Quote:
Originally Posted by mlifxs
Entity to be fair to you and the op it is worth mentioning that, per my orig response that I did the charcoal delete as well. So, you could be right about K&N filters and I could still be seeing a genuine improvement in hwy mpg due to the charcoal delete .... I did not isolate each in my testing. I don't know of course but it seems plausible that removing the charcoal filter is improving airflow in a beneficial way.
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Maybe. I'm not even sure why there is a charcoal filter past the airfilter element anyway. Seems to be BMW over-engineering to me. What I don't understand is what benefit the charcoal filter provides that it's worth sacrificing 1.5 (or any amount) of MPG. Considering BMW has one of the worst records meeting US CAFE requirements, they'd not put anything in the intake path that would restrict airflow and MPG. I'm assuming the charcoal filter is there to double clean the already filtered air to protect vital sensors in the intake tract. I've not wanted to remove the charcoal filter once I discovered it was there simply for fear of causing drivability issues.
It's good that you have been taking a somewhat scientific method to determining if the K&N adds benefit to the performance of the car (acceleration and/or MPG). Other than straight dyno runs on both filters on the same day can any appreciable determination be made.