Despite the onslaught of hybrid and electric vehicle announcements from car manufacturers, they are still busy trying to get as much efficiency out of internal combustion engines as possible. It's Toyota's turn to improve its engines, such as optimizing its 2.5-liter in-line four-cylinder in the Camry 2018, to be more efficient and more thermally efficient.
Engineering Explained is back with another great uh, explaining how Toyota's tweaks work. Including Changes in Inlet and Outlet Valve Angle and Hub / Bore Ratio:
Toyota applies its new thermal efficiency enhancement strategy to a number of "Dynamic Force Engines". That specific engine is the updated 2.5-liter inline four-cylinder that debuted with the Camry 2018, but they've also done work on the 2.0-liter inline four-cylinder. The focus of the changes is on increasing the thermal efficiency or basically how much beneficial energy the engine receives when burning fuel.
Toyota has redesigned the cylinder bore design to achieve a new ideal stroke-to-bore ratio of 1.18, maintaining a similar volume over the old 1.09 stroke-to-bore ratio, but the width of the bore reduces a longer piston stroke.
The second change increased the angle between the intake and exhaust valves from 31 to 41 degrees, straightened the path of the intake airflow and created a better circulation for the fuel mixture in the combustion chamber.
Both of these slight changes make this possible faster combustion. As the video shows, Dynamic Force Engine combustion extends the full width of the cylinder at the same time that the older engine extends about half that distance.
This faster combustion, along with new electronically variable control systems for the thermostat, water pump, oil pump, and other systems that can be controlled to dissipate less power from the engine, contributes to increased thermal efficiency of 40 percent for hybrid engines. Motor with a 13: 1 compression ratio or 41 percent for the hybrid setup with a 14: 1 compression ratio. Just a few years ago, the average thermal efficiency of an internal combustion engine was less than 35 percent.
Along with the increased thermal efficiency, Toyota claims that the engine also gains slightly more torque and horsepower with the changes, which is always welcome. The Camry 2018 with the 2.5-liter non-hybrid setup is rated with 203 hp and 184 lb-ft of torque, and the hybrid is 208 net HP and 163 lb-ft of torque. Both reach over 40 MPG highway. The increases seem marginal, but a little better is still better.