My clutch it going out, so I'm going to have to replace it soon. One of the reasons the mini's have such soggy throttle responce at low rpm's is because of the heavy flywheel.

I'll be going with a single mass flywheel instead of the dual mass oem setup, so that will shed a few pounds.......but has anyone taken a flywheel to a machine shop and had them machine off a few more pounds? Lighten things up a little more? I'm assuming they would have to reballance after they did their machining.

 

Just going to a SMF kit will decrease the rotating mass by about 8-10 lbs vs a DMF setup.

There isn't much cast to remove on the SMF to lighten it, the only other option would be to run an aluminum flywheel.

 

If I remember right, the valeo flywheel is about 3 lbs lighter than the dual mass OEM flywheel....according to the documentation on the valeo. Is that enough to even notice?

 

If the factory DMF weighs about 30 lbs, and you cut 3 lbs from it with a SMF that is a 10% decrease in rotational mass, which theoretically would and does make a difference. Not life altering difference, but a difference.

There just isn't enough mass on the SMF to lighten them more, aluminum flywheel is going to be your lightest option.

 

FWIW I just measured the flywheel weights:
Stock DMF: 24.5 lbs
Valeo SMF: 25.5 lbs
Spec Aluminum SMF: 13.5 lbs

 

My stock DMF was 26# and the SMF replacement was 19#. You can definitely feel a difference.

 

Justa here w/ SPEC aluminum - dramatic difference revving. Just remem w/ less mass that stallling is easier off idle, but you'll get used to the change.

 

Be aware going from a DMF to a lightweight SMF. The potential for lightweight flywheel chatter goes way up. I did NOT get that going with the Valero kit but had to change the set up in my BMW. With an aluminum flywheel, the car sounded so bad it was embarrassing. It sounded like an old coffee can filled with ball bearings on a shaker table. I don't know how light you have to go to get that in a mini. You also lose smoothness of the motor the lighter the flywheel gets. There are some nice positives, just be aware of the negatives as well.

 

I think my chatter is more surrounding the SPEC TOB (throw-out-bearing) vs the flywheel. I never considered it'd be fw. Interesting info.

 

Where is the chatter coming from? A solid flywheel, or any other solid people of metal for that matter, it's going to chatter on it's own.

I'm pretty sure the chatter is coming from the throw out bearing. That's the only thing that is spinning, and doesn't have any pressure on it when the clutch peddle is not being pressed to the floor.

 

Although our throw out bearings suck and fail often, it may not be that if you have a lightweight flywheel. The chatter comes from the momentary impulses the motor makes as each cylinder goes through its firing cycle and you hear them in the gears inside the transmission. The heavy two part flywheel (actually the material between them) is what absorbed those impulses reducing NHV in new cars. That's why car companies love them. They are smooth and quiet and they last the life of the warranty. They are not a performance part at all. The lighter the flywheel, the less it can absorb and the more chatter. If you notice, the stock clutch is a solid hub, the Valeo is a sprung hub clutch. SMF cars have to have somewhere to absorb those impulses so they use sprung hub clutches instead of the DMF. Also changing to thicker transmission fluids help cushion the impulses. Race cars don't care about NHV and run SMF with solid hub clutches and make all sorts of noises. Let me see if I can find a link to a much better explanation than I am giving.

 

Here it is.

http://www.uucmotorwerks.com/flywheel/gear_rattle.htm

The other thing I recommend is taking the flywheel and pressure plate to a machine shop that will balance the flywheel separately then when paired to the pressure plate. For most applications, this is overkill but if you like to spend time at the higher RPM range, it's worth the $50. Most quality parts are pretty good but are still not perfect. It made a noticeable difference in my BMW track car.

 

That makes good sense

 

Hi My clutch let go also a few years ago, it was the release bearing for me which died at about 40k miles aprox 60k Kms. I ordered an osgiken clutch for piece of mind. the kit came with flywheel and it was half the weight of the original.


the result was more hp to the wheels. the first sensation you get when you drive is that the car reaches red line so much faster it spools up and a quicker rate. at the time I could not understand why because I'm not well informed on cars but what I knew is my car just gained some power from somewhere without me making any other mods.


on a side note I do get some chatter but I don't care it does not bother me much anymore.

 

A lightweight flywheel does not result in more HP. Just because we started a scientific discussion, I'll add this to the thread. As a spoiler, both of us will end up being correct.

http://store.uucmotorwerks.com/artic...-HOW-WORKS.htm

 

wow that was a really good read! love to learn new things. so would lightening the flywheel (which "lightens the car") also increase your mpg?

 

Since we are getting scientific and all. Can you please explain to me why a 210 hp at the crank car only has 173 at the wheels? Where is the hp that was lost and why was it lost. I think i know what i'm talking about but thats for you help.

 

Parasitic loss of power through the drivetrain comes from friction, windage, overcoming inertia,
etc. that occurs from various places between the crankshaft and the asphalt.
If it didn't occur, your transmission, cv joints, bearings, clutch, and tires would always
remain exactly at room temperature, but they don't.

 

Okay but there is friction in the transmission and heat. And my lighter fly wheel was imediatelly felt on acceleration. For the sake of the OP my poit was simply that i felt more power in the car and having a light solid flywheel made a difference that i felt imediatelly. So i do highly recomend it especially with so many clutches including it as a kit.

 

Don't forget the energy it takes to run the alternator, AC, etc. As Cristo states, everything from the crank on back to the tires uses some fraction of energy. Older automatic transmissions used a lot of power. Wheel bearings use energy to turn. Oil in the motor, transmission and differentials create drag and steal some power. The more efficient a cars driveline, the more power that the engine produces gets to the wheels. That's why race cars do things to increase the efficiency that just won't do on street cars. They use water thin oils in their motors, transmissions and differentials instead of 90W-140. They are only interested in making 500 miles on those parts. They are not looking to get 150,000 miles out of them.

All these variables make it very difficult to use the standard Dyno to get accurate numbers on a motor. You can measure what you put down at the wheels but unless you pull the motor and go to a standardized motor dyno, you are only making a guess at what the motor is actually putting down.

 

As I stated, your observations are correct. We really are getting into the splitting hairs of terminology here. I am in no way discounting what you are saying, just trying to clarify so people don't go around the internet stating a lightweight flywheel will give you 20 more HP. It will feel like you have more hp but what you have done is reduce rotating mass. Your car will spin up a faster. Lighter flywheels are all about reducing rotating mass. That's why race cars go the lightest flywheel and clutch they can get away with. Acceleration is improved. Top speed (a crude way of measuring HP all other things being equal) will not change. Where people lighten their flywheel is also very important. Taking off weight at the perimeter of the flywheel is much more beneficial than taking the same amount off at the hub. It changes the amount of energy required to change the inertia of the flywheel. To take things on a completely different level, in NASCAR, they were shortening lug studs on the wheel in order to lighten the rotating mass. Chad Knaus figured he gained the equivalent of 1hp by shortening 20 of them.

 

And to over simplify things, this is why having lighter wheels by 5 lb's each, we'll make a car feel faster than just removing 20 lb's of overall weight.

I run into these scenarios all the time with my other hobby, Home Theatre audio video, just because there are minute "measurable" differences, doesn't mean that you personally will be aware of those differences.

 

Okay perfect. Sorry I must have read the previous message too quickly this morning.