What is a clutch-by-wire system? PH Explains
How doing away with cables and hydraulics can grant improved efficiency and enable more assistance features
A 'clutch-by-wire' system is one that does away with the mechanical or hydraulic connection between the clutch pedal and clutch itself.
Instead, the position of the clutch pedal is monitored by sensors and an electromechanical actuator is used to remotely operate the clutch.
Consequently, in a car equipped with a 'CBW' system, the driver is presented with a familiar-looking pedal and transmission arrangement - and the car otherwise drives just like any other manual transmission-equipped vehicle.
However, the CBW system can also automatically operate the clutch or alter the behaviour of its actuation. This automatic clutch control capability grants a wide range of additional safety, efficiency and assistance benefits.
For example, automotive CBW systems - such as those unveiled by Bosch in 2013 and ZF in 2015 - can automate clutch control at low speeds. This means the driver can creep in traffic, in first gear, without having to operate the clutch.
How do clutch-by-wire systems work?
In a clutch-by-wire set-up, the pedal assembly is replaced with one that features a sensor which monitors the pedal position - just like the pedal assemblies used in many electronically controlled throttle systems.
Signals from the pedal are then transmitted to a control unit which triggers the electrically driven actuator that operates the clutch. Because there is no direct link between the pedal and the clutch, the overseeing control system can ensure that the driver's inputs are translated into the most appropriate clutch action.
If a driver were to release the clutch pedal too quickly, for example, the overseeing control system can slow the engagement of the clutch - preventing judder, lurching or a stall.
A further benefit of such a configuration is that the pedal travel and clutch actuation will remain consistent throughout the life of the clutch, as the actuator can automatically take up any slack caused by wear in the system.
Similarly, the use of CBW also makes it easier to integrate hybrid technology into a conventional manual transmission-equipped car - which can help keep costs down while boosting efficiency.
What are the benefits of a clutch-by-wire system?
The motivation behind developing clutch-by-wire systems was one of cost and functionality. A manual transmission with a CBW reportedly costs 50 per cent less than a conventional torque converter-based automatic while offering many similar advantages - such as the ability to coast with the engine off and reduced driver workload.
German manufacturer Schaeffler claims its CBW system, among other benefits, can reduce fuel consumption and CO2 emissions by up to 10 per cent thanks to the coasting function alone. This enables the engine to be automatically decoupled from the transmission, and then shut off, when the car is coasting - reducing fuel consumption.
There are also myriad assistance-related functions which are enabled by CBW systems, including an anti-stall feature, complete clutch automation at low speeds and emergency braking aids. The behaviour of the clutch could also be altered depending on the conditions.
One of the potential pitfalls, however, is the potential lack of meaningful feedback through the pedal - which has been a reported issue with prototype CBW setups, as well as other similar 'X-by-wire' systems. The pedal itself could be engineered to deliver suitable feedback, though, in order to emulate the feel of a conventional hydraulic assembly.
CBW systems have seemingly met with little success so far, though, perhaps due to ever-advancing, increasingly inexpensive fully automatic transmissions and more efficient engines. That said, some manufacturers - such as GM - are beginning to develop and test their own systems. As safety and efficiency demands continue to rise, some may subsequently start to use CBW set-ups in their vehicles.
It's bad enough how numb, electric steering systems try to override your inputs, the same for throttle and brake by wire, not to mention electronic handbrakes, and now a clutch you have to second-guess too!
As ever, the lowest-common-denominator rules. All cars are being built to favour the clumsiest and least competent, and everyone else must suffer being patronised too.
As a previous poster has said, it's like electric power steering, electronic hand brakes and another who host of automated systems that have been crammed in to vehicles recently, which allegedly make our driving experience easier but in reality frustrate and annoy the driver ever more.
And before anyone comments that electronic systems are far more reliable and less likely to strand a driver, recently I have had an electronic hand brake switch disintegrate - disabling the car, a Mercedes electronic key / ignition switch completely fail - disabling the car, and a throttle sensor fail - disabling the car. In 27 years of driving I have never had a manual handbrake, metal key or cable throttle issue that has stranded me or indeed has cost me the money these three have.
Also, surely clutch control is one of the key things for learning to drive in the first place. With a system like this, the learner will not be learning. Gone will be the kangaroo starts, stalled hill starts and engine running emergency stops, which to me seems like another chunk out of the skill of driving for the younger generation.
All those robotised-manual semi-autos that have been common for the last decade/decade and a half? The only difference here is that the driver's explicitly telling the clutch what to do, not the ECU deciding it.
And if you don't get hung up on "electronics", just an automated disconnect between direct operation from pedal to clutch, then how about the Citroen DS hydraulic box in the mid 50s?
king cares) and to pass nonsensical emissions programs, give us a 1st gear that creeps at tickover at 3mph. and 2nd at 5mph, and 3rd at 10. Like my old cars used to do before this ridiculous economy gearing was introduced. Give us a nice long 6th/7th gear of cruising, but make the rest of them useful for goodness sake.
Just a faff in my opinion. Surely less efficient too. I've already got a leg, why wouldn't I use it?
It's bad enough how numb, electric steering systems try to override your inputs, the same for throttle and brake by wire, not to mention electronic handbrakes, and now a clutch you have to second-guess too!
As ever, the lowest-common-denominator rules. All cars are being built to favour the clumsiest and least competent, and everyone else must suffer being patronised too.
Why couldnt they keep on with carburettors? And whats with modern ignition systems? Even nowadays you get hese fangled multi-grade oils. And windscreen wipers! And air conditioning! What's wrong with opening a bloody window!
king cares) and to pass nonsensical emissions programs, give us a 1st gear that creeps at tickover at 3mph. and 2nd at 5mph, and 3rd at 10. Like my old cars used to do before this ridiculous economy gearing was introduced. 
My 1.4 Will happily lurch slowly onwards at 4mph in 1st, and 6mph in 2nd
king cares) and to pass nonsensical emissions programs, give us a 1st gear that creeps at tickover at 3mph. and 2nd at 5mph, and 3rd at 10. Like my old cars used to do before this ridiculous economy gearing was introduced. My 1.4 Will happily lurch slowly onwards at 4mph in 1st, and 6mph in 2nd
king cares) and to pass nonsensical emissions programs, give us a 1st gear that creeps at tickover at 3mph. and 2nd at 5mph, and 3rd at 10. Like my old cars used to do before this ridiculous economy gearing was introduced. My 1.4 Will happily lurch slowly onwards at 4mph in 1st, and 6mph in 2nd
To me that says nat-asp petrol engine, ideally with either big-cubes or some form of variable-valve-lift. Oh dear, they don't make them anymore because of emissions!
king cares) and to pass nonsensical emissions programs, give us a 1st gear that creeps at tickover at 3mph. and 2nd at 5mph, and 3rd at 10. Like my old cars used to do before this ridiculous economy gearing was introduced. My 1.4 Will happily lurch slowly onwards at 4mph in 1st, and 6mph in 2nd
To me that says nat-asp petrol engine, ideally with either big-cubes or some form of variable-valve-lift. Oh dear, they don't make them anymore because of emissions!
Ticks most of those boxes!
As for my opinion on clutch by wire, I wouldn't mind - This could play in perfectly with the modes that manufacturers tend towards now, with a smoothed mode for regular operation, and a "natural" mode for direct control of the clutch without nannying.
Surely this would even allow for semi automatic shifting; Just pop the shifter from n to n and the automatic clutch could do the rest, which might prove a nice relief in clutch pumping traffic.
Autos and manuals are both great and both have their place and so too would a hybrid transmission (servo on clutch with automatic functionality, but full manual control for when you want it) but a dummy clutch pedal seems like the stupidest idea ever, the driver is essentially becoming maggie in the simpsons opening credits and pretending to perform a function thats actually automated... next you'll be telling cars have fake piped engine noise.
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