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...”