PeachParts Mercedes-Benz Forum - got it this time

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- - got it this time - egr bypass 606 turbo (http://www.peachparts.com/shopforum/showthread.php?t=168261)

Quote:

Originally Posted by hobbitss (Post 2282384)

So, what exactly happens when you simulate a Cold Engine???

That is precisely what I am trying to filgure out. Heck, I would be happy with a hint as to where the sensor is. I can modify it from there and SEE what happens...

-Jim

Quote:

Originally Posted by KarTek (Post 2112102)

It's actually a pot. Here's the theory of operation of the EGR operation validation:

The EGR transducer is fed a unique 12v from the k40 relay - hot with ignition. (red/green wire in the picture) The transducer is connected to ECU pin 35 by another wire (green/gray). When the proper conditions are met, the ECU makes pin 35 low to activate the transducer and open the EGR valve.

When the EGR opens, there is a corresponding decrease in the flow of the intake air through the MAF sensor which is read as a voltage drop on the MAF signal feed to ECU pin 21. (yellow/white).

Problem 1: You can't just unplug the transducer because the ECU wants to see a load across the EGR transducer power feed and ECU pin 35 or a code will be set.

Problem 2: You can't just plug the vacuum line going to the EGR valve or plug the EGR feed tube because the ECU won't see the desired effect of the voltage decrease on pin 21 and again, you get a code.

So, to tackle problem 1, I first snipped the ECU pin 35 feed and then simply placed a 1/4 watt, 1k resistor inline between that and the EGR transducer power feed to simulate the load of the transducer. Now, that creates problem 2 because the EGR isn't opening and creating the MAF flow reduction.

To deal with problem 2, I needed to simulate the voltage reduction on ECU pin 21 on cue from ECU pin 35. Conveniently, when pin 35 goes low it makes a great place to shunt off some of the MAF signal voltage. I inserted a variable resistor there to make adjustments and find out exactly how much resistance was required in order to get the desired voltage drop. Now that the circuit has cleared all the codes, all I have to do is measure the resistance at the current setting and then swap in a fixed resistor in place of the variable one.

The reason for the diode is that you have two voltages going to the same pin (ECU 35): The <=12v from the transducer feed and the <=5v signal feed from the MAF. The diode keeps the higher voltage from spilling onto the MAF signal feed and altering it's value.

So that, in a nutshell is how it works.

Update - Here's a preliminary schematic:

http://i3.photobucket.com/albums/y71.../EGRDefeat.jpg

I just picked up a 99 e300 and I am very interested in bypassing the egr. I have some ideas on another method I wanted to bounce off you... clearly you have given this a lot of thought. Between this being my first post and the fact that I have barely begun to look around this site, I'm not sure if the following idea has been brought up before...but here goes anyways;

What about hooking up an electric air/smog pump to the egr instead of the exhaust pipe? If the pump doesn’t have an internal check valve, it would be easy to put an external one on...so boost loss wouldn't be an issue. Getting filtered air to the pump wouldn't be an issue. The entire egr system could function as designed, but with fresh air. The pump would ideally be wired to come on only when the egr valve opens, to avoid having the pump run continuously. The old egr exhaust feed could then be blocked off. Electric air pumps came on a lot of GM vehicles, so getting one for cheap wouldn't be an issue. What do you think?

here's a thread I found on google about a guy using a electric pump for another reason, but has pictures and the guys states the the pump will push 3psi
http://www.modularfords.com/forums/showthread.php?t=131228

Hi, welcome to the group!

As you can see reading through this thread that the idea has been refined to pretty much the nth degree.

A few others along with me, are running one version or another of the electronic mod with success - myself for over a year now. The solution has been reduced to 3 components totaling less than a dollar (probably could be 2 components if you left the EGR modulator in place and capped the vacuum line.

I don't know how much simpler it could be... :)

I've ordered an occiliscope kit and I'll be using it to analyze the circuit to help develop an extension of this mod to remove the MAF as well.

Quote:

Originally Posted by KarTek (Post 2334096)

It's hard to argue your point...the electronic mod is very appealing. I guess my problem with it is that I cant get it out of my head that the MAF doesn't play a bigger role with fuel delivery, air/fuel, etc. You haven't noticed any ill effects from the mod in terms of fuel delivery, overall power, fuel economy, driveability, throttle response, etc?

I went the chip mod route in which they "dialed down" EGR to zero in the firmware flash and it seemed to work fine. I can tell you however that I think most of the problems with EGR come from not driving the car in a "spirited" enough manner as to keep everything clean. When I bought mine in January of '05 I cleaned the intake out and drove it for 3-4 years before removing it again. After about 50K miles it wasn't too bad and didn't need cleaning again and it never gave me any trouble. If you drive like a little old lady you will get more crud in the intake than if you drive it with more pedal. I only elected to dial it down because I was having the chip mod done anyway and it was only a nominal cost option to have it eliminated.

I installed the EGR bypass today

I installed the EGR bypass today, as per Evan and Scott C. It seemed intimidating, once I got into it, it was simple.

About 6 months ago I was getting indications of MAF issues, I changed to the MAF the CDI engines use, this alternate showed good results. My turbo was back and stayed. I made no other changes, so for me the alternate MAF for the CDI (MB part# A6110940048) proved to be a durable solution,… good until the last few weeks. This turbo shutdown issue was coming back, shutting down after a few minutes of driving. After reading a bunch of posts here, I now suspected EGR issues. I could likely clean up the EGR and fix it, but the bypass is much more intriguing. I installed mine as Scott C did; using taps, I just did a test run and all is good for now. I’ll report back with a few more miles on her.

At this point, can I get rid of the EGR valve? If so what to do??? Some new plumbing?

Thanks everyone, this forum rocks!

Quote:

Originally Posted by trapeze (Post 2339434)

I installed the EGR bypass today, as per Evan and Scott C.
I installed mine as Scott C did; using taps, !

Can you explain to me this? couldn't see any reference to it? :confused: Just curious to know if there is a different method.
Got mine like Evan's said, still working well :D
Thank you to the master :bounce:
Olivier

Could you write down what components i need to build this solution and som picture would be nice

thanks // Akraf

Quote:

Originally Posted by Olivier (Post 2339814)

Olivier, I am referencing this whole thread. I suggest you read the whole thing.

The solution I used is from KarTek (Evan) Look at post #102 of this thread. I installed it like scott19_68, (Scott C) using taps instead of soldering it . Look at post #119 of this thread.

Quote:

Originally Posted by Akraf (Post 2340512)

Could you write down what components i need to build this solution and som picture would be nice

thanks // Akraf

Akraf, as I wrote to Olivier, I am referencing this whole thread. I suggest you read the whole thing.

The solution I used is from KarTek (Evan) Look at post #102 of this thread. I installed it like scott19_68, (Scott C) using taps instead of soldering it . Look at post #119 of this thread. The pictures and diagrams I used are at those posts.

Quote:

Originally Posted by trapeze (Post 2340685)

Hi Trapeze,
Thank you for this, I thought it was another way, I could not understand the "tap" thingy.
I didn't solder it either, I free a wee lengh of the wire from the isolation and wrapped the "mod" wire arounf the naked wire then tape it tightly.
All good and still going strong :)
Vroom vroom :D

Quote:

Originally Posted by Olivier (Post 2340701)

Glad you going strong. So far so good for me...

What MAF are you using, original or the one from the CDI engine?

Did you get rid of the EGR pluming?

The MAF I have is the one that came with the car, I guess its the original. There is a thread of someone trying to get rid of it, I would like this too, as if the MAF goes, its expensive...
Is the CDI engine MAF make any difference? Any part numbers on this?
I was going to remove all the EGR but I had a vision of me, sitting in a motionless car on the highway due to a limp mode trigger by the MAF as the EGR was not functioning properly as the MOD failed. For this I left the EGR there. If the MOD fail, I take it off and reconnect the vaccum pipe and off I go :)

Quote:

Originally Posted by Olivier (Post 2340716)

The part number is in my thread above, (MB part# A6110940048) This site has them.

Do a part # search, and search for 6110940048 (remove the “a” from the part number)

The difference for me is this MAF is less prone to send fault codes than my original.

Keep in mind I have a 99 model, may be a different MAF then yours.

Cheers,
I'll stick with mine then. I think we must have the same car if you are in the state as mine is 1997 but it arrived in the states in 1998.
All the best.
Olivier