I’m going to start with a tech diagram of the induction system up to the turbo compressor inlet.
Now, we can start the discussion.
Starting at the beginning of the intake system, there has been some hear-say that the removal of part #14 (31474516) is both easy and gives more supercharger noise. This piece acts as a shield for the “short ram” snorkel that leads into the air box. It can supposedly be removed by simply removing the grill and taking it off, as it’s “not really held in with anything.” I have yet to do this myself, so I cannot comment on if it affects sound or not. It is also worth considering that this shield covers the inlet to a very short snorkel that also lacks verticality, so you could be putting yourself at risk of dust, or worse, water intrusion into the air box during a storm.
Next, I don’t really understand the function of the other snorkel #11 (31474519) which leads to #12 (32252710) and #13 (31474518). The combined, yet separated, snorkel inlet (also part #10 31474810, but looking up that pn will just bring you to the snorkel tube, just trust me when I say the inlet separates these two snorkels) to the air box would place the outlet for this snorkel directly under the inlet to #20 and therefore the MAF sensor. Here is the system fully assembled:
These snorkel systems remain fully separated as they enter the air box. Don’t ask me why. All I can tell you is part #11 feeds to the bottom section which gets aimed directly at the MAF inlet while the short ram (part #10) gets fed to the top section and sent to the rest of the filter.
I would suspect that blocking off the larger, longer snorkel (part #11) combined with a removal of part #14 could lead to an increase in induction noise and potentially more airflow. Alternatively, you could dremel out the separation between the two. I have no idea how either of these options may affect the performance of the vehicle.
Briefly, you can replace your air filter (part #2) with a high flow drop-in of your choice. I have a K&N drop-in (33-3065) personally, and I can confirm it gives slightly more induction noise, especially supercharger whine under heavy load around 2k-2.5k rpm. Alternatively, you can replace your entire air box with a cold air intake system like a do88 or MST kit. My car threw a lean code when I did that, all for what I felt was equivalent sound to a drop-in, ymmv.
Moving on to part #20 (31657599). This is called a “bellows” intake hose on the catalog. The material composition of this part as well as its shape dampens sound. Luckily for us, EuroCompulsion already has a bolt on solution for this part called the V1 Intake System. I don’t have this on my car yet, but I plan to get it soon. Some report it increases sound just a slight bit. Link: V1 AIR INTAKE SYSTEM | (VOLVO SPA T6 ENGINES)
Now, here comes the (not) fun part. Starting with part #17 (32222167). This is the craziest 90 degree intake turn I have ever seen. On the end closest to the air box, you can see it has what appears to either be carbon filtration material, sound deadening, or both.
On the other side, you can see its resonation chamber to cancel sound and where it connects to part #39.
The connection to part #39 (32222165) and part #39 itself is where **** hits the metaphorical fan.
You can plainly see where part #17 connects to it. It’s the right half of the image where there is an open hole with more resonation chamber. However, there is this extra left part with three openings. This section appears sealed off from part #17, but yet still connects to it. This will make more sense once I show you the other side of this part. For now, know this is where your PCV connects to as well as what I assume are vac references.
This is the other side of part #39. The right side connects directly to the supercharger air inlet, while the left side would have a throttle body (part #53 31459842) attached to it to mostly bypass the supercharger. You can also see they have a resonated connection between the two. This would indicate this is the only area the supercharger can get air from, which seems mighty tiny to me. It also means the extra area with the three holes on the other side of the part we mentioned before is likely a vacuum zone to cancel noise, similar to what some exhaust systems have, and to suck out PCV gases and the like.
Now we split into two intake systems. One for the supercharger and one for the supercharger bypass. If we follow the bypass, we get to part #48 (31474846) which comes directly after the aforementioned throttle body, and is once again called a resonator. This one actually seems that it would be fairly trivial to replace with a standard intake tube. However, it is buried behind the motor and is covered with a heat shield. So it would need to be replaced with either a heat resistant tube or a ceramic coated metal one.
If you follow the the track through the supercharger, you will arrive at part #47 (31439783) which is also a resonator, and is the outlet for the supercharger. This one resembles part #17 to an extent.
This all feeds into part #27 (32222128) which is the funkiest intake pipe I’ve ever seen, with two inlets and one outlet, and (I believe) it all feeds into the turbo. This pipe also appears to have its own tiny resonation boxes molded into it, so it would need to be reverse engineered and fabricated without them as well.
The turbo has a resonation box just after the compressor outlet. However, it is easy to access as shown here: Turbo Muffler? and could easily be replaced with a standard piece of charge pipe. It is also replaced by the do88 intercooler piping and big pack kits: https://www.do88.se/en/artiklar/hose-kits/volvo/s60-v60-xc60-s90-v90-xc90-spa/index.html
Brief side note, it has also been confirmed that removing the foam that covers the supercharger increases the whine, especially around 3k rpm as seen here: Supercharger Whine
There was some discussion of the possibility that foam was for heat insulation, but truthfully, given the location of the supercharger (crammed between the engine and the firewall), I highly doubt it has much if anything to do with heat. Plus, removing the foam also means you can actually see the beautiful supercharger hanging off the back of the engine. However, I must say to do this only at your own risk.
As you may be able to tell, a lot of this intake system pre-turbo would require custom fabrication and a ton of labor-intensive work to remove and replace with non-resonated parts. I would love to one day replace all of these resonators with straight through pieces to get as much induction noise as possible from the motor, however I do not think it is a reasonable goal for someone with a skill set like mine (i.e. no fab experience or time to do so). Out of all of them, I believe part #39 would be the most difficult to replicate and replace, along with its connection to part #17. If anyone takes the plunge, please let me know what you come up with.