"In this entry, I start her up and go for a drive. Was it worth it? Tolerances vary, read and listen carefully! "
- Matt

It sounds different.

I had a JB racing aluminum lightweight flywheel and Sachs Heavy Duty clutch on the E46 M3. I like to say it’s like dropping a bucket of bolts in a blender at idle.

The DCT lightweight flywheel sounds quite different. I can best describe the sound as a slower, metal sliding sound. It’s unlike any other lightweight flywheel sound I’ve heard - you really need to look for it with headphones.

The sound differences originate from the vastly different design of a DCT transmission. Most notably; it has no throwout bearing, clutch fork and slave cylinder within the bell housing.

They are common source of rattling even in a stock E9X M3 manual transmission. You can make it out starting at 20sec, oil at high temp, no trickery that hides chatter.

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

My first impressions. 

On my first test drive, I thought the clutches were slipping off. I unwillingly hit the 8,600 limiter a few times, catching another gear much faster than it used to. 

It drastically improved the DCT’s shift operations; they all happen quicker. The throttle blips on downshifts are more aggressive than ever. 

Improved mid-range. 

The flywheel fixed a common complaint about the sluggish mid range of these engines: you feel catapulted from 3,000 into the 5,000 + zone. 

The reduced moment of inertia is most impactful in the low to mid range as this is where it takes most energy to get the crankshaft rotating. The flywheel has less impact on the upper range response and in higher gears. 

Think of it as a Spinning Class, getting your bike's plate moving is a strenuous effort. Once it gets going, the mass nearly moves itself. 

Notes on power modes. 

With the solid mounted subframe, carbon driveshaft and polyurethane differential bushings, my driveline is considerably stiffer than original.

As a result, the Sport Plus power mode in M Drive felt too aggressive on upshifts. It's usually torque bump through the gears added jerkiness. I softened the throttle response and most commonly use normal or sport. 

It allows more precise throttle input, while improving throttle response. 

Is this made for every S65 DCT owner? I don't think so. You will be giving up comfort in the process.

Was it worth it for me? Entirely.
It transforms the drivetrain and gets us ever closer to challenging GT3s.

I like the sounds: it's mechanical - like a 911R, who famously came fitted with a lightweight flywheel.