heinzboehmer's 2002 Topaz 6MT Coupe

[Slideways]

I can't say for certain, but the fit of the filter is pretty bad along the bottom edge. Sand does collect outside the filter lip on the airbox, but there's no obvious sand inside. Might be worth scanning and printing some TPU inserts to seal up the gaps.

I wonder if your brake duct scoop is making the sand intrusion situation worse.

Genuine CSL airbox after about 15k miles with new BMW filter



My guess is that the BMC filter allows more flow, but is worse at filtering fine dust particles. Even the non-CSL paper filter allows some stuff to go through, just not nearly as much.

[0-60motorsports]

Genuine CSL airbox after about 15k miles with new BMW filter



My guess is that the BMC filter allows more flow, but is worse at filtering fine dust particles. Even the non-CSL paper filter allows some stuff to go through, just not nearly as much.

I just installed the blue ECS one....lets see how that does.

[Bry5on]

Genuine CSL airbox after about 15k miles with new BMW filter



My guess is that the BMC filter allows more flow, but is worse at filtering fine dust particles. Even the non-CSL paper filter allows some stuff to go through, just not nearly as much.

That’s what mine looked like until I added foam. Now it’s totally sand free with just a thin vapor layer of motor oil from the crank case vent.

[heinzboehmer]

I don't have a picture of mine handy, but it's nowhere as bad as that.

Thin film of oil though? Definitely