K & N 451 air filter question please!

[Nicholas]

For those who changed over to the K & N air filter for the smart 451, what part number is it and have you noticed any real preformance inprovement? Possible better "pick-up" or any increase in gasoline mileage? If any change, can you back-up your beliefs, not just a "feeling".

[WhiteNBlack08]

Part number is 33-2417. It's officially listed on K&N's site now. I installed one shortly after getting my smart, it did "feel" peppier, but for real world results, I did start getting about 2 mpg better after installing, and I didn't change anything else on the car.

[mvaldes]

Subjectively, I felt more "oomph" after installing the K&N than the DTH exhaust! No real change in gas mileage that I can attribute to it. However, the car was pretty new when I put it in. And, as many have found, my mpg increased as the mileage on the car increased, at least up to about 7k. While it's slightly off topic, one thing that I did find that gave me a consistent 2 mpg increase was an air scoop - that was a very pleasant surprise from what I planned as a cosmetic mod.

[toibenz]

Don't notice a bit of difference in mileage or power. I average 40 mpg. I do like their superior filters though.

[scdaf]

Originally Posted by toibenz

Don't notice a bit of difference in mileage or power. I average 40 mpg. I do like their superior filters though.

K & Ns are actually a MUCH less effective filtering device than stock paper filters. They let more air through by offering less resistance to its travel by having larger, less restrictive openings in the filter media. The reason they became so popular in racing is that they offered decent filtration without a lot of constriction on engines which people expected to rebuild every few racing hours.

Since I hope to go 250,000 miles or more without rebuilding my smart, I'll stick with the superior paper media.