1993 Mercedes 300D TD EGR removal fiasco
 

Hello people,

Many, many, almost all out there, recommend to remove EGR as to gain power, MPG and keep clean air manifold. I did remove it and results after one complete tank after disconnect it was very dissapointing in fuel economy. I don't perceived any change in power either. Air intake manifold is too short time to see.

I expected some important gain in mileage, but nope. See graph attached. Best performance was obtained two tanks before EGR was inhibited. Mileage decreased a lot for the tank before last (half with and half without EGR action) and last tank got definetily the poorest mileage of the three.

I don't remember to have seen someone that sustain that EGR removal will improve engine performance, that can exhibit proof of that.

My opinion is, the only way to test if EGR removal has produced an improvement is keeping all other variable unmodified (ceteris paribus) and measure MPG in real time on the same route track, at the same speed, same load, same everything:

Go first with EGR connected, set a fixed speed, calculate the mean MPG over a km. Then come back and do the same in the opposite direction. This way one take out influence of wind and slope.

Then go without EGR connected, forth and back, calculate the means, then the total mean as before.

Only then one can make a valid comparison.

Why? In a whole tank of driving, in my case I drove about 700 km in my normal life. How can I compare fuel economy of one tank with another, if everything has changed? Temp and density of air, road topography, traffic, kind of road surface, people onboard, to mention some, besides EGR?

I would appreciate any documented test of EGR removal.

Thanks in advance.

Oldbeaver

There are a lot of people who say a lot of things, but the truth is that EGR does next to nothing with regard to mileage and absolutely nothing with regard to performance.

The reason that there's little impact on mileage is that a Diesel engine runs with excess air. All EGR does is displace some of the excess. It's true that too much EGR will increase soot formation...that's why newer cars have more advanced electronic controls. The only real downside: even if well regulated, EGR will produce sooty deposits in the intake manifold, which should be cleaned out on long lived engines.

The reason that there's zero impact on performance is that when you drop your foot, EGR is automatically disengaged.

If you want to understand this better. Install a T on the EGR vacuum port, and temporarily plug in a vacuum gauge. As you drive, you will see the EGR control vacuum rising and falling...it's zero at idle, zero when you have your foot into it, and proportional to throttle position in between. The manufacturer designed the controls so that you have as much EGR as possible without excessive soot formation, and none at all where it can't work.

On cars with vacuum operated waste gates, a malfunctioning EGR is detected by the electronic controls, and the waste gate will be locked open. The various components involved don't last forever. When you see gains from removing EGR, it's usually because it was a poorly maintained car to begin with. Everything else is bloviation and hand waving.

Removing EGR on a Diesel motor increases NOx emissions by 4x. It's an irresponsible thing to do, with or without benefits.

What do you mean by "air intake manifold?"

When the EGR is active, the computers on the OM60x turbo engines may reduce boost. While there is no effect on full throttle power, there may be an effect at part throttle. Probably negligible effect on MPG. This assumes the EGR system is working normally and the valve is fully closing with no vacuum applied.

The advantage of a non-clogged intake is debatable, but anyone who has cleaned it once, generally doesn't want to repeat the job.

:shutup:

On my 6.5L Detroit it made a big dif, on my 2.5L not so much

Just checking here… because of this, the tang can only show up at the right stroke of the engine, right?

If it was on the opposite stroke, 14ATDC, the tang would not show because it would be on the opposite side of that flywheel device in the IP, right?

Some folks warn about checking cam lines, the FSM doesn’t. I think that’s because if you’re relatively properly timed, the tang will only be visible on the correct stroke of the two options, right?

And then the second reason why I’m here. I have the IP out and open. I don’t really want massive power, if anything I want similar performance and better economy. But I will take a modest increase in power if viable :)

What’s the best bet when longevity is considered in terms of mods I might consider while the IP is out?

Or is it a bad idea to do anything to a rod bender 3.5L?

https://i.imgur.com/4qr9VWsl.jpg

https://i.imgur.com/KxnwnlZl.jpg

Also the oil residue in the bottom seems thick and nasty, any good way to clean/flush out the IP?

https://i.imgur.com/STpONuGl.jpg

Just to be definite, I think that’s only the 602.96, not the 603, no?

My 602.95 2.5L has the computer interlace and is a prospect for a pressure actuated wastegate.

Maybe the 603.971 in my 93 has a more complex system, I forget.

But does the 603 in the 1987 w124, and the 3.0/3.5L 603 engines in the w126 have a computer based wastegate/boost control?

I thought not and that a bb solves the issue….

Thanks!

Compared to the crankshaft - yes. But it's the camshaft you need to worry about, the cam and IP must be on the same stroke.


See above. You can have the IP and crank correct, but if the cam is 180° out, it will run really, really badly.



Nothing will boost economy significantly, but maxing out the full load adjustment will provide a moderate power gain. Search the forum for a writeup, I think it was posted 10-15 years ago? You don't have to go to the maximum (~1.5 turns on screw 2f) but I'd go at least 0.5 if not 1.0 to see a difference. Lots of other fiddly adjusting required along with this mod, trial & error on the linkage lengths, yadda yadda. The writeup has details. Beyond 1.5 turns, there were reports of the engine not wanting to return to 600rpm idle.



Generally, longevity isn't a big concern, as the 602/603 is pretty robust and the power gain from the full load adjust is only 10-15% or so. That said, if you don't have an EGT gauge, I'd think twice before laying a brick on the throttle for WOT climbing a mountain for several minutes or longer. I didn't see issues with a maxed-out stock IP on a 2.5L or 3.0L engine.


Good question. I don't know if there's any concern about the 3.5 but I assume your engine may already have the good rods, if it's not drinking oil. Personally I wouldn't worry too much if you are only adjusting the full load, with stock 5.5mm elements. You can also increase the rev limit (aka 'high idle') setting, I think the .970 had it abnormally low, while the .971 was closer to 2.5/3.0 specs. (?)



Not that I know of. I wouldn't worry about it, just wipe clean what you can access with it apart.

:stuart:

I believe all 1990-up OM60x had computer-controlled vacuum wastegates, EXCEPT the 603.970 engine, which retained the good old manual pressure control.

That’s right…. Time to find a good bb to insert in there!

Now I’m concerned/confused. The cam turns at half the speed of the crank too, right? Two full rotations of the engine should get the cam back to where it was.

One full rotation of the engine and you won’t see the tang on the IP because it is 180 degrees out. Right?

Reason why I’m concerned is because Inset my engine to 14 degrees, the lock tool wouldn’t go in, so I turned the engine over 360 degrees, twice, to slowly get the tang back in view, and then locked it. Since I turned it over twice I can’t see how the IP and cam could be out of phase.

If I’m not mistaken, you can’t have the engine on the timing marks on the balancer, and the locking tang in the viewing port, without the engine being in the right position. The onky other option is to have the timing marks on the balancer in the right place, but the tang not visible.

I don’t think it can be any other way. Or am I being dense? The engine goes through two rotations, which is four strokes, and then repeats. So two rotations from any point is the same point, same valve/cam positions….?

If everything remains in sync, yes.



I assume you meant 720°, but yes, if rotated 2x and the tang locked, that's fine.



If nothing else was taken apart, yes, everything should be in sync. Still, it does not hurt to double check everything when you are done, before starting the engine.



Yup, but this is assuming everything remained perfectly in sync during the work performed.


:turned:

Yes, 360 degrees twice… 720 in total. Im not sure how anything but the timing device could get out of sync. And even the timing device, given the use of a basket, notionally the timing device stays in time unless I mess with it.

Hopefully I can install the pump tonight. I will turn the engine 720 degrees and verify timing with my tool. Probably will do that two or three times just to let oil get back into the IP, tensioner, and get some fuel moving back through the IP and lines.

Thanks again as always!

Yes that's what I've seen. Max no load RPM on the .970 was set at like 4100 rpm. It's higher on the .971, I don't know offhand what the factory number is.

The 603.970 has totally mechanical boost control. I believe the .971 uses the computer to control the wastegate like the late 5 cylinders. I also think the .971 does not have the vacuum amplifier / boost modulator in line to the transmission pressure modulator like the .970 cars.

-J