Evening everyone. Came across something today that some folks may find interesting. This most likely only applies to North American M5's. Disclaimer, I don't know what, if any EPA regulations require these, and, if you mess up your car due to ingesting dirt, bolts, fod, etc., accidentally left on the top of the air filter, your fault. Don't come looking for me!
After reading the thread about the stock air boxes and if they have aluminum block-off plates, I decided to check mine. Had a few minutes to spare, so I decided to unscrew them and take a look. Sure enough, right below the orange air filter, there they were, aluminum patches...but above the air filter...woah...what's that? Charcoal Filter!
The North American F10 M5's have a charcoal filter. Very similar to the S85 engine. They sit in the top of the air box and from my understanding their purpose is to control any back-flow of hydrocarbons when the car is shut off. Removing them on the E60 resulted in better throttle response, and some claimed 15HP on the dyno. Hmm...could it be the same?
Removal on the S85 required a step-by-step procedure with pictures. Lots of potential to rip the filter sending charcoal on the intake side of the filter, clips that were difficult to remove, and required removal of the air box lid. On the S63B44TU it's super easy! Just for sake of being complete, here is what you'll need tool-wise:
- Torx T25 driver
- Torx T25 bit
- Small ratchet
- Flathead screw driver
- Some duct tape
All of the photos posted are of the left air box (drivers side). Procedure for the right is exactly the same.
1. Start by unclipping the hose from above torx screw #1. Once complete, begin loosening all screws 1-6. Don't worry. Unlike on the airbox clips on the S85 the screws did not seem to fall out. Note, I only removed them enough to get the lid loose.
2. Using the torx bit inserted into a small ratchet with the bit taped in place (so it does not fall out) unscrew torx screw #7. If you have an articulating joint and some extensions you could do this too...I don't have those laying around. The lid should now be free.
3. Once the lid is free, tip it back. If you are in North America, you should see this. I didn't take a picture of it in the car, but you will see the little notches around the outside of the filter.
4. Here is a photo of both filters removed from the car. Note the red arrows. This is the slot I used to remove the filter. It is the tab facing the front of the vehicle, roughly next to torx screw #3.
5. Reassemble. Optional: Take a peek to see if you have a hole in your air box (not required). Be sure the top of the orange filter is clean and nothing is inside the air box, and slowly set the lid back onto the lower portion, being careful not to pinch the filter with any of the torx screws sticking out of the bottom of the lid. Tighten all of the screws down, and clip the hose back in place. Voila!
6. Rinse and repeat on the passenger side.
I took the car out for a quick jaunt, and my very unscientific method of measuring change in performance (AKA butt dyno) told me that it seems as if the throttle response was indeed better, and, the car pulled a bit harder. I plan on getting the car dynoed again once it has become familiar with the Akra exhaust, but it will be interesting to see if there are any gains. Unfortunately, I cannot baseline just this change without removing my exhaust...that ain't gonna happen!
Let me know if you see any improvement if you remove your filters!