Project E90 M3: Part 5 – K&N Filter

We gave our M3 a quick and easy bump in power by swapping out the factory air filter for the industry-leading High Performance K&N air filter.  We have seen some impressive gains from K&N products and feel there’s no reason you shouldn’t have one on every car you own!  But how much power can really be gained over the OEM BMW air filter in this highly stressed and finely tuned 8,250rpm screaming V8?  Read on to find out!

I can’t say enough about K&N products or them as a company.  I have used their filters for decades on everything from go-peds, scooters, motorcycles, cars, trucks, and racecars.  I’ve always felt a performance increase and have never had an issue or negatives whatsoever from using their filters.  Due to their quality of construction and ability to be cleaned and re-oiled, K&N filters have outlasted my ownership of each vehicle.

K&N is so confident in their products that on top of the K&N Million Mile Limited Warranty, they have an unbelievable Consumer Protection Pledge:

K&N Consumer Protection Pledge

“We want to make sure that when you buy a K&N Lifetime Air Filter or Air Intake System, you can be confident your vehicle’s warranty will not be impacted.  We also want you to feel confident that even if you experience a difficult dealership, we will step-in and resolve the issue, so you won’t have to.  Therefore, we make the following Pledge:

K&N pledges to our customers that they will not be taken advantage of and charged for a repair due to a dealership warranty denial blamed on the presence of a K&N product.”

If that doesn’t give you the confidence to buy their products, even for your brand new car under the factory warranty, I don’t know what will.

At MotoIQ we like to dispel myths and give you the most objective and scientific data possible through proper back to back, A-B comparison testing.  To continue this trend, we headed back to our friends at Power by the Hour in Boynton Beach, FL to turn the drum of their 2,000hp capable Dynojet 224xLC.  PBTH is known for modifying Mustangs with everything from bolt-on supercharger kits to in-house developed turbo systems, suspension, brakes, fabrication, and dyno tuning.  They are such a pleasure to deal with and we really like the consistency of their dyno.

Project E90 M3 on the Dyno PBH
Unfortunately in Florida, 6 months out of the year is less than ideal for producing bragging-rights dyno numbers.  Rather than waiting months for the temperature to cool back down, we decided to go ahead and do our A-B testing of the K&N filter in the heat of summer.

With ambient temperatures in the high 90’s to triple-digits, brand new Continental ExtremeContact DW tires (which weigh more than old worn tires) and different wheels, we knew that we were not going to see the same power that our car made in the low 70’s with 0% humidity.
Project E90 M3 Dyno Pull Baseline HOT
Despite an early morning arrival, the intake temperature were reading 96*F with 44% humidity.  Our M3 put down 349.56hp and 271.49lb/ft of torque.
Project E90 M3 Baseline Hot dyno Pull vs cold Baseline
If you’re familiar with
Project E90 M3, you would know that our M3 put down an impressive 379.76hp and 276.63lb/ft of torque.  Other than the new wheels and tires, everything else remained the same, including the use of Mobil 1 0W40 motor oil.

The power and torque were even in the mid-range from 3,000-5,000rpm and a separation in power starts at 5,000rpm and increases all the way to redline.  Since high compression, high revving engines are sensitive to temperature and pull the most timing at high rpms to avoid knock, this 30.2hp and 5.14lb/ft of torque loss was likely caused by the 25*F hotter test conditions and 44% of humidity.

Despite weather not being ideal to compare to our previous dyno runs, as long as do our back to back testing under the same weather conditions, we should have a valid comparison test.  This is why baseline testing is important and it’s difficult to compare dyno runs on different days (or even the same day if the weather changes significantly), let alone different cars with varying wheel diameters, the model of the tire, how old the tire is, motor oil, final drive ratios, etc…

Because of this we try to keep the variables down by using the same oil, same tire, and usually we do a good job at ensuring the weather conditions are as consistent as possible, but this article was purely for an A-B test of the K&N filter and we didn’t want to wait until winter just to see peak numbers above our previous 379.76hp pull –which will happen once the weather cools back down.

Project E90 M3 Airbox
The 4.0L V8 has eight individual throttle bodies (ITB’s) under that massive intake plenum which is fed by a large, oval intake tube that connects to the airbox housing a round air filter element.

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