The HPS Performance Parts intake hose kit also comes with stainless steel T-bolt clamps instead of run of the mill hose clamps. T-Bolt clamps provide evenly distributed pressure around the sealing area and reduce the probability of leaks. Care must be taken to always ensure the proper size t-bolt clamp is used as they have a smaller operating window than worm style clamps. The HPS t-bolt clamps have wrap around flanges that not only help distribute the clamping forces, but also help avoid cutting into the hose.
Now that you have an understanding of the parts we will be testing, it's time to get to it! As far as we know, our M5's S62 V8 has been unmolested in its 130k miles of life – other than the Corsa exhaust we installed in a previous article.
The S62 is fed through two large, high flowing air boxes that sit on the front side of the engine behind the headlight housings. The two boxes right in front of the firewall are the in-cabin filters and have nothing to do with the engine's air intake system, but they do make the engine bay look pretty buff.
The OE air boxes get their air from the ducts under the headlights pictured above. The inlet for the ducts are right behind the bumper and they're simply getting air from the void left between the bumper mounts and the bumper. There's definitely an opportunity here to reroute or customize things in order to feed the engine with a much cooler air supply or even create a ram air effect.
Installation of the K&N drop-in filters is very easy, you technically don't even need tools. We used a flathead screwdriver to make it easier to reach and pop off the OE clips that hold the two halves of the stock airbox together.
After releasing the four OE clips you simply lift the top half of the airbox and remove the stock air filters.