"These build journal entries are part of a Special series on the development of the S85 CSL Style Carbon Plenum written in collaboration with the design & engineering at Infinity Design.

In this entry, I cover the initial tuning tests, the tuning dilemma of the OE+ variant of the plenum, my AlphaN realization and chat on MAF map compatibility.

In a true echo to the V10 M5 ethos, this entry has best reflected a 3 months cycle of lows and highs with my E60."
- Matt

A streak of V10 lows. 

Since September 2022, I've since ran into a few cases of V10 lows. The failures created an environment of generalized anxiety: a common dynamic of the V10 M5 ownership. 

• The radiator electrical fan went on eternal vacation 
• My lithium-ion battery tests failed as it wouldn't handle cold temperatures and the E60's energy needs.
• I didn't push a PCV hose on the installation leading to slight oil leak and fuel smell. 
• Three (3x) dowel pins sheared off my OEM clutch, causing the SMG's 6th gear actuator casing to crack.

I misinstalled the driver side PCV hose on the OE+ CarboProject plenums. The guys at Innov had a good laugh about my DIY skills. 

To add insult to injury, I broke my 3rd hood latch handle & bracket in a year. 

The lowest low. 

I installed the plenum in late October and we started her up using my MAF/MAP stage 3 tuning file. It immediately got codes for air leaks. 

The car wouldn't idle for extended period of times without trigger codes. 

• INPA read bank 2 misfire codes, and cylinder 8 would shut off.
• The remaining cylinders were on reduced power without a complete limp
• The pre-cat 02s of bank 2 had issues hitting the voltage requirements
• The misfire detection monitoring system of INPA would validate the misfires and cylinder 8 shut off.
• I monitored the idle control actuators: they weren't able to compensate for the air leak.
• Adaptions showed -10.00 air leaks on bank 2.

This prompted Sal and I to drill down troubleshooting of the plenum down to every single bolt and gaskets, along with testing out 20+ tune files between MAP and AlphaN. 

We were so anxious about the plenum being a source of air leaks, we couldn't think it was anything else but the plenum or its peripheral accessories. We swapped 2x Positive Crankcase Ventilation (PCV) valves. This still wasn't it. 

None solved the problem entirely. It had to be the CSL plenum eh?

MAF tuning didn't work then. 

The stock S85 V10 uses Mass Air Flow (MAF) sensors located on the intake inlet tubes to monitor air flow. They are extremely sensitive sensors when wired to the MSS65 DME of the S85. 

Throughout this entire time, MAF tune files simply wouldn't work considering the air leaks code. 

The Sealed Carbon Intakes have the MAF bung integrated on the upper carbon inlet tube. 

AlphaN was the only way forward.

Snow quickly settled in on the North East of North America. The M5 is my Winter daily driver. 

It had to be drivable.

AlphaN is the state of engine mapping required to run an S85 as an open air V10. It's always used when fitting velocity stacks. Considering the long term air leak adaptations, AlphaN was the only way the car would remain operable in most circumstances.

I thoroughly documented AlphaN and the various BMW M engine mapping types in an earlier journal entry here.

TL:DR; I am not going back to MAF engine maps; AlphaN was, and is the only way forward.

The culprit: a case of confirmation bias. 

While AlphaN made the car much more enjoyable to drive, it didn't solve my idle air codes. 

After weeks of trouble shooting, monitoring and further testing, we found the culprit with the guys at InnovAuto. 

Exhaust manifold (headers) gasket failure. 

When fitting the Infinity V3 headers, we didn't change gaskets as an experiment. That didn't work out. 

Further validation.

To validate we did indeed go crazy, a few plenums were sent out to members Sal and I know well to do testing. They didn't have the air leak issues I had.

Alex was the second V10 owner to get this fitted. I envy the complete matte kit. 

The final word on MAF compatibility. 

Some members have to run MAF compatible tunes on their V10s due to emissions regulations and testing in some juridiction of the world. 

California. 

As each V10 engine has different state of sensor readiness and long term adaptation values, Sal does individual MAF calibrations to ensure full drivability of your V10 M5.  

If you're outside California and aren't subject to similar regulations, I personally recommend AlphaN.

The end of the tunnel. 

In a true echo to the V10 M5 ethos, this Build Journal entry has best reflected a 3 months cycle of lows and highs with my E60. 

With the latest combination of the lightened flywheel, carbon driveshaft, CSL plenum and AlphaN tuning, I'm nearing the end game of my S85 Ultimate Response blueprint. 

The combination of naturally aspirated mountain of power, emphatic intake and exhaust sounds, and peeling away to discover the raw, and analog potential of this chassis is an automotive experience I wish to all BMW M owners with the pockets to endure. 

The driving experience is nothing short of magical. It is the highest high in M world. Whether I'm dosing off on endorphins now that it's fixed is an entirely different debate. 

Up next: I finally get to document my driving impressions of the CSL S85 plenum in OE+ variants

[...] with sound clips, finally!

New mid range CSL'esque tunes, more volume across the board, this is a must have. 
- Matt