New Auris 1.2T Engine

In April of last year, Toyota announced its plans to introduce a series of newly-developed, highly fuel efficient engines, applying several combustion and loss-reduction technologies that until then had been reserved for hybrid engines. The new 4-cylinder 1.2T engine is the second engine from this family to come to Europe under the Toyota brand, after the 3-cylinder 1.0 engine that went on sale in AYGO and Yaris last year. Like the 1.0, the 1.2T uses advanced technologies that allow the engine to change from the Otto-cycle to the Atkinson cycle under low loads, vertical vortex high tumble air flow intake ports, an exhaust manifold integrated in the cylinder-head and advanced heat management.

To this, the 1.2T adds a direct injection system, as well as a water-cooled turbo and heat-exchanger. Furthermore, the VVT-i (Variable Valve Timing — intelligent) system known from the 1.0, is upgraded to a VVT-iW (Variable Valve Timing - intelligent Wide) system, which allows even more flexibility in the valve-timing.

The combination of these technologies results in outstanding performance and efficiency. For a displacement of 1197cc, the engine delivers 116 DIN hp (85kW) and a constant torque of 185Nm between 1500 and 4000 rpm. It will push the New Auris, the first model to which it is applied, from 0 to 100 km/h in 10.1 seconds. 5^th gear acceleration from 80 to 120km/h takes just 13.7 seconds, and the top speed is set at 200 km/h. All of this is achieved despite a strong focus on fuel consumption and CO₂ — the car achieves 4.7l/100 km* on the combined cycle, and delivers just 109g/km* of CO₂.

Better performance for lower consumption

The key to achieving outstanding fuel consumption without compromising performance, is to apply a higher compression. But generally, as the compression increases, so does the risk of uncontrolled combustion, also known as knocking.

The 1.2T's high compression ratio of 10:1 was made possible thanks to the adoption of a series of key technologies that improve control over the combustion process. That way, the risk of knocking could be avoided.

First of all, the intake ports have been designed to generate a more intense flow and a 'vertical vortex', and also the shape of the piston has been optimized to improve in-cylinder turbulence. As a result, fuel and intake air mix faster, and a more homogeneous mixture is formed. This leads to a higher combustion speed — which helps prevent knocking.

Advanced heat-management is in itself a great way to improve fuel economy, but it is also another way of reducing the risk of knocking. The engine was designed in such a way, that the temperature of each individual part can be optimized. For example, the bottom of the pistons is cooled by oil-jets and the cooling of the cylinder head is separated from that of the engine block. This allows to reduce the temperature in the combustion chamber, whilst keeping the block itself hot enough to reduce friction.

Direct injection contributes as well, as it helps to dissipate the heat in the combustion chamber. And the charge air passes through the intercooler, which uses an independent low temperature cooling circuit.

Low-end torque and quick response 

A low-inertia turbocharger, the VVT-iW valve system and the D-4T direct injection system work hand in hand to ensure excellent torque delivery from the lowest engine speeds. Together with the limited volume intake system, this ensures an immediate response to the accelerator pedal.

The injection system has been newly developed for the 1.2T engine. Compact in design, it is perfect for utilisation in a small displacement engine. It allows multiple injections per cycle, and the optimized width and reduced length of the fuel spray ensure the quality of the combustion, regardless of the engine regime and load.

From Otto to Atkinson 

The VVT-i (Variable Valve Timing - intelligent) system operates on both the intake and the exhaust side, and allows maximizing torque at all engine speeds. In addition, the new VVT-iW (Variable Valve Timing - intelligent Wide) allows for the intake valve closing to be delayed, which means that the engine can operate in both the Otto and the Atkinson cycle. The latter is used in extremely low load conditions, when the intake valve remains open for a fraction of time, after the compression stroke has set in, allowing part of the gas charge to be pushed back into the intake. As a result, the effective compression stroke is shortened. Pumping losses are reduced, since the pressure on the piston is lower, and also the throttle valve can be opened wider.

Quick and smooth Stop & Start 

A new start control was developed to ensure a quick and smooth engine restart. When the system shuts down the engine, it controls the stop position to leave the piston half way in the compression stroke. Then, upon restart, it applies stratified injection in the first compressed cylinder to counter vibrations. And by retarding the ignition, torque increase is kept in check, preventing the engine from revving excessively, hence ensuring a confident and tranquil take-off.

*Subject to final homologation