Having read a couple of threads on the subject of foam filters in the airbox, I thought I’d just add my two-penneth…
In the last week I’ve ridden with no air filter, and ITG filter and a JHP filter and my findings are as follows: -
1) No filter – enormous amount of induction noise, immediate but quite harsh throttle response, plenty of coughing and spluttering on a neutral throttle and small birds appear trussed and roasted out of the Termi’s if they fly too close to the air intakes…
2) ITG foam filter over the bell-mouths – much less induction noise, throttle response still immediate but now much smoother, although there was still plenty of spluttering and backfiring to be had around town. Power according to the patent arse-dyno seemed a little down on the no-filter option but was more usable as the front wheel stayed on the ground more often when accelerating hard due to the predictable delivery.
3) JHP foam filter over bell-mouths – less induction roar than with no filter and a smoother throttle response than either of the other options. The power was not noticeably down on the no-filter option but, again trusting the buttock-o-meter, there seemed to be a little more ooomph than with the ITG filter although it was still very smoothly delivered. There was also less chunter and back-firing around town.
The bike is a 996SPS with the Termi chip installed, hence a certain amount of coughing and spluttering around town is to be expected, and each run was over the same roads in the same conditions.
While the science may say that these filters are bad for throttle response and power, in the real world all I noticed was less bucking and backfiring on a neutral throttle and more predictable drive when I twisted my wrist.
I’ll be sticking with the JHP filter to protect my precious internals (and those of the engine) from debris and the odd thrush/blackbird/starling.
Handy Hint: If you’re trying to install one of these filters it’s a real pain to get it to stretch all the way over the front bell-mouth as there’s not much room down in the depths of the airbox for your fingers to get around. Stick your fingers through the hole for the rear inlet and position the filter by pushing it into place over the front bell-mouth from inside the foam – it’s much easier.
Linear Mode
