Inform February 2014 77 76 Inform February 2014

Supplier feature

Dual Mass Flywheels -OE for a reason

Over 120 million vehicles have been fitted with a Dual Mass Flywheel as Original Equipment since its launch, and because modern engines continue to get smaller, lighter and more powerful, they are here to stay.

Dual Mass Flywheels have been around for nearly 30

years now, and love them or hate them they are fitted

as OE for a reason. The 3 largest OE clutch suppliers

(LuK, Valeo and ZF) have all designed and produced

versions of the DMF for original fitment.

The reason they are so popular is simple.

Vehicle Manufacturers are not only constantly striving

to meet ever tighter government emissions targets,

but also to satisfy vehicle driver aspirations for

improved refinement from ever more powerful

vehicles, so they have turned to DMF in their

droves to provide the solution.

After many years of throwing emissions hardware at

today’s engines - such as Common Rail, GDI, catalytic

converters, DPF etc. etc., there is still only so much

you can do to an internal combustion engine to

reduce emissions.

It is now more common for VMs to take weight out

of the car and include smaller, lighter engines that

produce high levels of torque at lower engine speeds.

The Ford Ecoboost engine is a good example, it

produces a peak torque of up to 200Nm at 1400rpm

from a 1.0 engine!

The latest ultra-light 7 or 8 speed gearboxes are also

contributing to the rise of the DMF. Weight used to be

the major vibration absorber - adding a weight

(a mass damper) to a vibrating gear mechanism arm

and you transform it from a poor quality flimsy

gear change to something a BMW driver

would be happy with. The big BUT is that the more

weight you carry leads to increase in both fuel

consumption and emissions levels.

All of these weight saving measures, such as the

smaller, lighter engines and gearboxes, downspeeding

and the engine running slower (to reduce friction)

simply result in an increase in vibration levels and

hence the need for a different technology.

The DMF has been the answer to this

problem since 1985, and it continues to be the

go-to solution for pretty much every

manufacturer building vehicles today.

So how and why does it work?

The term ‘dual mass’ simply means splitting the

flywheel in two, and attaching one half (mass) to the

engine and the other half to the gearbox. Doing this

reduces the resonant frequencies to something well

below idle speed so they are virtually undetectable.

In addition, a pair of large arc springs between the

two masses provide up to a massive 186 degrees

of rotational movement in some DMFs, capable of

absorbing even more vibration.

Newer designs incorporate additional springing to

add further absorption capacity, and the very latest

versions borrow advanced aircraft engine technology

- specifically in the form of the Centrifugal Pendulum

Absorber (CPA).

First used in the emissions busting BMW ‘Efficient

Dynamics’ engines, CPA equipped DMFs are now also used

by VAG in low emission variants such as the Volkswagen

Passat, Audi A5, Seat Leon and Skoda Superb.

Ford Ecoboost Engine

DMF with CPA technologyThe Dual Mass Flywheel

Case study three: Khalid, Universal Clutch

Using non-DMF technology, or parts not validated by the

VM can, in many cases, lead to critical component failure.

Khalid from Universal in Luton, one of the UK’s

largest independent clutch specialists, said:

Supplier feature

So why do they go wrong?

Just like any other component, DMF’s do eventually

wear out, and some conditions make them wear out

quicker than normal.

It is simple logic - a DMF is designed to absorb

vibration, and if it has to absorb more than it was

designed for then service life can be shortened.

After a while it will not be able to absorb as much

vibration, which instead will make its way into

expensive components like the gearbox and,

of course, it will begin to be noticed by the driver.

What shortens a DMF lifespan?

• Enginechiptuning

• Prolongedmisfiresorimbalance

• Towingexcessiveweight

• Overloading(especiallyLCV)

• Constantlydrivingintoolowagear

The benefits of DMF:

• Better fuel economy

• Reduced emissions levels

• Comfortable, vibration free driving

• Tested and approved by the VM

• The originally fitted technology

• Protects the drivetrain

• LuK warranty and technical support

• Saves money in the long term!!!!

Case study one: Mike, Headlands Garage

Case study two: Kevin, Spannerama

A conversion kit is usually sold on the promise of ‘long life’ and ‘reduced cost’, but

nothing is mentioned about its reduced capability to absorb vibration, the additional

weight, the potential for damage or the increase in fuel consumption! Which is why

fleet managers are returning to the original and best - the DMF.

Mike from Headlands garage converted some of his extensive

taxi fleet as a trial, thinking that he would save some money:

Conversion kits usually contain a Long Travel Damper (LTD) which provides a little

more rotational movement than a standard damped plate, but still only a maximum

of 29° compared to the maximum possible 186° (but usually around 100°) of a DMF.

To overcome the limited vibration absorption capabilities of the LTD,

a solid flywheel adds weight, effectively putting back the mass that the

vehicle manufacturer removed by originally fitting a DMF!

This extra weight brings its own problems, as broken crankshafts are not

uncommon in both Ford Transits and Skoda Octavias due to the extra strain

put on the drivetrain - as Kevin from Spannerama in Glasgow discovered:

“We thought we could save a few quid but we monitor fuel

consumption accurately using tracking systems and the annual

fuel bill for our fleet went up by almost £35,000 (15%) after

conversion. On top of that drivers were slipping the clutch to

overcome judder issues which bought our average clutch life down from

70-100,000 miles for a DMF to just 20-25,000 miles with a solid...”

“We look after a large fleet of Octavia Taxis and we saw

6 crankshaft failures in 6 months following the fitment

of Solid Flywheel conversion kits. We also had a spate of

early driveshaft failures after just 12 to 15,000 miles”...

SOLID CONVERSION

!

+15%

For more information about Dual Mass Flywheels,

including leaflets and posters for your garage

customers, call LuK customer services on

01432 264264 or visit:

www.schaeffler-aftermarket.co.uk OR

www.RepXert.com

“We never use 4-in-1 conversion kits, but we get a load of Transits in with bearing and slave cylinder failure

after they have been converted and we always convert them back to a DMF. We keep the bits that fail after

converting in stock now (like slave cylinders and release forks), because we are seeing loads of them...”