Kia’s new clutch-by-wire gearbox for hybrids can relive fun of manual driving

Kia Motors has revealed details of its new intelligent Manual Transmission (iMT), which has been designed for a range of mild-hybrid electric vehicles. The ‘clutch-by-wire’ system is engineered to boost fuel efficiency and reduce CO2emissions, while retaining the driver engagement of a conventional manual transmission.

Instead of a mechanical linkage, the iMT’s clutch operates purely electronically, and is integrated seamlessly with a 48V MHEV powertrain. The iMT works with the mild-hybrid starter generator (MHSG) to switch off the engine earlier than Kia’s Idle Stop & Go start-stop system when coasting to a halt. This improves overall fuel efficiency and can reduce CO2emissions by around 3% in real-world driving conditions.

The chosen gear remains engaged even with the engine off. The engine restarts in the same gear as soon as the driver presses either the brake or accelerator pedals thanks to the burst of power provided by the MHSG. The transmission restarts the engine in neutral (with an open clutch) if the driver pushes the clutch pedal to change gear, or if the vehicle speed is too low for the current engaged gear.

This is how the clutch-by-wire gearbox works

The gearbox is helpful when coasting. The driver leaves the car in-gear as it starts to coast, gently slowing the car down. While in-gear, the iMT sends an electronic signal to the gearbox and MHSG to seamlessly switch off the engine and open the clutch. With the engine switched off, the car continues coasting, with the open clutch limiting deceleration and allowing the car to make the most of its kinetic energy. As the driver pushes the accelerator to pick up speed, or engages the clutch to change gear, the MHSG restarts the engine in the driver’s selected gear, or in neutral. Electric power from the MHSG and 48V battery instantly brings the engine and transmission up to the correct speed. If the car drops below a certain speed, the engine restarts with assistance from the MHEV system, and the clutch closes, to avoid labouring the engine in the engaged gear.

Kia’s new iMT has been developed at the Hyundai Motor Europe Technical Centre in Offenbach, Germany, overseen by Dr Michael Winkler, Head of Powertrain. Dr Winkler comments: “We are always looking at new ways to improve powertrain efficiency and performance, and the iMT is one such innovation. An automatic or a double-clutch transmission suits a lot of drivers, but European drivers in particular still love changing gear for themselves. Alongside the increasing demand for electrified models, the iMT is a result of us exploring ways to electrify the ‘classic’ manual transmission."

Dr Winkler continues: “Electrification is an overarching development theme across our European powertrain division, and our work encompasses the development of 48V mild-hybrid powertrains, through to the new ‘clutch-by-wire’ iMT as a complementary technology. We want to continue providing drivers with a familiar and engaging manual gear change, so this is an ideal solution for the new range of MHEV powertrains we are rolling out across Europe in the months ahead."

Although the iMT introduces a new clutch-by-wire technology in place of a mechanical link between driver and transmission, it retains the same operation and driver engagement as a conventional manual. The new system allows drivers to enjoy the uniquely engaging drive that comes from using a manual transmission. The clutch pedal operates in the same manner as a conventional manual, with greater controllability due to the electromechanical control of the clutch and a ‘biting point’ that enables drivers to change gears smoothly.

The iMT makes its debut in a pair of MHEV model lines with the brand’s latest ‘Smartstream’ engines. The first is the Ceed model family, now on-sale in many European markets with new ‘EcoDynamics+’ variants, powered by a 1.6-litre CRDi diesel engine and mild-hybrid system. The iMT will also be fitted to the upgraded Kia Rio EcoDynamics+, due on-sale in Europe during the third quarter of 2020 with a new 1.0-litre T-GDi gasoline mild-hybrid powertrain. The new transmission will be adopted across a number of future Kia models, with the brand set to introduce a range of new engines and MHEV powertrains later in 2020.