Announcement

Collapse
No announcement yet.

Dual-mass flywheel discussion

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Dual-mass flywheel discussion

    I wanted to have a discussion regarding the m42’s dual-mass flywheel.

    For me – it works. After having gained an understanding of why/how it works – I can say I appreciate it.

    In a nutshell, the dual-mass wheel is an overly-heavy, spring-loaded ‘middle man’ between the engine crank and the transmission. It harmonizes. It cushions vibrations. In theory, makes life easier on engine and transmission. I like that. The counter-argument is that less rotating mass helps the engine spin-up faster.

    I strongly recommend that flywheel and pressure plate assembly be professionally balanced at a machine shop. That should go without saying. For that heavy mass to not be balanced – would be an ugly thing.

    My former driver was a first generation, flagship-model Acura Integra. Holy shit – was that car fun. It drove with impeccable, almost ‘hyper’ response to driver input. It had the throttle response of a car that would have a light ass flywheel. I could drive it around soft like a grandma – but that took a measurable amount of effort and talented finesse.

    Of all cars, it was a friend’s Saturn vehicle (mid-nineties hatch?) with a manual transmission that struck me. It was uncanny how easy/nonchalant the car was to shift around town. In retrospect, it drove like it had a heavy-ass flywheel. Like a car that would be world’s-easier to drive for someone who had little ‘stick’ experience.. and I recall having fun tooling around in it regardless.

    Traffic driving. Stop light to stop light. That is where much of time behind the wheel is spent. The biggest enemy for me was environments of frequent on/off toggle-response from pedal – where the whole car lurches at the cut-off of pedal pressure.

    I wanted to build a car with a clear sense and balance for where it would be driven. I wanted to be able to drive the car smoothly through stop/go traffic without having to focus overly much on it. After some months of drive time – I think a nice balance is achieved with the factory’s dual-mass decision. I don’t feel a motivation to lighten it (at this time). If it saved gas or made the car actually ‘faster’ – I think I’d feel differently. It is appealing to me to think that the heavy, spring-loaded flywheel helps my engine and transmission live longer.

    On twisty, country roads – where curves and elevations changes influence a second or third gear selection – the fucking weight of the flywheel is moot. One should be smoothly accelerating/rev-matching/braking anyway. Smoothness is where it’s at when it comes to driving correctly.


    All that said: for as semi-hyper as the m42 is naturally – and for the questionable issues regarding it’s half main bearings – I am feeling like the dual-mass wheel is actually desirable hardware.

    Discuss.
    -----Zen and the Art of e30 Maintenance - / - Zen TOC - / - Zen Summary

    #2
    I still got the duel mass. Never driven a single mass but with my chip and the little head work I have done, the car is fast and spins up quick enough. I am mostly in the 4k rpm+ braket though so it dose not affect me so much lol.
    sigpic

    Comment


      #3
      The DM flywheel was spec'd to maximize smoothness, drivability, and fuel economy. The 16v replaced the inherently smoother 6 cyl. eta as the fuel conscious 3-series offering, hence the m42's expensive-ass hydraulic mounts.

      If I autocrossed my car regularly or was a street racer dipshit I'd make changes.

      Comment


        #4
        ... street racer dipshit ... LOL.
        Parts Collector and Former Houndstooth interior junkie.

        Comment


          #5
          I agree that the car is smoother and easier to manage in traffic with the stock heavy-as-shit flywheel. However, I love my M20 flywheel. The flywheel itself is 10lbs lighter than the M42's, but the beefier clutch assembly makes the whole thing come out 4.5lbs lighter. It still makes a very noticeable difference (I stalled the car the first time I got in it after the swap). The shape of the flywheel also has a lot to do with it. The M20 flywheel has a lot less material toward the outer diameter than the M42 flywheel, which greatly reduces the moment of inertia (which is the real thing that causes the difference). Since moment of inertia is proportional to mass x radius^4, any little bit of mass that you move toward the center makes a difference. Hell, they could weigh the same, but if one had most of the mass around the middle, it would rev a lot differently.

          Think of this. You have two 10lb objects that you want to spin. One is a long 1" diameter steel bar. The other is a very large diameter circular piece of 14ga sheet metal. They both weigh 10lbs, but guess which one is a lot harder to spin by hand (assume it is mounted on some perfect no-friction bearing).

          Personally, I think that the lighter flywheel is worth the added effort in traffic. It makes as much of a difference in feel as a chip does on this motor.

          Transaction Feedback: LINK

          Comment


            #6
            For reference:

            M42 flywheel


            M20 flywheel


            M42 flywheel + PP + clutch disc


            M20 flywheel + PP + clutch disc

            Transaction Feedback: LINK

            Comment


              #7
              I understand the dual mass, but because racecar, single mass is the way to go.

              -NICK

              Comment


                #8


                Because racecar :up: Whole setup is about 26lbs. Havent finished the car yet so im not sure how it drives. ill let you guys know

                Comment


                  #9
                  yep im running a 16 lb fly. shits kewl beans.

                  Turbo M42 Build Thread :Here
                  Ig:ryno_pzk
                  I like the tuna here.
                  Originally posted by lambo
                  Buttchug. The official poster child of r3v.

                  Comment


                    #10
                    Is there stronger dual mass FW clutch replacement for turbo M42?

                    Comment


                      #11
                      Originally posted by mr ilia View Post
                      Is there stronger dual mass FW clutch replacement for turbo M42?
                      Not that I've ever heard of.

                      The dual-mass makes the car more pleasant to drive, but the single-mass makes the car more fun to drive.

                      I ran a euro 323i flywheel. 13.5lbs
                      Originally posted by Gruelius
                      and i do not know what bugg brakes are.

                      Comment


                        #12
                        Originally posted by KenC View Post
                        Not that I've ever heard of.

                        The dual-mass makes the car more pleasant to drive, but the single-mass makes the car more fun to drive.

                        I ran a euro 323i flywheel. 13.5lbs
                        about that, did you have to do any modifications to run it? and do you know any good shops locally to balance and lighten a flywheel? I have a feeling that light flywheel would be more fun and get better gas
                        Transaction Feedback: -click here
                        [e30: '91 318is coupe|brilliantrot||e36: '98 318ti|fern green|California top|M-Tech]
                        [URL="http://www.r3vlimited.com/board/showthread.php?t=300453"]

                        Comment


                          #13
                          It's an M20 flywheel. So just the normal mods to get that to work.

                          Don't know any shops.
                          Originally posted by Gruelius
                          and i do not know what bugg brakes are.

                          Comment


                            #14
                            I had a shop machine some weight out and balance an M20 flywheel for me. 15 lb flywheel plus the usual stock clutch. I really went with the setup for a bit more holding power, as I think the M42 clutch is rated to 160 ft-lbs or something and I'm definitely making more than that. It's still heavy enough that it doesn't vibrate much more, and I was able to actually tune out a lot of the vibration using megasquirt, which I wasn't expecting. I also have my idle set a little higher to smooth things out.

                            Aside from holding power, I really wanted it for the faster revs. In normal driving, the M42 would hang revs a little longer than I like; it's pretty close to perfect for me now. I can also rev match miles better than before, especially at an autocross, where throttle blips used to have to be a lot more than just a blip.

                            Project M42 Turbo

                            Comment


                              #15
                              Originally posted by Balleristic31 View Post
                              I understand the dual mass, but because racecar, single mass is the way to go.

                              ^This. I run a euro M40/M42 non-ac single-mass FW, 19lbs.
                              -03/2005 E46 330D Touring 6spd(204hp/410nM) Sapphire Black/Naturbraun Sport...300k KM & 35mpg(mixed)

                              Comment

                              Working...
                              X