Toyota is introducing a new 1.5 litre petrol engine to the European Yaris range to replace the current 1.33 litre unit. This new ESTEC engine is superior to the outgoing motor in every way – offering more power, more torque, faster acceleration, improved fuel economy and lower CO2 emissions.

Developed in anticipation of the future Euro 6c emissions standard and RDE (Real Driving Emission) homologation requirements, the 1.5L is a member of Toyota’s ESTEC (Economy with Superior Thermal Efficiency) engine family. It is being manufactured in Poland as part of a €150 million production investment programme by Toyota Motor Europe.

In the Yaris, the naturally aspirated four-pot develops 110 bhp and 136 Nm of torque at 4,400 rpm. Compared to the 99 hp 1.33 litre unit, it is 0.8 seconds quicker in 0-100 km/h, while at overtaking speed the improvement is more than a second, moving from 80 to 120 km/h in 17.6 seconds compared to 18.8. Fuel consumption is down by 12% in the NEDC cycle.

Toyota says that its experience in hybrid tech has proved valuable in addressing the challenges presented by Euro 6c and RDE, as this new engine achieves 38.5% thermal efficiency, close to the world’s best 40% claimed by the Prius and Hyundai Ioniq Hybrid. This has been achieved by using a high 13.5:1 compression ratio, adopting a cooled exhaust gas recirculation (EGR) system and extending the VVT operation so that the engine can switch between Otto to Atkinson cycles.

The higher compression ratio has been made possible by the combustion chamber design and new pistons, which promote a homogenous air/petrol mixture and rapid combustion. Cooled EGR reduces combustion temperature and also helps prevent the occurrence of engine knocking. The volume of reinjected inert gases also allows for a reduction in pumping losses at low and medium loads, improving overall efficiency.

The adoption of a new variable inlet valve timing system – VVT-iE – allows the engine to switch from the Otto to the Atkinson cycle (and vice-versa) in a fraction of a second. Controlled electronically, closure of the intake valve is delayed, reducing the compression phase and further helping reduce pumping losses (Atkinson cycle), and enabling a prompt return to the Otto cycle for better performance under high loads The phase shift of the exhaust camshaft is hydraulically controlled.

Engineers also focused on improving fuel consumption at sustained highway cruising speeds, leading to the use – for the first time on a Toyota – of a water-cooled exhaust manifold. By limiting gas temperature, this avoids the need for mixture enrichment to reduce combustion temperature at any highway driving speed. As a result, both fuel consumption and exhaust emissions are reduced.

Like other Toyota ESTEC engines, this 1.5 litre unit benefits from the latest measures designed to reduce friction losses.