Toyota to use Atkinson cycle in non-hybrids: 10% efficiency boost, "no power loss"

[MetroMPG]

Reports today say Toyota's going to start using Atkinson cycle engines in 14 non-hybrid models. They're starting in the Japanese market with 1.0L and 1.3L engines.

The 1.3-liter engine will achieve thermal efficiency rates of 38 percent, while the smaller one delivers 37 percent. Higher efficiency means more energy from internal combustion is captured to power the wheels and less is lost through heat.

The outgoing engines have thermal efficiencies of 35 percent.

The new efficiency rates are on par with the 38.5 percent ratio achieved in the current engine of the Prius hybrid.

Atkinson is known for efficiency, but also low power/torque. They increased compression ratios to gain poiwer, and are carefully managing knock with 3 approaches:

• new technology increases the combustion speed to consume more fuel before knocking can occur
• scavenging and expelling unburned elements, so as not to overheat intake air
• using a water jacket around the cylinder to regulate heat

Full article: Toyota unveils new generation of fuel-efficient gasoline engines

[MetroMPG]

Ha: first comment posted under that article...

Have they started the recall yet?

[Daox]

Originally Posted by MetroMPG

• new technology increases the combustion speed to consume more fuel before knocking can occur
• scavenging and expelling unburned elements, so as not to overheat intake air
• using a water jacket around the cylinder to regulate heat

Great article. Its cool to see how all the OEMs are tackling the new emissions and mileage regulations differently.

I'm pretty sure point #2 and #3 are supposed to be one though. They're using cooled EGR to not overheat the intake air. They do this by running it through an EGR cooler like a diesel has (and the latest gen Prius' engines). They need to cool the EGR because putting too much hot EGR into the intake mixture will cause knock instead of help prevent it, which is one of the advantages of EGR to begin with.

[MetroMPG]

May be. But then what's the third anti-knock strategy? (They mention 3.)

[Daox]

I dunno, but having a water jacket around the cylinder isn't exactly new technology.

[cRiPpLe_rOoStEr]

I wonder if either this 1.3L or (less likely) the 1.0L are going to be featured in some U.S.-spec car. At least in the Yaris they seem to be a good option, but the 1.3L could also be reasonable in the Corolla...

[MetroMPG]

Depends on the power output! 1.3 in the U.S. Yaris, possibly. Doubtful in the Corolla.

[cRiPpLe_rOoStEr]

The Corolla is already available with a 1.3L engines in some markets. In Portugal it's currently the only gasser available.

[RustyLugNut]

Originally Posted by Daox

I dunno, but having a water jacket around the cylinder isn't exactly new technology.

There are techniques to control cylinder wall temperatures via coolant flow control. A simple by pass or such can keep the cylinder walls in a narrow range of operation and help with detonation control.

[gone-ot]

There is NO WAY an Atkinson-cycle engine, of exactly the same dimensions, will produce the SAME horsepower...when TORQUE is "shifted" toward lower RPMS, Horsepower falls-off drastically, since HP is a direct function of RPM. Yes, the higher CR helps, but at what cost to FUEL "knock" sensitivities?

Toyota marketing has been listening to Detroit Marketing too much!