Daryl’s BMW 5-Series:
“SKUNK5”

INTAKE MODIFICATION

This is my second attempt at a Ram Air setup for this car. I started by removing the headlights and the front bumper. The idea was to use the cover right next to the passenger side fog light as the receptacle for the cold air duct. With the bumper removed, you will see the silencer (air cowl) right behind the bumper guard.

To remove it, you will have to unbolt the bumper guard. There are 3 main and 2 positioning nuts that hold the bumper guard to the frame of the car. Once the nuts are removed, you can pull out the bumper guard, unscrew the silencer and remove it. This modification by itself should give a 4.4L about 4-5hp and 4-5lb-ft. torque increase. And it's FREE.


Next step was to put together some type of air duct as big and as smooth as possible to route the air to the air box. I used 2x3 plastic gutter ducts and a flexible duct found at your local Lowe's. I riveted all the parts together to make sure they stay put. I had to modify the plastic bumper cover to accomodate the 2x3 gutter cup. I had to cut the horizontal strip in the center and a hole for the cup.

It looks like the best place to put the cup is in the lower left hand corner of the cover. In this position you should have no problems later with assembly in the bumper. Next step is to install the duct in the air box and somehow attach it to the chassy. I used 2 large sta-ties.


Put the bumper back on and align everything. It should just fit. Enything bigger probably would not have fit. The duct will run just behind the fog light.


The last step is to put the cover back on. I used only two rivets to hold the cup to the cover at the top. The cover mounts to the bumper at an angle, so that if you attach all sides of the cup, it will also be at an angle and my not align properly into the duct. This way I have some flexibility, and if I want to rivet the other sides once the cover is in, I can.

I wanted to see the effectiveness of this setup so I installed a thermocouple in the intake box (before the filter) and in the center of the plumbing between the filter box and the manifold. I first tested it in the evening when the outside air temperature was 80 deg. F. The intake air temperature averaged 90 deg. through the stock plumbing at highway speeds up to 80 mph, in city driving it went up to 92 deg. Next morning the outside air temp. was 68 deg. F. At highway speeds up to 80 mph. the intake temperature sat around 78 deg. It looks like the stock plumbing with this bumper air ducting is keeping the intake air temperature to about 10-12 deg. higher than whatever the outside air temperature is. This is not bad considering the plumbing runs right between the motor and the radiator that can emit temperatures up to 200 deg. F.

Performance wise, the motor SEEMS to rev a little easier and there is an improvement in intake growl, but it only gave a small gain in output power.

Recently I changed to a tube CAI from http://www.revhighmotorsports.com Very nice design. I went with a K&N filter, but he also has an ITG setup if anyone is interested. The butt dyno does not feel any difference. It does look nicer under the hood and some waight was removed. I still think the 1st step should be the removal of the air intake silencer in the bumper. It is the main restrictive device in the intake system.