No need, the fix is very simple. Replace the vacuum actuator on your turbo with a normal pressure actuator. There is a guide to doing this on the forum if you search for it.

Hi Olivier!

I'm a Maxwell and I'd happily help my fellow Scottsman! :) Expect to see some results of this final round of testing in mid March.

Looks like there's a bit of a line forming. Hope I don't let you all down...:eek:

Hello,
THank you , thank you, thank you :huepfenic
This is great news. Middle of march is more then OK, the car as been breathing soot for the last 10 years :sick3: , a bit more will not hurt it.
Can I email you my details if this is OK with you?
All the best.
Olivier

Thanks Forced - I have that fix on one of my 92 300ds and it's working great. I thought this was an easier way to disable the EGR and keep the turbo.

OK, an update: For those keeping score at home...

I'm currently running the EGR mod version 2.0. I'm also looking at a permanent solution as v2.0 uses a mechanical relay which, I found last night, buzzes like crazy when the engine is revved.

This is not good as it will certainly wear out in a matter of months or a very few years. as Mercedes owners we want PERMANENT, long lasting solutions!

Well, here's some hopefull news. I was doing some testing last night and the ultimate setup I believe will also be ultimately simple and best of all CHEAP! The "solid state relay" I have been investigating is turning out to be totally inappropriate for the job however but I'm working on something better...

Stay tuned!

Hurray!
 

Your the best. Well done.
Thank you. :bowrofl:

Heck, if nothing else, solder in a base for the relay. Then you can keep a handful of them in the glove box. Change them as needed. Maybe change it every time you change the oil.

-Jim

Another update:

I just got in from doing a rough, temporary install of the new component. The goal is a single 20 cent part soldered stragically across two of the sensor wires on the ECU.

Alpha testing of v3.0 begins!

Latest update: I'm up to version 3.2 now after some failures and limited success. Since I don't have any scanning equipment, every time I set a code, I have to let it time out and that takes quite a while. I ordered a Scangauge II today so hopefully, that will help things out. If nothing else, it'll be fun to play with... :) Compounding problems is that my thermostat is hosed up and the engine won't reach operating temp. So the codes don't easily clear themselves... :(

Here's a picture of my current setup:

http://i3.photobucket.com/albums/y71...s/IMG_3707.jpg

It ain't too pretty right now but it's functional... :D We'll see what tomorrow brings.

Success! Codes cleared themselves this morning! So, ahead is some more component testing and then I'll post the final results and a schematic.

Looks like a diode, a potentiometer, and a resistor. Or is the blue thing a tunable inductor? Some kind of resonant circuit?

-Jim

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

Thank you for all the updates, great work. :)

Super Job Evan! I look forward to the finished product.

Here is a question. Anyway to eliminate the MAF entirely and have the car use the MAP? The fuel delivery is probably most determined by the MAP and TPS anyway.

In the 80's the camaro and firebird tuned port injection systems first used a maf system and then used a map system only. There was also a kit to take the existing older maf system and convert it to the map system.

I figured if it was possible, you would be the man for the job Evan!

If the maf could be deleted somehow, bypassing the egr would probably go with the program. Or maybe there is a way to delete the maf and bypass the egr all in one configuration.

Do you think it is possible Evan?

I have only had one problem with the MAF. Replacement proceeded and still there was a problem because I was using the El-Cheapo suggestion that didn't work well with a programmed PCM. Changed that to the recommended one and life is good again. I'm sure that if you totally reprogrammed the tables you could do it but would the effort be worth the cost?

We had a 89 Merkur XR4Ti that we switched to MAF from Vane Air but even that was a little bit problematic sometimes. Was it worth it? Yes because Vane Air was causing more resistance and the spool up was quicker with MAF. In this case, I don't think it is worth the effort.