Higher compression ratio improves thermal efficiency by as much as 38 per cent
TORONTO—Toyota Motor Corp. has released more details on its intriguing new line of gas-powered engines that use hybrid technology to boost fuel efficiency.
Using the Atkinson cycle, a type of internal combustion engine developed in the late 1800s, the new Toyota powerplants were developed in the automaker’s hybrid platforms and are said to boost fuel efficiency by at least 10 per cent compared to their current counterparts thanks to improved thermal efficiency.
Known to sacrifice power for the sake of efficiency, Toyota said the Atkinson engines will not be underpowered.
According to Toyota, using the Atkinson cycle allows it to run an increased expansion ratio and cut waste heat through a high compression ratio—13.5:1 in the 1.3-litre variation—that give it a maximum thermal efficiency of 38 per cent.
For perspective, the 2014 Toyota Yaris sporting a 1.5-litre engine, the smallest gas-powered engine in the automaker’s Canadian stable, has a 10.5:1 compression ratio.
Combined with a new intake port shape that generates an air-fuel mixture that flows in a vertical swirl—known as a tumble flow—inside the cylinder prior to combustion and a cooled exhaust gas recirculation (EGR) system and electric variable valve timing, Toyota said the 1.3-litre four-cylinder will burn 15 per cent less fuel than its current A-series engine.
Meanwhile, Toyota said a 1.0-litre engine jointly developed with Daihatsu Motor Co., Ltd. achieves similar maximum thermal efficiency results—37 per cent—using the same tumble flow intake port, a cooled EGR system, and a high compression ratio, but sees fuel efficiency spike 30 per cent compared to the current powerplant.
The engines also employ idling stop technology, a system that automatically switches the engine off when the vehicle is stopped.
According to the automaker, it plans to introduce 14 variations of the engine globally by 2015.