As emissions regulations get tighter, congestion gets worse and consumers demand better fuel consumption from their cars, manufacturers are being forced to delve deep into their engineering kitbag for clever ways to save fuel. The latest brand to unveil a smart new eco-friendly engine is Toyota, which has released a parsimonious 1.5-liter for the Yaris.
Although some brands have stuck put their faith in downsized, turbocharged engines for better performance and efficiency, the new engine destined for the Yaris in actually 200cc larger than the one it replaces. It's also still naturally aspirated, ignoring the current focus on strapping a turbocharger onto every available engine block.
Power is up from 63 kW (84 hp) to 82 kW (111 hp) in the new engine, and the peak 136 Nm (100 lb.ft) of torque is a handy 15 Nm (11 lb.ft) more than before. Thanks to these gains, cars fitted with the fresh engine will hit 100 km/h (62 mph) in 11 seconds, an improvement of 0.8 seconds. Performance between 80 and 120 km/h (50 and 75 mph) has also improved, although you're unlikely to win any rolling drag races given the 17.6 seconds it takes.
Although the extra power is nice, the real reason for the new engine is the upcoming Euro 6C emissions regulations, along with a new Real Driving Emissions test. To make sure it shines under the strict new conditions, designed to deliver more accurate real-life results than the current emissions testing procedure, Toyota has turned to lessons learned while developing petrol engines for its hybrid range.
The engine runs with a sky-high 13.5:1 compression ratio, made possible by new pistons and a new combustion chamber designed to deliver the perfect air/fuel mixture every time. A cooled exhaust-gas recirculation system helps lower combustion temperatures, crucial for making sure you don't suffer "knock" while running such a high compression ratio.
Depending on the type of driving, a variable inlet valve timing system (VVT-iE) allows the new engine to switch between the Otto and Atkinson cycles on the fly. Under light loads, the electrically-controlled system runs the engine on the Atkinson cycle, keeping the intake valve to open beyond bottom dead center in the piston stroke. When the driver calls for more performance, it switches back to the Otto cycle.
The result is a claimed 12 percent improvement in fuel efficiency under the current testing cycle. You can expect to see it in the facelifted Yaris, set to launch this March.
Source: Toyota
