Running a BX on LPG

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mtbxathena
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Running a BX on LPG

Post by mtbxathena »

Anyone out there thinking of running their BX on LPG? I bought my LPG 1.6 Athena just over 18 months ago, and up until having it written off a few weeks ago, ran it on gas every day. I put in £30 of lpg and this lasts for 300 miles around town, motorway driving 400 to 450, I kid you not. I took advantage of the free BX turbo diesel from Runcorn to use as a stop gap and will look around for another Athena to swop the gas conversion on to. 1.6 smooth motoring with better than 1.7 TXD economy. Regards, mtbxathena

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MULLEY
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Post by MULLEY »

Did you fit the LPG yourself?

mtbxathena
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LPG BX 1.6

Post by mtbxathena »

No,
Last edited by mtbxathena on Fri Jan 18, 2008 10:01 pm, edited 1 time in total.

mtbxathena
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LPG BX 1.6

Post by mtbxathena »

No,
Last edited by mtbxathena on Fri Jan 18, 2008 10:00 pm, edited 1 time in total.

mtbxathena
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LPG BX 1.6

Post by mtbxathena »

No, it had been professionally fitted for the previous owner at a cost of £950 in 2001. When I started filling up at Morrisons in 2005 gas was 37.9 a litre, on the last fill up this Christmas it was 45.9. The only drawback I found was that the 90 litre tank took up a lot of boot space but there are tanks that will take the place of the spare wheel. MICK.

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MULLEY
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Post by MULLEY »

You'd have to do quite a lot of mileage to get a return on that?

Only reason i asked is that i have a gti that i would love to run more regularly, but at 30mpg its just not worth it, i use my diesel bx instead which is nowhere near as much fun to drive....

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Post by jeremy »

If the thing cost 10p per mile to run on LPG - its about the same or only a tiny bit cheaper than diesel isn't it?

This means that you'll never see the cost of the conversion back.

My DTR Turbo estate is doing about 45 mpg at the moment - and at £1.089 per litre diesel costs £4.95 per gallon. So my cost is 11 p per mile.

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Post by MULLEY »

To true Jeremy, however, i know which car i'd have more fun driving, slow diesel or Gti.....

But makes no economic sense to me as you've already mentioned, on the other hand if you could pick up a kit cheaply & fit it yourself then that would make it a more viable proposition, outside of my skill levels though....

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Mike E (uk)
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Post by Mike E (uk) »

Why not salvage the LPG kit from the damaged BX?

It would not cost much to have it re-fitted to a similar BX.

Conversions to non EFI cars is very simple, but are not as efficient.

LPG makes a lot of sense if you do not like diesel.

My friend runs a big 3.2 litre V6 4x4 and it costs the same per mile as a petrol hatchback. The 4x4 was cheap to buy too, as 3 year old petrol cars depreciate heavily. The conversion was professionally done for £2000 but that was paid for long ago.

A friend runs a jag which he converted himself for £650, about 4 years ago, and another a Range rover which was converted in 1997.

The spare wheel dohnut tanks tend to be a bit small. You need more volume of LPG than petrol for the same range. Also the weight of the tank is significant on a light car like a BX, but in place of the spare wheel you would loose no boot space.

So if you want the ultimate in economy, an old diesel car and a splash of veggie oil is the way to go.

Mike
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MULLEY
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Post by MULLEY »

Have to agree with you there Mike, diesel & veg = cheap.

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Post by Kevin B »

Ref: Bx Athena LPG conversion.....

I would be interested to know if this car was a Venturi or a Multi point system. As when I looked into an LPG conversion on a BX 1.9 Carb a number of years ago, I could not find a venturi that was compatible with the Solex carb for love or money. Hence if its a venturi type conversion what make is it ?

It also did occur to me that one thing that the Solex / Webber carb has in its favour (when compared to other less sophisticated carburetors) is the anti run on device (solenoid) on the carb, which if connected to the LPG / petrol change over valve would prevent both petrol and LPG being simultaineously being drawn into the engine during the change over phase, and having a full float chamber when you need to switch back to petrol from LPG

Some years later I am now contemplating an LPG conv again. This time on a BX 4x4 estate (just to make it even more complex !!!). As these cars are well known for being thirsty on petrol. However the venturi problem would still need to be overcome.

Thanks in anticipation.

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Re: Running a BX on LPG

Post by DavidRutherford »

mtbxathena wrote:I put in £30 of lpg and this lasts for 300 miles around town, motorway driving 400 to 450,
That strikes me as not being set up properly. £30 of lpg is well over 60 litres, probably just over 70 (which makes sense if you have a 90 litre tank and an 80% fill)

Which means it was doing 19mpg round town, and up to 28mpg on a run. Which is rubbish. Given that LPG is so different than petrol, it does take some fairly serious modifications to the engine to make it burn efficiently. LPG is about 120 octane equivalent, so you can do things like run with a lean mixture, advance the ignition, or if you want to be very serious about it you can build an engine with a higher compression ratio to make best use.

I know someone with an LPG converted Range-Rover. He modified the engine quite dramatically to suit (compression ratio is now around 14:1) and he gets similar consumption figures as quoted above.... from a 3.5 litre V8 automatic car, weighing around 2 tones!
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Re: Running a BX on LPG

Post by Kevin B »

Whilst you are quite correct about the octane rating aspect of LPG, the economy aspect needs further explanation as follows:

LPG contains significantly less calorific value than the same amount of petrol hence your MPG figures when running an unmodified petrol engine on LPG at first glance appears to be dismal, however the saving is made due to the price differential between petrol and LPG.

By comparison diesel oil has a higher calorific value than petrol which is why a diesel car will be more economical than a comparable petrol engine car.

If you read up on engine design from the likes of 'Ricardo' you will note that when an engine is optimized for the fuel it runs on, ie use the highest compresion ratio possible you will obtain the maximum thermal efficiency and hence economy.

Hence an LPG conversion on a car with an engine that has only had minor modifications (harder spark plugs, changes to ignition timing, etc) is a compromise between a number of factors, but it will continue to offer savings in running costs for the vast majority of users as long as there is a price differential between LPG and petrol.

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Re: Running a BX on LPG

Post by Way2go »

An interesting and reasoned post. :D

Just wondered though, in relation to the following point:
Kevin B wrote: By comparison diesel oil has a higher calorific value than petrol which is why a diesel car will be more economical than a comparable petrol engine car.
How does the calorific value of diesel compare to bio-diesel and veggie oil? Presumably if the alternatives are not equal to or above this figure then the savings are not all they are cracked up to be? :?
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mtbxathena
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LPG BX 1.6

Post by mtbxathena »

To Kevin B. Hi. The venturi adaptor is made by Lovato Italy. The reason I chose LPG was that I wanted diesel economy with petrol smoothness, and with my BX I got it. No matter how you look at it, the simple truth is that at todays fuel prices £10 of gas took my car on very short journys around Sheffield 100 miles. Yes it could be set up better, but on the coldest mornings it started on gas and apart fom fitting harder spark plugs and changing to petrol one day a month the compressions still read 160 PSI after 18 months use.. When a suitable petrol BX crops up I shall transfer the gas system over myself and pay to get it certified at a registered LPG installer. Regards, mtbxathena.