dual mass flywheel and high HP

[jfdmas]

well, today i was doing a clutch job on a nissan spec v because of supposed slipping clutch. i tear the thing apart and the clutch looks great but the DMF has tons of play and is obviously warn. Now this is on a completely stock spec v with lower miles. Now im currently running my stock flywheel with 125k miles and ive been putting some decent power through this thing with out issue yet, but i cant help but to wonder where the threshold on these things is?

DMF's are engineered to work with a given torque/hp curves and some are designed different from others. Does anyone know which style DMF we have and I guess id like to know if anyone has destroyed one before from too much power? i just dont understand how a dmf designed for 1xx whp/tq can handle 600+whp.

I love what DMF's do for the drivetrain and i would love to keep runnin mine at high hp levels.

[chikinhed]

could you imagine what would happen if the DMF sheared during a high power pull? Would the rev limiter be able to save the motor?

[a32guy]

Never really thought of it, but yeah that could surely fail. I would just replace with new dual mass, personally.

I could imagine something similar to this would happen: http://www.youtube.com/watch?v=SP3EIHp3AqE

[So Live]

Epic video... Tempted to tack in some protection sometime soon.

John id love to know this too. I love my DM wheel. It feels great with the unsprung clutch disc.

[bluejeansonfire]

My car came with a very worn DMF, to the point where over 90 derees of rotation was possible before the crankshaft offered resistance. I believe 3 degress is spec, maybe 3mm? So shortly after my first clutch job, I sought to replace the entire assembly. I personally didn't enjoy my dmf, but i guess that might be to the poor shape i experienced it in. Ever since I changed it, I have encountered loads of chatter. But on the upside, I have found that with a lightweight flywheel, you can powershift much more aggressively and maintain grip from the reduced momentum. But that was NA, when grip was a simple thing. I havent been to the drags enough to make a good enough guess of how differently my car would be with a dmf, if i'd be able to let out the clutch sooner between shifts, though I currently don't have a huge issue at my low power level, grip after second is usually good on a dry track.

Though I don't know the exact limits of the bmw dmf, i do know this: e46 Ms/330/328/e36 m3/328 all have relatively similar flywheels. HPF cars with SMG, without any exception I know of, uses a dmf to exceed 800whp. Granted none of them have run a 10, so the level of load at low speeds/gears when grip is at a premium is questionable. But in high gear/high load situations, it puts the power down and they hold together.

[EMC]

Though I don't know the exact limits of the bmw dmf, i do know this: e46 Ms/330/328/e36 m3/328 all have relatively similar flywheels. HPF cars with SMG, without any exception I know of, uses a dmf to exceed 800whp. Granted none of them have run a 10, so the level of load at low speeds/gears when grip is at a premium is questionable. But in high gear/high load situations, it puts the power down and they hold together.

That's what I was thinking too. I've never heard of one of these dual mass flywheels having a catastrophic failure. The clutch disk or more likely the pressure plate will probably fail long before the flywheel. If it's not a track car, I'm sticking with the stock dual mass flywheel....then again, I don't have 600rwhp.

[jfdmas]

well, i like the DMF because its heavy and help assist in launching with slicks and helps hold momentum. I have launched the car tons of times and i never realy considered whether or not its a risk until now. everything felt solit when i retorqued my pressure plate the other day. maybe i should go back to being blind and not thinking about stuff.lol

[protomor]

I drift with a DMF and have no problems so far. I'm only 350whp tho. Spec stage 4 unsprung 6 puck.

[Quicksilver328i]

I broke the DMF in my 350z in <15k miles (I think upwards of 150 passes at the track - 5,500+ RPM launches). It sheared and collapsed on itself so the clutch got like 50 lbs of pressure on it. Drove the car home, ordered a new flywheel and clutch the next day, and wished I'd stayed dual mass.

On my current setup I want a heavy single mass chomoly but I can't find one for <$900, and found a used LTW al for $100. Until I destroy that flywheel I'll live with single mass - but dual mass is so much nicer for shifting/launching driving.

And for what its worth, I'm the only one I know of who has done this.

[WCM3]

well, i like the DMF because its heavy and help assist in launching with slicks and helps hold momentum. I have launched the car tons of times and i never realy considered whether or not its a risk until now. everything felt solit when i retorqued my pressure plate the other day. maybe i should go back to being blind and not thinking about stuff.lol

I currently have a UUC LTW Stg 2 flywheel and UUC spec clutch. I ran it at the track maybe 15 times and had it for about 2 years. Now I notice when I'm coming from a stop, the car shakes until it's off moving. It doesn't have problem holding the power, but the pedal is extremely light and it's tough in traffic. I wanted a move drivable clutch so I was thinking about the clutchnet red and buying a brand new DMF, but I'm worried if it will hold up to 600rwhp.

[LukeG]

Epic video... Tempted to tack in some protection sometime soon.

John id love to know this too. I love my DM wheel. It feels great with the unsprung clutch disc.


You should feel my upsprung 6puck (now about to be 4 puck) disc on a alloy flywheel, it feels great!



dual mass FTMFL

[SiGmA]

You should feel my upsprung 6puck (now about to be 4 puck) disc on a alloy flywheel, it feels great!



dual mass FTMFLReally Luke? I enjoy my DMF, and am thinking about replacing it with another low-mile DMF not a single piece... Hummm...

[BadBoostedBmwM3]

Doesn't the s54 engines use DMFs?? If so, I know HPF makes one use their "OEM" flywheel with their clutch setup.... and they haven't been having any problems yet.

[jfdmas]

well, like ive stated already ive been running my stock dmf and its held up fine and still feels fine. I guess its just a superior design to other manufacturers to be holding up so strong after so many miles. I dont wanna sacrifice drivability for a single mass flywheel. Hopefully this thing holds up fine for 800+whp. i guess theres only one way to find out.

[black bnr32]

800+whp

:alright

that is all

[Morfeus17]

Go with JB Racing Flywheel. It's Single Mass but almost as heavy as stock.. I love mine. It has the same dimmensions of the DMF without the pivoting center section.

[BMWManiac]

I've never had a problem with my stock DMF and I will never change it out!

[bluejeansonfire]

Go with JB Racing Flywheel. It's Single Mass but almost as heavy as stock.. I love mine. It has the same dimmensions of the DMF without the pivoting center section.

I think if this is to be chosen, and the driveability to be maintained, perhaps a sprung hub clutch. One part of the assembly with give should be as good as another. And the clutch disc, to me is the more intuitive obvious good idea as far as this goes. Granted, a lot of dms flywheels last a long time. But my 200whp stock car and its previous owner somehow fragged the stock one on my car in under 40k miles. This instilled distrust in the piece. But considering you're using the same flywheel to make so much power and HPF is going to around 1kwhp with it, it should hold. But it seems simpler to me to use a one-piece flywheel that is more guaranteed to have a long life and a clutch disc with a sprung hub, this allows you to put the movement in a more disposable piece. Also granted, the stock flywheel can be purchased directly from Luk cheap.

[jfdmas]

meh, i think HPF is a bad example here. Dont get me wrong, what they do is impressive but there cars dont exactly make tons of torque which is what breaks stuff. Like for instance when i was runnin stock m52 cams i would peak torque at 4500-5000ish rpm around 600wtq and 620 whp. the torque came on instantly in relation to spool and this sudden increase of torque is what concerns me.

[Rob Levinson]

Hey guys,

In all reality, DMFs of any size are not stressed by power loads... that's not their primary cause of failure.

The cause of failure is simply internal wear. What's inside a DMF is spring-loaded set of gears used to allow the primary and secondary disks to have limited (about 15° or less) damped movement between the two. Looks like this:

http://www.uucmotorwerks.com/flywheel/images/dual_mass.jpg

The failure itself is either at the center bearing or at one of the gears. The wear that accumulates is from it's normal movement, which happens every time there is an application of power and then removal of power... whether it's accelerating through the gears, or just easing off the gas in traffic. Each time there is power applied or removed, that internal mechanism gets exercised, and it eventually wears out. Directly from speaking with Sachs engineers, any DMF over 70K should be replaced at time of clutch replacement as a standard maintenance item.

On a side note, to address some comments above about "i like the DMF because its heavy and help assist in launching with slicks and helps hold momentum"... time to let go of old misconceptions. If a DMF is "helping" your launch, then there's something wrong with your clutch release technique. If you think it's somehow making you launch harder, that's another fallacy... once a clutch is fully engaged, additional flywheel mass is simply slowing down your acceleration. Read more about that here:
http://www.uucmotorwerks.com/flywheel/there_is_no_torque_loss.htm

The only time there is an exception to this has to do with some turbo cars - repeat some, not all. Some turbo applications are tuned using a large turbo whose efficiency is affected by load, and in such cases a heavier flywheel would be recommended. There are sources for single-mass flywheels in steel to accommodate those needs. Keep in mind this only applies to large turbo setups, not smaller turbos and definitely not any superchargers.

Hope that helps!

[LukeG]

What I love about my clutchnet setup is the eas of rebuild. I seized my clutch to the pp and flywheel. I sent everything in to clutchnet, got a new flywheel friction surface, new pressure plate surface and performance check, and a new 4 puck clutch disc all for $225. Can't beat that...

[Turbo Charg Dynam]

Hey guys,


On a side note, to address some comments above about "i like the DMF because its heavy and help assist in launching with slicks and helps hold momentum"... time to let go of old misconceptions. If a DMF is "helping" your launch, then there's something wrong with your clutch release technique.
Hope that helps!


I think a 1.581 60ft time speaks loudly about his ability to drive the car at the dragstrip.

[Rob Levinson]

I think a 1.581 60ft time speaks loudly about his ability to drive the car at the dragstrip.

Or a lot about the power. ;-)

My point being, and you know this well, Todd, is that the "aid" factor of flywheel mass in launch technique is more myth than fact.

Here's a real comparison of big-power drag racing with heavy vs. light flywheels. If drag racing is your thing, this is required reading:

http://www.uucmotorwerks.com/flywheel/LWF_DRAG_TEST.pdf

[jfdmas]

Or a lot about the power. ;-)

My point being, and you know this well, Todd, is that the "aid" factor of flywheel mass in launch technique is more myth than fact.

Here's a real comparison of big-power drag racing with heavy vs. light flywheels. If drag racing is your thing, this is required reading:

http://www.uucmotorwerks.com/flywheel/LWF_DRAG_TEST.pdf

I think we all understand that the lighter flywheel will make more power. I personaly dont care about the 5-10whp when im already making ver 600whp. The problem is when i launch my car without any boost aid the car bogs and bogging = broken parts. Its very important to build boost and have a limited slip at the slicks inorder for thing to get moving and not shock and destroy the drivetrain. If i had a lightweight flywheel i dont think i would be able to build the boost i do with my turbo at idle/launch and the inertia to spin the tires which is critical wouldnt be there as well. I dont think its a fair comparison to be comparing v8 torque montsers that dont have to wait for a turbo spool and about 5-6k rpm to make max torque to get the car moving. Thats where the heavy flywheel comes into play, As long as i can get 2-3 rotations out of my slicks while waiting for spool to come on to make power to keep me going. Yes once im going the lightweight would be better but we cant have it all.

[Rob Levinson]

I think we all understand that the lighter flywheel will make more power. I personaly dont care about the 5-10whp when im already making ver 600whp. The problem is when i launch my car without any boost aid the car bogs and bogging = broken parts. Its very important to build boost and have a limited slip at the slicks inorder for thing to get moving and not shock and destroy the drivetrain. If i had a lightweight flywheel i dont think i would be able to build the boost i do with my turbo at idle/launch and the inertia to spin the tires which is critical wouldnt be there as well. I dont think its a fair comparison to be comparing v8 torque montsers that dont have to wait for a turbo spool and about 5-6k rpm to make max torque to get the car moving. Thats where the heavy flywheel comes into play, As long as i can get 2-3 rotations out of my slicks while waiting for spool to come on to make power to keep me going. Yes once im going the lightweight would be better but we cant have it all.

First, to clarify a fundamental misunderstanding about the physics of a lightweight flywheel: no power is actually "made". What is happening is a reduction in "virtual mass" - less mass (which is not the same as weight) against which your engine has to push.

Not sure if you had a chance to read the link I posted earlier about torque loss, but here is the pertinent point as to what you said about "inertia to spin the tires". Look at this section of a dyno curve:

http://www.uucmotorwerks.com/flywheel/images/clutch_dump.jpg

That added inertia is only doing something while the clutch is being slipped - after that, once the clutch is fully engaged, it is acting against the car, to the same effect of adding almost 400lbs of ballast.

This is true regardless of having a 7.0l V8 or a 1.6l turbo.

But again, as I explained earlier, if your turbo is tuned to require resistance to build boost rapidly, then a heavier flywheel would help you (assuming that delta in boost is enough added power over time to equate to the loss in acceleration over mass).

What value is this discussion to you then? At the very least, a better understanding of what you are experiencing. Knowing the "what" and "why" of how your car works lets you tune it better and get better performance.

[jfdmas]

First, to clarify a fundamental misunderstanding about the physics of a lightweight flywheel: no power is actually "made". What is happening is a reduction in "virtual mass" - less mass (which is not the same as weight) against which your engine has to push.

Not sure if you had a chance to read the link I posted earlier about torque loss, but here is the pertinent point as to what you said about "inertia to spin the tires". Look at this section of a dyno curve:

http://www.uucmotorwerks.com/flywheel/images/clutch_dump.jpg

That added inertia is only doing something while the clutch is being slipped - after that, once the clutch is fully engaged, it is acting against the car, to the same effect of adding almost 400lbs of ballast.

This is true regardless of having a 7.0l V8 or a 1.6l turbo.

But again, as I explained earlier, if your turbo is tuned to require resistance to build boost rapidly, then a heavier flywheel would help you (assuming that delta in boost is enough added power over time to equate to the loss in acceleration over mass).

What value is this discussion to you then? At the very least, a better understanding of what you are experiencing. Knowing the "what" and "why" of how your car works lets you tune it better and get better performance.

whats the difference between clutch slip and wheel spin when it comes to interia? Ive already stated how important wheel spin is in order for a slick to work properly while absorbing shock from the drivetrain. Those couple seconds of wheel slip "false torque" is what gets the vehicle moving initially while waiting for boost pressure to push the heavy flywheel. By the time the wheels stop spinning from false torque (which is created by the flywheel intertia) the turbo is loaded up and power is readily available at that point.

I did read the article you posted and it even shows how the interia carries over into each gear before the torque loss from the mass. It also states that the only gain from a heavy flywheel is within the first few seconds which happen to be critical in drag racing. Yes, i could probably run a lighter flywheel, but then i would need to launch my car at 7000rpm instead of 4500rpm to get the desired wheel spin and acceleration while waiting for turbo spool. You make great points but i think there only valid for vehicles that make max torque very low and dont have to wait for there power adders.

[Rob Levinson]

.

We're entirely in agreement, except for this:


whats the difference between clutch slip and wheel spin when it comes to interia?

While the clutch is slipping, the overall final drive is temporarily different. Wheel spin is just dissipating power. At a specific engine output, what would be accelerating faster... tires with full grip, or tires that are slipping?

For drag tuning, refer to what I mentioned earlier; is your artificial temporary bump of sufficient advantage, better than, the performance gain of lower MOI of drivetrain? It may very well be. You can test/tune it yourself, just like in the drag racing article to see which way works better.

- Rob

[Willy10]

I’m trying to buy this stage 4 fx400 clutch but it says I need a single mass flywheel or will the dmf still fit