GEARBOX SPECIALISTS

SPECIALIST REPAIRS FOR AUTOMATIC AND MANUAL GEARBOXES

WHY CHOOSE A GENUINE DMF OVER A LIMITED (LTD) CONVERSION?

Over 120 million vehicles have been installed with a Dual Mass Flywheel (DMF) as Original Equipment since its launch, and because modern engines continue to get smaller,lighter and more powerful, they are very much here to stay. So why do some garages still insist on converting the originally fitted technology to something that just wasn’t designed to do what the vehicle manufacturer intended?The DMF was originally developed for mass production by LuK in 1985, and today all 3 major OE clutch suppliers (LuK, Valeo and ZF) all design and produce 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 1400 rpm from a 1.0 Litre 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, down-speeding 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. Newer designs of DMF 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 (or 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.

So, why do DMFs go wrong ?
Just like any other component, a DMF will eventually wear out, and some conditions make them wear out quicker than normal. So what can shorten the life of a DMF ?

• Engine chip tuning
• Prolonged misfires or imbalance
• Towing excessive weight
• Overloading (especially LCV)
• Consistently driving in too low a gear

Drivers believing the DMF is the root of their problems are regularly sold conversion kits 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 average 15% increase in fuel consumption!

Mike from Headlands Garage converted several of his Taxi fleet as a trial hoping to make some savings, but encountered numerous issues:

“We thought we could save a few quid but we monitor fuel consumption accurately using tracking systems and our annual fuel bill for the fleet went up by more than £30,000 (around 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 20-25,000 miles with a solid…”

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 VM 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.

Kevin from Spannerama in Glasgow suffered with major problems:

“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, and we also had a spate of early driveshaft failures after just 12 to 15,000 miles…”

Using non-DMF technology, or parts not validated by the vehicle manufacturer can, in many cases, lead to critical component failure. Khalid from Universal in Luton, one of the UK’s largest independent clutch specialists, said:

“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…”

So there you have it, the DMF is still very much the go-to technology for vehicle manufacturers needing to efficiently control drive train vibration in today’s modern lightweight high-torque engines.

Fitting like-for-like when the time comes for a replacement is the only way of maintaining the fuel consumption, emission levels and driveability of the originally fitted parts – because they are the originally fitted parts! Do your customers a favour, fit genuine DMF and keep their comfort levels high but their fuel bills low! It could also help you avoid a large repair bill if things go wrong…

 

SOURCE: LUK