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!
Would be neat to hear what others have to say. LPG is only used here for public transit buses or farm equipment (mostly).
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
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
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.
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.....
BTW Im happy to take some pictures of the conversion I have if you decide to go ahead with it.........
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 ??? :'(
Quote from: Tony66_au on 06 October 2012, 07:36 PM
Oh and unless the price of LPG in BC is far less than half the price of petrol its a waste of time.........
... surely depending on how many kilometers one does ?
( currently experiencing all the problems noted above, running LPG on my 450SEL K-Jet )
Quote from: scraf on 14 October 2012, 05:25 PM
Quote from: Tony66_au on 06 October 2012, 07:36 PM
Oh and unless the price of LPG in BC is far less than half the price of petrol its a waste of time.........
... 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.
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
Quote from: Tony66_au on 14 October 2012, 08:36 PM
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.
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.....
Quote from: Major Tom 6.9 on 15 October 2012, 04:07 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.
.
Economical and you can easily make biodiesel if you wish. I made several 55 gallon batches some years back when it was just becoming popular.
Or even convert to waste oil and skip using the caustic soda and methanol.
You'll drive by, they'll say: "Is that... bacon I smell?"
Many thanks for all the input here....fwiw, I'm using an Impco mixer on my shop truck, a '75 International...very simple and effective setup, which got me to wondering about something similar for the recent addition, the SEL.
Based on what I've learned here regarding the K-Jet system, I'm inclined to scrap the gasoline motor entirely and plant an OM617A in there...it's what I've used in W126 for the last decade, and there's plenty of rusty 300SDs around here.
Quote from: 76116 on 21 October 2012, 11:06 AM
Based on what I've learned here regarding the K-Jet system
Your car being a 1976 isn't a K-jet - it's a D-jet. I like the feel of D-jets more, however they tend to (in my experience) be more badly out of tune upon purchase and run severely underpowered. In theory they should be just as or more potent than a K-jet if in proper shape. '76 was a bad year though for US 450's, because they put the catalytic converters in the engine bay which causes nasty overheating problems You could swap the exhaust for an earlier one ('73 being the best) or remove the cats... On D-jets make sure you replace any hard rubber injector lines, lest one inevitably cracks and drips gasoline onto hot engine in vicinity of spark. And replace the timing chain. Those done the engine will last forever.
QuoteI'm inclined to scrap the gasoline motor entirely and plant an OM617A in there...it's what I've used in W126 for the last decade, and there's plenty of rusty 300SDs around here.
I support/encourage this notion. :)
Good one Casey, excellent points...there's 68K on the thing, one owner car - huge stack of bills and service history to go through. Chain will most likely be ok, but doing the tensioner cheep insurance...all vacuum rubber bits, old fuel lines etc will be refreshed in the meantime, and the cats will be dropped...much as I did with an '80 450SL, along with a few other updates.
A 1976 car could be either D Jet or K Jet, depends on the timing. They started the changeover to K Jet in September '75, so with the time lag in manufacture I would imagine that early 1976 cars might be D Jet
but by about mid '76 onward all vehicles would have been K Jet.
Do you US guys have annual inspections on your cars? I'd heard you have very strict emission laws that'd prevent cats being removed.... Were the cars originally designed for unleaded fuel (ie a small filler neck)??
Laws vary wildly by state, but generally not for cars over a certain age.
I have an LPG powered Jaguar XJ12. I think the person that converted it must have spent $10k on the conversion. It's got two tanks and the fill nozzles have been routed so that they come out of gas filler tubes.
I just bought two XJ12 parts cars and I plan on converting it back to regular fuel injection as I don't use the car enough to justify the hassle that this conversion gives me.
If anyone wants to buy the kit, as the v12 has two throttle bodies, I have pretty much everything to convert two cars :)