Your clutch is one of the most important components of your vehicle’s transmission system. Understanding the difference between a single clutch transmission and a dual clutch transmission can be vital to maintaining your vehicle.
“This is the simplest and lightest type of transmission available, as gear selection and gear changing is solely the domain of the driver. The gears contained inside the transmission’s metal housing — typically five or six forward gears, are accessed via a shifter in the cabin.
To change gears, the driver depresses the clutch pedal, which detaches the clutch from the engine. This allows the engine to spin at one speed, and the transmission and wheels at another. After selecting a new gear ratio via the stick shift, the driver connects the engine, transmission and wheels together again by releasing the clutch pedal.
Two pieces of tech have made it easier to shift gears over the years: synchromeshed gears and hill start assistance.
Synchromesh gears have not only removed much of the gear grinding that used to plague manuals, but has also eliminated the need to double declutch, where drivers had to declutch once to enter neutral and declutch again to select the next gear.
Hill start assist is a more recent development that tries to prevent manual cars from rolling backwards downhill during standing starts. It does this by keeping the brakes active for a few seconds after the brake pedal is released, giving the driver a bit of grace to operate the clutch and accelerator.
For the greater part of automotive history, manual transmissions have rewarded drivers’ efforts with more control, more gears, faster acceleration, higher top speeds, lower fuel consumption and, if driven well, smoother gear shifts. But with the computer-led evolution of automotive transmissions, some cars are reporting better performance and fuel economy figures with automated transmissions.”
“While enthusiasts revel in mastering the art of perfectly executed shifts and heel-toe manoeuvres, for many the act of declutching, selecting a gear and clutching is a burdensome chore. So, why not stick some hydraulics or servos onto a manual gearbox to operate the clutch for us?
Numerous car makers have dabbled with clutch-pedal-free manual transmissions over the years but, despite the simplicity of the concept, it’s an idea that is still yet to be executed well in road-going cars.
Jerky gear changes are the main problem with automated manual transmissions. In semi-automatic mode, where the driver changes gears via a +/- gate or paddles behind the steering wheel, this can be partially alleviated by lifting off the throttle when changing gears. As the driver is unable to finesse the clutch, it usually only serves to minimise the amount of lurching.
Many systems also offer a fully automatic mode, but these are plagued with either brutally aggressive or overly slurred gear shifts. Again, lifting off the throttle during gear changes helps, but it’s often less taxing to shift gears yourself rather than playing clairvoyant to the transmission’s electronic brain.”
“Although dual clutch transmissions (DCTs) are generally employed as replacements for traditional automatic gearboxes, their mechanical workings actually bear more in common with the humble manual transmission. In fact, it’s probably easiest to think of a DCT as housing two manual transmissions — one for even numbered gears and the other for odd numbered ones — each with their own clutch (hence the name).
Say, for example, you’re accelerating along in third gear. In this situation the even numbered gearbox will have fourth gear pre-selected and primed to go. When the transmission’s computer or the driver thinks the time is right to change up, the clutch for the odd numbered gears is disengaged and the even clutch engaged.
Changing from one clutch to another takes anywhere between eight and 200 milliseconds; that’s considerably faster than the half second or more required by most manual drivers to change gears. By wasting less time between gears, DCTs are often able to outsprint their manual equivalents.
Some transmissions have lightning quick gear changes, which are a delight to see in action. The downside with fast-shifting DCTs is that at lower speeds they tend to jerk and lurch around. In tight parking spaces, it can be a little frightening to suddenly lunge forward, even if it’s just a few centimetres, when you’re feathering the throttle with the greatest of care.
There are two types of dual-clutch transmission on the market: dry and wet clutch. Wet clutch models are so called because the clutch is bathed in a sea of oil and this type is often found in high-power cars. Dry clutch versions are more efficient but restricted in the amount of power and torque they can handle.
As with many new technologies, most car makers have decided to market DCTs under their own trademarked brand names. For some companies, DCTs are available on mainstream vehicles. For others, usage is restricted to high-performance models.”
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