Hi - There has been some discussion about this over in the W123 forum and great to find someone who has one this. A couple of quick questions

1. How hard was it to calibrate the W126 Speedometer to the Ofgear Controller or did you use the 722.6 output ?
2. Did you have to tune the ofgear controller or was it essentially pre-configured "out of the box"
3. How did you connect the Throttle Position Sensor ?
4. Is the rear transmission cross mount the same as that used for the 722.3 / 4 xx transmission

 

1. The speedo was extremely easy, the w126 has an electric speedo and you simply hook up the signal wire from the Ofgear and turn it on in the settings. I used a GPS speedometer and just drove and adjusted the calibration number until they matched, quite easy. The speedo pickup is on the driveshaft, just an inductive pickup catching the bolt heads on the flex joint. Ofgear page on speedo
2. It is basically pre-configured. There is a one page "first-start sheet" that you have to do out of the box, it is essentially just picking "gas or diesel," "turbo or NA," it's all explained in the paperwork
3. My throttle position sensor setup is a little unique. I took the trans linkage from the valve cover on a spare 617 and modified it to connect to the injector pump linkage, it works phenomenally since it's connected to the actual fuel (power) input and not the pedal, thus taking out all the slop in the worn-out joints. I'll take a picture and get it on here later today if I have time...College is keeping me pretty busy.
4. You can use a regular 722.3 cross member I think...However I did not so I cannot verify. I am pretty sure you just have to drill a couple of different holes on the bottom, but I fabricated my mount from a 722.3 cross member, I just did some cutting and welding because I didn't like the way it was fitting, plus I wanted to mount my speedo pickup with a fancy bracket.

Please link to this discussion any more questions, I would love to answer them and help others down this path, it is 100% worth it.

 

Wow !!
I’ve always thought dropping in m113/722.6 out of w220 s class would be an awesome swap

 

No way. How did I never see this. Absolutely amazing.

 

WOW! Impressive work! Thanks for posting.
I used to tow with my 85 300SD. That OM617 motor is an ANVIL! I had to leave the tranny in 3rd and let it spin to avoid smoking the torque converter. Tranny fluid/filter changes every 15K.
375,000 miles logged on original motor and tranny and no problems. Donated it to a worthy Non-profit.That car is probably still out there running somewhere. But the 722.6 is so much better. (I have one now in my E320 Wagon) Another anvil matched up to the OM617. Sweet!

 

WOW! Impressive work! Thanks for posting.
I used to tow with my 85 300SD. That OM617 motor is an ANVIL! I had to leave the tranny in 3rd and let it spin to avoid smoking the torque converter. Tranny fluid/filter changes every 15K.
375,000 miles logged on original motor and tranny and no problems. Donated it to a worthy Non-profit.That car is probably still out there running somewhere. But the 722.6 is so much better. (I have one now in my E320 Wagon) Another anvil matched up to the OM617. Sweet!

I use this thing like a tank, pulled uhauls for hours and trans never even got above 90°c

The ofgear controller is really amazing in my opinion

 

I squeezed some 116 euro taxi springs into the rear of the 300SD to help with the tongue weight.
But your OM617 and 722.6 set-up is about as close to a diesel locomotive as a car can get! And comfy to boot!
Awesome job!!

Don't do as much hauling these days, but my E320 wagon has standard RWD and self-leveling air with the 722.6, so I can just leave it in 4th and cruise with the trailer all day. Better than any pick-up truck IMHO! But it's no indestructible 300SD!

 

Nice work Blue!! I have been considering the same thing for my 85 300TD. In the process of rebuilding my OM617.952 and I would love a more modern trans to put behind it.

I'm with Sharkey and would gladly purchase a copy of your CAD file if you are able to track it down.

Cheers!
Alex

 

I think you had better give us a wide angle on that engine bay - there are a few inexplicable things on the RHS I wouldn't mind get a look at

 

Here ya go, AWIC, Hood stack, custom air filter stuff. Ask away!

 

The 4 horns must scare the living daylights out of who ever is coming .... Nice looking engine bay

1. What is the aluminium trapezoid box
2. And the black lidded box with wing nut in the middle
3. Do you get much soot on the windscreen with the smoke stack upfront

 

UPDATE ON CAD FILE: I have made phone calls, and it is in the process of being tracked down!

1. That is my air to water intercooler. It's an ebay special that I modified the inlet and outlet location to fit where the turbo is, I also modified the turbo and intake manifold by adding short aluminum pipes with beads so the silicone intake doesn't blow off. It runs just plain antifreeze with a 12v pump to a tiny radiator in the grille area, next to the AC fan.
2. The black box is actually a custom electrical box I made, it houses a small fuse block and four relays that are all linked to the switch panel in the console so I can just make all my connection in the engine compartment and keep it looking nice. Next time I'm under the hood I'll take some pics of it. It's where the electric rad fan hooks up, the air compressor, intercooler water pump, and other odd things get power.
3. The only soot that ever gets on the car and stays is if the car is wet or I'm driving in the rain, because the soot will blow away if it's dry outside. The hood also collects a lot because the clear coat is long gone as it's from my parts car. I was never going to cut up my perfect blue hood. Regardless I take good care of my paint (in my opinion) and all of the grime that accumulates just rinses away fairly easily. I built a shroud to hide the ugly hole in the hood, and the flap comes off the bracket with a simple quick-release pin thing.

I also have euro headlights and a 130? amp alternator from a Saab to drive all my electrical junk. The AC runs on "enviro-safe" r134a replacement, incredible stuff. The car is also on H&R lowering springs and on 205/75R14 Tires. It has a great look in my opinion.

 

You need an IAT gauge!

What do you run for EGT? What's your "limit"? Do you know how much boost it's making?

 

My egt gauge is in celsius because I bought it on ebay, but I have the soft limit set at 650C/1250F and at that temp the gauge will flash and sound a beeper, but technically I can go 750C/1400F for 5 seconds or so.

My boost is set up on a custom dual level boost controller, 12psi when the switch is off, and when you lift the switch cover and engage party mode, it goes to 22ish psi. It varies across the rpm range by a couple psi as its not really a boost controller as much as it's just a modification on the stock wastegate system.

 

Wow! I'm very impressed. So you're an engineering student?

I'm always very impressed with well thought out mods versus idiots just bolting on stuff and hoping for the best.

So why did you go with the vertical stack? While it looks kinda badass in a certain sort of way, it must be loud, and as noted above, sooty.

Cheers,

Kim G
Boston, MA
Where yesterday I won two drag races in my bone-stock '99 C280 against a late-ish model Audi A4, much to my surprise. And with two passengers on board to boot.

 

I am in awe of your mechanical talents.

 

This is fascinating! No idea how I missed this post as well.

 

I have returned to update everyone on the current situation on the files and anything else.
The files: I have been so far unable to find them, but all hope is not lost. I'll be making a trip home and I know that the file exists on an old computer, and I just don't think I can task someone at home to search for it and send it to me. I still haven't given up!

To follow up on CheckEngine's post, Honestly the stack came about when I was test running an HX35 turbo and I just made a quick stack for testing. It's actually a side step from a toyota pickup. However when I put the stock turbo back on, I took the hood off my parts car and kept the stack. It's not very loud inside at all, even at highway speeds. I am going to eventually go back to a traditional exhaust once I save up for some 3" stainless pieces.

 

I still haven't given up!

Thanks and would still be interested in the file but .... I ended up getting an adaptor from Holland - He uses a different pattern to you -(transmissions from M112 / M113 / M272 engines) so I have a 722.618 trans (from a 2004 320SLK), the ofgear controller and Speedbox Electric to Manual converter for the speedo (This is a W123 install). Bolts together nicely, just getting the tail shaft converted and playing with the old shifter to see if I can get all the gears (I have a W210 shifter but would like to make it as anonymous as possible)

 

Truly an impressive project, especially from someone so young. I'm sure that there are Mercedes purists here that cringe at this, but I love it! Your creativity and engineering prowess are to be loudly applauded! I'm glad that you shared your project with us, keep us up to date on future changes or enhancements! It's nice to see some younger folks taking interest in these old monsters, and appreciate the simple, but oh-so-durable design.

 

I really appreciate the kind words, a lot of people just don't appreciate what all is actually involved in doing something like this. Currently I'm in the process of trying to find a 450SL diff wit the 3.06 gears so I can put that in place of the w126 diff. This one is number 3 and I popped the cover last night and it looks like it's about to start failing. Plus the 450SL has the 210mm ring which means I can drop in a wavetrack lsd and finally be rid of all the diff problems that have plagued me so far. I guess increasing power isn't always the best haha.

 

It's definitely impressive. On the subject of diffs, I always read that the rear ends on these old birds are very stout and can handle pretty big power.
Do you think that's not true? Or just getting unlucky.
I'm just curious.

 

It's definitely impressive. On the subject of diffs, I always read that the rear ends on these old birds are very stout and can handle pretty big power.
Do you think that's not true? Or just getting unlucky.
I'm just curious.

I have no clue honestly. The diff that came with the car started making a noise after I got the dieselmeken pump, and I found one of the spider gears had shattered. The second diff (unknown condition from a parts car) lasted some time until the cross pin had about 1/8 too much clearance in the actual carrier. This diff (supposedly good ebay find) is just showing signs of wear. The roll pin that holds the cross pin has just broken but nothing has gained excessive play yet. I could 100% conceivably just have gotten unlucky, yet I assume my driving habits leave much to be desired for longevity. I'm going to pick up a 3.07 ratio diff from a 450sl, and keep a close eye on it while keeping "emergency" funds ready for a wavetrac carrier.

 

Now with data logging!

Small update: Ole's OFGear pc software has the capability to datalog the 722.6, and I have written a matlab program to plot that data and allow for analyzing. I've drawn up some quick and dirty annotations off of my old testing log. There is much more to it than you can see in this picture, but I plan to do some controlled logging pulls and such soon to be able to actually analyze something more than a normal drive up the road. The sharp peaks you can see are the shift solenoids turning on to shift, and the topmost line is vehicle speed. I'm still working on breaking down some of the data, but I thought it was an interesting project to share. I will gladly welcome any help from anyone who has any experience with the OFGear datalogging.

Not pictured here, but I was able to see that the 3-4 shift is irregular from the rest of them consistently, which will hopefully allow me to adjust it in the controller once I get some controlled tests with my current turbo and injectors.

To those interested, I think the CAD file for the adapter plate is somehow lost to time. I'm going to visit my parents for thanksgiving and I'll dig around some more, but It may be long gone.

 

Thanks for the updates and continuing to share your project with us. That said, I'm not sure I understand your last post, hehe. But I may not have studied it closely enough either.

What's up with the diff? Got a new one?

Cheers,

Kim G
Roma Sur, Mexico City

 

Well I'm still running on my less-than-healthy diff, I have a 210mm r107 diff with a 3.07 ratio to swap in though. Just waiting on a weekend free from classes with weather good enough to ride my motorcycle, can't do major work on my only vehicle as a college student haha

 

Thanks for the update. I'm following this thread closely as I'm toying with the idea of someday putting an M112 V6 and 722.6 transmission into a 300SE, and your problems are similar to what I suspect I'd face with such a swap.

A late 90's E320 would be a good donor car, and provide a nice bump in HP and fuel economy, along with a better transmission. I suspect the hardest part would be grafting the engine management system into the W126's old-school wiring harness. At this point, I haven't looked into it much; just had some random fantasies.

Cheers, and thanks again for the update. I'm very interested in your project and how it's coming.

Kim G
Roma Sur, Mexico City
Where a 30+ year old car is exempt from the "Hoy no Circula" rules.

 

More to update! The infamous (in my little town) hoodstack is gone, now i'm sporting a full 3" exhaust from turbo to tailpipe. The original blue hood is back and the 300SD has returned to sleeper status. I recently rebuilt my injectors with monark 261 nozzles, and this thing is mean. Sporting a 5.5 second 0-60 in a heavy old 3.0L diesel isn't too bad to me

 

Now this is an awesome build

 

I've often thought how nice a 722.6 would be in my SDL.... great build!!

 

Nice work, especially for a poor student! Did you have any luck finding the dxf file for the adapter. I have 280CE with a sad auto trans that either needs a rebuild or a replacement. I am thinking a 722.6 swap is the way to go. Being in New Zealand and earning South Pacifi peso's, I am reluctant to spend $700 euro on an adapter!