I cant see the vacuum being the problem as the egr valve has to close/open fully causing both extremes of vacuum pressure ?

Lamda sensor sounds the most likely bet, because thats its normal role with a petrol at least, sense the fuel mix ratio and adjust mixture to suit, makes sense to utilise this part on a derv for other purpouses like EGR management ? I dont believe there is such a thing as running rich or lean on a derv IIRC ? or am I having a blonde moment ?? self doubt creeping in when I consider we need a MAF lol

 

Interesting topic.
I've run my car with the Vacuum to the EGR disconnected for the past 6 months, no issues apart from the light in the cluster.

The fault is activated in the following way.

For every speed load point there is an airflow demand.
This airflow is the flow throught the MAF sensor.
If the measured airflow is greater than the demand the EGR valve opens.
If the EGR valve can't open then the demanded airflow can't be met, hence a fault is set.

The amount of EGR flow is corrected depending on sensor inputs, coolant, air temp, atmospheric pressure etc.
Thats one of the reason most cars drive better in the cold weather.

If you know an engineer at BMW or Bosch they would be able to re-map the car to reduce or totally remove the EGR demand.
Unfortunately I don't work for either

Jason

 

Thats uber usefull Jason thanks, a good starting point indeed !

 

Are you sure? The EGR recycle is after the MAF so there is no way it can tell how much extra flow the engine is getting from the EGR. It would need to recycle back to the airbox or piping before the MAF for this to work.

The MAF reading may well tell the EGR when to open but it has no way of knowing if it actually is opening

 

Are you sure? The EGR recycle is after the MAF so there is no way it can tell how much extra flow the engine is getting from the EGR. It would need to recycle back to the airbox or piping before the MAF for this to work.

The MAF reading may well tell the EGR when to open but it has no way of knowing if it actually is opening

 

Via the emissions detected at the Lambda maybe ? the EGR plays a part in air ratio with that valve im guessing ?

 

Yeah that could well be the case. With no EGR the mixture must be richer on light and part throttle. It will be fine @ WOT as the EGR is closed anyway.

 

As soon as i get chance im going to make up a few blanking plugs for the recirc pipe with different hole sizes to see what the smallest hole that can be used and keep the light off, maybe the smallest hole would give similar results to it not working ?
Ive done a few 100 miles now and by how much better to drive think the egr valve operation must be quite primitive, snapping open and closed with little precision, a bit like an old steam valve
As Paul says, the mixture must be a little richer but my economy is at least the same if not a little better.
I suppose the turbo is doing a bit more work spooling up quicker but wouldnt think that was a prob ?

 

My experience with complete removal of the EGR on my E46 320d was the following.........

1. Sharper throttle response.

2. A little better pull from mid range

3. More willing to rev through the RPM's

4. Around 3mpg better on average fuel consumption

5. Slighty less turbo lag/quicker spooling

I really think the best way to tackle this is to understand which sensor is throwing the error so we can actually do a full bypass, I can fabricate some bypass kits probably once we solve that issue.

When I get some time I will call a few people with the info we have currently and see if I can glean some definitive answers on the direction we need to take this

Here is a post all about my E46 experiences, You will quickly see why im kean to lose this EGR asap !

http://www.e46zone.com/forum/index.php?showtopic=3076

 

Id agree with 1>5 Mark plus stop to go pull away is also improved.

3 mpg is bizarre as i did around 400 mile at the weekend and saw around 3mpg better than id usually expect.