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Hopefully, most professional technicians are aware of the evolution of the dual mass flywheel (DMF), including hardware adaptations such as the incorporation of a centrifugal pendulum absorber (CPA) into some units. The addition of a CPA, a technology more commonly found in aircraft engines, basically allows the DMF to remove even more drive train vibration than traditional designs.

Schaeffler engineers, at various LuK facilities around the world, have been working with leading vehicle manufacturers to look at other ways in which the CPA could be used to deliver improved comfort and driveability, as well as to help meet fuel consumption and emissions reductions targets. They discovered that a transmission featuring a CPA equipped clutch disc and a solid flywheel provided an ideal damping solution for engines that required less vibration removal performance than offered by a DMF, but more than could be delivered by standard solid flywheel and torsion sprung disc combination.

The new CPA clutch disc and solid flywheel combination works best in smaller engines that deliver under 250Nm of torque, with engines above 250Nm usually requiring a DMF to absorb the extra vibration levels. As the CPA clutch disc is also a more cost-efficient solution, its suitability for specification on smaller engined vehicles is even more pronounced.

Two manufacturers that are benefitting from the technology are Hyundai and Kia, whose 1.6 CRDI engines are originally equipped with a CPA clutch disc. You can also find it in corresponding LuK RepSets for all relevant vehicles.

Note that CPA equipped products cannot be retrofitted. If the component removed is a standard DMF or a clutch disc with torsion dampers, they must be replaced like-for-like. For the latest application information, always refer to Schaeffler’s free TecDoc powered online catalogue, which can be found at both www.repxpert.co.uk or https://aftermarket.schaeffler.co.uk/en-gb.

Why do we need them?

The speed at which engines are expected to run is getting lower and lower, as the slower the engine runs the less fuel it burns and hence the fewer emissions it will produce. At Schaeffler, we have been talking about ‘downspeeding’ during our transmission training sessions for a long time, usually to help explain the reasoning behind the need for such technology as the DMF.

Drivers want to be comfortable at all speeds in all gears, expecting a smooth drive at engine speeds of around 1000 revs in the highest gear, without significantly impacting driveability. However, drive train vibration cannot be avoided at such low engine speeds, and with it comes resonance-induced buzzing and rattling. To remove these unwanted effects, advanced torsional vibration damper systems are needed to ‘soak up’ the vibration – hence the need for a DMF or CPA clutch disc.

Note: When installing a CPA clutch disc, the centrifugal pendulum absorbers may move, and the resulting noises are normal. This is not a defect, but an indication that the technology is working as intended.

Technical Tip: PRIMING SHOCK ABSORBERS

Technical Tip: PRIMING SHOCK ABSORBERS

Occasionally, a shock absorber will be diagnosed as faulty when removed from its packaging for installation. However, this may not be the case and the fix is often very simple: priming.

Occasionally, a shock absorber will be diagnosed as faulty when removed from its packaging for installation. However, this may not be the case and the fix is often very simple: priming.

Shock absorbers are generally stored and transported horizontally. This can cause the gas and hydraulic fluid within a shock absorber to mix with one another.

Shock absorbers are generally stored and transported horizontally. This can cause the gas and hydraulic fluid within a shock absorber to mix with one another. Pockets of air begin to form within the oil, affecting the damping force of the shock absorber.

Pockets of air begin to form within the oil, affecting the damping force of the shock absorber.

WHY PRIME SHOCK ABSORBERS?

WHY PRIME SHOCK ABSORBERS?

Whilst priming is not fundamental to the operation of shock absorbers, installation without priming can lead to customer complaints about unusual noise and/or ride harshness as the shock absorbers “break in”.

Whilst priming is not fundamental to the operation of shock absorbers, installation without priming can lead to customer complaints about unusual noise and/or ride harshness as the shock absorbers “break in”.

How To Prime Shock Absorbers

To avoid this, simply pump the shock absorber 4-5 times in its vertical working position. This will ensure that the oil and gas move to the correct areas prior to fitting.

How To Prime Shock Absorbers

To avoid this, simply pump the shock absorber 4-5 times in its vertical working position. This will ensure that the oil and gas move to the correct areas prior to fitting.