T1N EGR bypass mod

T1N EGR bypass mod - Bye Bye EGR!!

First off, I do not take credit for this mod. It was developed by Alex Crow an MB tech from UK.
His original thread is here:
http://forums.mercedesclub.org.uk/showthread.php?t=88374

I built a copy of the circuit that Alex designed and I copied the layout of Ben Tan (mercuxio), whose circuit is pictured in that thread.

This mod does not physically remove the EGR (though you could if you have the machine skills to make the pipe and block off).

This mod allows you to unplug your EGR (which will remain closed when off) and trick the MAF and ECU into believing that it is still plugged in and working.
If you want to make a block off plate for the EGR you may (for example if your EGR is broken and stuck open, or if you are of the opinion that at WOT vacuum will pull the EGR open or something) but I do not think it is needed.

Also, I have only tried this on my 03 OM612 engine. I suspect that it will also work on the 04-06 T1N OM647 engine, but the ECU pinouts may be different so you'll have to give it a try.
It appears to work on many MB diesel engines as evidenced in Alex Crow's thread. It may even work on NCV3, but I do not know.

This circuit supplies the ECU with the voltages that it expects to see with a working EGR.
When the key is turned to the on position, the ECU looks for proper voltages to ensure that the EGR is connected.
Then while the engine is running, the MAF sensor is monitored for changes in flow corresponding to an open or closed EGR valve.

Here is a diagram of the circuit as drawn by Alex Crow:

PWM is the pulse modulated signal wire for the EGR
MAF is the signal wire from the MAF

Here is a picture of the circuit made by Ben Tan:


Attached is a picture of my build. In the next post I will detail how I made the circuit and where it attached in the OM612 engine.
You may notice in my build that the transistor is reversed.
That is because I used an equivalent to the BC337 that has a reversed pin out (2N2222).
Additionally, I used a 1.8K & 1K resistors in parallel to achieve the 647 Ohm listed in the diagram (as suggested by Alex Crow)
The diode used is 1N4004 - Radio Shack part #276-1103
(Thanks to Dieselman here: http://forums.mercedesclub.org.uk/showthread.php?t=68928 )

PS- I apologize for the massive size of the pictures. I don;t know how to re-size them in line.

So, after building the circuit, I connected it to the ECU, and unplugged the EGR cable at the EGR.
All 4 wires are piggybacked to wires at the ECU, connected with wire taps.
This means that you do not have to cut any wires for this mod.
You can cut out the mod and reconnect the EGR if you wish at a later date.
If you want the EGR cable plugged in (so as to appear untampered with), but EGR disconnected and bypassed, you can clip the EGR cable somewhere that will not be easily visible.

In my build Red goes to 12v switched. You can use any 12v switched source.
(I connected it to Yellow/Red wire at Pin 33 on the ECU C3 connector, which is the MAF 12v supply and uses the same fuse as the EGR 12v supply -which I could not find).

Green goes to EGR Valve control - Red/Yellow wire at pin 40 on the ECU C4 connector.
Be careful here as the ECU C4 connector has at least 1 other red/yellow wire at pin 18 = Engine oil sensor 5v.
My ECU C4 connector also had another red/yellow wire at pin 1. No idea what that one is as it isn't listed in my chart.

Yellow goes to MAF Sensor Signal - Yellow/Dark Green wire at pin 18 on the ECU C3 connector.

Brown goes to EGR Sensor ground - Brown/ Black wire at pin 17 on ECU C4 connector.

I have attached the pinouts below.

Remember that you want to leave the EGR cable unplugged at the EGR. Probably best to tape it closed (and the EGR connection too) to keep dirt and water out.

Reserved for more if needed

Great work Al!!
I made a PDF file out of your first post in case someone wants to print it out. Hope you don't mind!

Colorado Al's EGR mod (updated)

Thanks. But the real work was done by Alex Crow and Ben Tan. I just followed their instructions.
I think this mod will easily work in the 04-06 OM647 engine. Alex Crow says he developed it on a MB W211 with CDI3 electronic EGR valve and 648 (IL6 320 cdi) engine.

I am curious as to if this will work on an NCV3 too.

Edit- I just checked and it appears that the OM647 has the same ECU pinouts and color codes.

PS-
I have enough parts to make 1 more. If someone would like it, PM me and we can work it out.

This looks like something I should have in my tool kit so I can trouble shoot LHM. It would tell me if I had a bad egr by tricking the computer It would be nice if you had a modular plug on it and it could be connected instead of the egr.

Dan

Check your EGR vac transducer for leakage. Mine still allowed some vac through to the valve even when disconnected. So I shoved a small ball bearing up the pipe, just like in the old days.

Also, whats the story with having the transistor? On my ML270 (OM612) I just did the simple circuit like DieselMan posted http://forums.mercedesclub.org.uk/showthread.php?t=68928 and its been working fine for ages now.
EDIT: wait I see it now, my ML is on CDI2, yours is CDI3 with electric EGR so your circuit is different.

Colorado_Al said:

PS-
I have enough parts to make 1 more. If someone would like it, PM me and we can work it out.

Click to expand...

Just making sure, this is for troubleshooting? This to for bypassing the emissions? If it's the latter, what advantages have you seen?

-Randy

The main advantage is that the EGR on OM612 engines is prone to failure and causes limp mode.
This is a known defect and MB does not stand behind the ($900) failed part.
If your EGR has failed you can make sure it is closed/install a block off, install this mod, clear your ECU codes, and away you go.
Side effects of EGR removal are no soot in intake, no further buildup of sludge in your intake manifold and beyond, less smoke from the tailpipe,
supposedly better mileage and acceleration (not sure how that is possible to have both), and unfortunately higher NOx emissions.

owner said:

Check your EGR vac transducer for leakage. Mine still allowed some vac through to the valve even when disconnected. So I shoved a small ball bearing up the pipe, just like in the old days.

Also, whats the story with having the transistor? On my ML270 (OM612) I just did the simple circuit like DieselMan posted http://forums.mercedesclub.org.uk/showthread.php?t=68928 and its been working fine for ages now.
EDIT: wait I see it now, my ML is on CDI2, yours is CDI3 with electric EGR so your circuit is different.

Click to expand...

Right. The CDI3 checks for proper voltages at power on. CDI2 does not.

Side effects of EGR removal are no soot in intake, no further buildup of sludge in your intake manifold and beyond, less smoke from the tailpipe,
supposedly better mileage and acceleration (not sure how that is possible to have both), and unfortunately higher NOx emissions.

Click to expand...

..and higher coolant temperature...

The EGR's job is to partially fill your cylinders with oxygen-poor air. That limits the amount of "real" air/oxygen, which in turn means you're not going to be burning as much fuel per cylinder load.
Remove the EGR effect, and each cylinder load gets more oxygen, which means it can burn more fuel per load.
More fuel burned means higher power per bang (hence the acceleration boost), with the concomitant rise in cylinder temperature (hence more NOx) and the increased transfer of excess heat to the coolant (higher water temperatures).
I'd suspect that the chance of "better mileage" is due, in part, to the fact you're no longer wasting power pumping a volume of up to 40% of the displacement of "useless" pre-burned exhaust gas in and out of the cylinders... everything that goes through now provides power. i think there's an efficiency boost by dint of the higher temperatures, too.

--dick (an example of EGR if there ever was one)
p.s. what i want to learn is how Colorado_Al got a picture wider than 900 pixels into his posting.... i'm jealous

Thanks for the explanation. As a WVO burner, hotter cylinder temps and hotter water temps are actually beneficial.
Also the idea that there is more fuel burned per cycle without exhaust gas leads me to believe that unburnt fuel was exiting with the exhaust. Now it is getting burned and providing power instead of being wasted. Hence more power and better mileage.

autostaretx said:

p.s. what i want to learn is how Colorado_Al got a picture wider than 900 pixels into his posting

Click to expand...

The pictures that are bigger than 900p are linked from another website by using the insert image button while posting.

Hi Colorado_Al, congratulations for your success

If you want to keep the EGR connected with its own connector, you can add a switch and (if you want more) a LED to know which one is active (EGR or simulator); you can see the scheme with some images here: http://www.mbfaq.com/viewtopic.php?f=36&t=188820&start=45 (sorry but text it's in Spanish language... ).

The simulator base is, as your, from Alex Crow
The main difference it is that you need to cut (only) 1 wire (PWM) in ECU box (as other connections).

I have installed it in an OM648 (E320CDI) and OM647 (E270CDI) and the results are very good (as we explain in the previous link).

With the simulator active, the heating system begins to increase its temperature later because you have the EGR closed and the heating system only receive temperature from the engine and not from the 'heat intercheanging' piece after EGR valve. The 'inconvenient' is only during 2-3 minutes after turn in the engine... after that, you can't feel differences in ambient temperature.

Sorry if my English it's close to 'Spainglish'...

BR

grinich said:

The main difference it is that you need to cut (only) 1 wire (PWM) in ECU box (as other connections)

Click to expand...

I see. Thanks!
So you install a switch on the ECU that can toggle between the bypass circuit and the EGR Valve control, and toggles the Sensor ground as well? and leave the EGR cable plugged in?
Is it possible to just toggle the EGR valve control wire if you do not want an LED indicator?
Sounds great!
Thanks!

Colorado_Al said:

I see. Thanks!
So you install a switch on the ECU that can toggle between the bypass circuit and the EGR Valve control, and toggles the Sensor ground as well? and leave the EGR cable plugged in?
Is it possible to just toggle the EGR valve control wire if you do not want an LED indicator?
Sounds great!
Thanks!

Click to expand...

Yes it is possible; in fact, it is real (my brother's car and mine are running with this simulator). The LED it is only if you want know if the simulator is active or the EGR is (we have: if LED is on, the simulator is active). But, if you don't want it, the LED its only to confirm the visual aspect of the switch, it is not compulsory if you remember what means the position up/down of the switch ... Allways the EGR connector it is plugged in; the switch cut the ground wire to EGR valve.



PS I'm in mercedes forum UK too... where you just posted about "someone called grinich"...

Thanks!

Colorado_Al said:

Thanks for the explanation. As a WVO burner, hotter cylinder temps and hotter water temps are actually beneficial.
Also the idea that there is more fuel burned per cycle without exhaust gas leads me to believe that unburnt fuel was exiting with the exhaust. Now it is getting burned and providing power instead of being wasted. Hence more power and better mileage.


The pictures that are bigger than 900p are linked from another website by using the insert image button while posting.

Click to expand...

Have you felt any difference in power? I would like to see the fuel mileage results as well in a couple of weeks?

flman said:

Have you felt any difference in power?

Click to expand...

Hard to tell. Before 2 days ago I had been driving in limp home mode (low boost, RPM below 3500) since the EGR was malfunctioning. I actually repaired the EGR malfunction (wire short open circuit) but then implemented this baypass. I will say that with the bypass installed it drives just like it should but no idea if it has more power than with functioning EGR. Theoretically it should but I think you'd have to dyno test to actually see it.

flman said:

I would like to see the fuel mileage results as well in a couple of weeks?

Click to expand...

Since I drive primarily on WVO, I don't do hand calculations of fuel mileage since I don't have a good way to measure actual fuel used. I use a Scangauge II which does a fair job of estimating the fuel mileage. I will let you know if I see any change.

Al, great work on bringing this mod to T1N owners. I'm sure this is going to help a lot of T1N owners who are suffering from EGR issues.