Mercedes diesel engine questions:- fitting modern to W114?

[madmog]

I have a Merc W114 which I intend to add a modernish Merc diesel. I probably won't do the engine swap myself as I don't have time. I'd appreciate any advice on the following


I've seens some threads here about fitting the OM605 from the C250TD (Joe76) and have also been advised to go instead for the 4 cylinder OM646 from a C220CDi.

The former is simpler, cheaper to get hold of, maybe runs vegoil, the latter gets even better fuel economy but is more complicated; more to go wrong.

The former would need the braces from bulkhead to inner wings removing which I guess would send me to BIVA hell. I've just seen on the German /8 forum that the models that didn't have the braces had all engine bay panels thickened from 0.8mm to 1mm to compensate. I love that precision but am left reluctant to cut them.

I've driven a couple of potential doner cars and both engines seem just fine. As these modern turbodiesels have 5 and 6 speed gearboxes respectively, is the power band so narrow (especially on the C220Cdi) that mating to the original 4 speed will make driving hard work and/or not pleasant? It's not going to be practical to try to run a 5 or 6 speed box through the column I think.

Finally, what's the cheapest way to upgrade the brakes and suspension? Are W124 and W123 parts backwards-compatible?

Thanks

[Dez]

you wont need to upgrade brakes. they're already WAY topside of their job if in good condition, and easily as good as w123. a friend of mine has just discovered w115 front calipers are the same as baywindow vw ones, so they can stop some weight. some better shocks and stiffer springs wouldnt go amiss though.

turbodiesel powerbands are comparitively narrow, yes. about 1500rpms, from 2000 up to 3500 is normal. the actualy number of gears doesnt matter too much as long as you can always keep it within that band, what will be an issue is finding a diff ratio tall enough for you not to be over-revving it at cruising speed. youre going to need something below 3:1, even as low as 2.5:1, which I'm not sure is available bolt-in. v8 auto w126 possibly has something around those figures though.

ive looked at upgrading the engine in mine (w115 220d), and the merc options are a total minefield, and its difficult to get the right motor (my preference would be an om605 or 606 with a manual pump, so no electrickery going on) with a manual box unless you get very lucky, or throw a lot of money at it.
there is a combination of parts that will work but i forget what is is right now, and if you car will have any of them. i think you need the flywheel from a 240d. but then it needs rebalancing as back then merc balanced whole rotating assembles rather than individual components, so you cant just chop and change them.

I'm pretty convinced a full package (incuding diff if neccessary) from a bmw e34 TDS is a better, cheaper, more coherent option, and unless my tape measure lies, should drop more or less straight in without cutting. they're reasonably easy to find manual, but it would mean going to floor shift. the only bit i don't have answers for is reparding the locationg of the engine mounts and the length of the prop, but neither are particularly difficult issues.

[madmog]

Thanks Dez, do you have the braces between the firewall and inner wings and will you remove them or leave well alone?

[Mark]

Out of those two, I'd pick the OM605 all day long, ideally with a 773.4 autobox but I understand yours is a column-shift 4 speed manual so I imagine you'll want to keep that. Have you considered swapping in a more modern petrol such as the M110 280E engine from the W123? It will suit the refinement of the car better and should be an easy enough swap as the W114 had M110 fitted from the factory. You could also consider the M102 from the W123/124 for better fuel economy. You could also consider swapping the column shift manual for a column shift auto to free up gearbox options

If you're fixed on diesel, it's also worth looking at the Musso engine btw, it's basically a larger capacity OM602 with a different injector pump set up.

[madmog]

Nov 19, 2014 10:59:26 GMT Mark said:

Out of those two, I'd pick the OM605 all day long, ideally with a 773.4 autobox but I understand yours is a column-shift 4 speed manual so I imagine you'll want to keep that. Have you considered swapping in a more modern petrol such as the M110 280E engine from the W123? It will suit the refinement of the car better and should be an easy enough swap as the W114 had M110 fitted from the factory. You could also consider the M102 from the W123/124 for better fuel economy. You could also consider swapping the column shift manual for a column shift auto to free up gearbox options

If you're fixed on diesel, it's also worth looking at the Musso engine btw, it's basically a larger capacity OM602 with a different injector pump set up.

Thanks Mark
I want the economy of diesel and low revs at motorway speeds. Apart from having the 6 cylinder engine mine is extremely basic spec - no sunroof, no heated rear window, manual windows, no hazards, no central locking. It wouldn't be a big drop to go down to 4 or 5 cylinders for me. Or if I could find one cheap, one of the V6 3.2 diesels with manual box. They're a bit expensive at the moment though and I've only seen them in Germany.

I have thought of column-shift auto, I'd probably prefer auto but am a bit put off by the Merc boxes having electronics. Another one in favor of the 605 - I think you can retro-fit manual injection pump from an earlier engine.

I can't find anything online about the 773.4 autobox. What vehicles was it in or did it have another designation I can look up?

Ta

[Mark]

My 230.4 is a great motorway cruiser (for what it is) but is brutal on fuel! How about petrol engine & a good LPG system?

Avoid any of the Mercs with electronic gearboxes, will end up costing an absolute fortune as you have to buy an independent gearbox controller etc. The same goes for the engines but there are a few guys out there who've worked out how to make the electronic pumps work.

Avoid anything newer than the OM605/606, they get incredibly complicated and less reliable.

Apologies re autobox numbering, I meant 722.4 which is commonly found in loads of Mercedes cars.

I looked into this relatively extensively a couple of years ago and worked out that I'd need a OM605 engine, a 722.4 gearbox, a diff from a 500SL, an OM602 mechanical pump (either from turbo version available in europe or modify an N/A version which is easily found in UK) and a lot of time and effort. You're also likely to have issues with the turbo fouling the steering rack so some modification will be required there. This will not be a cheap conversion and it's relatively specialised so I'd imagine it would be difficult enough to find someone to perform it in the first place! In the end I decided that it'd be better to spend the money on fuel rather than do the engine swap, but decided that if/when the engine goes pop I'll swap it for a 4 cylinder petrol from a W124.

[madmog]

Thanks Mark, duly noted. I was thinking of going here:

www.m-bv8conversions.co.uk/

Originally planning a V8 but in talking to Martyn (who has been very knowledgeable and helpful) I brought up diesel and he recommended the 220CDi and is able to hack the electronics for that engine but not the autobox.

He's against the 250 as being slanted (so fouling the braces) but is all for the 220 4 cylinder. There seem to be a lot of 220s made and out there so perhaps that would help with electronics (lots of parts in breakers and high demand to solve problems in the future).

Realistically I don't have time (and maybe not talent) to do it myself but want to get it right for the long-term.

[Mark]

Interesting re the 220CDi - is that the OM611? Apparently they're pretty strong engines - it's definitely a conversion I'd be interested in learning more about

[welshpug]

engine itself is decent, but let down by the control systems, leaking injectors causing massive carbon buildup is common.


Interesting that the ecu's can be run in older cars after some work, makes diesel conversions much more worthwhile as the older ones aren't that brilliant on fuel.

[ettorebugatti]

Mercedes did do a om611 swap into an 190d, looked interesting:
www.autobild.de/klassik/artikel/mercedes-190-cdi-968706.html
www.autoguide.com/auto-news/2009/09/report-bored-mercedes-engineers-drop-modern-250-cdi-diesel-into-190-e-chassis.html

You could have look to swap the complete Vito/Sprinter wiring loom + electrical systems in, is less complex than from a passenger car.

Probably more expensive, but it is another way out:
www.specialist-components.co.uk/engineering/diesel-engine-management/

[BenzBoy]

Nov 19, 2014 10:27:50 GMT madmog said:

Thanks Dez, do you have the braces between the firewall and inner wings and will you remove them or leave well alone?

If your car is a W114, I thought these didn't have the braces so that there was room for the six pot. Could be wrong though.

[Mark]

Nov 19, 2014 21:55:13 GMT welshpug said:

engine itself is decent, but let down by the control systems, leaking injectors causing massive carbon buildup is common.

Unfortunately this can happen with pretty much all common rail diesels

Nov 19, 2014 22:12:27 GMT BenzBoy said:

If your car is a W114, I thought these didn't have the braces so that there was room for the six pot. Could be wrong though.

That's what I thought too!

[madmog]

Mark, yes the OM611 or possibly OM646 if I've got my engine numbers right and 646 is a derivitive of 611

Welshpug could you clarify what you mean by "Interesting that the ecu's can be run in older cars after some work" do you mean later OM611 ECUs in earlier OM611 engines?

Leaking injectors seems a simple fix but I wonder if there's a better seal that can be fitted or it's just a consequence of massive pressures and not cleaning the threads.

Also, I wonder which of the control systems could be removed from an engine going in a '68. Eg any EGR stuff could be deleted.

Benzboy, I'm certain the single cam sixes had braces, at least to start with. The Twin cam 280 needed them gone and apparently other panels in the engine bay were upped from 0.8mm to 1.0 mm to compensate. Perhaps once the 280 TC was in the lineup they did all engine bays the same without braces.

Which leaves the question, if the braces are cut does that then require a BIVA test and Q plate?

[Dez]

I wouldnt worry about the braces, the fact some cars had them and some didn't is more than enough to explain away their abscence if necessary. Or, if you're worried about strength, just make them bolt-in.

[Battles]

Isn't there a guy on here putting an OM606 in a Landie?
I'm sure that thread either states, or links to, the killer combo of a fully mechanical, vaguely modern Benz diesel by listing the pump, engine, etc. required.
If it's not in there, maybe look on the Landie forums, I gather Benz swaps are common for them.

Might need some dynamat to maintain the tranquility of the cabin though.

[madmog]

Nov 19, 2014 9:59:44 GMT Dez said:

there is a combination of parts that will work but i forget what is is right now, and if you car will have any of them. i think you need the flywheel from a 240d. but then it needs rebalancing as back then merc balanced whole rotating assembles rather than individual components, so you cant just chop and change them.

Just re-reading this thread, Dez I wanted to clarify something you said - when you said 'there is a combination of parts that will work' which engine did you mean and did you mean in terms of connecting the newer engine to the column-shift box?

Thanks

[hario]

I think he means the Mercedes OM605/606 with a mechanical pump from an OM602/603, unfortunately the 5-speed electronic auto they come with (722.6) doesnt clear the W114/5 transmission tunnel, and the stand-alone controller to make the box woth is £700+. So the 6-speed manual from the C 200 Kompressor (?) is a direct fit to the above engines, but it doesn't solve your column-shift issue..

But you would have a completely mechanical 5-6 cylinder diesel engine and 6-speed gearbox combination for about £650 all in from ebay.

[welshpug]

I saw black smoke racing have an om648 running out of its donor vehicle last week

[Dez]

i found and then lost a thread of a guy in the states fitting a 605 or 606 to his original gearbox, and he said he'd used a 240d flywheel, and possibly the ally bellhousing adapter plate they have too.

i cant remember if it was a 4 or 6 cyl car to start with though, and cant find the thread again either. i suppose it would make sense if it was a 240d 4cyl box? there is the possibility he meant he'd used 240d 3.0 parts, but i think they're the same anyway?

as i understood it, the 605/606 is related to the 616/617, and the 616/617 had a different flywheel and a bellhousing adapter plate to make it fit a standard 4 cyl 115 gearbox.
meaning, the 616/617 parts can be used to mate a 605/606 to your original box, which i believe is the goal here?
ive not done it, so i cant say itll work, but i have found various people discussing the feasability of it online.

[madmog]

Thanks Kario & Dez.

Coincidentally I've picked up a donor car today. In the end I went with a nice C250TD manual. The C250s seem to be much cheaper for a good one than the 220CDIs. I was also looking on mobile.de when I heard the Germans got 320CDis with manual box (too expensive at the moment) and spotted that there's another model that the UK market doesn't get, E290 - a 5 cylinder 2.9TD which may be the same thing as in the Ssang ?? Musso. Oddly the E290TD seems to have lower power than the 250.

Pokes around for an engine bay picture of an E290
ipocars.com/vinfo/mercedes_benz/e_290_td_avantgarde__xenon__el_glasschiebedach_-1997.html

looks like the OM602 was kept going a bit longer in some markets

I digress
So there's i have an engine and even a back-up gearbox sorted if I can't get the column-shift mated.

The donor is so nice I might just use it as is for a while and get a scrap OM605 block in the meantime and have a play to see how close it is to fitting the column-shift box.

Is there much of a mpg penalty or other disadvantage to running the mechanical injection system apart from buying it in the first place? There are a few posts out there on chipping or reprogramming the ecu to give a bit more power and reduce lag. Would the mechanical system need much 'tuning' (if that's the correct term) to get it right?

Actually,

Presumably the mechanical injection means a bunch of sensors (MAP MAF) can also be omitted?