From digest.v7.n540 Tue Nov 4 20:29:51 1997
From: mulhouse_at_juno.com (Dave Mulhouse)
Date: Tue, 4 Nov 1997 16:07:48 -0600
Subject: E30 cold air intake (how to)

There seems to be some interest in cold air intake systems for our BMWs on the digest. To help out, I will describe how I made my own K&N cold air intake system for my 84 318i. This should apply to the E30 325s as well.

For supplies you will need: one foot of 3" PVC tubing (3" id 3.5" od), a 45 degree 3" PVC elbow, and a K&N filter. I used K&N part # RU-3130 (3-1/2" flange, 4-5/8" base, 3-1/2" top, 7" long) This is a good safe size K&N. Anything bigger might rub against the headlight bucket. All of this together will cost about $30.00

To start you will need to hack apart the stock airflow meter mounting bracket. You need to cut off the front section and the buldge. The 45 degree elbow will press onto the airflow meter with the stock rubber gromet. Cut enough material off so the elbow will angle tword the headlights without hitting anything. I used about 3 cutting discs on a dremal tool to modify the airbox. You can throw the lower airfilter housing away.

Next, you need to cut about a 2-1/4" section from the 3" PVC. The K&N will clamp onto one end of this tube, and the other end will need to be glued/sealed onto the 45 degree PVC elbow. Next, attach the the whole setup to the airflow meter. You may want to remove the airflow meter, and press the elbow onto the meter with the unit on a bench. The stock rubber gromet between the airflow meter and what was the airfilter box makes a very tight perfect fit. You may need to bend and play around with the airfilter box/airflow meter bracket to make clearence for the whole assembly.

If everything has gone well so far, you should have a cute little K&N cone filter sitting neatly behind the drivers side headlights. Don't forget to remove the black plastic headlight sheild. If you leave it in place, you might as well forget doing this whole procedure.

Now for the most important step! Shield the airfilter from the rest of the engine compartment. After doing this modifaction to my car, I firmly believe that any airflow advantage gained by an open air filter is almost completely removed by the hot engine compartment air. I did not notice a performance improvement untill I sheilded the air filter. To do so, I simply cut up a reflective "windsheild sun shade."

After sheilding the airfilter, the car felt much faster. I am certain that I gained a few hp by doing this modifaction. I would like to estimate 5 hp, but that may be pushing it.

If anyone is interested, I may be able to scan a few pictures of my current setup.

mulhouse_at_juno.com