Why did BMW use a much more restrictive carbon impregnated filter in the US, but a higher flowing non carbon filter in the rest of the world and on their competition vehicles?
Why?? Because it is better and they did not have to worry about the EPA.
So, the answer is that replacing the restrictive US filter is worthwhile, but most gains are going to the less restrictive German version, as designed by the factory!
Originally Posted by TrackRat
Simply bad data as you would expect from a chassis dyno. That's why car makers use engine dynos and steady state testing in accordance with SAE test standards. Chassis dyno data isn't worth the paper it is printed on.
Those who understand how an engine functions and airflow vs. engine speed, would know immediately that the dyno data is bad data. If you don't understand how an engine functions, then yes I can see where you could be duped by bogus dyno data or performance claims like 30% more airflow. As a trained professional, specifically in the area of advanced engine design and dyno development, I post technically accurate comments to help people better understand how an engine actually functions.
BTW, you misunderstand the bad dyno data. There was not a 13 WHP gain across the rpm band. You could have completely removed the air filter and not gained 13 WHP or even 13 HP anywhere in the operating band.
I am aware that many enthusisats want to believe these types of foolish claims, but they are just that foolishness. Don't be duped by those looking to cash in on your lack of technical knowledge. Don't you think that if BMW could get 13 HP or 10 HP or 5 HP by changing the air filter, they would? On a $60,000 car a $3.00 air filter is not even a cost concern when they spend MILLIONS to develop these engines.
2009 Space Gray Carbon Leather E90 with DCT, Tech package, and EPS. Mods: Fabspeed 200 cell cats, Xpipe w/resonators and no secondary cats, BPM tune, Euro DCT software, Eisenmann Sport Mufflers, Vorsteiner Rear Diffuser II, SWS8 subs, JL Audio XD400 bridged 2X200W, built in radar