"These build journal entries are part of a Special Series on the development of the S85 SMG3 OE+ forged steel lightweight flywheel.

This specific journal entry covers my unboxing impressions of the flywheel and a dive into its technical specs."
- Matt

The M5 V10 life forces you into positivism [...]

In August, my V10 M5 broke down as I begun testing of the prototype carbon fiber driveshaft.The radiator's electrical fan failed and the S85 would quickly overheat in stop and go traffic.

[...] and finding irrational ways to make up for time at the shop. 

I ended up doing just that: I got with TTV Racing who developed the S65 DCT lightweight flywheel and got to task developing the SMG3 S85 Lightweight flywheel.

TTV Racing already had the specs to make this. I quickly received the flywheel via DHL express later in September 2022 and unboxed it to cover its technical features. 

The specs. 

It's machined from carbon forged steel. 

The flywheel is made from carbon forged steel; it's a higher density material than commonly used aluminum. This flywheel comes in at 8.5 kg / 18.7 lbs. 

Carbon forged steel is also materially stronger. It matters most to us V10 owners due to its increased resistance to deformation from heat & torque. 

It works with OE clutch.

Carbon steel offers a wider range of machining optimization possibilities: you can occupy the same space with less weight, or more space with similar weight. 

TTV Racing designed and machined the flywheel to fit with the OEM clutch: it integrates dowel pins, threaded holes and machined reliefs to align and bolt an OE clutch kit.  

Furthermore, the OE+ flywheel is machined to fit with the OE starter and crank sensors. The alignment is guided by a slightly larger bolt hole. More information will be found in the journal entry covering the installation. 

It's high speed balanced. 

TTV has 2x high speed balancing machines in house designed to achieve OE matching balancing to match with the inductive sensors of the S85. This is critical as it has a direct impact on the camshaft positions.

The balancing is done by machining speed holes on the flywheel: taking away weight at areas specified by the balancing machines. The 3rd balancing hole was punched through. This was deemed inconsequential by Ben at TTV after balancing validation.

Up next: time to install this and give you a few tips.