Lancelot

EGR = Exhaust Gas Recirculation. The EGR-valve lets exhaust gases into the intake when not under full throttle, this gives a less oxygen rich mixture and a lower burn temperature (flash above the piston) to control NoX output. However it also causes more soot and more damp exhaust gases. Since a portion of this is going back into the intake everything can get very clogged up with soot and sludge on our older cars. Often the EGR-valve gets stuck in half open condition, causing exhaust gases getting sucked into the inlet even when under full throttle. I've been reading up on the possibility of disabling this to prevent future problems. It can be done on our older diesel (non-CDI) engines.

This week I went to the dealer and as it turns out there's an original MB coverplate to close the EGR valve! "cuz these engines have also been available without EGR", lol!

Did the project today and what a difference! The engine is much more responsive and runs quieter. I've been driving around in the afternoon, city traffic and stepped on it on the highway upto 160km/h (100mph). The car pulls better and feels smoother, and no EPC warning!!!

Here's a pictorial. I guess it's the same procedure on a 300 Diesel OM606 non-turbo engine it's the same block just with two more cylinders. On turbo's I'm not sure cuz these have a metal inlet header and I think the EGR is routed different...

The parts: (coverplate and two gaskets on each side)


Thick layer of soot buildup inside the throttlehousing:


Soot on the throttle itself:


Throttlehousing cleaned up:


Coverplate installed between EGR-valve and throttlehousing:


Everything still looks OEM:


Soot buildup in engine inlet channels:


Inlet channels (and also header-innards) cleaned:

texholdem

Can the same be done for gas engine?

Thanks!

Lancelot

I really don't know but I tend towards 'no'. Why? On my Diesel the only thing measured is inlet mass airflow, then the throttlevalve and EGRvalve are controlled by vacuum hoses. The ECU simply applies vacuum to the EGR at certain engine-load conditions, nothing is measured anyfurther. With a petrol (gas) engine there's a lambda (oxygen) sensor and I think other things that might trigger a limp-home-mode especially on newer cars. i.e. A "Euro-4 or 5 emmission norm" CDI diesel goes into limp mode if you close the EGR. The EGR valves on these models also have an electronic connection so the ECU can actually 'see' if the valve is opening etc.

Semikolon

the OM611/612/613 - 220/270/320CDI does not have any electronics on the valve. only a vacuum line. But it still goes into limp mode if I disconnect the vacuum or blind the exhaust...

Does anybody know what electronics are on these engines that may cause this? I'm willing to do almost whatever it takes to get rid of this ****. It's screwing up my engine really bad!

Lancelot

On Dutch forums I've read about chiptuning for the CDI engines. A tuner can remap the ECU, telling it to open the EGR very very late, effectively preventing an error/limp mode.

Semikolon

oh, ok. Maybe I'll ask my mechanic if the company he buys his tuning software from is able to do something with this

a good excuse to get the engine chiptuned too can't really afford it, but I may be able to kick up something

TMAllison

This post explains how to fool the ECU with the EGR blocked on the 606.962 engine.

Would prob work on the gassers too.

Start at the back and follow "Kartek's" more recent posts.

http://www.mercedesshop.com/shopforu...d.php?t=168261

Semikolon

this looks really interesting. I don't see any reason why it shouldn't work on the 611.961...

Lancelot

@Semikolon:

I see a big reason why it would NOT work on your engine. The linked article is about an earlier OM606 Turbo Diesel engine. This engine still has a mechanical injection pump with some electronic control (like my engine). Yours is a CDI engine, a totally new generation, these have fully electronically controlled direct injection and if I'm not mistaken even a engine-knock-sensor and stuff. You do not want to start snipping wires based on a tale about an older engine. Your wiring is probably totally different to begin with! I would look into the chiptuning thingy, or maybe you can find a 'powerbox'. Those are widely used on TDI/CDI/HDI etc. engines...

Below some pics of a late W210 220CDI Amterdam taxi. The engine looks pristine until they remove the EGR.
- and they say this is better for the environment than NoX output - *cough*

Semikolon

that's how my intake was after 230 000km...

I would think it would work to emulate an EGR-opening with a voltage drop on the MAF, but what do I know?


I had a plan to create a second inlet parallel with the MAF to open when the EGR is supposed to open. Don't know if this will work...

Lancelot

You dunno if the MAF is hooked-up the same on a CDI, but you can always try. I guess a second inlet will not work because the voltage-drop on the MAF seems to be created by a low-oxigen rich volume. (the exhaust fumes mixed with the intake air)

Anyways after two days of driving around, I keep noticing the following:

Even after a cold start the engine is more responsive. (used to be sloooow until warm)

When driving at a steady city traffic speed (like 50-60km/h) I always noticed a slight rpm variation, this is now gone.

I haven't seen the ABS-ASR-BAS error that's been plaguing me for so long now, the engine fires instantly after preglow. Maybe the alternator is now immediatly suplying the correct Voltage?! I'm sceptical about this, maybe I'll start believing in it after a few weeks without the warning showing.

Semikolon

Isn't the voltage drop caused by reduced airflow through the MAF? Or are there sensors INSIDE the engine?

Lancelot

I think we're all just guessing here Semikolon. If you scroll upwards you see a throttlevalve in my pics. On my inlaws' C250 TurboDiesel I've noticed that part is just a hollow tube, NO valve inside it!? The EGR is positioned the same; exhaust gases are fed into the intake BEHIND/AFTER the MAF so I don't know exactly what change the MAF is sensing with the EGR valve opened...

Semikolon

what the hell.. got my car chiptuned today and hopefully the egr mapped away.. have to test it for some days though..

The guy who changes the software confirmed to my mechanic that the egr could be mapped away. But he couldn't guarantee that it would really work the way I wanted it to. But at least the car runs better But there is actually less black smoke I think...

michakaveli

Lancelot, our NA OM605/6 engines do not have a MAF. The sensor in front of the EGR assembly is I believe, a temperature sensor. Nice find on that blocking plate. Can you post the part numbers? Up until now I've disconnected the inlet tube leading to the EGR, rotated it 180 degrees so that the short bent is closer to the EGR assembly and the longer portion is aimed toward the firewall and I have attached a breather filter to it. Your method makes it nice and clean, and it's OEM! Nice find.....

Lancelot

blocking plate: A 603 142 00 91
gasket: A 604 142 05 80 (used two of these, one on each side of the blocking plate)

Good luck and post results here!

michakaveli

Thank You!!!

now, what bolts did you use as the OEM's I would think are a bit too short? Yours are shiny and new looking

michakaveli

There is a member on MercedesShop.com that has created such an item....

Start reading here... this works on a non-CDI OM606.962 got it this time - egr bypass 606 turbo

Semikolon

That is what we was discussing starting from post 7.... And I concluded I don't want to start with it. The wiring is probably different..

Anyways, my problem is solved, EGR is mapped completely away in the ECU

Lancelot

I just got 5mm longer galvanized bolts and matching washers with a metric 13mm head. The OEM 'ouside'-torx heads were a b!tch to remove in the first place!

Semikolon

The results of disabling the EGR-valve is just amazing! The engine runs MUCH smoother in ALL conditions now a week after disabling it (and a week with "cleaning" with a heavy pedal foot ). I had my intake cleaned about 12-15 000 kms ago, so it didn't require very much to get rid of just enough dirt to make the ride smooth again

Before the engine was a bit unstable on idle, now it's usually not a sign of unstability, only when I start it cold, there are some rev variations for a few seconds. It now shakes much less than before when stopping the engine, and braking down to a full stop is much smoother

It's simply amazing! I can recommend this to everyone!

Lancelot

I've been getting PM's from peeps wanting to know the part# for the blockingplate (which is posted above, people READ!) but since this isn't a US spec part it might be easier to get a gasket and use it as a template to cut and drill your own blocking plate...

Lancelot

I found out why the turbo-diesels and CDI engines go into limp mode when disconnecting the vacuum to- or disabling the EGR valve.

The ECU performs the following check to see if EGR is functioning:

Whenever the warm engine is idle for more then 10 seconds, the ECU closes both the throttle- and EGR-valve for 2 seconds. As you can see in my pics above the throttlevalve has a straight edge so some air can always pass. After these two seconds the ECU opens ONLY the EGR and looks for a pressure drop (of only a few milliBARs) on the MAF. Since the MAF is located BEFORE the throttlevalve and the EGR BEHIND the throttlevalve, the suction past the closed throttlevalve should lower slightly when the EGR opens (sucking in exhaust gases now) If on two consecutive trips this test is failed the EPC warning is triggered and the car goes into limp-home-mode.

On non-turbo diesels (my OM604 220D and the OM606 300D) there's no MAF! It looks like a MAF but is actually an inlet-air-temperature sensor. This is why we can get away with closing the EGR on these engines...

Semikolon

So then it should be able to emulate an EGR opening on the CDI engine the same way as on the regular DT engines.. Just have to find the right wires

torehol

Hello from Norway
Had that cold start unstability on my 220d-96.
I just disconnected the vacuumtube connected to the EGR "controller".
The engine is now running smothly in all conditions.
(I blocked the vacuum tube with a screw)

Good Luck from Torehol