Project E46 M3: Part 14 – Short shift kit and lightweight clutch and flywheel testing!!


Please excuse our inability to include torque, but this was another day we couldn’t get a good tach pick up. Anyway, when it comes to dyno testing lighter drivetrain components like a flywheel, it’s been my experience not to expect too much of a gain in the higher gears. This is the before-and-after comparison of our stock vs Clutch Master FX400 and aluminum flywheel setup. While the gains and losses are not very significant, you can see a slight dip in torque in the low end with slight pick-up in the top end. We’re bummed we didn’t hold this run thru to the redline as we probably would have seen another pony or two. But you can see there is a little over 3 WHP up the very top, even though peak numbers remain the same 311 WHP.

Having tested flywheels on the dyno three or four times before this, I’ve always found the big gains to be in the lower gears. So let’s see that comparison below.

Here are lightly shifted runs between second and third gears. Notice right when I hit the throttle in second gear, there is momentary jump with the heavier stock flywheel because it retains more energy. The lines even out and then the Clutch Masters setup takes over from midrange through redline. That’s good for over 12 WHP at the top of 2nd gear (and 9 WHP in third). That’s going to make a difference because in lower gears we’re also putting less power to the ground overall (therefore, it’s a higher percentage gain). In fact, that’s a peak 4.5% improvement in power in second gear.

Granted, what we’re talking about here is regarding short bursts of RPM time, but when compared to stock, the flywheel helps gain a 0.07-second advantage from 20-65 MPH in second gear, as well as from 70-100 MPH in third. Therefore, it’s pretty safe to say that a flywheel is good for around a tenth of a second up to 100 MPH.

I’ve also done this test in an E36 M3. In first gear I saw the biggest gains. However, we skipped testing first gear because, in the case of an E46 M3, it’s much harder to keep traction on the dyno with nearly 100 more horsepower.

Another characteristic change you’ll see with a lightweight flywheel can be seen in the graphs as well. Take a look at the point right right when the clutch is depressed, the revs with the Clutch Masters setup falls off much more quickly when compared to stock. Because there is less energy stored in the lighweight flywheel, it hits idle speed at 1 MPH sooner than with the factory setup. That is something you’re going to have to get used to as quicker shifting will be necessary to maximize acceleration. On a heel-and-toe downshift you’re going to have to be a little quicker as well. Thankfully the shorter, quicker throws of our new UUC Evo 3 shift kit helps with this. On the flip side, you’ll notice that a little blip will now go a much longer way than before, so time is saved there as well.

Driving the car in cruise mode with the new clutch is fantastic. I don’t really notice it unless I’m really getting on it and, when I do, there’s a faint “whine” of the aluminum flywheel as it rips up to redline. Vibrations from either the clutch or the UUC bushings are pretty much non existent. I don’t notice the new clutch until I fully press the clutch pedal and feel my way through the gears. It makes me want to drive faster, and not be cruising at a constant speed. The clutch pedal feel is exactly like stock–that’s the only way I can describe it.

If there is one way I can feel a “loss” with the flywheel, it’s cruising in sixth gear, and suddenly stabbing the throttle. Have you ever repeatedly stabbed the throttle to jerk the car back and forth to annoy your significant other (am I the only one who does this)? You won’t be able to do that anymore. It’s too smooth due to the lack of energy stored in the flywheel.

Having a well sorted clutch and flywheel combination, along with a good short shifter and tranny bushings, gets our Project M3 feeling one step closer to that racecar feel, but without the compromises so often heard about. This was a win-win upgrade!

For those of you wondering about how the car drives with the AC on, the flywheel rattle is very light, and nothing like I used to have with the unsprung discs. I am very pleased. It should be noted that after this installment we haven’t had any extra tuning of the AEM Infinity, including with the idle. But that’s changing soon!

Well, how nice is this? While testing our Project E46 M3, Modified by KC had an E46 M3 racer. Let’s check it out. With sticky Toyo race rubber and a Stoptech big brake kit, you know it can tackle corners very aggressively.

And yes, that’s a new Z06 that MKC got over 900 WHP out of fairly quickly.  But staying in the spirit of BMW M3, let’s check this one out, shall we?

A nice, large front splitter for the front keeps more weight over those large, front tires at high speed.


    1. hi and funny you should ask because–while I’ve sold the car a year ago to my father in CA (and I’m in KC)–he was actually sitting 5ft away from me when I saw this note so I was able to ask him and he says it’s relatively quiet. Can hear the chatter a bit during idle and of course if you turn the AC on but it’s not obnoxious or anything like that. thanks for reading!

    2. Hey I have the car currently! It’s pretty low key you won’t be able to tell while driving obviously, sometimes at idle although you here a lot of chatter lol. I personally think it’s amazing, after first gear it’s super forgiving. Per the clutch it’s very easy to set off, catch and rev match or heel toeing ( I guess part of that is owed to the flywheel too) and the stiffness imo is perfect. Short shifter is the cherry on top.

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