Are Performance Air Filters Worth It?
Performance air filters claim to increase horsepower and improve acceleration, but do they actually work?
The idea behind performance air filters is two fold. Number 1 is that a less restrictive air filter means the engine doesn’t have to work as hard to bring in air. If it doesn’t have to work as hard, which means it’s more efficient and makes more power. Number 2 is that it could also mean the engine pulls in more air, and with more air, the engine can inject more fuel to make more power.
Jason from Engineering Explained on Youtube conducted a series of tests. He took four air filters which were the stock filter he already had in the car (Dirty Stock), a brand new stock filter (Clean Stock), a low cost aftermarket filter (Cheap AM) and a K&N Aftermarket Filter (K&N). To test them out as accurately as possible, he ran the same car on the same Dyno, with the only thing that changed being the air filters. He tested each filter 3 times and picked the bet result. He then tested each filter out in the real world to see if there was in fact a noticeable difference.
Starting with the dyno runs:
First up was the old air filter, it’d been in the car for around 6000 miles and had bugs and dirt all over it. This should mean that less air can pass freely through the filter as it’s clogged up. Taking it on to the dyno he saw these stats, which will act as our base stats:
Dirty Stock Filter results -
He then swapped out the filter with a brand new stock filter. So without the grass, dirt and bugs this should mean that air can pass through more freely.
Clean Stock Filter Results -
So that shows an increase of 1.8 horsepower and 0.2 in torque just from replacing the filter with a brand new one.
Up next, he swapped out that filter for the low cost aftermarket filter. So again the idea behind performance air filters is that they offer less restriction to air flow which means that potentially, more air can pass through so that more fuel is added to the mix, giving more power. But also, the engine shouldn’t have to work as hard to pull the air through, which should also mean better performance. With that, here’s the results from the low cost aftermarket filter’s dyno run:
Cheap AM Filter Results -
So from the dirty filter to the cheap aftermarket filter we see an increase in Horsepower of 5.07 and an increase in torque of 3.57.
Moving on to the premium K&N Filter, the actual box it came in promised improved horsepower and acceleration. K&N are one of, if not the top brand for performance filters. They offer reusable filters that you simply wash out and throw back in the car which are built using quality goods that should in turn provide better results. Let’s have a look!
K&N Filter Results -
So comparing it to the dirty stock filter he originally had in the car, that’s an increase in Horsepower of 4.17 and an increase in torque by 5.28. When comparing the aftermarket filters the K&N actually performed worse (-0.9) than the budget alternative in terms of horsepower, despite it being one of their selling points. They did however perform better in torque than the other aftermarket filter (+1.71).
Real world test
Moving on to the real world tests, Jason did 3 runs of each test, tracking the times the car took to get to 60mph, from 20mph just in 2nd gear.
Dirty Stock took 8.96 seconds to get from 20 to 60, and 3.59 seconds to get from 45 to 60.
Clean filter took 9.01 seconds from 20 to 60 and 3.61 seconds to get from 45 to 60.
Cheap AM Filter took 8.91 seconds to get from 20 to 60 and 3.56 seconds to get from 45 to 60.
K&N Filter took 8.81 seconds to get from 20 to 60 and 3.49 seconds to get from 45 to 60.
So from these results we can see that the results between dirty and clean filters are extremely close, so having a dirty filter doesn’t make a whole lot of difference. Upgrading though, we do see a difference however it really isn’t a big one, or even noticeable.
The difference between the best performing aftermarket filter (K&N) and the stock filter is about 2.5%, which you really wouldn’t notice unless you’re testing them in a scientific way with precise tools. Just driving along this 2.5% wouldn’t be noticeable, although aftermarket filters sometimes do make the car sound better!
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Special thanks to Matti from MWM Digital for helping us with the blog!