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

by Martin Gonzales

So far, the goals for the modifications to our BMW E39 M5 project have been to enhance the performance of our ultimate driving machine without straying far from its original design or ruining its daily drivability. Will these goals always remain? Probably not, but before they change we're going to continue to extract every last bit of “no bad side effect” performance out of our M5. In this installment of Project E39 M5, we will test two very easy to install intake upgrades – the high flow K&N drop-in filters and HPS Performance Parts silicone intake hose kit. We will be doing individual dyno tests for each part to see if they will free up the S62's intake tract and yield some easy power gains.

Although the E39 isn't the latest performance offering from BMW, it was produced at about the start of the new era when manufacturers started to really optimize the peripheral parts of their engines in order to squeeze every bit of efficiency (aka MPG) out of them. Modern vehicles intake systems are so well engineered that it's usually very difficult to find significant power gains from simple intake bolt-ons. Gone are the days of being able to bolt-on a well designed cold air intake and experience double digit gains.

The E39 M5 is no exception to this new trend towards engine efficiency since it was one of BMW's technical flagships at the time of its production. The E39's S62 comes with a short tract, dual intake system from the factory that seemed to be pretty high flowing. So, we were a bit skeptical going in about being able to find any real gains from just panel filters and silicone elbows.

The first part we will be testing will be a pair of drop-in replacement K&N high flow air filters. The M5 has an intake tract for each bank of cylinders to maximize flow so two filters are needed. The K&N filters drop right in to the M5's large dual air boxes with zero modifications needed.

The K&N high flow filters are washable and reusable. They are also covered under K&N's bulletproof million mile warranty. On top of that, all K&N filters are backed by K&N's Customer Pledge. K&N will stand behind their products and will warranty costs caused by legitimate claims of any damage specifically caused by their filters.

K&N drop in filters are made as a direct OEM replacement element that directly takes the place of the stock filter with no modifications or fuss. They are perhaps the easiest mod you can perform to any vehicle. But, will it perform as claimed and yield positive performance results?

The K&N filter is pleated to give an increased surface area for more filter element in a given area, which increases its filtering potential. The stainless steel mesh surrounding the cotton gauze filter element is used for support of the soft fabric, especially when the filter element gets dirty and needs to be washed off. The filters can be cleaned with K&N cleaner and water, and then retreated with K&N filter oil to restore it to as good as new performance. The black polyurethane seal molded into the filter assures that no unfiltered air can leak past the element.

The HPS Performance Products E39 M5 dual intake hose kit comes with everything you need to replace the OE intake elbows. They have a constant large diameter and are smooth internally to help improve air flow over the corrugated OEM hoses. The HPS hoses are made out of high-temperature silicone rubber, reinforced with 4 plys of polyester. This results in a stiff hose that won't collapse at wide open throttle.

2 comments

Joe says:
January 22, 2019 at 12:08 pm
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. Martin Gonzales says:
  January 23, 2019 at 11:41 am
  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!