Originally Posted by EXPLICIT

Re: panel filters.

Our UK counterparts have conducted some flow rate tests on the replacement dry filters. STI Motorsport unit came last - factory paper filter was best value for money with the typical non oiled aftermarket 'green' and hks filter coming up as the best flowing unit.

Seems the homologation STi filters whilst they are a motorsport unit, their intended use is for homologated Group N use. I.e. offroad. Sythentic weave material filters very well and the metal screen is effective in keeping the rocks at bay. These positives have an effect on flow capacity for the sake of reliability.

Interesting stuff no doubt.

Originally Posted by type25

when you consider that group n cars have 32mm restrictor on the inlet to the turbo...

air filtering quality becomes more important than air flow quantity.