Single mass flywheel discussion…?

[Chanman1029]

I think I’m definitely going to go with the ACT kit, part number BM4-HDSS. It uses their steel single mass flywheel with a sprung clutch disc. It’s even on sale for less than $1200, which is about where the N54 flywheel kit is, and significantly less than the steel JB racing, which is around $1600. It might be a good 2 months before I get my motor put back together, but I’ll be sure to report back with the drivability of it.

[Obioban]

After going through 4 different clutch/flywheel combos on my s50b32, I have no intention of moving off stock on the e46. I hate the noise at idle and enjoy the stock unit not expediting harmonic balancer failure.

[Chanman1029]

After going through 4 different clutch/flywheel combos on my s50b32, I have no intention of moving off stock on the e46. I hate the noise at idle and enjoy the stock unit not expediting harmonic balancer failure.

Realistically, how much harm would a steel single mass of comparable weight over time? What’s the longevity of something like this?

[Obioban]

Realistically, how much harm would a steel single mass of comparable weight over time? What’s the longevity of something like this?

I don’t know the rate, but if you looked at cars that have had the harmonic balancer fail (often taking the engine with it), they almost all have non stock flywheels.

[Syfon]

I don’t know the rate, but if you looked at cars that have had the harmonic balancer fail (often taking the engine with it), they almost all have non stock flywheels.

It's likely said failed s54's with lightweight flywheels are race cars, tracked regularly or driven very hard on the street where the motor is held at and sees high rpm's very regularly...

[digger]

Best way to reduce harmonics is big heavy ati vibration damper at front and light FW at the rear. This is what racers of long crank inline 6 have found ( much longer flexible cranks than s54 cranks).

[bjz!]

Best way to reduce harmonics is big heavy ati vibration damper at front and light FW at the rear. This is what racers of long crank inline 6 have found ( much longer flexible cranks than s54 cranks).

I bought an ATi and... Heavy as fuck, i sell it. Also a VAC crank pulley (for no AC cars) and.. i think is in a box somewhere, i'm going to sell it too, keep stock.

[Chanman1029]

I bought an ATi and... Heavy as fuck, i sell it. Also a VAC crank pulley (for no AC cars) and.. i think is in a box somewhere, i'm going to sell it too, keep stock.

Well I definitely dont plan on getting a new or different dampener. The steel one piece flywheel from act is probably only slightly lighter than oem, and since my oem flywheel is already going bad I’m just gonna send it on this one.

[Obioban]

Well I definitely dont plan on getting a new or different dampener. The steel one piece flywheel from act is probably only slightly lighter than oem, and since my oem flywheel is already going bad I’m just gonna send it on this one.

If I did a light weight flywheel, I'd make the (stock) damper a routine replacement item.

A lot of the aftermarket front dampers seem to have failure issues, so don't think I'd be comfortable "upgrading" to them.

[jbfrancis3]

If I did a light weight flywheel, I'd make the (stock) damper a routine replacement item.

A lot of the aftermarket front dampers seem to have failure issues, so don't think I'd be comfortable "upgrading" to them.

How would you define "routine"?

[Chanman1029]

If I did a light weight flywheel, I'd make the (stock) damper a routine replacement item.

A lot of the aftermarket front dampers seem to have failure issues, so don't think I'd be comfortable "upgrading" to them.

What are some warning signs of a bad damper? Most likely it will already be off the motor, I dont know if LRD in lake forest will install that on my block. $1000 is pretty steep, so I’d like to be able to inspect mine first to make sure I’m not buying something that isn’t needed.

[Epoustouflant]

I run TTV's forged carbon steel lightweight flywheel on the E9X M3. Spent quite some time chatting with Ben @ TTV on his preferences to using steel over aluminum. In a nutshell, the only reason you'd go aluminum is to save cost. Most racing teams will run single mass steel flywheels.

Here's the E46 M3 version. It weights 5.3kg, stock is about 11.x kg.

[Arith2]

I can't even tell I have a lightweight flywheel and it's the JB Racing aluminum one. It also is doing well with the full CSL software. My number one complaint was how the SMG did not like it on downshifts. Tuning the engine helped significantly. Some mornings, if I had just driven the car hard right before shutting it off prior, the engagement is rather hard. Other than that it's done well. Other people would complain but I'm happy. When installed it, I did not like how there were helicoils in it. One day I'll swap them to timeserts.

[F1Dryvr]

I'm about to install a tilton twin disc. Somewhat lighter than stock flywheel. I too am wondering about the ati damper vs replace w new stock. What's the weight difference btw ati and stock? And if I were to go stock what would be a sign of failure if it were a routine maintenance item

[F1Dryvr]

Just some data to add to the discussion: I contacted vac about the ati vibration damper which weighed in at 12lbs. Realoem.com lists the stock damper at about 7 lbs so a 5 lb weight gain up front negating some weight savings at the flywheel depending on how light you go. The stock clutch/pp/fw system weighs 37lbs according to oem weights.

Other items ive found via trial and $$ and error being in this part of the car twice in the past year:

1. If you decide to swap the pivot pin for steel, buy the "genuine bmw" part. I think its 10$ more, but other version(i think i bought through bimmerworld) did not seat all the way down in the bellhousing. The genuine bmw steel pivot pin is hollow where it goes into the belhousing and thus is able to seat. The other one i bought was solid and wouldnt seat all the way and was sticking out about 2-3mm, despite some aggressive coaxing: hammer/sandpaper. May not matter in grand scheme of things but that was my experience. Apparently brass fails or deforms very quickly and the stock nylon is also a reasonable option as it lasts without issue for over 100k plus miles.

2. The "FAG" "OE" pilot bearing is about 20$ cheaper than "Genuine BMW" pilot bearing, however, the "FAG" part is ever so slightly looser fit in the crank than Genuine BMW. When i pulled the trans the FAG pilot bearing just fell out, and when installing it it barely needed tapping with a socket to get it to seat in the crank, basically was able to be pressed in 95% of the way by hand. Again small potatoes here but i found the "Genunine BMW" needed tapped the whole way in and was a much more snug fit. This was the case with 2 separate "FAG" pilot bearings so i tried the bmw part and again this was my experience FWIW