How Does the Kia Sorento Hybrid Actually Work?

Kia Sorento is the brand's first hybrid for the market, starting at ₹27.99 lakh ex-showroom for the Diesel and ₹29.49 lakh for the Hybrid. It also comes with a diesel option, both with AWD available.

Here's everything you need to know about how the hybrid system works and what sets it apart.

The underlying TMED Platform

Hyundai and Kia use an architecture the group calls TMED, short for Transmission Mounted Electrical Device. In plain terms, the electric motor is bolted into the space between the petrol engine and the gearbox, in the bell housing where a torque converter would normally live in an automatic car.

Kia's own transmission arm describes it exactly that way, as a conventional automatic gearbox in which the torque converter has been replaced by an electric motor, an engine clutch and a torsion damper.

Also Read – Tata CJLR AND Mahindra INGLO Architecture Explained

The engine clutch is the part that matters most, and it is the part nobody mentions. It is a physical clutch that can completely disconnect the petrol engine from the rest of the drivetrain. When it opens, the engine is not just switched off, it is mechanically severed, spinning nothing and dragging on nothing, while the electric motor drives the wheels through the same six-speed automatic gearbox the car uses at all other times.

When it closes, the engine rejoins the party, and because the motor is already spinning at the same speed on the other side of the clutch, the motor itself can spin the engine up to match before the clutch bites.

That is why a Sorento restarting its engine at 60 kmph does so with a faint shove rather than the shudder you get from a normal start-stop system.

The whole system is one engine, one motor, one clutch between them, one ordinary six-speed automatic, and a small battery.

Also Read – Kia Announces Carnival Hybrid MPV With 1.6 Turbo Petrol
 

How It Works?

When you press the start button and pull away in traffic, the engine typically stays off and the clutch stays open. The battery feeds the motor, the motor turns the gearbox input shaft, and the car creeps and accelerates gently on electricity alone.

This is unremarkable to sit in and is the whole reason hybrids do so well in city driving, where a petrol engine is at its least efficient and spends most of its life idling or lugging at low load.

Ask for more than the motor can supply, whether by accelerating harder or climbing a flyover, and the control unit spins the engine up through the clutch and brings it in.

From there the two work together. The engine handles the bulk of the load at the efficient part of its rev range while the motor fills the gaps, particularly the low-rpm hole that a small turbocharged engine has before boost arrives.

Also Read – JSW MG Unveils New ADAPT Platform For Future Hybrids

A 1.6-litre turbo petrol on its own would feel hesitant hauling a two-tonne three-row SUV away from a standstill. With an electric motor delivering its full twist from zero rpm, that hesitation disappears, and that is the real reason Kia paired a 1.6 with a car this size rather than a larger naturally aspirated engine.

Lift off the accelerator or brake, and the process reverses. The clutch opens, the engine shuts down so it is not being dragged around against compression, and the motor becomes a generator, turning the car's momentum back into electricity and putting it in the battery. 

This is regenerative braking, and the brake pedal is blending two things under your foot at once, the electrical resistance of the motor and the ordinary friction brakes, handing over from one to the other so smoothly that most drivers never notice it happening.

Cruising at a steady speed on a highway is where the system does the least and the engine does the most, because a petrol engine at constant load is already reasonably efficient and there is little braking energy to harvest. Even here the clutch earns its place.

Ease off on a downhill stretch and the engine can be shut down and physically disconnected while the car coasts, which is something a hybrid without a disconnect clutch cannot do as cleanly.

The Sorento Hybrid Is Different Than The One Found In Maruti-Toyota Cars

Most Indian buyers who have experienced a strong hybrid have done so in a Toyota or a Maruti, whether an Innova Hycross, a Grand Vitara or a Hyryder. Those cars use a power-split system with a planetary gearset and two motor-generators, and no conventional gearbox at all.

The Sorento has a real six-speed automatic with real ratios and real shifts. The engine revs rise and fall with the gears exactly as they would in any other automatic SUV, and the hybrid part of the system is felt as extra shove rather than as an unfamiliar noise.

Also Read – Maruti Victoris Strong Hybrid Explained: How the Technology Actually Works
 

How the Sorento Hybrid Differs from a Plug-In

Kia's Sorento Plug-in Hybrid, sold in Europe and America is not a different kind of hybrid. It is the identical layout, the same 1.6 turbo petrol, the same engine clutch, the same six-speed automatic, with two components scaled up and one added.

The battery grows from about 1.5kWh to 13.8kWh, roughly nine times the capacity, which is enough for around 57km of electric-only running on the European WLTP cycle and about 50km on the stricter American test. 

The electric motor grows in proportion so it can move a two-tonne SUV on its own at proper road speeds rather than just in traffic, and combined output rises to approximately 265PS and 350Nm. The addition is a charging port, on the right rear flank, taking a standard Type 2 connector at up to 3.3kW.

Also Read – Check Out These Upcoming Hybrid Cars In India

Images Source: Kia India