Toyota unveils all-new 2.5-liter TNGA engine

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Toyota has unveiled an all-new 2.5-liter, direct-injection, inline four-cylinder engine that forms part of its new line of ‘Dynamic Force Engines’. Toyota states that it has ‘completely rethought’ the engine’s basic layout through the TNGA principals.

The new engines employ high-speed combustion technology and a variable control system. Designed with efficiency in mind, strong emphasis was placed on reducing friction and thermal losses, with particular attention paid to the exhaust and cooling systems, and the movement of mechanical parts. Toyota states that the 2.5-liter engine has ‘one of the world’s best’ thermal efficiencies, achieving 40% efficiency when used in gasoline-powered vehicles and 41% when used in hybrid vehicles (HVs).

In addition to the new engines, Toyota has also announced new 8- and 10-speed automatic transmissions (Direct Shift-8AT & Direct Shift-10AT). Much like the 2.5-liter engine, the two transmissions have been designed to minimize energy loss and heighten transmission efficiency. Gear tooth surfaces were processed using a new technique for a lower coefficient of friction when the gears engage, and the configuration of the friction material used inside the clutch was optimized to reduce clutch torque loss by approximately 50% during rotation (compared to a conventional 6-speed transmission). The new automatic units are more compact and lighter than comparative conventional transmissions, lowering a vehicle’s fuel requirements. Again playing to Toyota’s TNGA mindeset, an additional benefit of the compact units is that their lower center of gravity results in both improved straight-driving stability and better cornering stability.

Furthermore, widened gears and a newly developed high-performance compact torque convertor combine for a broader gear lockup range. The resulting quick and smooth response to accelerator pedal operation creates an “as desired” direct driving feel.

In the case of the Direct Shift-10AT, even though the number of gears has been increased to 10 (compared to eight gears in the case of the Direct Shift-8AT), the use of close-ratio gears optimizes the range of use of each gear, particularly in the low-to-mid speed range. 

Toyota also states that within the five years to the end of 2021, it plans to introduce 17 versions of nine engines, including the aformentioned 2.5-liter engine, 10 versions of four transmissions, including multi-geared automatic transmissions and a new kind of continuously variable transmission, and 10 versions of six hybrid systems.

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About Author

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Dean has been with UKi Media & Events for over a decade, having previously cut his journalistic teeth writing and editing for various automotive and engineering titles. He combines extensive knowledge of all things automotive with a passion for driving, and experience testing countless new vehicles, engines and technologies around the world. As well as his role as editor-in-chief across a range of UKi's media titles, he is also co-chair of the judging panel of the International Engine of the Year Awards.

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