EGR bypass
 

Re 82-300td
When I refered to the clean air side this would be after the air cleaner element surely..???

Peter

prs, disregard the first part of my previous reply. I think 82 and I both misunderstood what you were asking, and in different ways.

The reason you can't plumb from the air cleaner to the EGR valve input is that there will be no pressure differential from one spot to the other, so no air would flow through the EGR valve. To avoid setting an error code and the check engine light, air must flow through the EGR valve when it is opened. By checking for a corresponding drop in flow across the Mass Airflow Sensor when the EGR valve opens, the computer knows whether the EGR is actually working. To get airflow, you must take it from someplace that is at higher pressure than the intake tract at the EGR valve. This also explains why the mod won't work on the OM606 Turbo - the intake tract is at higher than atmospheric pressure at that point.

Rick, So I take it the EGR senses both airflow and pressure. Question, I'm assuming it senses/operates at low pressure so as to cut down on emmissions at low load i.e. idle - 'coasting'. So removing the source of high pressure, 'load', would leave the EGR open and you would just have another source of filtered clean air as depicted on the mod. Legality aside, I don't see as this would cause a prob on a non turbo.

The EGR itself senses nothing. It's simply a valve that lets exhaust gases into the intake tract.

However, the computer can monitor the function of the EGR indirectly through the mass airflow sensor. The EGR is plumbed into the intake tract AFTER the MAF, so when the computer gives the command to open the EGR, then there should be a corresponding drop in airflow across the MAF. In order to get that, you have to have airflow into the intake tract through the EGR valve. And to get that, you have to plumb it to someplace that has a higher pressure, which the exhaust system does.

The EGR is actually most open at partial load and closed at both idle and full load. Opening the EGR input to the atmosphere (with a filter) would work fine on a non-turbo. What I said would not work was Chuck's suggestion of simply disabling the valve. However, it seems the 95 E300 is unique (in the U.S.), having no turbo or check engine light.

They'll have to pry the Benz from my cold, dead hands :)

I don't think many states require emissions testing for diesel vehicles.

Related thought. If the EGR is disabled then the intake will not become covered in soot. Given this new, clean environment, I wonder if the extrude hone "powerflow" treatment to the intake would help the motor breath better (and yield more power).

http://www.extrudehone.com/price_list2.pdf

If I had an extra intake manifold I'd be tempted to give it a shot.

Rick, Thanks for the explanation. The E300D 95 has the same basic motor as your car but different computer/sensing/diagnostic input. Hence the 606.910 - 606.912. The author of this post has had no problems driving his 95 in this fashion, says it operates smoother etc. I was inquiring as to any downside to the mod (sans legal). Does not seem to be one as per the discussion so far.

I would hate to have the feds come across this and think that I was giving you information to help you disable your EGR. For that reason, you will not find ANY professional tech on this board who is willing to discuss the EGR at all. And I don't blame them.

You folks can certainly do what you want, but my cars are staying legal, and I'm content to periodically clean out the intake manifolds. We're fortunate that the MB designs don't clog up nearly as bad as the VW intake manifolds. The VW has a very poor oil separator that lets a bunch of oil in from the crankcase ventilation system. That oil combines with the soot from the EGR to make a nasty black goo.

I posted there as well.. same thread as this one in the tech side with no hits...

EGR bypas
 

Thanks to all for the explanation, now I comprehend.

Peter

We've already discussed this in the Tech Help section. EGR thread.

See my post above as to why the pro's won't respond. In the 5 years I've been on this board, they've been asked many times!