hotrod2448

Because the emissions thread is over 400 pages long now and ranges across a lot of areas it seems like we should have a central place for discussing the operation, failure, maintenance and deletion of the EGR system specifically. I'm going to link several of the more recent posts/threads into here and if anyone has access to a schematic of the EGR system, a how to for removal, recommendations on ways to delete it (block off plates, tunes, etc...) it would be great if you could post it in here. I'll update this post as we figure stuff out.
https://rennlist.com/forums/cayenne-...r-that-is.html
https://rennlist.com/forums/cayenne-...l#post15974056
https://rennlist.com/forums/cayenne-...l#post15980102
https://rennlist.com/forums/cayenne-...l#post15980337
https://rennlist.com/forums/cayenne-...l#post15980575

What we know:
*The EGR system appears to be prone to significant buildup in the system.
* This buildup has caused a CEL for multiple users.

What seems likely:
* The emissions fix seems to significantly increase EGR usage making buildup more of an issue.
* People have reported the swirl flap has not made any witness marks in the gunk, as if it is open all the time now
* People have reported improvements in drivability from cleaning the EGR.
* Stop and go driving likely accelerates the rate of buildup

Questions:
* Does cleaning the system correlate to an improvement in the lag so many of us experience?
* Can we just block it off with a block off plate? I'm leaning towards "no" based on people reporting CELs due to it blocking itself off, not sure how a block off plate differs but, I'm not familiar enough with system to know for sure.
* Do you need a tune to safely run with the EGR disabled? I think it wouldn't hurt, losing inert EGR in the cylinder means air will replace it, more air present leads me to believe the engine may be leaner depending on where air is metered in the system.

Rawtek sells the Malone stage 2 tune which it says requires their DPF and EGR delete kit. When you follow the link it brings you to a area with a DPF and DEF delete kit. It doesn't make any more mention of EGR. Clarification on if the EGR is addressed via the tune or not would be good.
https://www.rawtekinc.com/collection...=3378714247192

VAG Documents:

Eskimo1

EGR is turned off as part of Malone's "off-road tune". I'd bet if you really wanted to, you could contact Malone and tell them you don't want any performance change, you just want EGR turned off, and they could do that. You can't just block off the EGR with the stock programming though.

The "lag" (could also call it "off-turbo driveability") did improve after I cleaned the intake tract. It's still obvious when the turbo spools up, but before that is better, no doubt.

With a diesel, there is no "lean", at least not in the way we think of it in gasoline engines as being harmful.

hotrod2448

Yeah, lean condition seemed liked the easiest way of saying that red neck bypassing the EGR without a tune that compensates for it may lead to a situation where the factory tuning doesn't take into account that the cylinder is no longer receiving a certain amount of exhaust gas and it has been replaced by atmosphere. In my mind the concern would be higher than normal EGTs in part throttle situations where you get a hotter burn from having more oxygen available and the possibility of the electronics being smart enough to figure out that something isn't in spec and throwing a CEL. All that is just speculation on my part.

user 83838290

That's not how diese engines work. Diesels always work with "too much" air compared to gas engines, they are in "lean" conditions most of the time. Throttle body was only introduced in later diesels for emissions reasons, older diesels didn't have anything like that.

It's completely safe to do a redneck block off of the EGR. I've driven over 400k miles on various diesels (Vw, audi, bmw, mb...) during the past years I owned them with EGR blocked off. Some engines would throw a code, some won't but any tuner can fix it easily.

chsu74

Anyone have a source for an EGR plate? All I can find on ebay are for 4cyl VW/Audi motors.

hotrod2448

Ok, I had the fueling EGT relationship backwards. I spend most of my time on petrol engines where lean=hot and my engines also thankfully don't have to pass emissions so no EGR crap to deal with. Either way it sounds likely that just blocking off the EGR will most likely lead to a CEL (as people who have had the EGR fill itself with crud have seen) and will need to be addressed via tune. I'm assuming any flashing to the ECU, even if not increasing power output can/will result in the much discussed TD1 flagging which is less than optimal.

So how is the ECU figuring out the EGR is plugged/blocked? Is it referencing pressure, flow, EGTs, all of the above, black magic? Maybe if we understand how the CEL gets triggered there can be a decent work around to keep the block off from triggering the CEL that doesn't require a flash. Also, why are people reporting an improvement in performance from cleaning it out? Why would there be a difference in that respect between a block off plate and a wall of carbon?

Eskimo1

The improvement came from restoring the flow of the intake tract to how it came from the factory vs. the 50% restriction it had from all the EGR residue built up.. Just shutting EGR off won't help performance.. it'll just help the intake stay clean..

mafpolo

Please forgive my ignorance. What is an EGR and a CEL?

chsu74

EGR, as I understand it, is opened during vehicle starts and low speeds. This is to improve tail pipe numbers. The swirl flap is then closed during higher speeds.

Many of the NA 1st gen new diesels(07-08) can delete swirl flap/EGR without issues. 09 and newer diesel motors(Mercedes OM 642s as an example) added sensors on the swirl flap linkage to verify movement etc. That's why newer diesel motors are harder to do these bypasses even if they are the same motor.

mafpolo

Also, I have lousy acceleration lag when the car is at certain angles such as turning onto a steep on ramp.

skiahh

Since the engine will run hotter, it might also help performance, too. Putting garbage gasses into the exhaust to cool the combustion seems to me to inhibit the ability to use the full fuel charge, too. So removing the burned gasses and replacing them with fresh air can only help, I'd think.

Add to that the clean, wide open air flow and voila - back to raped ape performance!

EGR and the swirl flap are different things.

EGR activates when the engine is running at higher temps, to route some of the exhaust gasses back into the intake system to help cool the combustion process and reduce NOx.

The swirl flaps are used to, theoretically, improve low speed/RPM performance by providing a better charge mix to the cylinders to enhance the combustion. They open fully at high RPMs to make sure there is enough air in the system for the higher power demands.

Same here, which is really weird. 90* turns to a slight uphill are the worst.

How is a good question. Probably a flow sensor in the EGR hoses. No gas flow with EGR activated = CEL.

Simply blocking off the EGR plumbing would have no negative impact on engine operation, except to keep those gasses from going back to the intake system. It should, actually, increase performance by letting the diesel engine do what it does best. As noted above, diesels always run with 100% air flow; they are, essentially, air pumps! The more air, the better they work. Take away some of that air and replace it with, say, burned exhaust gasses and it loses some of it's oomph. But does produce less NOx.

I'd guess that the plugged EGR CEL is based on an air flow sensor somewhere in the system. Maybe several including in the EGR plumbing and intake plumbing.

If there are flow sensors in the EGR plumbing, it would need some kind of a tune or trick to fool the ECU into thinking it was there and not throwing the light.

Here's a pretty good video that explains EGR, NOx, DEF, DPM etc. But not the swirl valve; plenty of articles and/or videos on them, too.

hotrod2448

Wait, is this buildup in the actual intake tract or just the EGR piping leading up to the intake? I guess I was naively assuming it was just in the EGR pipes and the intake tract was comparatively clear. If it is restricting the intake plumbing I totally understand why performance would suffer.

skiahh

It's downstream of the EGR valve, so from EGR to cylinders. But also includes the EGR valve, so really, downstream of the EGR tap off the exhaust manifold.

lightemup67

Yup, the throttle body downstream of the EGR piping leading to the intake, and the intake itself were full of carbon and pretty plugged up. The throttle body upstream of the EGR piping wasn't bad at all.

My fear is that even after clearing out all the carbon from the intake and EGR, that I'll still need the CPU/TCU "flashed" as some other members have said the dealer did when replacing their EGR.

hotrod2448

Does anyone have an exploded view of the EGR system for these engines specifically?