Let’s talk S65 lightweight flywheel

Let’s talk S65 lightweight flywheel


I’ve always been weary of lightweight flywheels and was anxious to installing this considering the labor involved.

I have a lightweight flywheel and race clutch on the E46 M3 from an unknown brand. I like to say it’s like dropping a bucket of bolts in a blender at idle. 

This is an unedited clip to show the true, sound and effects the TTV flywheel has on the S65 & DCT. 





I can only describe it as a slow, heavy metal sliding sound. It’s unlike any other lightweight flywheel sound I’ve heard - you really need to look for it with headphones.

One of the reasons why is the DCT has no throwout bearing, a common source of rattling even in a stock E9X M3 manual transmission.

The TTV flywheel is a single mass design milled from carbon forged steel. It’s higher density than aluminum, commonly used by other brands.

This allows is to be machined to a tighter package, further limiting rattles. 

You can make it out starting at 20sec, oil at high temp, no trickery that hides chatter. 

Why I did this.

The TTV flywheel shaves about 8 lbs off the updated & lightest OEM DCT flywheel. It will shave off 18 lbs off the early production DCTs.

The science to it is simple; reduce the initial moment of inertia to improve performance.

As you reduce rotation weight further out to the radius, the more drastic the effects are at low rotational crankshaft speeds.

On my first test drives, I thought the clutches & flywheel were slipping off each as it was so much faster.

Maybe tires were too.

They weren’t.

I unwillingly hit the 8,600 limiter a few times, catching another gear much faster than it used to. 

It fixed a common complaint about the sluggish mid range of these engines. 

It drastically improve the DCT’s shift operations; everything happens quicker now with no added jerkiness.

No tune or adaptations needed.

My bottom line

It changes the driving experience and gets us ever closer to challenging GT3s. 

It’s definitely something that should be on any DCT’s owners list. Stay tuned as I set up another winter pre-order.

Background Development Information

The TTV Racing DCT & MT S65 lightweight flywheels were initially developed in 2011. 

The first units were tested on race cars at the Nurburgring for 12 months before made commercially available.  

They were then brought to market mostly to European race teams in 2012. 

This remains TTV Racing's main market considering their UK manufacturing headquarters.  

The flywheel is milled from carbon steel and the spline is hardened over the OEM dual mass flywheel.  

It is high speed balanced at TTV's facilities as seen on the last picture.  

Further Development

There is one known failure in the world on a DCT M3 race car.  

The flywheel was later tested on supercharged S65 race cars for high temperature applications and a nitrite coating is now standard on all DCT applications.  

Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface.

DIY Notes

The flywheel isn't exactly a DIY install: the exhaust, driveshaft and transmission are all coming off. 

It's something you do usually while you're in there with other maintenance and upgrades to the transmission, driveshaft, etc.  

You can't reuse the OEM bolts are they are encased in the flywheel. You need to get 9x new BMW flywheel bolts (11227520706). 

You dip them in engine oil while bolting them in, and you torque them criss-cross. 

Pay careful attention to aligning the bolt hole with a different shape to the matching hole on the crank. 

This is your engine starter alignment. 

Take it from me, you don't want to have to do it twice (oups!). 

More M applications 

They have other applications for M cars and I look forward to generating more awareness for TTV in M world. 

@silver gsr has the E46 M3 and E39 M5 flywheels in hand, and I will get the E60 M5 SMG flywheel as well.

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