"This entry is part of a Special Series on my S65 lightweight flywheel experiments as a part of my Ultimate Response Blueprint.
I’ve always been weary of lightweight flywheels and was anxious to installing this considering the labor involved
In this entry, I get my hands on the 6spd variant of the S65 forged steel flywheel. I compare both transmissions' vastly different mechanisms, and document the technical specifications of the 6spd unit. "
Same S65, very different transmissions.
The M3 V8's DCT unit was the first double clutch transmission in any BMW M production car. It took years for lightweight flywheel offerings to make their way to the market.
Since late 2020, I've been sourcing and bringing to market new drivetrain offerings with TTV Racing. The DCT was the first product I personally tested, and marketed in collaboration with the Englishmen.
The DCT uses a unique flywheel design and mechanism. In short, the flywheel never comes into contact with anything. It is purely a balancing and engine start device bolted on the crankshaft.
This is my DCT flywheel installed in November 2021 [...] 40,000 km later. Little else than dust had come into contact with it.
The gear shifting happens internally.
The two clutches have different diameters, and operate off separate shafts. There's a plethora of discs. I will dive deeper in a future series on DCT clutch replacements.
The traditional 6spd unit.
Many 6spd GS6 owners jumped on board and got their specific variant. I had never gotten my hands on it, until now. Below, I go through the technical specifications of the 6spd design from TTV Racing.
It's a traditional flywheel design engineered to be bolted to the original 2009+ clutch or equivalent.
The flywheel has the required threads and dowel pins to align, and bolt with the clutch. It spins as a complete assembly off the crankshaft.
Here's my S85 SMG3 lightweight flywheel and OEM clutch bolted together.
The S85's SMG3 lightweight flywheel weights approximately the same as a Genuine BMW S65 dual mass flywheel.
Why bring up the V10? Well, this flywheel will also fit the S85 with the S65 clutch and slave cylinders if you have an original 6spd, or a conversion. The SMG3 was just different.
The flywheel is relatively light, coming in at 13.2 lbs. Due to the design differences, it is heavier than the DCT flywheel.
However, there's a positive catch: the weight delta with the original flywheel is bigger as it weighs 27.5 lbs. In short, you will feel a bigger difference on the 6spd.
This area is where the first clutch disc comes into contact with the lightweight flywheel.
The 6spd variant is machine from forged carbon steel just like the DCT. It's preferred over aluminum for its higher density, allowing the flywheel to be machined to a smaller package for similar weight to aluminum, while having higher thermal capacity.
This is the engine side. The design hollows up this section and is where most of the weight is removed.
The flywheel's outer section is machined with a dual teeth outline.
The upper section allows the crankshaft position sensor to feed data to the MSS60 to performance its calculations.
The lower section is for the engine starter gear. Here it is pictured at the top.
The flywheel itself is aligned with the starter motor with the slightly out of round bolt hole. This is matched to the crankshaft.
As always, TTV Racing dynamically balances all flywheels in-house.
Each hole is carefully machined to a specific depth, shaving off a precise amount of weight.