W108 Mercedes 280SE diesel conversion project

[pryantcc]

Work is proceding on stripping the donor vehicle. Its slow and painstaking, but going well so far. It doesn't help that I'm paranoid and being super-careful about tracing and labelling every cable.

The donor car:


Here's the power plant. It's had some boy-racer treatment, but doesn't seep to have suffered badly, still runs sweetly and very cleanly.

[pryantcc]

Great progress made now, just 1 wire left to sort out, then the whole lot will run on the ground with a battery attached. Hopefully I'll get that sorted by the end of the week and start the mechanical stripping of the donor car!

[pryantcc]

I'm very excited, I've finished the electrical strip down, wohoo!
I can make the engine run now with only 4 12V connections and 2 fuel pipes. It's such a relief as the electronics are the part I was most worried about for the whole job. I just have 2 permanent 12V feeds, 2 which are switched by the ignition key and 1 for the starter solenoid. Its very satisfying.
The wiring all still looks a bit of a mess but I can tidy it up once I see where to put everything in the project car.

This spaghetti is mainly the old instrument cluster connections (I hope to find a tacho and glow plug indicator light in there) and the computer diagnostic port connection.


On the other side of the donor engine bay is another box of tricks, power for the ECU comes from here and some other stuff.


The interior isn't looking great. It turns out I didn't need anything from in here and could have left the dash intact, but I needed to get in there to trace some wires in order to learn this! I'll know for the next one


So, this is it with all the required electronics sitting on top of the engine. Attention now moves to the mechanical strip down!

[TerryG]

That looks like it was a pain in the bum! Well done on working out what does what.

[Luxobarge]

Following this thread with great interest.

I love it when someone doing an engine swap actually gets the thing running in less than 3 years......

Keep up the good work, and keep the updates coming, great stuff!

Cheers

[pryantcc]

Thanks guys!

That looks like it was a pain in the bum! Well done on working out what does what.

Terry, I took the reverse approach and tried to work out what doesn't do what! I just removed bits one by one and checked to see if the engine still ran! There are still some wires attached which, when I remove them prevent the engine starting, but I still have no clue what they are for! I probably wont find out either unti lsomething stops working and i have to dive in again!

I love it when someone doing an engine swap actually gets the thing running in less than 3 years......

Keep up the good work, and keep the updates coming, great stuff!

Cheers

Don't count chickens now Luxobarge! There's still a half-finished Alvis under a cover in the garage and its taken several months just to get this project started. I do really, really hope that I won't be still posting progress updates in 2017 though!

[cdodgyd]

Another hats off to you sorting out all that wiring - just looking at it is enough to give me nightmares!

I too look forward to the finished result. If the engine has been tuned you'll be looking at close to the 200bhp of the original 3.5L with half the fuel consumption.

I've always wondered how the higher powered W108's must handle, especially the 250bhp 6.3! I've had mine sideways in the wet (swing axles) and it scared the life out of me.....and I've only got around 90bhp!

[pryantcc]

Another hats off to you sorting out all that wiring - just looking at it is enough to give me nightmares!

I too look forward to the finished result. If the engine has been tuned you'll be looking at close to the 200bhp of the original 3.5L with half the fuel consumption.

I've always wondered how the higher powered W108's must handle, especially the 250bhp 6.3! I've had mine sideways in the wet (swing axles) and it scared the life out of me.....and I've only got around 90bhp!

There she is, swinging in the breeze! The auto box has been removed and I've ordered what I hope will be the necessary bits to install a clutch and flywheel. Time will tell!!!
No tuning done at all, I plan to run it completely standard, so about 170bhp and bag loads of torque. Who knows, I might get enthusiastic further down the line, but This will be my daily driver, so fuel economy is a factor too.
To be honest, I haven't really driven it much with the petrol engine in it, but it handles pretty well, brakes are great!

[rich.]

nice would it be easier to run it with the autobox? (im a big fan of autos)

[pryantcc]

nice would it be easier to run it with the autobox? (im a big fan of autos)

Hi Rich,
That would be the ideal solution, the 722.6 gearbox which I'm chucking out is a very highly thought of piece of kit. They are ridiculously robust and will deal with 4 or 500HP, but unfortunately, computer says "no"!
The gearbox controller needs a road speed signal from the ABS computer. Even if I did add ABS sensors to my car to generate a signal, the fact that the rear diff ratio is different to the original would make the computer think the car or the gearbox are slipping and cause it to sit permanently in limp mode.
It is possible to get aftermarket controllers, but these seem to be best suited to very high power, race type driving rather than daily road work. So, at the end of the day, it made more sense to go manual due ot the lack of computing involved. It also gives me a taller final drive ratio so will help to keep the revs down when cruising. Auto is 1:1 in top, manual is 0.84:1, or 0.82:1, or something like that.