"These build journal entries are part of a Special Series on the development of the S85 CSL Style Carbon Plenum and S85 CSL Competition Complete Carbon Intake System.

In this entry, I made it! I share my notes further documenting the decibel and tone differences.
- Matt

How sound clips should be made.

It needs to be said: I despise bullshit marketing - and there's a ton of it in the world of BMW M modifications. 

One of my biggest pet peeves are sound clips for S54 CSL airboxes, S65 carbon plenums and S85 carbon intakes filmed with microphones in the engine bays and altered, enhanced noise. 

These brands and YouTubers are only setting people up for disappointment on expensive purchases that are first and foremost about sound enhancements. 

How you should listen to sound clips  

These brands would probably make the case they compensate for people's crappy smartphone speakers and their lack of quality headphones on hand. 

They wouldn't be wrong, but I don't think their solution is right. Appealing to your intellect through transparency is my preferred method. 

My filming & sound recording gear.

Life, death and supply chain issues delayed my plans to record the plenum one too many times. 

I finally got all the required gear 3 weeks ago. 

My setup

• A7iii by Sony
• 16-35 2.8 G Master lens by Sony
• MKE 400 shotgun microphone by Sennheiser
• Dual Suction Mount by SmallRig 
• Do not use this outside your car. You'd need a triple mount for a DSLR at minimum. 

The final setup is quite bulky, but I couldn't sacrifice quality.  

Mods that may affect sound. 

It's also important to specify the modifications that may influence the final sound spectrum when recording your clip. 

These are the ones that matter:

1. Sealed Carbon Intakes
2. OE+ CSL S85 Carbon Plenum 
3. AlphaN Performance Tuning
4. Long Tube & Catless Long Tube Headers
5. SMG3 Lightweight Flywheel 
6. SMG3 Carbon Fiber Driveshaft 

The sealed carbon intakes made great noises already, but there was always something missing coming from the S65. 

My driving impressions.  

Before we get to the video, I'll touch on my driving notes cumulated over the last months of driving with the plenum fitted. 

If you WOT it 

This is carbon airbox, intake & plenum 101: if you want to hear it, you need to go WOT for the most part. 

It's the major difference between exhaust and intake modifications. Idling sounds are unchanged: the V10 still sounds like a diesel without an exhaust system. 

If you go WOT, you will be hearing more intake noises. 

[...] it will be louder all over the range.

What makes the E60 experience so unique was BMW M's decision of bolting the S85 to a luxury sedan chassis. Answering the what-if question is why the swap market is so popular. 

The E60 is well insulated and road noise is minimal [...] in stock form. My OE+ Carbon Plenums were thus mostly heard about 4,000 RPM. 

The CSL Carbon Plenum finally solves the complete range equation for V10 intakes: you can hear the increase in decibel across the entire range at WOT with sweet spots.

The VANOS zone 

The VANOS cam overlap is responsible for the sudden change in power in the mid range, propelling the S85 to its legendary redline with stupendous force. 

I used to avoid 4,000 to 6,000 range before fitting the lightweight flywheel and carbon driveshaft. The drivetrain modifications finally made the mid range responsive. 

The S85 was unfortunately muted in that range, and it shouldn't be. 

The V10 M5 is infamous for its relative flat spot in the mid range.

 

[...] is the CSL zone. 

The VANOS cam overlap is also responsible for signature induction noises in the S54 and S65. 

The CSL Carbon Plenum was the answer to get those signature induction frequencies out of the V10. 

The 4,000 to 6,000 range is now both highly responsible, and puts on a grin on my face as I hear the new melodies make it out of the engine bay.

I purposely short shift at 6,000 right into the 4,000 rpm range on my daily commute. The sound is godly. 

The sound spectrum: take a listen. 

Filmed in Mexico. The G90 was all in my head :)

 

You can order your CSL OE+ plenum here.

Up next: we're levelling up and I'm documenting the development of the much await Competition Spec variant of the S85 CSL Plenum project. 

More sound, and maybe, hopefully, even more power.