K&N Cone Filter

Pros: Easy To Install, Improves Intake Sound
Cons: Possibly hurts performance especially in hot weather
Cost: $149

In January of 1997, I purchased the K&N Filter Charger from Bavarian Autosport for $149. Once installed, it made a noticeable change in sound. I think I can tell a performance difference but, it is hard to judge what this upgrade alone would produce. Previously I upgraded the exhaust and I think I’m dealing with a “the sum is greater than the parts” issue here. The installation instructions were pretty well written but didn’t contain any pictures. You might want to take a look at my on-line instructions before installing yourself.

7/1/97 Update:

Since the installation (02/28/97) it has gotten quite hot here in Texas. This exposed a flaw in the K&N cone filter design. Since the filter is not vented with outside “cooler” air I think this upgrade is actually loosing power. So the K&N cone filter has come off and is currently sitting on the shelf.

10/1/97 Update:

I tried building a heat shield to protect the filter from the engine heat (a tip that was recommend on the message board). However I wasn’t pleased enough with the results to allow it as a permanent solution (filter remains on the shelf). At this point I’m not very happy with this product, especially in hot weather.

11/29/97 Update:

Someone e-mailed me and offered to buy the filter charger from me. They own a 318ti and live in Alaska (I’m not making this up), given the Alaska climate the shortcomings of this upgrade are probably negated for him.

12/29/97 Update:

Received an e-mail from the purchaser, he loves the cone filter. So if you live in a cool climate the cone filter is a good investment (especial if you can buy one of a Texan that can’t use it).

Installation of K&N Cone Filter

This is an OCR/Scan of the original instructions.

1. DIRECTIONS: Be sure your engine is cool and ignition is OFF. We recommend you lay a fender cover or a blanket on your fender to protect it before beginning the project. Locate the factory air box on the driver’s side inner fender.
Get familiar with the layout, and figure out exactly what it is that you will be replacing. The area surrounded in red will be replaced.

2. In the front of the air box is a sensor. Depress the clip so the wire plug will pull out. Then remove the actual sensor from the box.
Remove the entire air sensor from the stock air filter box. Press the silver wire thing in and the plug comes right off. Make sure you pull out the sensor.

3. Depress the two clips that hold the top of the factory air box to the air flow meter.
Depress all you want, it’s going too take a screw driver to pop these brackets off. Let me also point out that the instructions assume I knew what the air flow meter was, I didn’t. It took several cycles of reading this sentence and staring at this contraption before I understood.

4. Next, unclip the top portion of the air box from the bottom half of the air box.
Pretty straight forward, I unclipped the top portion from the bottom portion. However I think they also intended for me to remove the top of the air box, it was a couple steps later when I actually did. The four arrows in the graphic point to the clips but the top and left clip can’t be seen in this picture. You will have to look around and under to find them.

5. Undo the two studs attaching the base portion of your factory air box to the inner driver’s fender. On some models the cruise control may also be attached to these studs. If the cruise control is connected to these studs you must reconnect the cruise control after you install the new filter system. You will need to remove both studs from the factory air box.
The nut heads easily came off, let me also say that if you drop one it will fall all the way through and roll back to your rear tire. The crap about the cruise control you can ignore, it’s not attached here on the Z3.

6. After you undo the nuts on the studs you need to wiggle the base of the air box as it has an air duct attached to the housing near the radiator. Once it has come free of this duct you can take out the base of the air box.
During this step is when I figured out the top should have been removed back in step 4. Because I still had the top on this step was more difficult for me. Once I removed the top I could see the part that was catching and I wiggled her right out of there.

7. Put the small black hose on the air flow meter.
Okay, this step got me a little angry. First of all, I think I know what the air flow meter is. But where the hell is this small black hose? When someone uses the word hose I think of a tube, like a drinking straw or fuel line. I’m also not sure if this small black hose is something that’s already in the car or is it a piece that came with the kit. Well after several minutes I noticed the same phrase “small rubber hose” on the “Kit includes” list, and deduced that they must be talking about this rubber ring.

8. Then install the new air filter and position the filter so the small hole in the neck of the filter faces the driver’s inner fender.
My silver bracket was shipped already installed on the filter. The instructions later tell you about installing this, so unscrew and remove it now, then just push on the filter over the rubber ring thing.

9. Position the metal bracket so the end with the cup on it will seat around the rubber bushing at the top of your frame rail. The other long end goes to the inner fender and is secured by the one stud that was attached to your original air box.
What metal bracket? Oh, this thing that came with the kit. The Cup end? two of the ends are “cupped” but one is cupped more than the other. Rubber bushing at the top of you frame rail? What the hell is a frame rail? Well after trying several different interpretations here’s what I came up with, a picture is worth a thousand words, above is what they were trying to explain.

10. Before securing this stud you need to position this bracket on the new air filter with the clamp. The clamp is designed to hold the bracket to the filter assembly and the filter to the air flow meter. remember you must not cover the small hole in the filter and the hole must be pointed toward the inside driver’s fender.
Good thing I’ve got this thing figured out in my head because the instructions are getting worse. I think the K&N people recognized this, because the ONE picture that is included in the instructions is useful in this step.

11. Carefully push in the sensor you took out of your original air box. It should sit snug in the small hole in the side of the new filter.
When your doing this push the sensor in until you can’t see the green rubber ring on the sensor. Also position it so the fatter end doesn’t rub against the filter rim.

12. Carefully tie strap the wire to the one metal bracket so it is away from the fan belt on the car.

13. Tighten the clamp holding the filter in place against the bracket assembly.

The instructions warn you to make sure the filter is not touching the radiator. However when I attach the bracket with this rubber screw thing it pushes the filter into the radiator. The instructions are unclear but originally the rubber side was on the left but this pushed the filter to far, I got around this by moving the rubber side of the attachment bolt to the right. This kept the filter out of the radiator but it was not tight so I pulled one of the gold spacer clips off the original box and it worked great.