Author Topic: LPG/Propane setups for 450SEL?  (Read 5125 times)

76116

  • Enthusiast
  • *
  • Posts: 82
  • W116 Enthusiast
  • Location: Victoria BC Canada
LPG/Propane setups for 450SEL?
« on: 06 October 2012, 09:03 AM »
Anyone willing to share notes, pictures?   I just landed a tidy 450SEL, would like to do a tidy conversion that uses the gas tank space for cylinders and preserve most of the trunk space. 

Pictures to come, it's a silver over blue '76....80K kilometers, no rust that I've found (yet)....there's a set of 7J 14" bundts to refinish, or staggered AMG 16" Monos...good times!

thysonsacclaim

  • Vintage
  • ***
  • Posts: 518
  • Location: DeLand, Florida, United States
    • Fortasse | Action at a distance
Re: LPG/Propane setups for 450SEL?
« Reply #1 on: 06 October 2012, 09:21 AM »
Would be neat to hear what others have to say. LPG is only used here for public transit buses or farm equipment (mostly).
Adam


Fortasse
[Personal Ramblings]
http://www.fortasse.com

Morbid Rodz
[My Brother]
http://www.morbid-rodz.com


1974 450SE, Ikon Gold, Tan interior

TJ 450

  • W116 Addict
  • ****
  • Posts: 4,264
  • Location: Rockingham, Western Australia
    • Tim's Insulators Downunder
Re: LPG/Propane setups for 450SEL?
« Reply #2 on: 06 October 2012, 09:29 AM »
I don't think anyone has been enthusiastic enough about LPG systems to really document any hard and fast recommendations.

There has been quite a few conversions though.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

oversize

  • W116 Addict
  • ****
  • Posts: 1,330
  • W116 Nut
  • Location: Melbourne, Australia
Re: LPG/Propane setups for 450SEL?
« Reply #3 on: 06 October 2012, 04:55 PM »
Well where do I start???  I've always been a fan of LPG until fairly recently.  I bought a 6.9 with a system already fitted and thought it'd be ideal.  But the old mixer was stuffed and it didn't want to idle.  I thought the tank needed to be retested (more than 10YO), but I've since found it's ok.  It was last tested in 2007.  My problems with LPG lie with more weight due to the tank being far heavier than the petrol one.  Then there's a drop in power and economy.  The latter being a greater concern as these cars were's the best anyway, so the car ends up having quite a limited range.  The biggest advantage was the price difference, being far cheaper than petrol.  But that has changed here and it's much dearer than it used to be.  You really have to crunch the numbers based on your current consumption.  Then there's originality issues where you're dilling holes where there wasn't any and it doesn't look right under the bonnet.  So the advantages are evaporating quickly and I'm probably going to convert the car back to petrol.  I'm fortunate enough to have all the parts available from a donor car.

I did intend to use 2 x mixers on the 6.9 due to the fuel requirements and even twin tanks, as a single valve outlet won't flow enough near the top end.  Probably not an issue on a 450.  I have charts and can look up the CFM requirements based on RPM and capacity if you'd like.

Below is a link to the mixer I intended to use x 2 and I was gunna mount them on the side.  I've seen these mounted on a hot rod where they worked well, but I've heard that using two may present tunability difficulties.

http://www.ebay.com.au/itm/180288198777?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
1979 6.9 #5541 (Red Bull)
1978 6.9 #4248 (Skye)
1979 6.9 #3686 (Moby Dick)
1978 6.9 #1776 (Dora)
1977 450SEL #7010 white -P
1975 450SEL #8414 gold -P

Tony66_au

  • Vintage
  • ***
  • Posts: 896
  • Dirty Hands
  • Location: Vic, Australia
    • EuroTrash FB Group
Re: LPG/Propane setups for 450SEL?
« Reply #4 on: 06 October 2012, 05:35 PM »
Don't do it!

I have a K jet 450 on duel fuel and as others have found K jet and LPG dont mix.

The main issue is the air metering system on a K jet engine which is a bit fragile, add LPG and you will experience a backfire at some stage and this will screw your air metering system.

The other issue is cold starting and the extra air added to the system when cold to compensate for the cold start injector via the WUR, although your car should start with a squirt of fuel and then within seconds switch to LPG the whole cold start system, AAV WUR etc will still pour extra air into your intake system producing a VERY lean LPG mix.

So unless you are prepared to run a dedicated LPG system and remove every trace of the original intake and cold start system id stick to fuel.


Tony66_au

  • Vintage
  • ***
  • Posts: 896
  • Dirty Hands
  • Location: Vic, Australia
    • EuroTrash FB Group
Re: LPG/Propane setups for 450SEL?
« Reply #5 on: 06 October 2012, 05:36 PM »
Oh and unless the price of LPG in BC is far less than half the price of petrol its a waste of time.........

I would, Instead of LPG spend the $2000 or so dollars on fine tuning and repairing the existing fuel delivery system to provide maximum efficiency, add some cotton blue or K&N air filters, new leads, dizzy cap, rotor and some good plugs (NGK for pref) and add a new Bosch coil and get the sucker tuned by a Benz professional from base settings to remove any previous owner tweaks and messing about, perhaps get your distributor recurved to suit modern fuels and a dyno run to ensure it is smooth up the range.

I did this to my Fuel only D jet 450 (Except the dyno run and I did the factory reset/tune myself) and the difference it made was amazing.....
« Last Edit: 06 October 2012, 05:43 PM by Tony66_au »

Tony66_au

  • Vintage
  • ***
  • Posts: 896
  • Dirty Hands
  • Location: Vic, Australia
    • EuroTrash FB Group
Re: LPG/Propane setups for 450SEL?
« Reply #6 on: 06 October 2012, 05:44 PM »
BTW Im happy to take some pictures of the conversion I have if you decide to go ahead with it.........

oversize

  • W116 Addict
  • ****
  • Posts: 1,330
  • W116 Nut
  • Location: Melbourne, Australia
Re: LPG/Propane setups for 450SEL?
« Reply #7 on: 08 October 2012, 02:34 AM »
BTW a duel fuel setup has additional problems with even more weight, a severe loss of boot space and the inconvenience (and $$) of using a full petrol tank of fuel every 3 months.  Otherwise the fuel will go off, the car will ping, the injectors will foul, the car will start to misfire and eventually it'll cause damage to the whole petrol system rendering it useless....   >:( :( :o ??? :'(
1979 6.9 #5541 (Red Bull)
1978 6.9 #4248 (Skye)
1979 6.9 #3686 (Moby Dick)
1978 6.9 #1776 (Dora)
1977 450SEL #7010 white -P
1975 450SEL #8414 gold -P

scraf

  • Classic
  • **
  • Posts: 332
  • Location: Netherlands
Re: LPG/Propane setups for 450SEL?
« Reply #8 on: 14 October 2012, 03:25 PM »
Oh and unless the price of LPG in BC is far less than half the price of petrol its a waste of time.........

... surely depending on how many kilometers one does ?

( currently experiencing all the problems noted above, running LPG on my 450SEL K-Jet )
Mercedes 450SEL 1975 Pimp mobile
Mercedes 306D 1975 Ska mobile ( in hibernation )
Mercedes 300D 1974 W114 Ambulance

Tony66_au

  • Vintage
  • ***
  • Posts: 896
  • Dirty Hands
  • Location: Vic, Australia
    • EuroTrash FB Group
Re: LPG/Propane setups for 450SEL?
« Reply #9 on: 14 October 2012, 06:29 PM »
Oh and unless the price of LPG in BC is far less than half the price of petrol its a waste of time.........

... surely depending on how many kilometers one does ?

( currently experiencing all the problems noted above, running LPG on my 450SEL K-Jet )

Yes and no, on older cars with convertor and mixer setup the set up can and usually is far more inefficient with LPG than Petrol with as much as a 2 to 1 ratio of usage plus maintenance costs are far higher than with Petrol alone because the ign and spark delivery systems need to be higher grade and far better maintained.

Most consumption figures are based on optimal systems and smaller cars and I have found through owning numerous Duel fuel cars that Mercedes and LPG without extensive modification to the system and dedicated LPG is not as economical as it used to be and amortising the cost of a system means you need to do fairly high mileage per year dependant on cost of fuel and cost of installation.

Tony66_au

  • Vintage
  • ***
  • Posts: 896
  • Dirty Hands
  • Location: Vic, Australia
    • EuroTrash FB Group
Re: LPG/Propane setups for 450SEL?
« Reply #10 on: 14 October 2012, 06:36 PM »
BTW its worth mentioning that because LPG is in recent times an Environmental Item the information regarding its viability can be somewhat politicised which confused me at first as the information I knew from the 70's and 80's had suddenly changed or become vague in certain area's.

And yet the delivery systems really have not changed since 1971 when it gained attention and wider use in Australia as a 50/50 Propane/Butane mix fuel, and yet fuel mix and quality varys a bit these days with higher butane content rendering the product less efficient at least in Australia although this mix may vary in Europe.

All of this hinges on a handful of local variations too so its worth noting Propane ratio first and foremost.

Tony

scraf

  • Classic
  • **
  • Posts: 332
  • Location: Netherlands
Re: LPG/Propane setups for 450SEL?
« Reply #11 on: 15 October 2012, 12:12 AM »
this mix may vary in Europe.

By the season as it goes. I was filling up in Germany the other month when I noticed the the mix was 40/60 or 60/40 depending on the season.

Thanks for taking the time to make your posts Tony, very useful information and well appreciated.
Mercedes 450SEL 1975 Pimp mobile
Mercedes 306D 1975 Ska mobile ( in hibernation )
Mercedes 300D 1974 W114 Ambulance

Tony66_au

  • Vintage
  • ***
  • Posts: 896
  • Dirty Hands
  • Location: Vic, Australia
    • EuroTrash FB Group
Re: LPG/Propane setups for 450SEL?
« Reply #12 on: 15 October 2012, 05:47 AM »
My pleasure Scraf, it helps that I think on global terms and don't just assume that the Australian way is universal.

Sadly here we get no such notice regarding the mixture of our LPG although for a while I bought 100% Propane which made a huge difference in the economy of the 4.0 lt inline 6 cylinder Ford I drove and increased the performance quite a bit as well.

But the engine specification for this car is also unique to Australia so any figures are fairly meaningless.

But on a K jet car as i have mentioned elsewhere the danger is in the damage caused to the air mixture device in the throttlebody by backfiring. and this is where Bosch systems are most at risk and why I believe that duel fuel K jet cars will always be difficult.

D jet not so much as it is merely a butterfly valve throttle body with a TPS as the air/fuel mix is controlled by the Manifold pressure sensor being an external device mounted on the LH inner guard in the engine bay and safe from backfire or popping.....


Tony66_au

  • Vintage
  • ***
  • Posts: 896
  • Dirty Hands
  • Location: Vic, Australia
    • EuroTrash FB Group
Re: LPG/Propane setups for 450SEL?
« Reply #13 on: 15 October 2012, 03:28 PM »
If money is no object, you can get rid of the K-jet system completely and go with LPG injection. Over here you can have installed such a kit for around $6000. However, if money was no object I'd fail to see the point of LPG at all.

Ya see that's what I cant understand, why the hell would you run LPG on a Benz in Australia.

And that Brown 77 450SE of mine had it fitted not long after the car was bought looking at the receipts.

In Europe as a daily driver I can understand it because the cost of fuel versus the average wage and cost of living is a fair way removed from our's and even though I pay $1.65 for a lt of 98 octane (Ron) my dollar also goes further.

Big_Richard

  • Guest
Re: LPG/Propane setups for 450SEL?
« Reply #14 on: 15 October 2012, 03:49 PM »
.
« Last Edit: 21 January 2013, 02:46 PM by Major Tom 6.9 »