New 1.5 l petrol engine for the Yaris
In anticipation of the Euro 6c standard and the RDE (Real Driving Emission) homologation standard, Toyota is fitting the Yaris with a new 1.5 litre petrol engine to replace the current 1.3 litre. Part of the ESTEC (Economy with Superior Thermal Efficient Combustion) family, this new 4-cylinder engine introduces new technical solutions which offer better performance, increased driving pleasure and, at the same time, a reduction in fuel consumption of 12%* in the present NEDC cycle.
To power this B segment model, the engineers have chosen a normally aspirated 1496 cm3 unit developing 111 DIN hp/82 kW and a torque of 136 Nm at 4400 rpm, with 118 Nm already available as low as 2000 rpm. The quick response of a normally aspirated engine of this capacity gives the Yaris a level of driving comfort which will be appreciated both in urban driving and on the open road. In comparison with its predecessor 1.3 litre unit, this improved performance is reflected in figures by a gain of 0.8 second on acceleration from 0 to 100 km/h (11.0 versus 11.8) and especially by an improvement of over a second from 80 to 120 km/h (17.6 versus 18.8).
To meet the requirements of the new Euro 6c standard and the new RDE homologation cycle, Toyota has benefited from its knowledge in the field of hybrid vehicles. In this new engine, this is revealed by a thermal efficiency value of 38.5%, putting it amongst the best. This performance is achieved by implementing a high compression ratio of 13.5, by adopting a cooled exhaust gas recirculation system (EGR) and by extending the variable valve timing, which allows to switch from the Otto cycle to the Atkinson cycle.
The higher value of the compression ratio is achieved thanks to the design of the combustion chamber and the use of new pistons, which promote a homogeneous air/petrol mixture and rapid combustion. By reducing the combustion temperature, cooled EGR also helps delay the occurrence of knocking. Furthermore, the volume of reinjected inert gases allows the reduction of pumping losses at low and medium loads which improves the efficiency. Finally, the adoption of a new variable inlet valve timing system - VVT-iE** - allows the switch from the Otto cycle to the Atkinson cycle and vice versa in a fraction of a second. Controlled electrically, the phase shift of the intake camshaft allows a delay in the closure of the intake valve beyond the piston bottom dead centre, so as to reduce the compression phase which contribute to a further reduction in the pumping losses (Atkinson cycle) or an advance of opening to a switch back to the Otto cycle for a better performance at high load. The phase shift of the exhaust camshaft is controlled by a hydraulic system.
The engineers also focussed on reducing fuel consumption and emissions at sustained motorway speeds. Therefore - for the first time at Toyota - the new engine is fitted with a water-cooled exhaust manifold. By limiting the gas temperature, this allows to avoid the enrichment of the mixture necessary for reducing the combustion temperature at any motorway driving speed, and hence reduces consumption and emissions under these driving conditions.
Like all the new engines in the ESTEC family, this new 1.5 litre naturally benefits from the latest developments designed to reduce friction losses.
* with CVT transmission
** VVT-iE = Variable Valve Timing intelligent system Electric Motor