Go Back   EcoModder Forum > EcoModding > General Efficiency Discussion
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 07-26-2009, 02:02 PM   #1 (permalink)
aero guerrilla
 
Piwoslaw's Avatar
 
Join Date: Oct 2008
Location: Warsaw, Poland
Posts: 3,747

Svietlana II - '13 Peugeot 308SW e-HDI 6sp
90 day: 58.1 mpg (US)
Thanks: 1,328
Thanked 749 Times in 476 Posts
Dual mass flywheel - 5% FE increase?

I was reading about dual mass flywheels today and one of the things I found was that it increases FE by 5% (Polish Wikipedia, which cites this article). Has anyone come across this info? Why would the savings be that big?

For those who don't know, here is a word about DMFs. Normally an engine has a simple, solid flywheel which helps keep the angular velocity of the crankshft constant. But there are still vibrations which need to be smoothed out since they can kill the transmission. This is usually done by some sort of spring setup at the clutch. A diesel engine has enough torque and vibrations at low rpm to still wreck havoc, so this is where the DMF comes in. It is actually two flywheels with a complicated mess of torque and vibration dampening machinery in between. This extends the life of the tranny and syncros, reduces noise and increases FE. The price you pay is pretty high: since it is so complicated, it needs replacing much more often than a normal flywheel or clutch and is much more expensive. About half of all European cars from the last few years have DMFs, and some owners prefer to replace their duals with a low-tech, solid flywheel when their time is up.

__________________
e·co·mod·ding: the art of turning vehicles into what they should be

What matters is where you're going, not how fast.

"... we humans tend to screw up everything that's good enough as it is...or everything that we're attracted to, we love to go and defile it." - Chris Cornell


[Old] Piwoslaw's Peugeot 307sw modding thread
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 07-27-2009, 01:04 PM   #2 (permalink)
Master EcoModder
 
Join Date: Mar 2009
Location: Northeast Ohio
Posts: 269

The Wife's Hot Rod - '09 Pontiac G8 GT
Last 3: 23.22 mpg (US)

Big Outback - '13 Subaru Outback 2.5i

Little Outback - '02 Subaru Impreza Outback Sport
Thanks: 0
Thanked 16 Times in 16 Posts
I'm thinking they work like very large harmonic balancer. My guess to the efficiency increase comes from absorbing the energy in a spring which is able to return it to the drive line. In a harmonic balancer the energy is absorbed by a hydraulic system or an elastomer damper.

I am guessing due to their cyclic working, the springs fatigue & break. Causing possible damage to the housings. It's like having to have your clutch replaced with expensive parts & lots of labor. Someone wrote that it cost him 1500 pounds-sterling, approx $2500, to have it replaced. Which makes a $900 clutch job look cheap.

Don
  Reply With Quote
Old 07-27-2009, 01:23 PM   #3 (permalink)
Master EcoModder
 
tasdrouille's Avatar
 
Join Date: Jan 2008
Location: Mirabel, QC
Posts: 1,672

The Guzzler - '08 Hyundai Elantra GL
90 day: 33.12 mpg (US)

Got Soul? - '11 Kia Soul 2U
Thanks: 35
Thanked 86 Times in 57 Posts
Interesting.

My car came stock with a DMF. They all go south eventually and everyone replace them with a SMF, because those lost pretty much forever, and are effectively a lot cheaper. I've never seen an impact on MPG being discussed on TDIClub.com. I highly doubt a 5% difference. That wouldn't go unnoticed.
__________________



www.HyperKilometreur.com - Quand chaque goutte compte...
  Reply With Quote
Old 08-17-2009, 01:33 PM   #4 (permalink)
EV OR DIESEL
 
Join Date: Dec 2007
Location: South Louisiana
Posts: 1,758

FarFarfrumpumpen - '03 Volkswagen Jetta Wagon GLS Premium

Quorra - '12 Tesla Model S P85
Thanks: 57
Thanked 113 Times in 86 Posts
Send a message via AIM to dremd
Ouch
Subscribed
About to swap in a SMF on my TDI (err)
__________________
2016 Tesla Model X
2022 Sprinter
Gone 2012 Tesla Model S P85
Gone 2013 Nissan LEAF SV
2012 Nissan LEAF SV
6 speed ALH TDI Swapped in to a 2003 Jetta Wagon
  Reply With Quote
Old 04-07-2010, 01:07 PM   #5 (permalink)
aero guerrilla
 
Piwoslaw's Avatar
 
Join Date: Oct 2008
Location: Warsaw, Poland
Posts: 3,747

Svietlana II - '13 Peugeot 308SW e-HDI 6sp
90 day: 58.1 mpg (US)
Thanks: 1,328
Thanked 749 Times in 476 Posts
Here is a link to the source article, google-translated into English:
Dual-mass flywheel - Google Translate
(I can't edit the first post, or I'd have put it there)
__________________
e·co·mod·ding: the art of turning vehicles into what they should be

What matters is where you're going, not how fast.

"... we humans tend to screw up everything that's good enough as it is...or everything that we're attracted to, we love to go and defile it." - Chris Cornell


[Old] Piwoslaw's Peugeot 307sw modding thread
  Reply With Quote
Old 04-08-2010, 08:16 AM   #6 (permalink)
aero guerrilla
 
Piwoslaw's Avatar
 
Join Date: Oct 2008
Location: Warsaw, Poland
Posts: 3,747

Svietlana II - '13 Peugeot 308SW e-HDI 6sp
90 day: 58.1 mpg (US)
Thanks: 1,328
Thanked 749 Times in 476 Posts
More in-depth talk about DMF's in 6 speed swap in to my TDI Golf 4 - page 5.
__________________
e·co·mod·ding: the art of turning vehicles into what they should be

What matters is where you're going, not how fast.

"... we humans tend to screw up everything that's good enough as it is...or everything that we're attracted to, we love to go and defile it." - Chris Cornell


[Old] Piwoslaw's Peugeot 307sw modding thread
  Reply With Quote
Old 04-15-2010, 09:44 AM   #7 (permalink)
Harebrained Idea Skeptic
 
Join Date: Jun 2008
Location: Alpharetta, GA
Posts: 211

The White Car - '84 Mercedes-Benz 300td
90 day: 28.84 mpg (US)

The Blue Car - '86 BMW 535i
Last 3: 23.86 mpg (US)
Thanks: 19
Thanked 13 Times in 9 Posts
They might help in constant-state driving, but in traffic a lower-inertia flywheel will be more efficient.
__________________

  Reply With Quote
Old 04-25-2010, 03:15 AM   #8 (permalink)
Master EcoModder
 
Join Date: Apr 2010
Location: belgium, wi
Posts: 262

Bus - '94 Ford School Bus huge

Stupid - '01 Chevy Blazer LS
90 day: 21.38 mpg (US)

hawk - '00 Honda Superhawk
Thanks: 2
Thanked 24 Times in 19 Posts
DMF's and heavy flywheels revealed

First post....

DMF's are heavy, and a single mass of equivalent size would provide the same benefits. The torque impulse of every single cylinder is harnessed into the rotating assembly. The flywheel is part of this. As the engine rotates (if we were looking at a single cylinder), after firing, it needs to do the work that you are asking of it as well as compress the next air/fuel charge. With a light flywheel, the engine can accelerate and decelerate faster, but it also does this within the four stroke cycle, causing loss of net power (tq). If you don't believe, or even feel slightly skeptical, take the blade off of your lawnmower and try to start it. Typically it will fire, rotate up the compression stroke to the ignition event and change directions, ripping the pull cord from your hands in a painful and violent manner. I hope this helps.
  Reply With Quote
Old 04-25-2010, 10:04 AM   #9 (permalink)
EV OR DIESEL
 
Join Date: Dec 2007
Location: South Louisiana
Posts: 1,758

FarFarfrumpumpen - '03 Volkswagen Jetta Wagon GLS Premium

Quorra - '12 Tesla Model S P85
Thanks: 57
Thanked 113 Times in 86 Posts
Send a message via AIM to dremd
Quote:
Originally Posted by autoteach View Post

DMF's are heavy, and a single mass of equivalent size would provide the same benefits.
Welcome to ecomodder!

If that were true manufactures would just install single mass wheels, mainly due to cost, but complexity, and failure rate would come it to play as well.
__________________
2016 Tesla Model X
2022 Sprinter
Gone 2012 Tesla Model S P85
Gone 2013 Nissan LEAF SV
2012 Nissan LEAF SV
6 speed ALH TDI Swapped in to a 2003 Jetta Wagon
  Reply With Quote
Old 04-25-2010, 01:31 PM   #10 (permalink)
Master EcoModder
 
Join Date: Apr 2010
Location: belgium, wi
Posts: 262

Bus - '94 Ford School Bus huge

Stupid - '01 Chevy Blazer LS
90 day: 21.38 mpg (US)

hawk - '00 Honda Superhawk
Thanks: 2
Thanked 24 Times in 19 Posts
Quote:
Originally Posted by dremd View Post
Welcome to ecomodder!

If that were true manufactures would just install single mass wheels, mainly due to cost, but complexity, and failure rate would come it to play as well.
Not quite sure what you mean with the failure rate but...the benefits that you are looking for, mpg, would be present in both a smf and dmf that weigh in at 25-30lbs. The difference for the dmf is that it absorbs shock like a crankshaft balancer. Balancers are dual mass as well, and absorb crankshaft speed variations as well as vibrations. That is the primary benefit of the DMF. They just always seem to be heavier, which leads to fuel efficiency.

As for manufacturers, they surely don't install the dmf for fuel efficiency. It is for the smoother drivetrain benefits. If manufacturers based everything they did on fuel mileage, there wouldn't be forums like this

  Reply With Quote
Reply  Post New Thread




Similar Threads
Thread Thread Starter Forum Replies Last Post
New CVT transmission electric-assist with electric assist Ptero Fossil Fuel Free 2 09-23-2010 11:41 PM
Using flywheels to increase FE NoCO2 EcoModding Central 47 12-17-2008 10:57 PM
Basic EcoDriving Techniques and Instrumentation SVOboy Instrumentation 2 11-17-2007 12:38 PM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com