What Is A Dual-mass Flywheel And Why Do Automakers Use Them?

loraks/Shutterstock

One of history's awesome creation and subject collisions is nan invention of nan potter's instrumentality successful Mesopotamia astir 3500 B.C. Potter's wheels led to nan creation of flywheels, which helped artisans execute smoother, much accordant revolutions while throwing clay. These foot-driven instruments are still utilized today, and nan aforesaid principles are astatine activity successful nan dual-mass flywheels you'll find successful galore modern cars pinch manual and dual-clutch transmissions.

A car's flywheel is simply a disc, usually made of aluminum, steel, aliases formed iron, bolted up to nan extremity of nan motor crankshaft. It's location to thief commencement nan engine, support it moving smoothly, and nonstop powerfulness to nan transmission. Automatics technically have flex plates alternatively of flywheels, but they're designed to execute nan fundamentally aforesaid thing.  

The teeth connected nan flywheel's outer separator mesh pinch starter gears to thief make nan oomph needed to get a diesel aliases gasoline motor to occurrence up. When it does, each powerfulness changeable creates a jolt of torque. The flywheel's weight and inertia thief soft retired that powerfulness delivery, harnessing power arsenic rotational momentum. 

A single-mass flywheel's aboveground engages straight pinch nan clutch, and nan clutch sheet springs supply immoderate dampening. But pinch a dual-mass flywheel, 1 disc that bolts to nan crankshaft, and a 2nd disc — hence "dual-mass" — syncs pinch nan clutch. The 2 masses are connected by springs that dampen for illustration suspension struts. Automakers will opt for a dual-mass flywheel successful applications wherever there's monolithic torque, less cylinders, aliases a desire to quell noise, vibration and harshness.

Sergey Ryzhov/Shutterstock

Imagine cranking a horizontal alloy rod pinch a 25-pound weight connected nan end. It's reliable astatine first, but gets easier and smoother to move arsenic nan weight picks up speed. This is what's happening erstwhile a flywheel spins, and really flywheels thief support nan motor moving erstwhile you're not accelerating. 

Once a single-mass flywheel starts to rotate, its unit is absorbed by nan clutch and transmission driveline. In a dual-mass flywheel, erstwhile nan first wide rotates, it compresses springs, which starts nan 2nd wide rotating on while absorbing immoderate much of nan daze coming done nan crankshaft. That intends little vibration is transferred to nan transmission.  

In high-torque situations for illustration towing, this equates to transmission preservation and longevity. This is why a dual-mass flywheel is appealing successful diesel engines, which outsell state successful heavy-duty trucks owed to their stump-pulling prowess, and thin to tally for eons.

In smaller engines pinch less cylinders, location are less overlapping powerfulness strokes. Automakers will fresh dual-mass flywheels connected four-cylinder cars, for example, to quell immoderate of nan harshness of those sporadic jolts — which are little of an rumor successful nan best inline-sixes. Volkswagen, for example, uses dual-mass flywheels crossed nan Golf GTI and Golf R turbocharged 2.0-liter inline-4 motor lineup, arsenic good successful Audi DSG transmissions. 

Dual-mass flywheels supply a comfortableness benefit, because they thief stifle nan clunky daze that tin travel erstwhile accelerating from a standstill astatine little RPMs. That tin make stop-and-go postulation a small much pleasant. The consequence is mundane driving pinch smoothness and refinement, acknowledgment to reduced drivetrain sound and vibration that mightiness different buzz done nan the cabin.  

PBabic/Shutterstock

Perhaps nan biggest disadvantage of dual-mass flywheels is that they are expensive. And while a single-mass flywheel isn't needfully cheap, it tin beryllium resurfaced, and that costs conscionable a fraction of a caller one. Dual-mass flywheels can't beryllium resurfaced — you person to switch nan full point if it fails. 

If there's 1 point nonaccomplishment loves, it's complexity. Two masses, springs, and associated parts present much imaginable problems. Single-mass flywheels are 1 coagulated lump. 

Another information is weight. Factory dual-mass flywheels are usually beautiful heavy, coming successful astatine astir 30 pounds. Where immoderate spot smoothness, others spot sloth. All that wide sitting betwixt nan motor and transmission requires powerfulness to push, and clip to unwind, which tin consciousness little responsive. This is why enthusiasts and aftermarket capacity parts companies move to lightweight, dual-mass flywheels, pinch immoderate coming successful astatine 10 pounds. 

Also from a capacity standpoint, dual-mass flywheel parts whitethorn beryllium tuned to grip a circumstantial powerfulness output from nan factory, which mightiness not clasp up if you adhd boost done a tune aliases caller turbocharger. In these cases, owners tin opt for a single-mass flywheel conversion, which up nan sound and vibrations, but present a much nonstop powerfulness engagement betwixt nan motor and transmission.