I didnt know flywheel was for comfort, its just funny how you said.
Why would engineers design comfort when engine block, crankshaft, bearing unidirectional loading is undesirable and can lead to reliability issues?
Comfort comes in when designing the engine mounts, how to damp the engine vibrations transferring into the chassis and not when designing the flywheel.

 

Heavy flywheels are used for smoothness and very nice engagement of the engine power to the transmission. But becuase they have a lot of mass to them, they result in more drivetrain power losses, and a less responsive motor.

I know your question was rhetorical, but I thought I would answer it anyways.

What type of engineer are you, BTW?

 

I think Z1 was saying that the CRANK pulley is balanced internally...not the engine.

Usually, OEM's will remove material from the forged crank, rather than adding to it. When we build motors, and rebalance the rotating assembly, we also remove material.

 

You know that The clutch and flywheel are the single most importan element of transmission operation. You can bet yo'r *** it's designed to be as comfortable and seamless as possible. The stock clutch/flywheel is designed with a maximum of comfort as a compromise. It is heavy to store a lot of kinetic energy to avoid having to rev to 5000rpm at every corner and stop, it has a dual mass construction to isolate torsional load spikes from the engine, etc...

I don't understand where reliability issues would come from?

911 has heavy dual mass flywheel (smooth and quiet, considerable drivetrain loss, slow responsivness)
911 gt3 has lightweight single mass flywheel (noisy, harsh, least drivetrain losses and maximum responsivness)

 

Lets no confuse the function of flywheel and pressure plate, which are independant of each other. Flywheel balances the unbalanced mass on the crankshaft, pressure plate mates with clutch to provide the right coefficient of friction or in layman's terms more friction. The two are packaged in a single unit for compactness.

911 and 911 GT3 I believe have different internals in the engine (crankshaft, con rod, pistons) hence has different unbalanced rotating mass on the crankshaft and thus the difference in the flywheel mass or design. From what I can recall GT3 engine had higher redline, higher compression ratio and higher hp/liter than 911 engine.

 

actually the difference was between the GT3 and the GT3 RS, both have the same exact engine... GT3 has standard dualmass flywheel, GT3 RS has singlemass lightweight flywheel.


let me guess... your car is bone stock?

 

Well, so there is only one way of designing things? At least not in my book. It may be possible to cleverly design a low mass flywheel by playing with mass distribution. I think the point I made was convieniently ignored. I dont feel the need to discuss this further.

Through this discussion I felt that you are saying that manufacturers have the habit of increasing the mass of the flywheel/pulley etc. for no reason althought it might be costing them more money because higher material costs to say the least and they have no reason or need to optimize it.

I dont know why this has to become personal and what it has to do with my Z being bone stock 3 months after I bought it. I thought we were discussing something here.

 

sorry, I was just kidding --> see smilie. Nothing personal, relax

I explained the reasons of a heavier flywheel and the dual mass issue. I explained how the flywheel scope is to store kinetic energy, I explained how everyday joe wouldn't enjoy a lightweight flywheel4... I don't think this as anything to do with costs, it's an issue of common sense.

as for manufacturing, For example: the stock pulley looks like it is cast and machined. I don't remember seeing any form of ballancing artefacts on it. It's heavy, rusted and looks like crap... I really doubt it's more ballanced or has better mass distribution or whatever than the UR pulley. (I also highly doubt it costs more to manifacture).

I don't quite get your point (I'm not ignoring it). I don't understand why a lightweight pulley or flywheel can't be ballanced?

 

Great topic, glad I found it!

 

why does a Z have a dual mass flywheel? As mentioned..comfort and ease of driveability for the masses.

Lot's of cars have similar flywheel designs. RX7's do..... but wait, they don't have pistons or cranks, the entire block weighs maybe 100 lbs and has a total of 6 moving parts inside...so why the need for such an elaborate flywheel?

Noise reduction, and ease of overall operation. As mentioned, as you reduce weight on the flywheel, you increase drivetrain noise and also require more driver input to "smoothly" drive the car.

Maybe you can design a lightweight flywheel that also behaves as quietly as a heavier one. To date, no such animal exists however. What manufacturers have realized is that there is a fine line with EVERY engine where too light of a flywheel, while making the engine ultra responsive, makes it noisy and not what most people (enthusiasts included, not just the masses), will live with. Imagine if the Z came with a Tilton from the factory?

Adam

 

I'd be as happy as a pig in shizzle.