Originally Posted by Used2be
Yes, I'm aware that warranty infractions that don't impact the function of another portion of the car won't affect factory repair of the unaffected part. But the engine is a very expensive component and I am assuming that BMW will be able to determine if the ECU has had a tune, even if that tune doesn't activate the CEL while it is installed, and even after the tune is removed. Please correct me if that is wrong, I wish it were.
GTHAUS, have you actually run the catless downpipes with the otherwise stock exhaust in place? Have you heard the sound of the exhaust in that configuration? Do you have an audio track for comparison?
As has been mentioned the BMW DME sw will "record/detect" a "tune" and if the car gets plugged into the BMW diagnostic system it is very likely the data will be sent to BMW NA.
This is actually totally out of the hands of the local tech , so even if you have a great relationship with your dealer/tech they can't do anything to filter/restrict data which is being sent to BMW NA (only option is not to plug in the car, which works if you have something simple done and it doesn't require coding/updates etc).
BMW NA has the ability to see data even the local tech can't see (such as RPM, torque, airflow meter reading, boost changes etc) . By correlating these "events" it is possible to at least build a case for the existence of a tune (ie if your car has different values for AF, boost etc than a "stock" car ). This is also how BMW NA will decide on warranty claims when it comes to transmissions/engines, for example on a manual M they've been able to if the engine has ever been over-revved etc and if it's the case they may void the warranty)
As a last note BMW has also been pretty aggresive on the N55/N54 based cars in voiding drive train warranties and sometimes even have folks buyout their lease etc (and please don't start arguing about the Moss Magnuson act...)
If you tune your car via flash/piggyback just be realistic and understand the possible side effects/issues.
Anyways just my 2c