MBenz- How did you disconnect this sensor? Did you unplug the electrical connection or what. I ran the vacuum line from the intake to the injection pump, completely bypassing the sensor, without any luck. I was told that this sensor cuts fuel if boost goes too high as a protection for the engine. I still think without EGR that the computer cuts boost also, as I do not hear the turbo whine.

I think Vhunter has the right idea but I don't know if I am ready to try that yet. MAF is the culprit. I don't know if the MAF has other functions other than EGR tattletale - could mess up other stuff doing the diode thing. I have not checked to see how many wires even go the the MAF.

The MAF information would be used by the ECU to determine how much fuel can be injected at any time, while keeping smoke and emissions to acceptable levels. With light loads, the O2 content in the cyl. is to great, and the fuel burns to fast and hot, giving a greater amount of NOX. While less air causes NOX production to go down, the soot generated increases. The engine control unit will attempt to balance things so that both soot and NOX are at a minimum. It does this by reducing the O2 content by recirculation of O2 deficient exhaust gasses, to keep flame temps down, and thus the NOX produced down. IF more power is required, then more air is needed and EGR amount is reduced, and the turbo pressure is increased to feed in more O2 rich air.

Like I have said before, this is how the VW TDI engines control emissions. It seems logical to think that the new MB diesels would be using the same control systems, but again, without more info on the MB engines, I am just guessing. Some of the more knowledgeable in this group might chime in on this subject for this "newbie". I hope to find out more on the electronic control systems of MB soon.

__________________
1985 300D - 190K Miles - 26 MPG on first trip home - getting rust fixed and repainted.
1987 MB 300 SDL - 238K miles - Sold
2003 DC Ram 2500 QuadCab 6 speed, 4x4 Cummins - 82K miles - 20+ MPG
1999 VW A4 Jetta TDI 5 speed - 83K miles - 50+ MPG is easy!

oldsouth,

My car has a very primitive EGR system and was bypassed very easy. I know that the systems on the turbo diesels are more complex.
I will take some pictures this week and mail them to you, so you can see what I have done and you can try what the effect on your turbo diesel will be.
I just disconnected the wire that goes to the sensor that is vacuum-line-attached to the air intake pipes and I disconnected the vacuum line that goes to the EGR valve.

I will send you some pics to show what sensors my car has (compared to your turbo diesel).

greetingz,

__________________
1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)

Thanks Guys!

oldsouth,

If you mail me, I can reply the mail with some pics and information about the disconnected EGR on my C250D.

greetingz,

__________________
1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)

I have a 1987 300D Turbo with the 603.960 engine. We cut a metal plate and bolted it between the EGR valve and the intake manifold. I did not remove any other wires or attachments.

I took the car for a 500 mile run up the coast this week and did not notice any problems. It does seem to smoke less at startup.

Do I need to remove the other connections to the EGR valve? Or is it wiser to block the flow between the exhaust and the EGR valve?

--Craig

292,500 miles and still cruisin'

Later model turbo diesels are more complicated to disconnect. You would have known it if the computer had cut your power. It is VERY noticable. I tried the blocking plate idea also but to no avail.

I am bringing this post back to life! I am ready to try the diode thing with the MAF sensor and was wondering if anyone knew which of the 4 wires going to this sensor is the one that goes back to the computer. I believe this vhunter said that is the one to put the diodes on.

This may not have any relevance for diesel apps, but I thought I'd throw it out here anyway...

On gasoline cars with EGR, sometimes the ignition curve is setup assuming EGR is present--when EGR is active, more aggressive timing advance can be employed because the quantity of inert gas in the combustion chamber delays the propagation of the flame front. Sometimes disabling EGR has been known to increase the chances of pinging under certain light load conditions.

I know that on gasoline and diesel engines, EGR is not usually active at idle or full load (WOT). Maximum occurs under very light load and gradually decreases as you dip further into the throttle. On forced induction apps, the quantity of EGR would drop naturally as intake manifold pressure builds anyway.

I can see how turbo lag can be aggrivated by EGR--exhaust gas is being bled away from the turbine. It would be nice to tap the EGR behind the turbo, but I guess this would reduce the quantity that could enter the intake--the gas isn't under as much pressure.

-Joe

Just my 2 bits worth here. Getting rid of the EGR will do nothing but GOOD for your engine. Injesting a steady diet of carbon does not enhance performance or engine life. Also injecting hot gas will reduce performance and economy. Pull the plug and do your engine a favor.

__________________
Mark
82 300SD 110k
91 Caprice SS
92 Jetta TD
97 Cadillac Concours(300hp)
84 Celebrity 4.3L diesel