[HwyKnight]

How strict is BMW being with voiding warranties for engine tuning? Are they tolerating minor changes like exhaust systems? Or has any change in the slightest caused them to void the warranty. If/when I get my X5 I would like to change the auto stop/start feature to be off all the time, would that void the warranty?

[DG-X5]

In order to deny a warranty claim, BMWNA needs to be able to prove conclusively that your modification led to the problem. Disabling ASS would not fit under that bucket. More complicated procedures (cat deletes, etc.) are where you get into dicey territory, though even then, it's usually going to be difficult to prove a causal link.

[mike@x-ph.com]

Originally Posted by DG-X5

In order to deny a warranty claim, BMWNA needs to be able to prove conclusively that your modification led to the problem.

+1

[Higgs Boson]

A rule of thumb regarding powertrain warranty,
Anything from the air filters forward won't cause a warranty issue
Anything after the cats won't cause a warranty issue

Anything between the air filters and the cats and/or a tune will probably give you a warranty problem. (turbos, intercooler, downpipes/cats, cams/engine work, etc)

[Taserz]

Originally Posted by Higgs Boson

A rule of thumb regarding powertrain warranty,
Anything from the air filters forward won't cause a warranty issue
Anything after the cats won't cause a warranty issue

Anything between the air filters and the cats and/or a tune will probably give you a warranty problem. (turbos, intercooler, downpipes/cats, cams/engine work, etc)

Why would replacing the cat or doing a downpipe give warranty issues. I mean obviously if that part fails or check engine light from o2 sensors but I mean stuff not related to it

[gqgambler]

Originally Posted by Taserz

Why would replacing the cat or doing a downpipe give warranty issues. I mean obviously if that part fails or check engine light from o2 sensors but I mean stuff not related to it

Lots of modern cars take measurements to determine the performance efficiency of combustion process and catalytic converter. Those measurements feeds back to the ECU/PCM and help the software to determine changes to how the car is running to meet output goals, so by making changes downstream that aren't calibrated you can directly affect the performance of the engine and change how BMW intended it to perform.

[Higgs Boson]

not to mention that removing the cat or going to "hi flow (inefficient)" cats will require a tune (which voids the warranty) in order to eliminate the CEL and in many cases properly account for the change in airflow.

[Taserz]

Originally Posted by Higgs Boson

not to mention that removing the cat or going to "hi flow (inefficient)" cats will require a tune (which voids the warranty) in order to eliminate the CEL and in many cases properly account for the change in airflow.

No you can just add an oxygen restrictor for the o2 sensor. That way it never will give you a check engine ligh from the high flow cat or 200 cell or lower cat.

[Higgs Boson]

Originally Posted by Taserz

No you can just add an oxygen restrictor for the o2 sensor. That way it never will give you a check engine ligh from the high flow cat or 200 cell or lower cat.

That's highly unreliable, been a method of trickery for 20 years and it works sometimes, sometimes it doesn't.

It definitely doesn't work for the cars that use the rear O2s to supplement the front O2s for fueling not just "cat presence."

The further away we get from the year 2000 and the closer we get to 2040 the less likely a rudimentary solution will be viable. The checks and balances get more complex every year which is why as I continue to replace my cars I will do so with caution up to the point where the next model year is locked out and untuneable.

My plan is to keep one of the last naturally aspirated 6, 8, 10, and 12 cylinder vehicle forever and rotate the other spots with FI and EV cars, whatever is next.

[Taserz]

Originally Posted by Higgs Boson

That's highly unreliable, been a method of trickery for 20 years and it works sometimes, sometimes it doesn't.

It definitely doesn't work for the cars that use the rear O2s to supplement the front O2s for fueling not just "cat presence."

The further away we get from the year 2000 and the closer we get to 2040 the less likely a rudimentary solution will be viable. The checks and balances get more complex every year which is why as I continue to replace my cars I will do so with caution up to the point where the next model year is locked out and untuneable.

My plan is to keep one of the last naturally aspirated 6, 8, 10, and 12 cylinder vehicle forever and rotate the other spots with FI and EV cars, whatever is next.

It's the same thing as a j-pipe it works