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LPG MPG Mine is shocking!


doddie
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Could I ask anyone who has LPG on a series 3 2.25 what MPG they are getting. Mine is Max 10.5. I have Fairey overdrive, engine serviced, New unleaded head from Turner, spark plug gaps at 0.65 (as suggested), replacement electronic distributor, free wheel hubs. Every time I rotate the dizzy it makes it worse (mpg wise). I have even bought a timing gun so it is set at TDC. Down side is roof rack (due to back having 90l tank in it) but this only dropped the mpg bu 0.5 mpg.

Had the lpg for 3 months and only saved myself five pounds :( and then only because petrol is so high at the moment.

Any further suggestions gratefully recieved. Oh yes next project is electric fan (already posted a question about that one!!)

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Could I ask anyone who has LPG on a series 3 2.25 what MPG they are getting. Mine is Max 10.5. I have Fairey overdrive, engine serviced, New unleaded head from Turner, spark plug gaps at 0.65 (as suggested), replacement electronic distributor, free wheel hubs. Every time I rotate the dizzy it makes it worse (mpg wise). I have even bought a timing gun so it is set at TDC. Down side is roof rack (due to back having 90l tank in it) but this only dropped the mpg bu 0.5 mpg.

Had the lpg for 3 months and only saved myself five pounds :( and then only because petrol is so high at the moment.

Any further suggestions gratefully recieved. Oh yes next project is electric fan (already posted a question about that one!!)

Have you got the power valve (aka economy valve) adjusted correctly? I found on mine that this has biggest effect on mpg. Supposed to have it wound all the way out when setting up vapouriser, then once idle is nice bring revs to approx 3000rpm and screw in the valve until revs drop then back it out half a turn.

i get about 18-19mpg on my 2.25 90, but i drive very conservatively (i learnt to do this when still forking out for petrol!)

As for timing, mine is set so that it is just pinking under heavy load on petrol. I have to drive around this when on the expensive stuff but spend 95% of the time on gas anyway so no biggy there. I set the timing up by ear, so have no idea where it is degrees wise. :ph34r:

You might want to consider going more advanced, as gas has a slower flame front than petrol and so needs to be ignited sooner in the stroke to stand a chance of burning fully. running 95 unleaded you should be about 6deg BTDC anyway i think?

Good luck

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.........

You might want to consider going more advanced, as gas has a slower flame front than petrol and so needs to be ignited sooner in the stroke to stand a chance of burning fully. running 95 unleaded you should be about 6deg BTDC anyway i think?

Good luck

Definitely, Timing varies from TDC to 6deg BTDC for petrol depending on grade and compression ratio, LPG likes to be more advanced. If you've got a Xenon timing light (i.e. it needs to be connected to the battery) make sure the sensitivity is set low as possible, I've known these give false readings.

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Thanks for the replies guys, will give it a go as I am down soon for my 5000 mile lpg service. Might take the timing light so the guy can get it set up properly while attached to the gas analyser!!

Cheers

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  • 4 weeks later...

if you are interested here are my calculations

Date / Mileage/ Fuel (l)/ MPG/ Notes

27/07/2008/ 10040/ 19.3/ 16.25/ urban

01/08/2008/ 10103/ 19.76/ 14.49/ urban

01/08/2008/ 10185/ 18.1/ 20.59/ motorway fully loaded without diff engaged

01/08/2008/ 10250/ 12.08/ 24.46/ motorway fully loaded without diff engaged

01/08/2008/ 10388/ 32.9/ 19.06/ motorway with diff lock engaged

03/08/2008/ 10467/ 19.89/ 18.05/ off-road and motorway

05/08/2008/ 10520/ 13.15/ 18.32/ motorway fully loaded with diff engaged

05/08/2008/ 10643/ 25.52/ 21.91/ motorway fully loaded with diff engaged

it doesnt seem to format too well on here, basically 24mpg on the motorway with th e freewheeling hubs free, two up and full of kit at 55mph although I think my speedo is 20% out so could be faster, I am quite pleased with this mpg, could do with a bigger tank though

just thought my odo could also be out which would skew my mpg calculations too

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I have run lpg for many years in many different landrovers, on a 2.25 you are going to average 12-15 on lpg with a bit of tweaking here and there. If your engine is not running right on petrol the lpg will find the weak spots for you, the quality of ignition components is VERY important an advance of 10-15 degs over normal is best. A spark advance device on sale from RPI is well worth the money.

Steve

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If your engine is not running right on petrol the lpg will find the weak spots for you, the quality of ignition components is VERY important an advance of 10-15 degs over normal is best. A spark advance device on sale from RPI is well worth the money.

Steve

Is it possible to promote pinking on Gas ? I think I probably know the answer :rolleyes:

And is that correct, that much advance over running on petrol :blink:

If so I'm going to give it a go when my 110 is back on the road, I might even do some road tests at different settings if time/money allows. It did seem sluggish last time out and I've set it close to pinking on petrol which is fine for petrol.

I don't mind altering it every time I change over, I've marked it with tipex on the dizzy base so it's quick and I don't do it very often, I only use petrol to lube the carbs every now and then.

So more advance it is then and when I'm back on the road in a week or so I'll post the results.

Very interesting <_<

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On some dizzies the fixing screw that holds the clamping plate to the block passes through a slotted hole in the plate, the idea being to provide a quick adjustment for octane rating.

It may be possible to set the dizzy so that one end is OK for petrol, the other for LPG. Perhaps even fix up a bowden cable to turn the dizzy from the driving position - just like my 1946 Riley did.

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On some dizzies the fixing screw that holds the clamping plate to the block passes through a slotted hole in the plate, the idea being to provide a quick adjustment for octane rating.

It may be possible to set the dizzy so that one end is OK for petrol, the other for LPG. Perhaps even fix up a bowden cable to turn the dizzy from the driving position - just like my 1946 Riley did.

Was thinking along those lines myself but have been laughed at so far. A friend of mine had a 12cylinder Langonda many years ago and the ign adv/retard was on the steering wheel.

Don't make cars like that any more.

I should be on it in the next few weeks when the gearbox and axle are done so I'll put a light on it and give it 30+ degrees at 3500 for a start and advance from there.

Might even slot the plate to suit the ign requirements, good idea. :)

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Whereabouts are you?

In Tiverton, Devon. Since I posted I have just recorded 15.2mpg on lpg. I was getting fed up with the economy I was getting so I took it to a local installer that a number of people recommended. He immediately told me the venturi on top of the carb had a 32mm opening which was far too big. He then manufactured a new one on a lathe with 3mm smaller opening and immediately the engine sounded sweeter (well as sweet as they ever sound), more power and straight away 12mpg round town and 3 days later on filling up again 15.2mpg. So hopefully that is looking better but will keep an eye on the results and will post on this thread after a few more runs.

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Is it possible to promote pinking on Gas ? I think I probably know the answer :rolleyes:

And is that correct, that much advance over running on petrol :blink:

If so I'm going to give it a go when my 110 is back on the road, I might even do some road tests at different settings if time/money allows. It did seem sluggish last time out and I've set it close to pinking on petrol which is fine for petrol.

I don't mind altering it every time I change over, I've marked it with tipex on the dizzy base so it's quick and I don't do it very often, I only use petrol to lube the carbs every now and then.

So more advance it is then and when I'm back on the road in a week or so I'll post the results.

Very interesting <_<

The spark device works in two ways, it boasts the power to the coil so you get a better spark and i has a built in adjustable timing retarding system that works from the points/pick-up and lpg solinode when you are on petrol it retards the timing to the correct setting, when you power up the lpg it resets to the lpg setting. So you can run big timing advances for lpg and still keep your petrol settings, but....... its not the cheapest of things :(

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  • 4 weeks later...

Just a quick update, the LPG is no almost 16mpg. I bit the bullet and took it to another installer who straight away saw the mixer on top of the carb had far to large an aperture for a decent venturi. He then made his own mixer on the lathe and hey presto the mpg has jumped by 5 mpg and more power also. Ithink the apeture was 33mm which he said would have gone on a BMW M3 in the old days of single point systems!!! Also found a blow on the exhaust down pipe which wasn't helping. Thanks for all the replies guys.....

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