Drivetrain Questions and info regarding transmissions, clutches, etc.

:: Car Tech Nerds, Question About Lightweight Flywheels ::

Thread Tools
 
Search this Thread
 
Rate Thread
 
  #1  
Old 03-10-2009, 03:09 PM
lekker_droom's Avatar
Registered User
Thread Starter
iTrader: (12)
Join Date: Oct 2006
Location: Dallas
Posts: 3,035
Likes: 0
Received 1 Like on 1 Post
:: Car Tech Nerds, Question About Lightweight Flywheels ::

Chatters and makes more noise than a damn preteen girl on the telephone...

Can someone explain to me why my lightweight flywheel just HAS TO sound like and 747 crashing into a scrap yard?

I mean, I knew it was going to be noisy but is there not anyway whatsoever to quiet them down? If not then why? I mean what is happening in there to make it so loud. It sounds like the flywheel is loose or something to that effect. Again I know its part of having a lightweight flywheel but I'm just curious why it has to be that way.

By the way, my flywheel weighs 9.9lbs, approximately.
 
  #2  
Old 03-10-2009, 03:47 PM
Jeff92se's Avatar
Red Card Crew

iTrader: (24)
Join Date: May 2005
Location: ɐʍ 'ǝlʇʇɐǝs
Posts: 37,810
Received 583 Likes on 496 Posts
Well if Nissan could make it quiet w/o having to use a dual mass, they would have.

My question is how are these ultra light flywheels not getting the same criticism about engine balancing as the pullies? These introduce way more vibrations, remove way more weight and have a much larger diameter to contend with.
 
  #3  
Old 03-10-2009, 03:53 PM
dofu's Avatar
Registered User
iTrader: (9)
Join Date: Sep 2005
Location: Silicon Valley
Posts: 10,820
Received 240 Likes on 196 Posts
Simply because they're different... the flywheel isn't a pulley... unbalanced pulleys are bad simply because they hold a belt connected to other pulleys. If you change the size of one pulley, you've sped up the rest, too.

A lightweight flywheel on the other hand, is as good for performance as a set of lightweight wheels.
 
  #4  
Old 03-10-2009, 04:02 PM
Jeff92se's Avatar
Red Card Crew

iTrader: (24)
Join Date: May 2005
Location: ɐʍ 'ǝlʇʇɐǝs
Posts: 37,810
Received 583 Likes on 496 Posts
Originally Posted by dofu
Simply because they're different... the flywheel isn't a pulley... unbalanced pulleys are bad simply because they hold a belt connected to other pulleys. If you change the size of one pulley, you've sped up the rest, too.

A lightweight flywheel on the other hand, is as good for performance as a set of lightweight wheels.
Exactly what difference is there to eliminate flywheels as a bad source of vibrations into the engine? You DO know what that chatter is right?

BOTH are installed on the end the crank.

An aftermarket pulley is probably just as balanced as an aftermarket flywheel.

And no, I don't give that oem elastomeric band on the oem pulley enough credit to offset the elimination of the dual mass flywheel.
 
  #5  
Old 03-10-2009, 04:22 PM
dofu's Avatar
Registered User
iTrader: (9)
Join Date: Sep 2005
Location: Silicon Valley
Posts: 10,820
Received 240 Likes on 196 Posts
Although the flywheel is connected to the crankshaft and does help dampen vibrations, it's main function is to transfer torque from the engine to the transmission, unlike the harmonic balancer that's usually on the other end...
 
  #6  
Old 03-10-2009, 04:27 PM
Jeff92se's Avatar
Red Card Crew

iTrader: (24)
Join Date: May 2005
Location: ɐʍ 'ǝlʇʇɐǝs
Posts: 37,810
Received 583 Likes on 496 Posts
Originally Posted by dofu
Although the flywheel is connected to the crankshaft, and does help dampen vibrations, it's main function is to transfer torque from the engine to the transmission, unlike the harmonic balancer that's usually on the other end...
I thought the pulley's pupose was to turn the belts that drive the power steering and ac?


Dual mass vs single mass. For a Diesel but same concept:
Some notes on application pros and cons:

The dual mass systems are designed to transmit less engine vibration to the driveline, and give a better more car like driving experience. They also reduce some of the jarring and stress on the transmission and remainder of the drivetrain. They work fine as long as the engine remains unmodified and the vehicle is not used/abused beyond manufacturers recommendations.

As soon as you start to increase the engine power over stock, or load the vehicle beyond design parameters, you run into problems. Dual mass flywheels are tuned systems and must be matched to the engine torque curve, engine resonant characteristics, vehicle load curves (including axle ratio/tire size calculations). They work by having a set of springs inserted between two rotating masses (thus dual mass). The springs are sized to soak up some of the resonant vibration from the diesel engine under load conditions. A dual mass fly wheel generally also contains an over torque friction release, so if it gets suddenly overloaded, rather than damage the springs, it slips. This works fine as a safety valve, but if it does it much it burns up. In short, overloaded they burn up and the springs get destroyed and they are worse than if it were a single mass FW.

The single mass part WILL tend to transmit more engine pulse (vibration) tot he drivetrain, and will seem a bit rougher. But it is straight forward to design a single mass flywheel and clutch package for pretty much any engine torque curve and vehicle loading combo you can come up with. Drives more like a TRUCK, but has much better reliability at extreme use levels.
 
  #7  
Old 03-10-2009, 04:33 PM
Jeff92se's Avatar
Red Card Crew

iTrader: (24)
Join Date: May 2005
Location: ɐʍ 'ǝlʇʇɐǝs
Posts: 37,810
Received 583 Likes on 496 Posts
A performance mag's definition: and 5 sec on google

http://www.europeancarweb.com/tech/0...els/index.html

Flywheels - On the Fly
Everything You Need To Know About Flywheels
By Anthony Gelinas


On the Fly
The function of a drivetrain is to serve as the conduit for power from the engine to the wheels. Depending on vehicle configuration, engine power is transferred to the driveshaft and rear wheels in rear-wheel-drive vehicles, to axle half-shafts and front wheels in front-wheel-drive vehicles, or to all four wheels in all-wheel-drive vehicles.

The drivetrain starts at the engine, where pistons spin the crankshaft, then the flywheel, clutch disc, clutch cover, transmission, differential, and ends at the drive axles. It is at the flywheel where we begin our drivetrain journey. The flywheel provides a smooth, flat surface for the clutch to operate properly and serves to take heat away from the clutch pressure plate and disc friction material.

Dual Mass Flywheel (DMF)
The OEM flywheel found in most modern manual transmissions (as well as semi-automatic transmissions like the Audi/VW DSG and BMW SMG) is classified as a dual-mass flywheel (DMF). The DMF is designed to eliminate engine vibrations before they are transferred to the drivetrain.
A DMF is tuned by the manufacturer to match engine torque and horsepower curves, engine harmonics, and vehicle load dynamics, based on transmission gear ratios as well as overall rolling diameter of the rims and tires. It is constructed by splitting the standard single mass flywheel in half. The primary section bolts to the engine crankshaft and the second section is where the clutch assembly is installed. Contained within the two sections is a complex system of varying rate springs, axle and radial bearings, and lubrication. The two halves are rubber-sealed. The aforementioned series of components is referred to as the friction pack. The main purpose of the friction pack is to absorb vibration, allowing for smooth, comfortable shifting, low speed driveability, and reduced drivetrain noise.
When increasing the horsepower of a vehicle, the DMF can be the weakest link. It is designed with an over-torque friction release. As engine torque is increased, the flywheel has the potential to overload. To protect itself, the flywheel will slip, causing a reduction in torque, protecting the internal springs.

Pros: Reduced noise, smoother shifting, increased fuel economy, longer engine life.
Cons: High replacement cost ($799-$1599), can prematurely fail if horsepower and torque are increased, can slip under increased load, 8-11 degrees of movement before clutch engagement.

Single Mass Flywheel (SMF)
This flywheel bolts directly to the crankshaft and the clutch assembly connects directly to the flywheel. The most common and reliable flywheel upgrade is to replace the standard dual mass flywheel with a single mass flywheel. The SMF is typically sourced from an earlier application within the model line. For example, when upgrading a clutch on a transverse-engined VW/Audi five-speed 1.8T, the stock dual mass flywheel is replaced with an SMF from a 1990-92 VW Corrado G60. In the case of the VW/Audi conversion, the matching clutch kit is also needed to make it work. Upgrades for BMW and Porsche involve scrapping the stock dual mass for the European-spec SMF from the same application. When Porsche released the specifications for the GT3, it was quick to point out the use of an SMF for increased performance.

Pros: Increased performance, increased throttle response, increased durability (vs. dual mass), increased service life.
Cons: Increased engine vibrations.

Aftermarket Lightweight Flywheel (ALF)
Aftermarket lightweight flywheels are designed to weigh less than the SMF and the DMF by at least 50 percent. The most common ALFs are constructed either of aluminum or steel. Most aluminum flywheels feature a replaceable friction surface, making them easy to rebuild. On the other hand, a steel flywheel can be resurfaced only once.

Pros: On a naturally aspirated vehicle, an ALF is a good way to reduce excess rotating mass, allowing for increased acceleration.
Cons: Excessive low end clutch chatter, premature synchromesh wear, and possible engine damage will occur if the ALF is too light or not properly balanced. If the ALF is too light, a lack of initial inertia can cause the vehicle to stall easily when moving off from a standstill.
Conclusions
A properly designed flywheel that is chosen to match the vehicle application is integral, since the flywheel is an energy storage device that determines the amount of power available to get the car moving. A heavier weight flywheel can store more energy as it rotates, which is perfect for cars with engine and gear combinations that need more power or inertia to make the car accelerate. A lighter flywheel creates less inertia at launch, but accelerates quicker through the gears. If the vehicle is turbocharged and German, sticking with an SMF steel flywheel around the same stock weight as the OEM works the best. This setup tends to give peak low end torque, smooth gear transitions and mid-range boost response. Consulting with a specialist who has experience with your vehicle type is vital to getting the best flywheel for your application.
 
  #8  
Old 03-10-2009, 04:43 PM
dofu's Avatar
Registered User
iTrader: (9)
Join Date: Sep 2005
Location: Silicon Valley
Posts: 10,820
Received 240 Likes on 196 Posts
You're right, the flywheel can be a concern, but when you remove the harmonic balancer (also known as the vibration dampner), you're just screwed.
 
  #9  
Old 03-10-2009, 04:50 PM
Jeff92se's Avatar
Red Card Crew

iTrader: (24)
Join Date: May 2005
Location: ɐʍ 'ǝlʇʇɐǝs
Posts: 37,810
Received 583 Likes on 496 Posts
Same mag discussing a pulley upgrade for the M3 3.0. Inline 6 though:

http://www.europeancarweb.com/projec...eys/index.html

I don't quite understand how they can justify the light flywheel but not the pulley. Although they specifically mention not doing both.
 
  #10  
Old 03-10-2009, 04:52 PM
Jeff92se's Avatar
Red Card Crew

iTrader: (24)
Join Date: May 2005
Location: ɐʍ 'ǝlʇʇɐǝs
Posts: 37,810
Received 583 Likes on 496 Posts
Originally Posted by dofu
You're right, the flywheel can be a concern, but when you remove the harmonic balancer (also known as the vibration dampner), you're just screwed.
How screwed??? More than removing probably 10x the mass and dampening power of the DMF?

I do agree that BOTH units serve to help dampen vibrations. The question here is why do these small pullies get bad rap but not these flywheels? Every time you engage the clutch, it's introducing much more vibrations to the motor/drivetrain than a power steering pump or a AC motor clutch
 
  #11  
Old 03-10-2009, 05:04 PM
dofu's Avatar
Registered User
iTrader: (9)
Join Date: Sep 2005
Location: Silicon Valley
Posts: 10,820
Received 240 Likes on 196 Posts
Originally Posted by Jeff92se
Same mag discussing a pulley upgrade for the M3 3.0. Inline 6 though:

http://www.europeancarweb.com/projec...eys/index.html

I don't quite understand how they can justify the light flywheel but not the pulley. Although they specifically mention not doing both.
Harmonic balancers are one of the single most important part of the car. The only motors balanced enough to go without one are usually small displacement inlines.

The point is, balance is not the flywheel's job... it's the harmonic balancer's job on the other end. Thinking otherwise is almost like saying your springs are in charge of absorbing impact while your struts and tires aren't important for handling at all.

Nobody claims there is no risk to a lightweight flywheel, but the lightweight pulley's risk is just that much greater.
 
  #12  
Old 03-10-2009, 05:18 PM
Jeff92se's Avatar
Red Card Crew

iTrader: (24)
Join Date: May 2005
Location: ɐʍ 'ǝlʇʇɐǝs
Posts: 37,810
Received 583 Likes on 496 Posts
Tell me, how does a think elastormeric ring on a small pulley rival the dampening effects of a 30lb+ dual mass flywheel that's 3-4x the diameter?

Or how does taking a small weight off a pulley make the engine so suspecptible to vibrations when taking something like 5x the weight off the flywheel isn't? (while completely eliminating the dual mass function of elminating engine vibrations)

How is the "purpose" of a pulley so very defined as a "dampener" and the purpose of a dual mass flywheel is not? Despite the magazine's very definition of it.

How is a little rubber ring doing more dampening of vibrations than an unit that weighs 5x more, is 5x+ the diameter AND has actually springs in the unit to lessen vibrations?

The only modern nissan that I know of that has a balancer to SPECIFICALLY reduce engine vibrations is the QR25. It's equipped with another rotating balancer near the crankshaft. Oddly enough in a lower displacment engine.
 

Last edited by Jeff92se; 03-10-2009 at 05:25 PM.
  #13  
Old 03-10-2009, 05:20 PM
dofu's Avatar
Registered User
iTrader: (9)
Join Date: Sep 2005
Location: Silicon Valley
Posts: 10,820
Received 240 Likes on 196 Posts
Sounds like you know, so please indulge us in your own words... tell me why lightweight pulleys are not as bad as lightweight flywheels...
 
  #14  
Old 03-10-2009, 05:24 PM
Jeff92se's Avatar
Red Card Crew

iTrader: (24)
Join Date: May 2005
Location: ɐʍ 'ǝlʇʇɐǝs
Posts: 37,810
Received 583 Likes on 496 Posts
Originally Posted by dofu
Harmonic balancers are one of the single most important part of the car. The only motors balanced enough to go without one are usually small displacement inlines.

The point is, balance is not the flywheel's job... it's the harmonic balancer's job on the other end. Thinking otherwise is almost like saying your springs are in charge of absorbing impact while your struts and tires aren't important for handling at all.

Nobody claims there is no risk to a lightweight flywheel, but the lightweight pulley's risk is just that much greater.
You analogy makes no sense
 
  #15  
Old 03-10-2009, 05:26 PM
Jeff92se's Avatar
Red Card Crew

iTrader: (24)
Join Date: May 2005
Location: ɐʍ 'ǝlʇʇɐǝs
Posts: 37,810
Received 583 Likes on 496 Posts
Originally Posted by dofu
Sounds like you know, so please indulge us in your own words... tell me why lightweight pulleys are not as bad as lightweight flywheels...

Isn't that what YOU are trying to convince me of?
 


You have already rated this thread Rating: Thread Rating: 0 votes,  average.

Quick Reply: :: Car Tech Nerds, Question About Lightweight Flywheels ::



All times are GMT -4. The time now is 04:21 PM.