Quiet Lightweight Flywheel?

[xansabi]

Yeah exactly, it's after I've been driving for awhile, when I put in the clutch at a stoplight. I've never heard it in 2nd. I only ever hear it when I put in the clutch and I'm not moving.

Lol phew. I thought I just completely butchered my manual conversion LOL

[fattycharged]

I told you my ACT is pretty quiet. I went with ACT cause I've run them for 20+ years and never had an issue, but I feel like I'm one of the only people on this forum running ACT, so you probably won't hear anyone else recommend them.

Per ACT - "Noticeably improved engine response and acceleration, OE to mild gear rattle"

I would say that's accurate... most of the time it's pretty silent, but sometimes at a stoplight on a hot day you can hear it complaining.

I run a LWFW in my e36 and the light rattle never bothered me, not sure how that compares with the e46, but if it's the subtle I'd be interested


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[Obioban]

I dont see any reason we couldn't do it at first glance. I'll discuss with Peter next week.

And then there were two.

Texted him this yesterday, and he said the same thing

S65 DMF looks pretty significantly lightened compared to the S54's.

S65:



S54:

[Chrisyphus]

And then there were two.

Texted him this yesterday, and he said the same thing

S65 DMF looks pretty significantly lightened compared to the S54's.

S65:



S54:

The amusing thing is that I had this exact conversation with a guy last week about the S65 flywheel. It'll obviously require more effort, and the juice will probably not be worth the squeeze, but the S54 flywheel does look more promising.

[xansabi]

Sorry to ask, is the flywheel rattling also present for people when turning the car off without clutch in or is that the driveshaft, and is it normal?

[EthanolTurbo]

Just wanted to say I spoke to Jed Pineda aka M5 Jed of Einhorn Industries, he makes a lightened dual mass OEM flywheel for the E39 M5 and he says he can experiment with lightening an OEM dual mass flywheel for E46 M3.

[1000hp]

Sorry to ask, is the flywheel rattling also present for people when turning the car off without clutch in or is that the driveshaft, and is it normal?

That's probably in the transmission, if it's anywhere in the drivetrain.
The driveshaft won't be spinning unless you're shutting the engine off while the car is rolling...

[Sharocks]

There has been a solution for a lightweight flywheel for the S62 for a few years now and it's not out of Virginia.

I am working on a solution for the S54 as well.

[jvit27]

I run a LWFW in my e36 and the light rattle never bothered me, not sure how that compares with the e46, but if it's the subtle I'd be interested

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The ZF320 is shorter than 420G and is less affected.

Just wanted to say I spoke to Jed Pineda aka M5 Jed of Einhorn Industries, he makes a lightened dual mass OEM flywheel for the E39 M5 and he says he can experiment with lightening an OEM dual mass flywheel for E46 M3.

I emailed them years ago about this and never got a response..

Chrisyphus what sort of extra effort would the S65 flywheel entail?

[Chrisyphus]

Chrisyphus what sort of extra effort would the S65 flywheel entail?

There are a few levers on this. One, the E39 flywheel is H E A V Y at ~40 lbs, and a ton of that weight is there on the outside of the friction zone- existing for the sole purpose of adding maximum rotational inertia. KE=M*V^2. If you double the weight of the flywheel by adding thickness, you will double the amount of work (horsepower) needed to accelerate it. If you double the velocity, you quadruple the work needed to accelerate it.

BMW Engineers knew that if they wanted to maximize the flywheel's effect on drivability and NVH, adding all that extra weight to the outside of the flywheel was the most efficient way to optimize damping, thereby minimizing added weight to the chassis. Clever. Also, convenient for Dinan, Einhorn, and us, because it means we can turn all that extra mass away in one CNC Lathe operation, and thanks to some clever fixturing, we are also able to shave the raised section inside the friction area down so that our flywheel can be paired with the Sachs Performance Organic clutch and their increased clamping force flywheel- the stock clutch and flywheel cannot handle the torque of our HO S62 builds without slipping. The Sachs Performance kit doesn't even think about slipping and is perfectly streetable.

The S65 flywheel, on the other hand, starts at 27.5 lbs. It is already lighter than the lightweight S62 Dual mass flywheels. Additionally, because it is a twin clutch disk system in OE form, there is added complexity in the stanchions on the flywheel edge- undermining these to remove the most critical mass in the system is not a readily available option- there is probably extra material that could be removed, but to do this without taking risks, we would need to do significant FEA analysis and real world testing- this is substantial engineering time. In addition, the material that can be removed would need to be removed via Milling rather than Lathe operations, which significantly increases the risk of throwing the balance off (compared to turning around the known rotational axis of the flywheel) and would require multiple operations.

All the while, all of this time and effort is in pursuit of removing material far closer to the axis of the flywheel, which, as discussed previously, is less effective at reducing rotational inertia.

Add to that the fact that BMW records show it increased the manual transmission flywheel weight in pre-production (and the DCT flywheel in early production in 07/2009) because it is not as simple as "if you have dual mass, you do not have transmission chatter." There is a necessary balance between the springs of the dual mass flywheel and the secondary mass (separated from the engine via the springs). The purpose of the dual mass is to decouple the acceleration/deceleration of the crankshaft at idle from the gearset in the transmission- the chatter that is observed with single mass flywheels is the noise of the backlash in the transmission gearset resonating with the frequency of the crankshaft speed oscillation. There is a minimum mass threshold that must be met for the inertia of the secondary mass to provide a smooth/stable speed, eliminating chatter. Adding too much lightness to the flywheel could defeat the purpose of a dual mass flywheel in the first place.

We could absolutely do it, charge the necessary premium for the OEM flywheel cost and the hours of labor/machine time to do it, and people would likely buy it. But as I have said in other threads, this is against the ethos of Partee Racing. We are not interested in just selling whatever people will (hopefully) buy. We are in this industry because we are die-hard enthusiasts, and we want to make the best parts we can. If something does not offer a material benefit or improvement over what exists, we will not do it.

There has been a solution for a lightweight flywheel for the S62 for a few years now and it's not out of Virginia.

I am working on a solution for the S54 as well.

We haven't re-invented the wheel or done anything special, but between one company dropping the product and the other's solution being a half-measure, we felt we had to step up and do it right.

Our lightweight flywheel is lightened and clearanced in one operation, mounted to the cut-off end of an S62 crank in our CNC lathe so as to ensure all weight is removed in a perfectly concentric manner to the doweled centerline of the flywheel. Then, we assemble the flywheel and pressure plate and balance the entire assembly to within one gram rotationally. Then we mark the correct alignment, and mark the bolts to ensure the end user can rebuild the assembly in the same way it was balanced.

All in a package where the actual cost of the flywheel is on par with our only competitor's. A solution may have existed for a few years now, but without question, the best solution on the market now is out of Virginia.

[EthanolTurbo]

The ZF320 is shorter than 420G and is less affected.



I emailed them years ago about this and never got a response..

Chrisyphus what sort of extra effort would the S65 flywheel entail?

I spoke to Jed and he's going to make a prototype.

[1000hp]

A solution may have existed for a few years now, but without question, the best solution on the market now is out of Virginia.

A solution for the S54? Or just for the S62?

[Chrisyphus]

A solution for the S54? Or just for the S62?

At the moment, we only do the lightweight S62 flywheel. We are discussing doing it for the S54, but there just isn't as much material to remove. IIRC the OE dual mass weighs 24ish pounds. It's already just over half the weight of the 62's flywheel. The bigger issue, though, is where we would remove the weight from. The aspect ratio of the E46 clutch disk to the flywheel is a good bit wider than with the S62, so it takes up a lot more space on the flywheel. This means there is less meat on the perimeter to remove, and, as discussed previously, removing weight from the middle, if any, has a minimal impact on the flywheel's acceleration compared to the perimeter.

It's a simple enough project, but it would be $800-$1000 for a flywheel that MIGHT(?) save a pound or two. It just doesn't present any sort of value proposition, it wouldn't make a material difference in performance/responsiveness, and it would take our CNC operator away from more meaningful projects. All to create a product that we do not necessarily believe in, for the sake of turning a little more profit.... That's not our style, so since we've discussed it internally, it looks unlikely that we will be doing the S54.

Sorry guys, I know that's not the answer you wanted to hear from us- we just dont want to sell something that doesnt make sense to us.

[1000hp]

Well thanks anyway for your input. Much appreciated.

Sounds like it's down to either heavy stock dual mass, or rattley transmission with a light single mass. Or maybe the other 6MT, which isn't worth the effort or cost, to me.

[jvit27]

There are a few levers on this. One, the E39 flywheel is H E A V Y at ~40 lbs, and a ton of that weight is there on the outside of the friction zone- existing for the sole purpose of adding maximum rotational inertia. KE=M*V^2. If you double the weight of the flywheel by adding thickness, you will double the amount of work (horsepower) needed to accelerate it. If you double the velocity, you quadruple the work needed to accelerate it.

BMW Engineers knew that if they wanted to maximize the flywheel's effect on drivability and NVH, adding all that extra weight to the outside of the flywheel was the most efficient way to optimize damping, thereby minimizing added weight to the chassis. Clever. Also, convenient for Dinan, Einhorn, and us, because it means we can turn all that extra mass away in one CNC Lathe operation, and thanks to some clever fixturing, we are also able to shave the raised section inside the friction area down so that our flywheel can be paired with the Sachs Performance Organic clutch and their increased clamping force flywheel- the stock clutch and flywheel cannot handle the torque of our HO S62 builds without slipping. The Sachs Performance kit doesn't even think about slipping and is perfectly streetable.

The S65 flywheel, on the other hand, starts at 27.5 lbs. It is already lighter than the lightweight S62 Dual mass flywheels. Additionally, because it is a twin clutch disk system in OE form, there is added complexity in the stanchions on the flywheel edge- undermining these to remove the most critical mass in the system is not a readily available option- there is probably extra material that could be removed, but to do this without taking risks, we would need to do significant FEA analysis and real world testing- this is substantial engineering time. In addition, the material that can be removed would need to be removed via Milling rather than Lathe operations, which significantly increases the risk of throwing the balance off (compared to turning around the known rotational axis of the flywheel) and would require multiple operations.

All the while, all of this time and effort is in pursuit of removing material far closer to the axis of the flywheel, which, as discussed previously, is less effective at reducing rotational inertia.

Add to that the fact that BMW records show it increased the manual transmission flywheel weight in pre-production (and the DCT flywheel in early production in 07/2009) because it is not as simple as "if you have dual mass, you do not have transmission chatter." There is a necessary balance between the springs of the dual mass flywheel and the secondary mass (separated from the engine via the springs). The purpose of the dual mass is to decouple the acceleration/deceleration of the crankshaft at idle from the gearset in the transmission- the chatter that is observed with single mass flywheels is the noise of the backlash in the transmission gearset resonating with the frequency of the crankshaft speed oscillation. There is a minimum mass threshold that must be met for the inertia of the secondary mass to provide a smooth/stable speed, eliminating chatter. Adding too much lightness to the flywheel could defeat the purpose of a dual mass flywheel in the first place.

We could absolutely do it, charge the necessary premium for the OEM flywheel cost and the hours of labor/machine time to do it, and people would likely buy it. But as I have said in other threads, this is against the ethos of Partee Racing. We are not interested in just selling whatever people will (hopefully) buy. We are in this industry because we are die-hard enthusiasts, and we want to make the best parts we can. If something does not offer a material benefit or improvement over what exists, we will not do it.

Thanks for the informative response. I'm embarrassed to admit I didn't know the (manual) S65 was a twin disc setup to begin with, so that makes more sense. I want to think the extra components inherently add a level of mass-damping, as the FI E36's I've seen that upgraded to twin disc setups had less chatter with ltw flywheels.

Thought I was onto something when I first saw the lightening of S62 flywheels but quickly learned how much heavier they were to start with over stock S54 flywheels. Makes sense given how much more displacement it has to dampen. IIRC they're lightened to be about the same, so moot as a mod. The true lightweight flywheels are non-options as far as many of us are concerned, which only leaves the 18lb steel single mass one and then it's subjective as to how much chatter one can deem acceptable for a street car. Not sure if adding a heavier Ross/ATI damper could offset this? The main pause I see with that is you've spent like $2k+ to sort of make it similar to stock.... question is would the rotational weight being closer inward give enough of a placeabo to make it worth doing.

Ok without derailing this thread I have to DM you a question about the Sachs clutch