Dual Mass Flywheel (DMF) Description and Function - AudiWorld Forums

Go Back  AudiWorld Forums > Audi Models > Audi Original "S" Cars
Reload this Page > Dual Mass Flywheel (DMF) Description and Function
Notices
Audi Original "S" Cars Discussion forum for the Audi Audi Ur S4, Ur S6, S2 & RS2

Dual Mass Flywheel (DMF) Description and Function

Reply

 
 
Old 12-14-2006, 11:25 AM
  #1
AudiWorld Super User
Thread Starter
 
UrS4boy's Avatar
 
Join Date: Feb 2001
Posts: 18,784
Default Dual Mass Flywheel (DMF) Description and Function

<center><img src="http://pictureposter.audiworld.com/15624/dualmassflywheelx-sec.jpg"></center><p>
What is the DMF's function? It is designed to isolate torsional crankshaft spikes created by high power, high torque engines including diesel engines with high compression ratios. By separating the mass of the flywheel between the engines and the transmission, torsional spikes can be isolated, eliminating potential damage to the transmission gear teeth. There are several components:

[IMG}http://www.lukclutch.com/images/flywheels/page04_a.jpg[/IMG]

Engine-side flywheel damper springs: The damper springs that are visible on the engine side of DMF are designed to dampen heavy torsional spikes that occur when the engine's torsional frequency matches the torsional frequency of the transmission. When torsional frequencies match (have the same amplitude), severe damage can occur to the transmission if not isolated. DMF's isolate the torsional frequency match between the engine and transmission to an r.p.m. range below the operating range of the engine (usually between 200-400 r.p.m.). These damper springs only work hard when the engine passes through 200-400 r.p.m. at vehicle start up and shut down.

DMF damper springs and/or damper springs nylon retainers usually fall because the engine is not running correctly. Bad fuel injectors, worn pistol rings, bad valves, etc, will change the resonant frequency of the engine. A change in the resonant frequency of the engine can force the torsional frequency match between the engine and DMF to fall within the operating range of the engine. This forces the damper springs to work continuously, resulting in failure.

Friction Ring: The friction ring located between the inner and outer flywheel is designed to allow the inner and outer flywheel to slip. This feature saves the transmission from damage when torque loads exceed the vehicle rating of the transmission. (Read: Burnouts/high RPM shifts) The friction ring will wear out if excessive torque loads are continuously applied. Loading the vehicle beyond the rated load capacity is often the root cause of friction ring failures in DMF's.

Center Bearing: A sealed double row center ball bearing carries the load between the inner and outer halves of the DMF. The leading cause of center bearing failure is often related to out of balance vibration caused by not aligning the pressure plate with the DMF dowel pins. The center bearing may also fall if the clutch pilot bearing is destroyed by a worn transmission input shaft (see Pilot Bearing) or if the rated load/towing capacity of the vehicle is exceeded.

Pilot Bearing: The pilot bearing supplied with most DMF's is a caged needle roller bearing. If it fails, the transmission input shaft must be repaired or replaced. If the input shaft is not repaired correctly or replaced, the lack of input shaft support will result in DMF center bearing failure.

Last edited by UrS4boy; 06-03-2009 at 05:27 PM.
UrS4boy is offline  
Reply With Quote
Old 12-14-2006, 11:38 AM
  #2
AudiWorld Super User
 
Join Date: Nov 2004
Posts: 5,327
Default

good read.
chefbob is offline  
Reply With Quote
Old 12-14-2006, 09:47 PM
  #3
AudiWorld Senior Member
 
Jonny K's Avatar
 
Join Date: Jul 2006
Posts: 841
Default

I read it, I'm not sure what it all means, but cool. :-)
Jonny K is offline  
Reply With Quote
Old 12-15-2006, 07:36 AM
  #4
New Member
 
Join Date: Nov 2006
Posts: 46
Default questions

The pic implies that the mass are unequal. Is is this true? and what dictates the Mass of each. Is there some sort of ratio that must be maitained. What would a symptons be if these masses were changed?
jblazeUrs4 is offline  
Reply With Quote
Old 12-15-2006, 02:56 PM
  #5
AudiWorld Super User
Thread Starter
 
UrS4boy's Avatar
 
Join Date: Feb 2001
Posts: 18,784
Default It means the stock flywheel is designed to a) reduce vibrations and b) save your tranny from...

shocks. IMHHEO, going to a non-dual mass flywheel could be bad for the tranny.
UrS4boy is offline  
Reply With Quote
Old 12-15-2006, 02:58 PM
  #6
AudiWorld Super User
Thread Starter
 
UrS4boy's Avatar
 
Join Date: Feb 2001
Posts: 18,784
Default No idea. I think the important part is the fact the there are springs between the two masses to...

help take up vibrations and torque shocks (to a point when the springs are fully compressed).

I think.

;&gt
UrS4boy is offline  
Reply With Quote
Old 12-15-2006, 11:53 PM
  #7
AudiWorld Senior Member
 
Jonny K's Avatar
 
Join Date: Jul 2006
Posts: 841
Default

Ohhhh, ok. :-)
Jonny K is offline  
Reply With Quote
Old 04-08-2009, 08:31 AM
  #8
New Member
 
Join Date: Apr 2009
Posts: 6
Default

nice read. I was wondering,because on other forums i have seen that dual mass flywheels say have a limit to power,is it possible to know how much that is and why?

My mechanic seems to think that it is better for higher power,even if it is heavier than those aluminium flywheels.

cheers
vasilis
A80Avant is offline  
Reply With Quote
Old 04-08-2009, 09:05 AM
  #9
AudiWorld Super User
 
Join Date: Oct 2005
Posts: 6,624
Default

I'm not sure how much power the DMF in the UrS can stand up to, but it makes sense that a DMF could have issues with increased power. A DMF is made up of 2 basic parts that can move independently to absorb shocks/vibradions from the engine and prevent them from damaging the trans. If you increase the amount of power being transfered through the flywheel there will be a point that the springs will not be able to hold the increased power and will fail.

A single mass flywheel is a solid piece of steel or aluminum with no moving parts to wear out or break.
ThetaTau87 is offline  
Reply With Quote
Old 04-12-2009, 08:59 AM
  #10
New Member
 
Join Date: Apr 2009
Posts: 6
Default

i was wondering if it is the abrupt increase of torgue that will cause damage to the DMF or the total amount of torgue/power produced in general.

Im currently running a DMF with the GT3071R setup and according to calculations im at around 530-560Nm of torgue crank.Im going to try about 500hp crank(now around 420-425) with i would imagine about 600-620Nm or torgue.Im going to be introducing boost gradually and then holding it to the red line,so there will be less stress on everything basically.
A80Avant is offline  
Reply With Quote
 
 
 

Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
ECS Tuning-Audi
S4 (B8 Platform) Discussion
4
09-14-2017 09:58 AM
ECS Tuning-Audi
Audi A5 / S5 / RS5 Coupe & Cabrio (B8)
3
02-04-2016 08:36 AM
bballfreak
A6 / S6 (C6 Platform) Discussion
4
10-12-2015 05:14 PM
iamdrewseph
A8 / S8 (D3 Platform) Discussion
5
10-01-2015 11:33 AM
ECS Tuning-Audi
A4 (B7 Platform) Discussion
0
09-24-2015 12:06 PM


Thread Tools
Search this Thread
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -8. The time now is 02:06 PM.


 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: