How to increase performance, air intake, turbo for $1. Disable EGR Mod. Observations

mercedesfan1983

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Ml270 CDI W163 2002 OM612
Hello All

I've had a Ml270 CDI W163 now for about a year. Love it. Stumbled across some forums suggesting EGR disable and looked into it. Actually my engine was leaking a bit of oil so I started cleaning the engine bay, tinkering and prodding.

Turns out the EGR Valve has quite a bit of oil in there and a loose compression fitting at the inlet manifold/exhaust junction/EGR Valve cooler.

I succeeded with the EGR mod with a few resistors and a diode. The difference is night and day! The SUV is a whole new beast now!

I did not figure this out, the original credits go to dieselman and soup nazi for posting. I am merely re posting with my experience, pictures and a different perspective in laymans terms for rookies and veterans alike to understand and apply the mod.

Parts Needed:

1x 1K Ohm Resistor (1000 Ohm), 0.25W, ¼W
1x 470 Ohm Resistor (or 2x 1K Ohm Resistors in parallel)
1x IN4004 Diode. 1 Amps Rated or Above.

Total cost for parts = around $1. Now actually when buying resistors anywhere they are so low cost they come in packs of 8 or 20 or whatever. So I actually just used two 1K Ohm resistors and tied them together in parallel to drop resistance to 500 Ohm. No need to buy separate 470 Ohm resistors – seems to be running fine.

Also I suppose any Diode above 1A can be used. I used a 3A Diode because had some laying around. It seems the bigger current rating, the bigger the diode, so I guess the 1A is around 1.5mm diameter. My 3A diode is around 4-5mm diameter. They are so common, perhaps you have a spare circuit somewhere that you can just clip off a diode from there.

We will be using a Voltage Divider Circuit to drop the Volts on the MAF signal Rail when the EGR Vacuum Transducer Signal Rail activates.

How To:

Locate the EGR Vacuum Transducer. With the two wire electrical connection, unclip the pin and pull that plug out. That's right pull that baby out till it pops. Go do it now!

Open up the black covers to reveal the ECU. Have a look at the grey plugs from left to right. Unplug the first squarish grey socket.

There is now a bank of three large plugs with each having a vertical grey latch. Press the black pins holding the grey latch and pull grey latch to the left all the way down, it should click and the large black plug should slightly pop up. Don't try to pull the black plug off, if it's stuck it means the grey latch has not been fully pressed down. :)

Curveball: The three large 'plugs' are actually just housings...each housing has two plugs! Have a close look and you'll see you can unclip the housing to reveal two long rectangular plugs. There are numbers on the ECU metal pins and on the bottom of the plugs.

We need the following pins:

MAF: Plug 2 Pin 24 Yellow/white stripe
EGR Negative: Plug 3 Pin 50 Grey with black stripe
EGR Positive: Plug 3 Pin 37 Red with Grey stripe

Curveball: at the MAF sensor the yellow/white may look like brown/white due to oil and dirt discoloring it! Mine had a bit of oil dirt in there!

With a razor knife gently cut into the insulation of wires but do not cut the wires. Pull away insulation around 1-2mm to expose the copper and attach the resistors and diode by pinching and tightly winding it around the signal wires.

Pay attention to the silver stripe on the diode. A diode acts as a one-way valve. This is the Cathode (negative) side and prevents the 12V Red/Black flowing into the 4V MAF Yellow/white Signal Rail.

Coincidentally the Grey/Black wire matches with the side of the diode's silver stripe....

My method is a Jerry Rigged version. You can't get any more crude than this! I did not yet solder them together they are just wound around the signal wires. Electronics professionals would probably scorn me for this! Don't blame me I'm South African! You can see the Grey/Black signal wire are winded up. I accidentally cut it while pinching the diode onto it.

Disclaimer: It's probably recommended to properly solder the wires or use proper connectors that pierce insulation to piggyback of the main wires.

All done. Replace plugs and black cover. Make sure the cover lines up properly, push and wiggle all the bolts into the holes first before starting to screw any of them in.

My Observations from driving without the EGR:

Substantially more power/torque, even at lower RPM.
Much more power/torque 'pull' from about 1200 RPM
Turbo audible from about 1400 RPM. Probably normal with/without EGR.
Increased Headlight Brightness. This is strange enough and unexpected. Although I have had dim headlights since getting the vehicle and thought I might need to replace globes. It just wasn't bright enough but now much brighter.
Fuel consumption city/freeway about the same based on the trip computer. Only been driving a couple days, should probably take it for a long freeway drive as well.

Admittedly I also adjusted the idle speed at the throttle unit (next to EGR Vacuum Transducer) with the plastic threaded bolt. This seems to also improve power/torque availability towards lower RPM when idle is set close to 900 – 1000 RPM and gives more power/response at slow speeds such as around roundabouts and stop-start corners. I just temporarily increased the idle speed to try and solve a cold idle that is up and down. Yes I've got the infamous up and down cold idle for 30 seconds or so (Long before the EGR Mod though and this resulted in further research).

Still, without higher idle speed there is a substantial improvement in drivability without EGR!

I suspect my engine needs a good service as well. Only had it for a year. Probably needs an alternator or tensioner pulley eventually.
 

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Craiglxviii

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970 Panamera Turbo; W221 S500L AMG Line, C215 CL500, W251 R350L AMG Line, plus several more now gone
Already posted on in much detail in the DIY forum.
 

umblecumbuz

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S204 and CLC 204 cdi, MX5, Kia Soul
Biggest thread on the forum - been going for years now.
Check it out.

Clear diagram you've posted here though.

Umble.
 

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