How to improve the sound and performance of the intake
The intake consists of a tube connected to the airbox and intake manifolds on the other side, an airbox containing the original filter, a tube that allows fresh air to be sucked in and a resonator. The latter probably allows you to improve performance at low revs and recovery, as well as reduce the resonant sound.
How to improve performance?
On a stock car it is advisable to only change the filter by placing a panel one (for example a BMC one); among other things, this is the only approved and legal solution (at least in Italy). The gains are minimal but the sound will also improve.
On a car that is used only on the track, you could aim for a direct intake with a cone filter, which obviously requires a remapping of the ECU. With this solution you lose a lot in the low revs, a little in the mids and you gain something at the top. Same thing for dynamic aspirations, CDA etc.
NOTE: removing the airbox and placing a cone filter directly there will result in a decrease in performance: in that position you will filter hot air! The airbox has a tube that already goes up to the bumper to draw in fresh air.
On a heavily tuned car, especially if done with R2-style specifications, you could aim for an R2 airbox: however, this solution is really expensive and the cost / benefit ratio is low. On a stock car it is useless. Obviously it needs mapping.
Another solution widely used in the UK is to replace the original airbox with one of the Clio 172 Ph1, which does not have a resonator
Car with ktec manifold and exhaust. Original airbox blue line, Clio black one.
Removing the resonator will drop performance around 2,000 rpm! (So changing the airbox, changing the hose, direct intake, cone filters, etc.)
How to improve the sound?
The cheapest solution, that is free, is to eliminate the credit card-shaped filter/bung present in the airbox; if you don’t see it, it has probably already been removed.
The next step is that of a panel filter which as mentioned before will improve the sound.
Another option, intermediate both for sound quality (which will increase a little) and for loss of bass performance (which will therefore decrease) is to remove the resonator and / or put a replacement tube like the Samco one.
As you can see, this sleeve removes the tube that ran down into the resonator.
Samco pipes cost quite a lot: as a cost / benefit ratio we are not there and for this reason this solution is rarely used. Furthermore, as mentioned above, the performance around 2,000 rpm drops!
BMC panel filter:
Ultimately: for 99% of cases I recommend that you remove the airbox filter and replace the filter with a panel filter. In case of a heavy tuned car you have to evaluate what you want in terms of performance (high, low, medium, recovery, etc.)