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An OM606 is just a very stout engine. It's a 6cyl inline 3.0L indirect injected diesel building in some respects on the tradition of its predecessors the OM61x and OM603. It has a basically indestructible bottom end, an efficient 24 valve DOHC head, an inline Bosch M-type injection pump, and it can be pretty easily and inexpensively made to reliably put out enormous HP and torque that melts tires and shreds drivetrains. People call it the "diesel 2JZ" because it'll rev like mad. In stock form it's no slouch but when you put the fuel and air to it (and some stiffer exhaust valve springs to combat valve float) it turns into an absolute fire breathing monster. But a pretty reliable one. It's also a fairly light engine as far as diesels go, comparable to an LS1, various BMW 6cyl engines, Benz M104, etc. Being indirect injected it's not as efficient as a direct injection engine, but a lot more forgiving from a tuning and fuel quality standpoint. Unlike DI engines, IDI engines require no modifications to injection nozzles even when pushing vastly more fuel.

Another thing is that converting one from a computer controlled engine to a fully mechanical engine is very simple. You just remove the Bosch EDC pump and install a mechanical pump from an OM603. The only major difference is in the governor. The EDC pump is "Electronic Diesel Control" or something to that effect--it has an electrically controlled actuator and an ECU and the mechanical pump has a flyweight governor like all the other mechanical pumps, steam locomotives, etc. That makes it attractive for swapping into older vehicles, you can do a brain transplant and turn it into a simple 1 wire engine in like an hour.

The problems with a heavily boosted high output OM606 (or any other diesel) aren't power or torque--you'll get a ton. It's making that power and torque in a way you can actually use, and that won't make obnoxious clouds of black smoke. Stock it makes something like 175hp/240ft*lb, which isn't bad at all. That can be pushed to a bit over 200hp on stock pump internals, or as high as you want (600hp+) with a purpose-built injection pump with larger pumping elements. But you have to feed it enough air to keep exhaust temperatures and smoke under control and that's the problem--big turbo means no boost until high RPM which is fairly limiting from the standpoint of like actually doing car stuff.

Personally, I don't really care about making huge amounts of top end power, I'd rather have a driveable engine. Stock power and torque output--or at least that which is reliably achievable with a stock pump and maybe an HX30 to flow a little more air more efficiently--is plenty. The thing that rocks about the OM606 is it'll go like that for 500k miles with (probably) just routine oil changes. And you'll get like 28-32+mpg the whole time (depending ofc on what you swap it into).

So all that is to say it's kind of the pinnacle of a particular stage of automotive diesel technology--I think it might be the "most modern" IDI diesel ever made. It's too bad the car they surrounded it with is such a pile of hot garbage.

I bet an LS1 E36 would be sick too.

EDIT: lmao just watched the Freightliner video. The one thing on an OM606 that is remotely like that is the overcomplicated fuel tubing on EDC-pumped engines. It has these dogshit plastic push connectors with orings, and some crazy convoluted fuel plumbing through a shutoff valve which basically doesn't do anything useful. The shutoff valve and each end of like a half dozen of these little plastic fuel tubes has o-rings in it which eventually fail and leak fuel everywhere. It's a bit ridiculously overengineered and solves a problem that isn't a big deal--normally to shut off a diesel you just pull the rack all the way back on the injection pump and wait for it to die. For some reason, on the EDC pumps when it does this the RPMs increase for a little bit before it dies. That's what this other electronic solenoid valve solves--by pinching off the fuel upstream of the IP at the same time as pulling the rack back this little RPM blip doesn't happen. But it comes at a terrible plumbing cost. Happily if you use Viton o-rings you only need to change them every 20 years or so. My car is currently disassembled because I'm doing that now :D. This whole system can be deleted if you don't care about the RPMs increasing a little bit when you shut the engine off, or if you do a mechanical brain transplant.

EDIT AGAIN: Ah, one more thing! I forgot about the glow plugs. So.. it's an aluminum head engine, with steel pencil-style glow-plugs screwed into it. These surface inside each precombustion chamber where they glow red hot during the start cycle. This helps atomize the fuel in the cold engine and makes it go brr. Once the engine has been running for a few seconds they shut off, because there's enough residual heat in the prechambers to atomize the fuel. Anyway, because you have steel parts threaded into aluminum parts in the presence of salt and road grime and who knows what on the outside of the head--not to mention the heat and carbon buildup on the inside--this is a recipe for a sticky situation. The torque spec for these things is I believe 27N*m which is not a lot and if you torque them anywhere past 40N*m they're very likely to snap. When one of these little fuckers breaks off in the head it's a very, very bad day. If you're exceptionally lucky it's just an entire day or more of uncomfortable contortions with an angle drill, some tapping, some helicoils, some loctite. But more probably the head is coming off and going to the machine shop. In which case probably you're gonna also want to deck the block.. and at that point why stop there? Best to just do a full rebuild. So, you do not want to break off one of those glowplugs in the head. So... what do you do about that? The answer has a part number: A 001 989 42 51 10. I don't know what this stuff is made out of but I assume it must be incredibly toxic. It's some kind of anti-seize lubricant that is bright white when you put it on the glowplug, and is still bright white when you remove the glowplug a year later. It spent 10000 miles millimeters away from the combustion chamber of a diesel engine and didn't degrade at all. There's also a special reamer tool which also has a part number but I don't have it in front of me. Every year I remove all the glowplugs, clean them, ream and clean the holes, re-apply the anti-seize, and reinstall them. Just to make sure one never gets stuck in the unlikely event I have to replace it.