Almost all of the current hybrid cars use Atkinson Cycle engines, meaning a late closing intake valve and an increased expansion ratio.
These engines have relatively poor low speed torque which is compensated for by the electric motors, restoring good performance.
Now manufactures, including Toyota and Lexus, are advertising "Atkinson Capable" engines on non-hybrid models.
Can someone please explain what is meant by "Atkinson Capable"?
It seems to me that it would take a pretty wide range in the variable valve timing to be able to move into and out of Atkinson Cycle mode.

 

Iirc, Atkinson Capable means the engine can run/switch to either Otto or Atkinson Cycle depending on load.

 

RCF engine has been using atkinson cycle

 

Lots of new Toyota/Lexus including Sienna, Highlander, Lexus F, new Camry

 

Toyota's engines announced in 2014 run on an on-demand Atkinson Cycle, starting off and running at low engine loads on the Atkinson Cycle, and switching to the more powerful Otto Cycle at high engine loads.

The Atkinson Cycle effectively has a shorter compression stroke than expansion stroke (longer expansion stroke); the intake valve is left open past bottom dead centre, meaning that some fuel-air charge is driven back into the intake manifold. This reduced charge reduces torque output but the longer expansion stroke makes better use of the fuel in the cylinder, extracting more power from a unit of fuel than an equivalent power Otto Cycle.

At higher engine loads, the valvetrain switches to run on the Otto Cycle so that the compression stroke is equal to the expansion stroke. The longer compression stroke (compared to the Atkinson Cycle) extracts more power but also uses more fuel.

The following engines (that I am aware of) use this Atkinson-Otto cycle valvetrain:

• The 3.5-litre V6 in the current Highlander, RX, Tacoma and new Camry
• The 2.0-litre turbocharged 4-cylinder in the NX 200t, IS 200t and GS 200t
• The 5.0-litre V8 in the RC-F

I don't know if the new 2.5-litre Dynamic Force 4-cylinder in the new Camry uses the on-demand Atkinson Cycle.

 

The intake valve on Atkinson Cycle engines is left open longer past BDC than on Otto Cycle engines.

 

And this is why these engines are such turds at low RPM.

 

Low torque does not necessarily mean an engine is a "turd". Not everyone cares about having blinding acceleration.

 

They only switch to Atkinson cycle in low load conditions. How much torque do you need when loafing along a flat highway at 70 mph?

 

I'm confused by some of the comments here.

My understanding is that Atkinson allows one to build an engine with a very high static ratio, say, 14:1, which implies an increased extraction of combustion energy. But the reason that conventional Otto engines don't use 14:1 is because the BMEP in the combustion chamber at 14:1 under wide-open throttle (low manifold vacuum) would be so high as to cause detonation. So the idea behind a smart engine is to use Otto up to the point that BMEP would reach the limit, then close the intake valves later to limit the charge in order to keep BMEP at that limit.

So Otto cycle under low load (to deliver as much BMEP or torque as possible), with Atkinson cycle when manifold vacuum is low (high load) to stay at the BMEP limit without exceeding it.