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LPG = 10 MPG :-(


mad_pete
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Having bought a new old rangie I have done a quick bit of maths and come up with the figure of 10 mpg while running on gas

( 55 litres = 130 miles in case my maths sucks )

While steeled for V8 thrist I find 10 a bit low.

So any advice ?

Power wise the engine is great loads of pull alll over the place

This weekend I plan to have a poke around in the dizzy, check the timing, check the tyres, put some new ignition leads on and maybe go mad with the irduim spark plug things.

I do have an RPI power amp with the LPG power retard but can't decide with to fit it or the ignition advance box of tricks.

The engine does seem to run slightly cold so maybe the viscous fan is jammed on.

Are there any other LPGers out there ? What sort of mpg is achievable ?

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Power wise the engine is great loads of pull alll over the place

Heavy right foot? :lol:

Seriously, what sort of roads/traffic, and what's your driving style like? With everything in good order I average about 15mpg on gas, can get it up to 18mpg cruising at or just below the motorway speed limit. On the other hand, if I drive round the Yorkshire Dales with my lead boots on I get single figures... :blink:

15mpg is mostly motorway with a small amount of town driving, so fuel economy round town is truly dreadful.

This weekend I plan to have a poke around in the dizzy, check the timing, check the tyres, put some new ignition leads on and maybe go mad with the irduim spark plug things.

At least nine times out of ten, if an RV8 isn't running as it should it seems to be traced to the ignition.

Definitely check the timing, don't buy fancy plugs - received wisdom is that the RV8 doesn't like them - fit NGK BP6ES. You may need to set the spark gap smaller than normal for LPG, as it's harder to ignite than petrol. I used to run 0.6mm with the dizzy.

If you fit new leads get either genuine land rover ones or quality - e.g. Mallory, Magnecor - aftermarket. Not el-cheapo or boy-racer supa-fast wikkid-innit guaranteed to turn your car into a racing thoroughbred jobbies.

New dizzy cap is also worth a try - fairly cheap, but only buy genuine.

Can't comment on the RPI power amp thingy, but the standard ignition is pretty pathetic, and very difficult to waterproof adequately for road use, never mind off roading. In theory at least it'll also allow you to run less compromised ignition timing - LPG likes more advance than petrol, so you have to set the timing in between the ideal for each fuel so that it runs okay on both. No harm in trying it, I guess.

I ended up chucking the standard ignition completely and going down the Megasquirt and EDIS route, which is completely waterproof, has a vastly better spark and can do completely independent switchable ignition maps for petrol and LPG.

The engine does seem to run slightly cold so maybe the viscous fan is jammed on.

Possibly. Also possible that your thermostat has failed open, so worth changing that. They're cheap, but a bit of a swine to get at on the RV8, as they're tucked behind the dizzy and water pump. Off is easy, getting the bolts back in rather less so...

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With the Air conn on and the caravan I can do 9

I've found the ignition advance works great on my draw through system as I loose a little power on LPG and this brings some of it back. I didn't fancy the RPI kit because it is advanced at idle and only drops back the timing above idle if it gets a signal, well the LSE is set at 10 degrees BTDC anyway, so with LPG timing that would be about 16 deg, it would never start.

I've found on multipoint that it makes much less difference though, I don't loose any power but my economy is not as good.

Bottom line the calorific value of LPG is lower than petrol, plus it's much less dense. The only reason Diesel is so much more economical is becuase it's so dense, in fact per Kg there is less energy in diesel than petrol.

P.S. the Iridium make no noticeable difference but have you tried your existing plugs with 3 thou less gap?

Make sure your rotor arm and cap are good, pattern parts tend to be a bit short and LPG shows up any weakness in the ignition system.

If it runs smooth though then there's not a lot you can do.

Fit a sports exhaust, pump up your tyres and take the lamps off the roof, of and DON'T DRIVE SO DAMN FAST ;)

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Thanks for the info, I've been doing a reasonable mix of motorway and in town and while I haven't been ultra econmical I haven't floored it everywhere either. THe chap I bought it off said he was getting about 130 miles on gas as he used the odometer to gauge LPG fill up as the little green lights don't work.

I'll see what the plugs and dizzy are like over the weekend.

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I pressed the button until it would take no more on the display read 55 litres. I think it is 2 x 35 litreish tanks, but LPG doesn't fill right to the top ?

That's correct, you have to leave some expansion space in the tanks. 75 litres tank capacity should give you about 65 litres actually LPG storage, so I'd guess you weren't completely empty.

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When mine was my daily drive it would do 17+mpg on a run, but only 8-10mpg when commuting in Leeds... Mind you that was on a seven mile journey that would regularly take anything from fifty to seventy minutes... I could have run it faster!

Rog

BTW - some great info in this thread :)

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pete, I'd say you weren't far out at 10mpg. My 4.2 does only around 2miles per litre in town, and a high of 3,5 pre litre on journey work, and can be as low as 8/9 when towing. When we were in France with the caravan last year, I got 3.5 per litre towing, but I put this down to the long straight roads and the lack of traffic.

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Having bought a new old rangie I have done a quick bit of maths and come up with the figure of 10 mpg while running on gas

( 55 litres = 130 miles in case my maths sucks )

While steeled for V8 thrist I find 10 a bit low.

So any advice ?

Power wise the engine is great loads of pull alll over the place

This weekend I plan to have a poke around in the dizzy, check the timing, check the tyres, put some new ignition leads on and maybe go mad with the irduim spark plug things.

I do have an RPI power amp with the LPG power retard but can't decide with to fit it or the ignition advance box of tricks.

The engine does seem to run slightly cold so maybe the viscous fan is jammed on.

Are there any other LPGers out there ? What sort of mpg is achievable ?

I am getting around 20l per 100km

Which equates to approx 14mpg imp. 0r 11.8mpg (US)

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Having bought a new old rangie I have done a quick bit of maths and come up with the figure of 10 mpg while running on gas

( 55 litres = 130 miles in case my maths sucks )

While steeled for V8 thrist I find 10 a bit low.

So any advice ?

Power wise the engine is great loads of pull alll over the place

This weekend I plan to have a poke around in the dizzy, check the timing, check the tyres, put some new ignition leads on and maybe go mad with the irduim spark plug things.

I do have an RPI power amp with the LPG power retard but can't decide with to fit it or the ignition advance box of tricks.

The engine does seem to run slightly cold so maybe the viscous fan is jammed on.

Are there any other LPGers out there ? What sort of mpg is achievable ?

About 10 mpg round town 14 mpg on a run, 4.6 classic

Regards Keith

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  • 2 weeks later...

When you say it runs slightly cold have you checked that the vaporiser is getting nice and hot?

When my thermostat stuck open the vaporiser was never more than lukewarm even after a long run.

New thermostat helped my mpg quite a bit and made the heater work too!

This was on a 3.9 but I expect the basics are the same.

Bob :)

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I had a 3.5 and on a run i was getting 15mpg

around town was a little less but not that much

but with gas at alittle less than half price of unleaded and half price of diesel

it was by the £ a lot cheaper to run than petrol and about the same as diesel

plus you get that V8 GROWL ;)

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I may well try swapping the thermostat out. I was just about to see what good the service had done and the LPG pump at the garage would only half fill me tanks ! ( I suspect it fills one tank and then doesn't swap over the the other ) So I have 140 miles on the clock without running out of gas ( 11.8 mpg ) but then didn't get a chance to fill up. So I'll have to wait till next time.

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I get about 10.6 mpg out of my 3.5 on Grizzlies. Same driving on normal road tyres gets about 12.5 mpg.

A run along quietish country roads nets about 14mpg on the Grizzlies.

I have the vicous coupling Borg Warner box. Don't know if that makes a difference

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  • 2 weeks later...

hmmm it was going so well and then yesterday a lot of coolant decided to escape into the engine from somewhere. ........ I suspect that is not a good thing although the last leg of the journey returned excellent mpg ( on the back of the bright yellow AA lorry ) :angry:

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First of all I would like to say big Hi :) as this is my first post. And secondly sorry to jack this thread. :D

I have a RR Vouge p38 I had mine lpg'd 8 mnths ago, Im sure it is the 95 litre tank I have. When I fill up its around £30 full. What I wanted to know is what miles should I expect to return from a full tank? coz at the mo I get around 120 per tank city driving. I am sure I should get more???? it is due for an oil change. Oh yeah its a 2001 model. Also when I mot''d it the chap said it was running rich, he also suggested me to change my sparks to a lower temp ones? Any ideas folks?

Many thanks

H

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