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Toyota introducing new series of gasoline engines with gain of at least 10% fuel efficiency; up to 38% maximum thermal efficiency

New 1.3L Atkinson cycle engine can reach a thermal efficiency of 38%. Click to enlarge.

Toyota Motor Corporation has developed a new series of fuel-efficient gasoline engines that achieve improved thermal efficiency. The new engines leverage combustion and loss-reduction technologies Toyota has refined in its dedicated hybrid engines (such as use of the Atkinson cycle) as well as in its conventional engines, and will deliver fuel efficiency improvements of at least 10% over current vehicles (based on the JC08 cycle).

In developing the new engines, Toyota focused on four key areas: rapid combustion; a higher compression ratio; reduced pumping losses (e.g., through using the Atkinson cycle and large-volume cooled EGR); and low friction.

New intake port and strong tumble flow. Click to enlarge.

  • Rapid combustion. Toyota is utilizing an intake port with a new shape that generates a strong tumble flow. (In a paper presented at the SAE 2014 World Congress, Toyota researchers described their work on an optimized combustion concept for turbocharged gasoline direct-injection engines that leverages optimized intake ports, dog dish-type curved pistons with a lip, and a fan injection spray to minimize flow disturbance and intensify in-cylinder flow.)

    The system on the new engines achieves unprecedented efficiency and tumble, Toyota said. The higher tumble flow enables more rapid combustion.

  • Higher compression ratio. A higher compression ratio leads to greater efficiency; it also results in knock. To avoid knock, Toyota is increasing scavenging efficiency in the combustion chamber.

    Further, Toyota is also preventing knocking by controlling the cylinder wall temperature.

  • Reduced pumping losses. Variable valve technology enables adoption of the Atkinson cycle in a conventional vehicle engine. Use of the Atkinson cycle provides an increased expansion ratio and reduces waste heat through a high compression ratio (13.5), resulting in superior thermal efficiency.

  • Low friction. Toyota has taken a number of measures to reduce friction, including a modified piston skirt surface; plastic-coated bearing; new structure water jacket spacer; reduced capacity oil pump; and auxiliary belt with reduced bending loss.


The engines will be used in models scheduled for partial redesign in the near future; a total of 14 new engine variations will be introduced globally by 2015.

1.3-liter engine with max 38% thermal efficiency. One of the engines is a 1.3-liter gasoline engine in which Toyota is employing the Atkinson cycle—normally used in dedicated hybrid engines—and a compression ratio of 13.5:1. Toyota is further improving the fuel efficiency of the engine by utilizing its other innovations including the new shaped intake strong tumble flow and a cooled exhaust gas recirculation (EGR) system paired with Variable Valve Timing-intelligent Electric (VVT-iE) technology to improve combustion and reduce loss.

As a result, the new engine will have a maximum thermal efficiency of 38%—top-level among gasoline-fueled mass-produced engines. The new features, combined with idling stop and other functions, will lead to fuel efficiency gains of approximately 15% by comparison with current vehicles, Toyota said.

New 1.0-liter engine. Click to enlarge.

1.0-liter with max 37% thermal efficiency. Meanwhile, a 1.0-liter engine jointly developed with Daihatsu Motor Co., Ltd. has achieved maximum thermal efficiency of 37% due to a similar tumble flow-generating intake port, a cooled EGR system, and a high compression ratio (11.5:1 in this case).

Combination with the idling-stop function and various other fuel consumption reduction technologies allows vehicles to achieve a maximum fuel efficiency improvement of approximately 30% over current vehicles.


  • Mitani, S., Hashimoto, S., Nomura, H., Shimizu, R. et al. (2014) “New Combustion Concept for Turbocharged Gasoline Direct-Injection Engines,” SAE Int. J. Engines 7 (2) doi: 10.4271/2014-01-1210



Will these new ICEs be called 'SKYACTIV' or 'SPACE ACTIV' or "TOYOTA ACTIV' or.....?


My current car is a dodge neon 2005. It appear that in 2023-2025 when I gonna be ready to change it then I would have a great choice of replacement to choose from. I will choose a 1.5 liter car normally aspirated that run on regular gasoline and have the start-stop system. No hybrid, no bev, no hydrogen because there won't be an hydrogen infrastructure in my area and anyway this seam costly. Maybe the only game changer could be a bi-fuel gasoline-natural gas car with a decent nat gas infrastructure, I hope so cuz nat gas is cheaper and pollute less and the car should cost only 800$ more approx.


Gor, I'm shocked!
Giving up on hydrogen!
Oh ye of little faith!
Sales of fuel cell cars in Canada in around 2023-5 will suffer as a result!


All he auto amkers are improving the ICE engien. There si nohting new here. BMW hand others ahve had varaible vlave lifing for a long time, FCA's MultiAir duplicates all of thsi except for the higher compression operation. Most new designs have cooled EGR too.

I await the introduction of HCCI operation that will raise the ICE efficiency to its theoretical maximum. Many of the advanced engine offerings by all the auto makers are getting awfully close tot having all the pre requiste changes and modifications needed to accomplish that HCCI operation.

That semi-diesel operation, will afford the diesel's fuel economy along with the substantially reduced weight and improved cleanliness of the Otto cycle engines.

The auto makers know how to provide an ICE with a ZEV toxic emission profile matching an EVs emissions, and 25% of California's cars meet it today.

The auto makers even suggested it to the regulators, in lieu of unnecessary and IMO stupid CO2 emissions requirements. Only to be double-crossed and to end up with both requirements.

No one knows how to modify a diesel for SULEV II cleanliness, even in the lab, never mind the street.

However HCCI or a derivative, offers the best of both worlds.


SULEV II on diesel was demonstrated in the lab a long time ago. Perhaps it was so long time ago that those who did it forgot about how to do it. I hope not… VW’s new 4-cyl diesel family has been designed to meet Tier 3 in the future. The will not leave the US market due to Tier 3 or LEV III.


The 1.5L has 38% efficiency and is 15% more efficient than current vehicles.
The 1.0L has 37% efficiency and is 30% more efficient than current (presumably 1.0L) vehicles.
That is quite a difference - are the current 1.0L ones very bad, or are the current 1.5 ones very good ?

I suppose what matters is not the peak efficiency, but the average efficiency under normal partial loads, as that is what most people spend their time at.

Anyway, it is great to see further improvements in ordinary ICE engines that will sell in millions - they will save a lot more fuel than a small number of super hi-tech PHEVs or BEVs.


Part load of this new engines is similar to normal load in atkinson Prius engine. The difference to Prius engine is that they can actually use full compression for higher power, where Prius 1.8L engine has puny 100 Nm in low rpm.

So I would guess that those new engines deliver a very good efficiency under low load.

And another question would be what will happen with next generation Prius engine? If it doesn't deliver >40% efficiency with similar tricks (16:1 compression?) I will be disappointed.


Would that push the lighter Prius III-B at about 65 mpg?


Diesel LEV III / Tier 3? Well, this apparently to happened a little bit quicker than I anticipated.

Regarding efficiency: I think we can find engines with ~37% maximum efficiency from other manufacturers. Toyota use CR of 13:1. This is high but Mazda has 14:1, even without Atkinson cycle. Many other engines are turbocharged, so it is a matter of charge pressure/temperature if one wants to compare CR with a naturally aspirated engine. One should also consider that a manufacturer can “optimize” CR for light load by retarding ignition somewhat at full load. This sacrifices maximum power and full load efficiency somewhat but provides a better compromise for low-load fuel consumption, e.g. in both a test cycle and in real life driving. Strange enough, this “part-load CR optimization” is seldom utilized by engine manufacturers. Apparently, maximum torque and power are still good selling points, so priorities are obvious. All features listed for this engine are well-known, so the question is where the actual progress is; if any (?). Toyota has not (yet) provided data on torque and power and I have not had the time to read the SAE Paper yet, so it is difficult for me to say (at this stage)...


we need more choices than just the mitsubishi mirage!!!

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