuel consumption disadvantage running LPG compared to Petrol
because the compression ratio will be dictated by petrol's lower octane rating (LPG is around 112 octane though it varies). Also because LPG is
admitted to the engine as a gas it displace some of the airflow when running on petrol.
We have also got to look at the hidden cost.
Most petrol engines now have 15,000 mile oil change intervals with (platinum) spark plug & air filters changed every 30,000 miles
Because it has a cleaner combustion on LPG the oil changes can be stretched a fair bit but the plugs have to be changed at 12,000 to 15,000 miles
however cheaper non-platinum plugs are used with LPG.
The LPG filter should also be changed every 12,000 to 15,000 miles.
You also have the added factor of the possibility of something going wrong with the LPG kit but that is going to cost 300 to 500 max to put right.
Diesel's may you less fuel but they need more frequent engine oil and filter changes and many demand more expensive oils and the latest models
need catalyst cleaning fluid top ups. Diesels generally are more reliable but when something goes wrong it tends to be very very expensive to fix.
Then you have to consider the type of driving you do.
If you do a lot of motorway driving LPG won't save as much as if you do mainly urban driving.
Diesels return good economy in town and at legal motorway speed because the diesel cycle is at it's most efficient at low and part
"throttle" (this because diesel's don't have a throttle as such), but start putting the foot to floor on diesel and
using higher RPM and the consumption sinks to petrol levels.
In to the decision you have to add the fact that diesel is unpleasant to handle and is the first fuel to get difficult to find in a fuel shortage.
LPG has fewer filling stations than petrol or diesel but as more and more forecourts close most us have to drive at least 2 or 3 miles to get fuel
anyway.
LPG also suffers from the the fear factor -- you have to convince "her indoors" that it won't engulf her nearest and dearest in a
fireball.
The way I see it is that LPG only makes sense for car that is Passat/Mondeo/Rover 75 size upwards.
Diesel is fine for Fiesta upwards but would be a very reluctant choice for me -- I truly hate diesel engines.
Petrol works best for sub Focus sized cars
Sometime over the next few months the family Rover is going LPG but my next car is likely to be a hybrid probably a Honda Civic IMA .
[Edited on 2/2/09 by britishtrident]
[Edited on 2/2/09 by britishtrident]
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zilspeed
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| posted on 2/2/09 at 10:02 PM |
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quote:
Originally posted by britishtrident
Sometime over the next few months the family Rover is going LPG but my next car is likely to be a hybrid probably a Honda Civic IMA .
[Edited on 2/2/09 by britishtrident]
It's feasible for you though.
You have pretty much the cheapest LPG in the country being sold just along the road from you.
I live in Cumbernauld and the same filling station is my nearest feasible one.
I could use one in Airdrie, but I don't ever go there for any other reason so why should I ?
I'm glad I've done it, but now have rather more questions than I originally did when I first converted.
I'm saying all this, but my gas system is coming out of the Golf and probably going into the Skoda.
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