got it this time - egr bypass 606 turbo - Page 3 - PeachParts Mercedes-Benz Forum

husk · #31 11-29-2007, 01:14 PM

cutting wires at the ECU and MAF are kind of scary, I can't wait to get some pictures I have noticed some oily gobbily goop leaking out of my EGR, so gettign rid of it would be great.

aklim · #32 11-29-2007, 01:20 PM

I would be interested if you have a kit for my 606?

mdisav · #33 11-29-2007, 06:35 PM

It is easy to snip the wire and solder it back if you want without complications.

I have to get the camera from my girlfriends brother because she is away. I should have it by the weekend.

scott19_68 · #34 03-05-2008, 02:49 PM

Quote:

Step 5 : Hook top (com) terminal to wire to maf, hook middle (NC) terminal to diode, hook bottom (NO) terminal to other end of diode which also has the wire to the computer hooked to it. Just make sure the diode flow is going from NC terminal to NO terminal.

I'm confused - I would think that normally open (NO) terminal would be connected to the diode anode and the NC terminal is connected to the cathode and the computer. This way when the sensor switches, the current flows out the NO terminal through the diode thus producing the voltage drop.

mdisav · #35 03-05-2008, 10:01 PM

I know it is kind of confusing getting it all straight in the mind as it was for me. But I think once the vacuum switch switches, the flow is out the NC creating the voltage drop. When it is not switching it flows out the NO giving a normal voltage reading.

How many people have tried this so far with success? I believe Joe has but I am not sure?? Anyone else?

Having the switch set to the proper vacuum setting is the key!

scott19_68 · #36 03-06-2008, 02:03 PM

I think I might give it a try as it sounds fairly simple. I like the thought of having my engine running on clean & cool boost - not to mention the elimination of caked soot in the intake manifold and cylinder heads. If it has the potential for reducing the probability of snapping a glow plug it's already worth the effort to me!

I like the idea of using a diode to reproduce the MAF voltage drop. I wonder if the 0.7V drop of a silicon diode is too high and requires getting the vacuum setting just right for no CEL - is the current too high for a germanium diode? Also, have you considered tapping the EGR transducer signal and do it 'pure electronically'? Not sure of the characteristics of these transducers but I'm up to experimenting...

mdisav · #37 03-06-2008, 03:33 PM

I think .7 volt would work. If not just use the one I recommend. Tapping into the tranducer is out of the question. It is the signal the computer receives from the maf that is important. The tranducer just receives input from the computer and lets the computer know it is plugged in.

scott19_68 · #38 03-06-2008, 04:42 PM

I think you are misunderstanding my response - I am suggesting that using the vacuum as an indicator to fool the MAF with a diode might also be accomplished purely with electrical modifications. Instead of the path 'electrical signal to EGR transducer to AirTrol vacuum sensor to diode inline with MAF', just do 'electrical signal to diode inline with MAF'.

I think I'll perform some experiments with the signals to the EGR transducer to see how the signal behaves. Once I get that info I should have enough information to draw up a circuit that should provide the same behavior on the MAF as your vacuum sensing setup. Customizing the K40 with an EGR on/off switch would be sweet.

mdisav · #39 03-06-2008, 04:55 PM

I see what you are saying. You probably would have to use an electrical switch or relay. I am not sure how may volts output is at the tranducers but it is worth checking out.

I would think that would have been the easier route in the first place too.

scott19_68 · #40 03-06-2008, 09:07 PM

Quote:

I would think that would have been the easier route in the first place too

After looking at the schematics I'm not sure it is going to be easier. Mapping the relationship between the EGR transducer signal and the MAF voltage should not be too bad.

I did learn more about the EGR mapping:

The exhaust gases are recirculated in line with the map stored in the IFI control module (N3/7) as soon as the following criteria are met:

* Coolant temperature between 60 °C and 110 °C
* Battery voltage 11 - 14 V
* Engine speed < 3000 rpm
* Fuel rack travel < 9 mm

I had it backwards - your posted circuit makes sense now.

KarTek · #41 08-13-2008, 08:15 AM

Quote:

Originally Posted by scott19_68

After looking at the schematics I'm not sure it is going to be easier. Mapping the relationship between the EGR transducer signal and the MAF voltage should not be too bad.

I did learn more about the EGR mapping:

The exhaust gases are recirculated in line with the map stored in the IFI control module (N3/7) as soon as the following criteria are met:

* Coolant temperature between 60 °C and 110 °C
* Battery voltage 11 - 14 V
* Engine speed < 3000 rpm
* Fuel rack travel < 9 mm

I had it backwards - your posted circuit makes sense now.

I did some investigating on this last night and I found a couple things:

1. I located the wires in the box and I'll post a picture tonight or tomorrow night.

2. While monitoring the vacuum signal to the EGR, I noticed that it went away after the car warmed up and never activated again. This seems to represent a very small portion of time when the EGR is actually active.

3. The voltage drop/rise seems to be about 4/10 of a volt depending on where it's measured to. It was getting dark when I was doing this so I'll have to come up with better numbers later.

I think I'm going to pursue the use of a relay that puts the diode inline with the signal wire every time it gets energized by power from the EGR actuator/modulator.

If no one has a firm reason why this won't work, I may try it.

mdisav · #42 08-13-2008, 03:27 PM

I am not sure if the relay thing will work. In theory it sounds fine and it takes the vacuum circuit out of it and makes it more direct. I guess the best thing to do is try it.

I do know for certain that the egr is active when the car is fully warmed up.

KarTek · #43 08-13-2008, 09:50 PM

OK, I messed around with it this evening and came up with some more information.

After I got home, I checked the vacuum signal from the EGR solenoid and it is now functioning with the engine warmed up. When I pulled the electrical connector to test it, the computer instantly set a code. Whsn I re-connected the solenoid, it did not resume working so I figure what messed up my readings the other night was the fact that I had turned on the ignition with the MAF unhooked which set another code.

The EGR circuit never functioned again properly until the code cleared today.

The impedence of the EGR solenoid is 14 ohms. One thing I'm afraid of is that it is controlled by pulsed voltage which won't work for the relay. I'll give it a shot anyway but I may have to get an impedence matching resistor to make the relay mimick the EGR solenoid.

Here's a couple shots of the computer box with the MAF wires identified:

Overall shot. Notice the little yellow flags in the upper left and lower right corners. There are four of them.

Here's a closeup of the computer harness with three of the four flags visible.

KarTek · #44 08-14-2008, 02:21 PM

Just an update,

I went out today and picked up the conponents at RS then breadboarded them into the correct circuit. I'll see if the ECU rejects the relay as a replacement for the EGR modulator this evening. If not, I'll move on to test the relay's action for the MAF.

Here's the circuit:

KarTek · #45 08-15-2008, 08:43 AM

Another update:

I soldered the whole thing in place yesterday and I'm having a couple unrelated issues that may be effecting performance and tainting my test results.

1. After testing to see if substituting the relay for the EGR control would set a code, the vacuum line fell off of the wastegate controller setting another code.

2. I also got a "brake wear" indicator.

Right now, the ECU is allowing no or very little boost and when the throttle is floored, RPM's will climb to 4500 and stay there with the tranny seemingly stuck in that gear.

Will the CEL being on cause this condition and will it correct itself when the light goes out. Or, is there still some un-resolved code?

OK, on edit:

It's all better now... I left a vacuum hose off. DOH!