Toyota engines aim to get more from less
New 1.0- and 1.3-liter units bring elements of hybrid power to standard gas engines.
In a press release this week, Toyota unveiled a new pair of engines designed to improve fuel economy. Now there’s hardly anything new in that; all automakers are scrambling to improve efficiency as government standards and customer expectations increase. What is new in Toyota’s 1.0-liter 3-cylinder and 1.3-liter 4-cylinder gas engines is the implementation of Atkinson cycle technology. Usually seen only in engines fitted to hybrid powertrains, the Atkinson cycle process increases the engine’s expansion ratio, reducing waste heat and improving thermal efficiency.
Toyota also modified the intake ports within the cylinder, and a cooled exhaust gas recirculation system mated to its Variable Valve Timing-intelligent Electric technology maximizes combustion while minimizing waste. Toyota claims increased combustion ratios will preserve torque loss usually associated with Atkinson cycle engines. The Japanese automaker estimates maximum thermal efficiency to be at 38 percent for the 1.3-liter 4-cylinder engine, which would place it in the upper echelon of large-production engines, with fuel efficiency gains of 15 percent. The 1.0-liter three cylinder is estimated to have a maximum thermal efficiency of 37 percent, with 30 percent gains in fuel efficiency over current vehicles.
Coming on the heels of Toyota’s deal with Mazda to use the rival builder’s SKYACTIV (no, we don’t know how they come up with these names) engine in its new subcompact, the question has to be raised: Why enter into the agreement with Mazda at all when these new engines were on the horizon? These new Toyota engines differ from Mazda’s SKYACTIV engines in that SKYACTIV engines employ what Mazda refers to as a “Mazda Miller cycle,” as opposed to the Atkinson cycle. SKYACTIV engines take the route of high compression ratios, but at light loads they run open-throttle to maximize cooling.
The bigger difference appears to be that SKYACTIV isn’t a system limited to engine technology — Mazda transmissions and chassis construction/components all are part of it’s SKYACTIV branding. This makes things interesting for the car that will replace the Toyota Yaris, which is slated to be built upon the platform of the well-regarded Mazda2, and will be equipped with a SKYACTIV engine. Curiously, Toyota wouldn’t answer questions from Automotive News recently regarding whether it would make use of the SKYACTIV engine alone, or incorporate chassis elements as well.
Toyota’s new engines are more ‘plug-and-play’ than the SKYACTIV engines, and this may hold the key to understanding its intentions for them. Toyota’s press release claims that 14 variations of these engines will be introduced worldwide by 2015, with the first examples arriving in subcompact, non-hybrid cars for the Japanese market. It isn’t inconceivable that we’ll see the 1.0- and 1.3-liter engines used in hybrids; possibly in upcoming Prius models, and perhaps even in a future Lexus CT hybrid.
Considering the relative youth of the current-generation Corolla and that these new engines are only the first products to come out of Toyota’s new Powertrain Development and Production Engineering Building, is it possible Toyota is attempting to simultaneously work new efficient engine technology into its lineup while developing a fully in-house SKYACTIV-style powertrain/chassis combination of its own?
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