I am about to change the BMC air filters fitted 12 months ago and which have done 3 track days and 4k miles. I change air filters (BMC cotton type) far more frequently than Porsche's schedule and normally just buy a new set. However this time I thought about using BMC's cleaning kit to clean a previous set that I hadn't thrown away (removed in September 2017). However having looked at the process on youtube, I decided that cleaning panel filters is simple but re-oiling cone profile ones is nigh on impossible to do properly.
Anyway, out of interest I thought I'd see how much debris was in one of the previous pair of filters. This example had been in the car for a little over 12 months and had done around 6k miles and 7 track days. The pictures are below; the pile of debris from just one filter (no idea whether it was fitted NS or OS) contained only very fine particles, significantly smaller than a grain of sand and some fine hair-like strands. No leaves, no cigarettes, no track rubber etc., so I assume the side intake grills are keeping larger stuff out. I did not think it politic to weigh the pile with my wife's kitchen scales but it measured 5mm x 5mm x 1mm and I presume the second filter would be a similar volume. It would seem likely to be brake dust with some road dust. As the car is used on track from time to time, the composition of my filter debris my be different from those with normal road use.
My conclusion is that if you run your car on track, you should change air filters at least annually and probably after a half a dozen track days.
Top Tip: don't empty the debris out onto a clean garage worktop although if you do, Iron Out does turn the dust purple and allow its removal...
Anyway, out of interest I thought I'd see how much debris was in one of the previous pair of filters. This example had been in the car for a little over 12 months and had done around 6k miles and 7 track days. The pictures are below; the pile of debris from just one filter (no idea whether it was fitted NS or OS) contained only very fine particles, significantly smaller than a grain of sand and some fine hair-like strands. No leaves, no cigarettes, no track rubber etc., so I assume the side intake grills are keeping larger stuff out. I did not think it politic to weigh the pile with my wife's kitchen scales but it measured 5mm x 5mm x 1mm and I presume the second filter would be a similar volume. It would seem likely to be brake dust with some road dust. As the car is used on track from time to time, the composition of my filter debris my be different from those with normal road use.
My conclusion is that if you run your car on track, you should change air filters at least annually and probably after a half a dozen track days.
Top Tip: don't empty the debris out onto a clean garage worktop although if you do, Iron Out does turn the dust purple and allow its removal...
