"This build journal entry is part of a special series on the development of my S85 Ultimate Powertrain Response Program.
This journal entry covers my learnings from the S65's program, and my road map with the S85 V10."
My learnings from the S65 DCT.
In November 2021, I complete the first phase of my E92 M3 suspension and drivetrain overhaul. My goal was to improve the S65's engine and drivetrain response.
Improving upon the S65 response requires comprehensive, complementary modifications through hardware and software changes.
The recipe combined a carbon steel lightweight flywheel, carbon fiber driveshaft, solid mounted rear subframe, OEM GTS DCT tune, MSS60 engine tuning and a stiffened electronic suspension.
It cured what I felt were the weakest points of the e9x M3: low and mid range hesitations and response along drivetrain flex during aggressive shifts.
The results were phenomenal and exceeded my expectations: it was the most impact set of modifications to the overall driving experience of my E92 M3.
The S85 SMG lightweight drivetrain program's.
After chasing and achieving superior powertrain response with the S65 DCT, I wanted to achieve similar results with the S85.
The weak points of the S65 are even more apparent on the S85: the low & mid range response, and the drivetrain flex are notoriously worst.
"There are, however, added challenges with the E60 M5."
It's just heavier.
The S85 engine response is further slowed down versus the S65 due in part to much heavier rotating assemblies.
The flywheel is heavier.
The driveshaft is lengthier.
The wheels & tires are heavier.
The brakes are heavier.
The suspension is softer.
The whole car is heavier.
It's still an M5.
It's heavy for a reason: the M5 is a luxury executive saloon with supercar DNA.
I personally use the E60 M5 for what it was designed for: daily driving duties, hauling groceries, bombing highways, and carrying friends & family to all corners of the Continental.
I would accept compromises, but none that would exceed comfort thresholds of passengers.
The aftermarket support is limited.
Once the pinnacle of BMW M aftermarket, the S85 aftermarket has dwindled down to a few vendors providing legacy parts. InfinityDesign is one of the few brands still putting efforts and ressources into new product development.
One of my goals with EuroConnex is to gather enthusiast owners and shine an honest light on ownership of these polarizing M cars. I hope this changes, and the lightweight drivetrain program is a cornerstone for revitalizing this platform.
"This is my road map to overcome these challenges and transfer some of the S65 learnings to the S85 SMG3."
Step 1: Improve engine response with more power.
I started here in January 2022 with the addition of the sealed carbon intakes and MSS65 DME tuning by Sal at InfinityDesign.
Power gains were felt and measured throughout the RPM range accompanied by sharper throttle response and a smoother overall power delivery.
This was reflected in my 100-200 times in the 8.7x range with these modifications alone. The S85 felt more eager, and the slight SMG tuning improvements by Sal made the SMG slightly more tolerable.
"We were still far removed from my M3 DCT."
Doubling down on power on increases.
I move forward with fitting the V3 long tube & equal length headers from InfinityDesign along with their specific Stage 3 tuning map for these headers.
The end results were amazing: the headers and stage 3 tune add considerable power to a stock S85: closer to 70whp.
It makes for exhilarating highway pulls and allows the S85 to punch way above its league.
"There's a caveat: it's all after 4,000 RPM."
It instead put a spotlight on the lackluster low and mid range response by improving the top end disproportionally.
Further power upgrades alone wouldn't solve the S85's weaknesses, and we were facing diminishing returns on a stock displacement V10 M5.
That part of the program was over for now.
"I'm eager to see if the S85 CSL Competition Spec Carbon Plenum by InfinityDesign further improves engine response with massively increased airflow and Alpha N tuning."
Step 2: Improve chassis response with more stiffness.
As I learned with the E9x M3, stiffening the chassis is a fundamental component to improving the powertrain's response.
I opted to follow a similar path to the M3 by fitting the EDC compatible, Bilstein B16 Damptronic electronic coilvers along with the Dinan's front and rear sway bar kit.
The chassis stiffness improvements were immediately noticeable on the powertrain.
As the E60 now squatted less under aggressive throttle applications, there were less flex in the drivetrain leading to improved engine and transmission response.
The SMG3's famous S6 shifts still unsettled the car, but to a lesser degree than on OEM suspension.
"Unfortunately, chassis improvements end here."
BMW M's selection of aluminum for the rear subframe makes it impossible to replace the bushings to solid aluminum due to material incompatibility.
The F10 M5 rear subframe was solidly mounted. We will never know the ultimate potential of the E60 chassis.
Step 3: Improve drivetrain response with less rotating inertia.
The next logical step was tackling the core component of the S85's weaknesses: the drivetrain.
Our choices here were unfortunately non existant to begin with.
The prototype carbon driveshaft
After having success with the e9X M3 carbon fiber driveshaft from YFCM. I convinced M. Lee to develop a prototype for the E60 M5 SMG3.
I received and installed the first prototype of the SMG3 Carbon Fiber Driveshaft by YFCM in August & September 22.
Lots of ink is spilled over these for all the wrong reasons. You can read more about the myths surrounding these here and what makes YFCM's patented product a proper solution.
I was able to road test it under various conditions and immediately noticed positive improvements without any downsides.
Unfortunately, the radiator electrical fan failed right after high speed testing. The car has since been at the mechanic awaiting the replacement radiator fan.
Once it's out of the shop, I will thoroughly document the improvements specific to driveshaft. Applications for the MT 6spd and M6 chassis will be available.
The carbon forged steel lightweight flywheel
The M5 V10 life forces you into positivism, and finding irrational ways to make up for time at the shop.
In August, I did just that.
I ordered and received the SMG3 S85 Lightweight flywheel by TTV Racing. I will write a detailed journal entry covering my unboxing impressions and the technical specifications shortly.
It's getting fitted while I await the radiator fan.
On any car, lightweight flywheels are a controversial modification: a lot of it has to do with subjective tolerances and preferences to drivetrain noises.
I personally dislike lightweight flywheels on manual transmissions with a 3rd pedal. I removed the JB Racing & Sachs HD Clutch combo on my S54 E46 M3 as it was unbearable in the city.
The reason is technical: the DCT doesn't have a throwout bearing.
"Throwout bearings in manual transmissions create more chatter, idle noises and in-gear backlash.
It's why you'll see owners of cars fitted with one push in the clutch pedal at stops.
The bad news: the SMG3 has one.
The good news: the ECU keeps it pulled at idle."
My hope is in-gear backlash is non-existent, and idle noises are similar to the S65 DCT. I expect low speed manoeuvres to be more jerky.
In anticipation, I deleted cold start to ensure I eliminate conditions under which lightweight flywheels are simply awful.