MPG on LPG

[Yoshi]

My 3.9 is on LPG and i get about 75 miles to £20, 39.9p a litre at me local morrisons.

I thought i should get a little better than that?  Or am i wrong?  Also sometimes when idling i can smell lpg, but have checked the tank and all that and its all secure and air tight and stuff, so could it be over fuelling?

[nickW]

i normally get 12 mpg on lpg on a 3.5 v8 efi

[baileys_1984]

we get about 60miles to £10 on lpg if that helps you

[Yoshi]

It only helps if you wanna swap!!! lol, i think i need to find out why mine isnt working right lol

[bezzabsa]

My 3.9 is on LPG and i get about 75 miles to £20, 39.9p a litre at me local morrisons.

I thought i should get a little better than that?  Or am i wrong?  Also sometimes when idling i can smell lpg, but have checked the tank and all that and its all secure and air tight and stuff, so could it be over fuelling?

thats 50 litres  :shock:  so you are going under 2 MPG ... i'd say you have a HUGE problem!!!!

[jjsaul]

i get about 12mpg ish out of mine...varies from 9-15 depending on use of the right foot and type of driving (mway/town/countryside a roads)

[auto]

i know multi point is far more efficient than single point, and i know land rover have never been anywhere near reasonable on consumption, but that sounds like a hell of a lot!!

I run a shogun 3500v6, and when caning that about (cany help it!) using all 268 horsies on petrol i'm getting about 170 to £20! Normally its 100 miles to a tenner!

Defo worth getting it checked out, maybe upgrading to multi point. You should be doing at least 20mpg on gas which would be equililent to 40, but then again its a landy so maybe they are just very good on gas either.

I have heard V8 discos up for sale stating 20-25, weather that is over stating to get rid is anyones guess!

[Garth]

I get 170-190 miles out of 70ltrs (£30 ish)

3.9 EFI draw through (collar on inlet of plenim)

[Yoshi]

I will take a photo of the engine bay at some point today so you can see what it is and someone might be able to tell me what it is lol!

[baileys_1984]

we get about 60miles to £10 on lpg if that helps you

our's is a single pipe to plenum thingy but the 60 to 10 was with bad head gasket and smell of gas from pipe as j clip was had it and a lot town driving start stoping by the way our switches to gas as soon as revs come back down after start were as dads car waits till car gets hot so now head gaskets done and new j clip will have to find out if any better opps forgot to say we done 320miles on full tank on a run hubby said that i sure it was 380 o well u get the drift

[nickW]

i know multi point is far more efficient than single point, and i know land rover have never been anywhere near reasonable on consumption, but that sounds like a hell of a lot!!

I run a shogun 3500v6, and when caning that about (cany help it!) using all 268 horsies on petrol i'm getting about 170 to £20! Normally its 100 miles to a tenner!

Defo worth getting it checked out, maybe upgrading to multi point. You should be doing at least 20mpg on gas which would be equililent to 40, but then again its a landy so maybe they are just very good on gas either.

I have heard V8 discos up for sale stating 20-25, weather that is over stating to get rid is anyones guess!

v8 disco's only do 16mpg off gas so 20 - 25 does sound rather a lot

[hairyasswelder]

i know multi point is far more efficient than single point, and i know land rover have never been anywhere near reasonable on consumption, but that sounds like a hell of a lot!!

I run a shogun 3500v6, and when caning that about (cany help it!) using all 268 horsies on petrol i'm getting about 170 to £20! Normally its 100 miles to a tenner!

Defo worth getting it checked out, maybe upgrading to multi point. You should be doing at least 20mpg on gas which would be equililent to 40, but then again its a landy so maybe they are just very good on gas either.

I have heard V8 discos up for sale stating 20-25, weather that is over stating to get rid is anyones guess!

v8 disco's only do 16mpg off gas so 20 - 25 does sound rather a lot

Normally EQUAL to... that is usually the price for price comparison

Bezza  :oops:  thats 75 miles on 50 litres.... 1.5 miles per litre..... x 4.55 litres in gallon around 7.8 mpg  

Mine does around 170 on a run and 130 knocking about on 60/65 litres

[Range Rover Blues]

RRR recons on up to 16mpg on p[etrol and 14/13 on LPG, brand new multipoint.  It has a lower calorific value, so you will use more.

If you need to feel better, my LSE can do as little as 9mpg, with the 'van on and airconn full-bore.

[Yoshi]

Mine is with no air con on.  If its over fuelling will it show the same way as with a petrol on the spark plugs?

Cheers :D

[Range Rover Blues]

That's a difficult question as LPG burns hotter so depending what plugs you buy it looks different anyway, but LPG doesn't produce soot in the same way no.

[skip]

First place i'd look for an overfuelling problem is the o2 sensor, provided it's a closed loop system. Injection is slightly better for economy and power but not massively as some people belive but still a definite improvment. but not worth the extra cost on vehicles made before 97.

RRB when I change my oil after 5000miles it comes out only slightly darker than when it went in, that's how little soot lpg produces 8)

[Yoshi]

This is the picture of the engine:

[barnhill4x4]

Your biggest problem is that airfilter, LPG Single point systems do not like ram air one little bit, they run better with a little restriction in the air intake.
  I just fitted a snorkle on mine and have to have the inlet facing back or the car will stall, even with it facing back, in high winds the car will stall on tickover.
   Put the standard airbox back on, I am sure you will notice a difference.

[Range Rover Blues]

Can we differetniate between single point systems and draw-through systems.

That one pictured just above is a draw through, it relies on the draught within the inlet and therefore the vacuum at the gas ring to regulate the mixture, one of the reasons the regulator (reducer, vapouriser etc) is so big.

A sibgle point sytem would cope better with the 'ram air' effect becuse it uses a feedback loop from the lambda sensor to regulate the fuel mixture, these are definitely better than draw through but still limited, they also still 'choke' the engine because of the shape of the gas ring.

A single point system should offer a good balance of economy and power, but will never be as good as a multi-point for power.  If I was worried about economy I wouldn't drive a 5.0l v8 though, would I?

[Yoshi]

Ok could someone put this in the english language and possibly tell me where i am going wrong and/or how to maybe rectify it!

Cheers :D

[Rossko]

It's probably running rich - too much LPG.  Clues being smell of unburnt fuel and low MPG.  You can't tell from the look of the plugs, but you might have a slow/laboured idle.

It might just need adjustment, this really is best done with an exhaust gas analyser.  Set up at around 3000rpm using the adjustment in the large gas pipe, looks like this is at a Y-piece. Then adjust at idle, but using the screw on the vaporiser.  Go round again and refine settings.

That assumes it is an "open loop" system, i.e. no electric motor/valve in the large gas pipe (can't be 100% sure from photo). These don't use the O2 'lambda' sensor.

If its a "closed loop" system with electronic feedback control, you'll need to identify the brand of the control box (not the one visible in the photo) - it might need a laptop to set up.  But first check the vehicles O2 sensor function.  (Both these systems are "single point" systems - the LPG is introduced at a single point, whether it relies on vacuum or is adjusted electronically.)

If it just won't set up properly, you may need a new vaporiser.  They do "go off" after some years, mostly rubbers hardening etc. but it's not worth messing with rebuild kits, just replace with new.  You'll get the cost back in a few tankfuls.  Have a sniff around the vapouriser when idling on LPG, if there's a big stink of gas coming from a half-inch vent hole the diaphragm is leaking.

cheers
Ross K

[Yoshi]

OK, and what for those who dont have access to the exhaust thingy or the money to pay for a garage to look?

[Rossko]

I dunno really, it's a bit like changing a wheel without a jack - do-able but maybe not the best way.

When its working right you should be saving about £30 a tank over petrol prices, maybe saving £5-10 a tank on LPG if its working right as opposed to working as badly as stated.  Work out how long it'd take to be back in pocket after paying for some help or a tool.  (not suggesting a Sun analyzer, but one of those £70 Gunsons CO meters should allow basic tuning with a little patience to allow readings to settle).  Or try approaching a few local garages for a half-hour cash job on their analyser.

If its not worth doing, so be it.

Did it turn out be a manually tuned system, no electronic control valve in the vapour pipe?

cheers,
Ross K.

[skip]

Get your multimeter out. I'm assuming that the rangie has a four wire sensor however the same still aplies to sensors with less wires just dissregard the colours you don't have. firstly find the wires coming from the sensor. try to get them away back from the zorst for obvious resons. Ignore the two white wires, these are for an internal heater one +12v one earth, test these if you wish to confim that power is there.

Next you have a grey wire and a black wire, now to test that this is working have The motor running on petrol at idle , if ive got this next bit the right way round the grey wire is earth and the black wire is the one you want to test, at any given revs the sensor  signal should cycle from 0 volts(lean mix) to +1 volt (rich mix), it'll be easier to see on an analogue meter but still possible to read on a digital.

If the signal is only deviating from a given value mildly say 0.7 volts the sensor is probably goosed as it's not reacting quickly enough. if it is cycling properly try switching to gas and see what happens but bearin mind alot of the lambda controlled mixer systems don't control the mix at idle (pre injection type) so it defaults to a rich mix. so have somone handy to hold the revs at about 2000rpm, on this type of system the cycling will not occur as quickly as on petrol as the gas system cannot react that fast, modern lpg injection should.

I hope any omissions or mistakes will be picked up by others but I'm pretty sure I got it right.

Done it myself enough times 8)

[Yoshi]

Just remembered that it stalls as well sometimes, so i will look at a standard air box next week :D

[Yoshi]

OK, now i got the motor working again this seems to be an issue, i dont understand most of whats said, so could someone do an idiots guide for the lpg setup you see in the picture! lol

[Range Rover Blues]

Forget all that stuff about tuning it using the lambda sensor, you don't have one.

If you don't have a lambda sensor then it's going to be a draw=through system, these use the slight pressure drop accross any restriction to measure the air flow and add the appropriate amount of fuel.  It's fluid dynamics, I'd say basic fluid dynamics but this stuff f***s my brain too.  It's all straightforward untill you relaise that air is compressable but then the same is true in a carburetor.

Anyway, that aside I'm not an expert on setting these things up but from what I can gather from the above you compramise a little on the tuning to get the best performance over a range of driving conditions.

Hence the setting up with the flow rate screw at 3,000rpm then the fine tuning with the mixture screw on the presure reducer/evaporater/diapragm thingy.


I would suspect however that if the car was driving ok and then began to run badly with no obvious cause that the LPG system could be past it's best.

[Yoshi]

the car runs fine now, its just i get a really strong smell of lpg when under the bonnet and it seems to be getting crap mpg on lpg!

[Range Rover Blues]

Ok then that's progress.  I'd suggest you check out the back of the pressure reducer (there will be a breather hole about an inch in diameter) for a stong smell of gas and check all the pipe unions with washing up liquid, sounds like you have a slow leak.

[Yoshi]

could be a leak, would explain my p!ss poor mpg on lpg lmao, btw, whats the reducer look like?