Z KN filters and exhaust

[50thZ]

I installed KN filters in my new 2025 Z and noticed that there is "more" black smoke stains on the exhaust tips. I ran the car with stock air cleaners and very little black stains. Put the KN's back and this is what I get. Any ideas?

 

[50thZ]

Has 2500 miles on the odometer.

 

[mikecarpage]

are those smoke stains or is the finish of the tip flaking or chipping off? when zooming in it looks like it's flaking or chipping on the left/upper parts. the lower part looks to be a stain

 

[5amp5on]

I’ve never seen soot on top like that, only a little on the bottom after aggressive driving.

I run the Mishimoto with oiled filters and don’t get anything like this.

 

[50thZ]

It is not flaking it cleans right off. I gave it some hard acceleration with both types of filters. KN more soot.

 

[thesilverbullet]

Mine does that before and after installing k&n filters. That is a product of running a rich fuel mix (a low a/f ratio) which is typical for stock setup especially for boosted engines.

she runs richer on cold startup and up top (higher revs) to prevent lean knock and many other conditions. So mainly dependent on your driving habits.

The k&n will provide more air creating a leaner fuel mix (cleaner exhaust) but computer will just dump more fuel to adjust to the higher air flow to meet the target a/f ratio. So possible the computer over compensates at first and will learn the increased air flow and not have to be as aggressive.

FYI- i noticed the stock ss tips have a dull finish, i hit mine with a little chrome polish and now they stay cleaner longer.

 

[50thZ]

Mine does that before and after installing k&n filters. That is a product of running a rich fuel mix (a low a/f ratio) which is typical for stock setup especially for boosted engines.

she runs richer on cold startup and up top (higher revs) to prevent lean knock and many other conditions. So mainly dependent on your driving habits.

The k&n will provide more air creating a leaner fuel mix (cleaner exhaust) but computer will just dump more fuel to adjust to the higher air flow to meet the target a/f ratio. So possible the computer over compensates at first and will learn the increased air flow and not have to be as aggressive.

FYI- i noticed the stock ss tips have a dull finish, i hit mine with a little chrome polish and now they stay cleaner longer.

Thanks for the tip.

 

[50thZ]

I found this article on the internet. Credit to Author: Landon Thistletown from an article on Bike and Car Styling Protector.

https://bikeprotector.co.uk/are-k-n-air-filters-bad-for-maf-sensors-the-surprisingly-honest-truth

 

[trackratZ]

K&N works for performance but for daily needs lots more maint from dirt and contaminants from streets etc. Check towards the end of this video when testing particle flows.

 

[Mugzilla]

If I had to do it over again, I would go with an open air filter (Instead of the KN CAI) so my deaf-@$$ can better hear the turbo blow-off sounds....