Project E39 M5: K&N Filters and HPS Intake Hoses


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.



  1. Hi Martin, and Mike,
    I love that fact you guys are doing a project E39 M5, as I’m working on mine as well. This intake article is very interesting, and would also like to see if you’d be interested in (dyno) testing another intake (AFE) that’s very easy to swap on. My E39 M5 came with it when I bought the car, and in design, it looks like it makes sense… very similar to the silicone hose + K&N setup you tested. Except, mine my AFE has a hard molded, smooth pipe and runs cone (K&N style) filters. Would you guys be interested in testing this setup as well? I am in Torrance, and the swap would take 5 mins. Please let me know if this is possible~

    *Reason I ask is, the AFE kit seems to have a negative gain on performance for the S62, based on an old dyno run someone did years ago. Looking at the design, I don’t understand how it could be worse than stock. I recently dyno’d my car and numbers weren’t bad. Wondering how it fares compared to your setup. -Thanks~

    1. Hi Joe,

      Thanks for reading! We’ve actually been wanting to test the AFE intake too. We’ll reach out to AFE to see if they would be interested in supplying us with one of their intakes for another test. We think that would be great info for the E39 M5 community to have!

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