EGR mod
From TDIClub
Various EGR mods disable the Exhaust Gas Recirculation system. Such mods are modifications to the emissions control system, and may not be street legal in North America. However, performing such a mod prevents intake clogging.
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[edit] VAG-COM Method
The VAG-COM method is a simple method that is free (if you have VAG-COM), and does not cause a CEL. but is not shown to be very effective in preventing intake clogging.
A VW specific scan tool such as VAG-COM is required for this procedure.
With the engine warmed up and running at idle in neutral with all major accessories such as air conditioning turned off, connect the scan tool cable and start the scan tool software.
Select engine control module. "Login" using 12233 as the access code.
Select "adaptation" and go to adaptation block 3. Give the accelerator pedal a quick "blip" to ensure that the EGR remains turned on for the next minute while you perform the following steps. Note that the display shows a default adaptation value of 32768 and shows approximately 250 +/- 20 mg/stroke of air intake volume. (If it does not show this, you are either on the wrong screen, or you have an older ECU that differs slightly - see next paragraph.)
If all is well, enter 33768 as the new adaptation value, and select "test". Note that the displayed air intake volume changes, usually to about 370 mg/stroke. The specification limit is 370 mg/stroke, so if you want to remain within OEM shop manual specifications for emission control reasons, you might have to enter a number slightly smaller than 33768. (If you don't care about road-legal NOx emission limits then leave it at 33768. Depending on the usage cycle, NOx at this setting can be increased by as much as 40%.) If all is well and you have a seting that you are happy with which results in an intake air volume of 370 mg/stroke or just a hair less, enter "save". This will slow down clogging of the intake manifold.
Note for '96 Passat and possibly other older ECU variations: The adaptation numbers are in a different range, and you won't be able to get feedback on what you are doing on the same screen. The EGR adaptation number for a '96 Passat with the original "BK" ECU is 188 rather than 33768 and you'll have to go back to "measuring blocks" group 3 to see the effect before "saving" the new setting.
As for warranty, no one has mentioned any problems nor should there be. This adjustment is also completely reversable should one be concerned.
Most provinces and states that do emissions testing on diesels, just check opacity, so this will not be a factor when testing.
[edit] Race Pipe Method
A device known as a "race pipe" can bypass the EGR system entirely. Various vendors sell these pipes. However, note that such a device is illegal on a road car. A race pipe will guarantee that the intake will never clog, however. Unfortunately, race pipes can and do cause CELs, and are easily detected. Also, on vehicles equipped with an anti-shudder valve, this valve is also bypassed.
[edit] Epsilonian Devices
An Epsilonian Device is a device which fools the ECU into thinking that the EGR system is fully functional. The purpose of this device is to prevent a CEL while having a race pipe installed.
[edit] Chipping Method
This method is probably the hardest to reverse, but also almost impossible to detect, except for increased NOx emissions. Some chiptuners have the ability to disable the EGR system in the ECU. The intake will not clog at all, as if a race pipe were installed. However, the anti-shudder valve will still function, and there will be no check engine light. Needless to say, this modification is not street legal.
