Fitting a LPG System to the 6.9

[AMG69]

OK, I'm hoping this Topic might generate some good information.  Firstly, has anyone got their 6.9 running on LPG? For the non Australian members we have seen Petrol ("gas" in the USA) go from $1 a litre to $1.45 a litre over the last year and the Press suggest $1.80 is likely in due course.  The Australian Government are rumoured to be about to announce an incentive payment to car owners to fit LPG systems to their cars - as LPG (of which we in Australia have so much of the stuff off the West Coast it should last a few hundred years!) is half the price of petroleum based fuels.

Sooooo, I am keen to find out all the Pluses and Minuses of fitting this type of system......OK.....off you all go.....

[alabbasi]

This conversion became popular with cars in the UK around 8 years ago. The government also gave incentives but only to newer cars. Most cars should run fine on LPG. You lose a bit of power and you lose a bit of fuel performance (somewhere between 10-20% of each) when running on LPG however, the cost of LPG was so much cheaper then Petrol it more then justified it.

They also made tanks that would fit into the spare wheel bay so you don't loose half of your trunk space.

I have no idea how an M-100 would run on LPG. Maybe you should consider cross posting this question to the m-100 forums (http://www.m-100.cc and http://www.m-100.net) to see if anyone else has done this conversion. In the US, propane is still pretty expensive and has not taken off as pumped fuel.

For some reason, the more popular option here is ramming a sweetcorn in your gas tank (e85 ethanol).

[BAR]

I have seen a few S class vehicle running around Sydney [Australia] with the Red LPG symbol on their number plates, indicating a conversion has been performed.

From my own experience, a friend had a more modern 4 litre Ford 6 cylinder engine that had been converted when the car was new, to run on dual fuel.  It needed to start on Petrol and quickly switched over when the car was warm.

To my mind the car had problems keeping cool.  The engine would run over normal in traffic, but if switched over to petrol, would 'cool' down again very quickly.

Definitely was cheaper to run.  Fancy a 6 cyl, 4 litre costing less for fuel than a 4 cyl 2 litre!  They used the Ford and then eventually switched to a Toyota Corolla and spent more money on petrol for the same travelling each week.

Would be nice to get the $2,000 rebate, but I am of the opinion that a conversion on an old Mercedes like ours would be over $5,000.

[olliparr]

Hi there,
I've nothing to say about 6.9's I'm afraid, but I've been running my 280se on LPG for about 4 months now and I can give you my limited experience. The 'conversion' is pretty minimal - it's not exactly rocket science - watch out for where exactly they put the gauge inside the car - too low down and you may find yourself contorting into strange positions to see how much gas is left. It cost me about 1500 euros (including the outrageous amounts of tax in Holland) - but I think I could have got it done for less. At lower speeds you do lose a bit of power, but at 80km or over I find more than enough compensation. I've been told that this is because LPG increases torque at higher revs. I'd love to know what it does for a 6.9....Consumption is certainly a bit higher than petrol but this is still offset by the price - 46 euro cents/litre here. My engine does run marginally hotter, but I've never noticed much of a difference on the temp. gauge except when I was driving over the Pyrenees this summer - but yours is quite different so that won't tell you anything. What is important is to fit some sort of valve lube to stop valve seat recession. There seems to be a bit of doubt as to whether this really exists but I've seen a car at my local garage that had a severe case of it, so take care. Flash-lube have the kit - but I fill up their drip with lead replacement stuff which does the same job.
The 100l tank takes up a lot of space and I have a bit of difficulty getting into the spare wheel well - worth thinking about. The car doesn't like reversing on gas - low revs are always a bit shuddery - I've tried tweaking the mixture but it doesn't help much, so I still tend to do most local driving on petrol and use gas on the motorways. On the plus side - you will be more environmentally friendly than most other cars on the road, which in a 6.9 will be a new and probably unique experience.
My kit is made by STAKO - in Spain where strangely enough you cannot find LPG.

[oscar]

Ollipar, I read some of your other LPG posts but missed what year your 280 is.  Given the year,  I'd really like to know whether it's got k-jet or d-jet fuel injection?  6.9's or otherwise I can't recall if any LPG 116's were k-jet equipped.

[olliparr]

Hi Oscar,
1977 which makes it K if that's any help.