Modified airbox (S4)

MRC remove the snow guard on the air box inlet and drill out 2nd inlet in the bottom then replace the OE cone filter with a K&N item. This is then joined using an 034 Motorsport large bore silicone intake tube.

The s4 has a cone filter as standard, inside the box. If you want sound you can modify the box as Cerbera said, which will give you the supercharger whine.
Don’t know whether you get gains from changing the pipe or if it’s a placebo effect from the additional noise.

Either way I am planning on doing it at some point

Cheap box mod consists of drilling out the hole at the bottom of the box. This is the same hole the 3.0tdi uses. It also has a snorkel attachment that sits under the front drivers headlight, you can buy this separate and add it if you like but just removing the blanking plate will suffice.

MRC uses a BCM filter, these are a dry foam filter as apposed to a K&N filter that uses oil to filter. Lots of posts about the oil from K&N ruining you MAF. I will not get into the fight about what filter is best.

I would recommend sticking to the OEM paper filter, save your money and just chang it more often. I'm sure a clean paper filter let's all the air in that the engine needs and filters it properly.

To let out the noise then there are a few who cut holes in the top of the box, this will let some noise out, I'm sure the OEM box for the S7 uses this technique. But you need to keep it small enough that the box still has positive pressure from the cold air feed from the front grille and your new hole (3.0tdi) at the bottom, this will stop warm air getting sucked in through your new "noise hole" at the top.

New 034 Motorsport intake pipe will help with airflow and with noise as the OEM disrupts air flow and has a resonator box thing on it to reduce noise.

If done right the whole thing can be a nice project and look good after.


OEM S7, Audi put the hole in for some reason. So it must do something.


Modified S4 box. Perhaps a bit much hole when compared to S7 above. A smaller hole will still let out sound and reduce chance of sucking in hot air from the engine bay.


A4/5 3.0tdi box and snorkel. Thread with more detail.



Airbox mod thread with some useful info.

And to really understand airflow and filters then read through this. Info Overkill

There is some damping on the airbox itself but I doubt that removing it will increase noise much . Changing the intake pipe itself to a simple silicone one should have most impact because the stock pipe includes both a damper and a Helmholtz resonator. Another simple mod would be to remove the multilayer damping plate which is screwed to the top of the supercharger housing. There are also a number of sound insulation mats around the supercharger but they are a lot more difficult to remove. Lastly there is insulation on the bonnet itself.

Interesting !
I’ve done the opening up the lower aperture on my A4 does any one know the part number for the lower scoop?

I’ve also made a number of holes in the upper grill but blanked the ones off on the top of the scoop with some carbon Fiber

Here are a few better pics of what I have done

Closed off the under bonnet inlet holes with some carbon fibre ( I can supply a couple more if these plates)
Then opened up the grill area and the bottom of the air box, the next thing I’ll be doing is making some vent holes around the fog light area and trying to source the 3.0tdi inlet snorkel