I use Pipercross filters £19 from Demon Tweeks,advised by engine builders at a car manufactures in Crewe that reducing the volume of any air box is a no no.

Shazaam's graph looks like my power runs with and without an over the bellmouth filter. I was amazed at the power gain just by removing it (and it was clean;)) And the noise is justification by itself.

That's compared to no filters at all.

If you're running the standard ones at the moment the Pipercross ones flow a little better (allegedly) so you'll probably get an increase, and you're unlikely to see a loss.

When you buy the filters, you need to use the plastic cage from the original ones, so don't go throwing them out just yet. ( I had to scrounge some from a dealers bin :) )

yep

i nearly got caught out with that 1 too, keep the black plastic covers

Piper cross for the 998.
Read loads of threads on here regarding this and thought it was the best way to go from standard.
Got mine from Cornerspeed, similar price to all above but you might get 10% if your a DSC member?

I run an ITG in airbox filter (ie., it fits over the bellmouths) on my 996. This is a simple option on the 996 'cos it doesn't have shower type injectors above the bellmouth - 998's etc with injectors sited above the bellmouth make this type of filter installation a lot more fiddly.

This set up lost 2bhp over no filter at all (also running carbon air tubes without provision for filters) with no obvious dips in torque - just a gradual loss from about 6000 rpm upwards - and was chosen because I planned to race the bike and wanted protection in the event of a get-off (using the tank as the airbox top means an airbox full of gravel is almost guaranteed in any serious 'racing incident'). To my mind this should be a serious consideration for any track-day junkies.

I don't have any data comparing this set-up with standard filters - but if we assume standard filters will not be quite as good as no filter at all then realistically the in-airbox job is probably costing about 1bhp and I defy most anyone to be able to spot a <1% bhp change without the aid of a dyno!

Does muffle out some of that airbox noise though.

Fitted piper cross, no filter in airbox, sounds great, and its livened things up....

RESULT

HAPPY HAPPY HAPPY

Geoff M:burn:

Er, whats that blue tube...............and no grommet?

It's the connection to a corsa-style crankcase ventilation system.