Everything You Need to Know About a Wet Clutch

If you’ve ever read about car clutches and other components, you’ve likely come across the terms “wet clutch” and “dry clutch” – what do these terms mean? What makes a clutch wet? Is it submerged in water? Is it constantly sprayed with a sprinkler type of system? In today’s blog, we are aiming to inform you as much as possible about what exactly a wet clutch is, how it works and why it can be beneficial for a car.

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What is a “Wet Clutch”?

First of all, it should be noted that a wet clutch performs the exact same function as a dry clutch, which is to transmit torque from the drive motor to the transmission and help aid shifting smoothly between different gear ratios. In other words, a wet clutch is still the same mechanical link between the engine and the transmission that a regular “dry” clutch is.

So, what’s the difference? In essence, the main difference is found in how they operate. Instead of transferring power through dry friction as a dry clutch does, a wet clutch transfers power through mechanical fluid couplings using engine oil as a lubricant. Furthermore, the structure is somewhat different as the wet clutch uses a multi-plate structure to operate.

Wet clutches are typically used in automatic transmissions, and very commonly in motorcycles as well. The covering of engine oil that they have allows them to stay cool, which thus makes them longer-lasting when compared to dry clutches which are more easily worn away by the constant forces of friction that work upon them.

Wet clutches are also favoured in cars with a powertrain that outputs more than 250 lb-ft of torque. The reason for this is that a regular dry clutch would too easily overheat in that kind of situation, whereas a wet clutch can remain cool and free from undue wear and tear.

Further below, we will discuss the wider benefits of wet clutches, but it’s also interesting to note that for some vehicles a wet clutch isn’t as suitable because there can be a loss of power created as some of the energy being transferred disappears in a parasitic way into the surrounding engine oil. This problem is mostly fixed by the use of multiple plates, however.

In motorcycles, wet clutches are also a popular choice because they are quieter when the bike is idling. This is important if bikes are pulled up at Stop signs and red lights in quieter, residential areas.

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What are the Benefits of a Wet Clutch?

More Durable

The first solid benefit of a wet clutch is that the lubricated structure allows the clutch as a system to resist wear and tear for longer, even when subjected to more abuse and strain. The engine oil fluid bath helps act as a kind of shield that protects the moving metal parts. Dry clutches relying on pure friction are fine in low-torque scenarios, but as soon as you dial up the pressure, they start to feel the strain and they would wear out much faster.

Greater durability means the clutch lasts longer, but also is less likely to need premature repairs. The day-to-day maintenance of such systems is therefore fairly low. It’s not to say that the unit itself would be cheap to repair or replace. Transmission repair is expensive regardless of wet or dry structures. The difference is in how frequently maintenance is needed and therefore the long-term cost consideration for wet clutches is better.

Allows for Higher Torque

This brings us to the next advantage. A wet clutch system allows car makers to create more torque in their vehicles. If every vehicle were to have a dry clutch, then in the absence of any other innovation, no car would likely be able to viably exceed 250 lb-ft of torque. With wet clutches, we are able to enjoy cars with much higher torque ratings, which makes for a more fun driving experience.

The mechanical reason that wet clutches offer more capacity for torque generation is found in their multi-plate design. Because there are multiple plates working together, the surface area is increased and thus there is greater surface friction. More surface friction means there is a greater capacity to generate torque.

Oil Removes Dust Particles

Besides the physical wear and tear that the dry clutch experiences, there is also a great deal of metallic dust that is created through its operation. Dust and other contaminants that might appear within a wet clutch system are carried away by the engine oil and captured by the oil filter, which helps to keep the system working more efficiently and effectively.

Quieter Operation

Wet clutches are generally much quieter than dry ones in their ordinary operation. When you’ve invested a lot of money in a car that is meant to reduce noise, it’s a great bonus to know that the clutch is contributing towards that.

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Are There Any Drawbacks of a Wet Clutch?

While there are clearly many advantages to using a wet clutch in both cars and motorcycles, they are not without their drawbacks and we shouldn’t think that they are the ideal selection for every type of vehicle.

There is Power Loss in the Fluid

Further above, we did touch on the problem of power loss that exists because of the presence of the engine oil “bath.” The problem of power loss can be somewhat mitigated by the use of multiple plates, but not entirely. Dry clutches do not experience the same loss of power because the torque has nowhere to go but to where it needs. The engine oil provides an alternative route of escape for at least some of the torque.

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Conclusion: An Important Innovation

Wet clutches aren’t a new or recent technology. They have been with us for a long time, but as our demands for more torque and performance increase, their use has become more common than before. When torque was low, we could keep things simple with a dry clutch, but now that our cars are getting more powerful and sophisticated, we expect to see more!