I think the discussions here indicate the pre ignition head pressure is the important parameter when discussing "compression ratio".

 

As a current Subaru owner, I constantly get questionaires from Subaru. The last one was all about what type of technology would I'd like to see in the next Subaru. I kept selecting "hybrid technology". I doubt that they will embrace this. The last article I read about an interview with the president of Subaru stated that he thought hybrids were "wrong" and diesel engines were the way to go.

 

Are you sure it is turbocharged (run by exhaust) or supercharged (run by engine shaft)? An Atkinson cycle engine with a supercharger is a Miller cycle engine and these have been successfully used in the past. Adding a turbocharger to the Atkinson cycle will work but seems less than optimum since a turbo adds power mostly at high RPM while a supercharger is better at boosting power at low RPM where the Atkinson engine is deficient.

 

http://www.keveney.com/Atkinson.html

Interesting diagram of the real Atkinson cycle engine.

WWEST

with respect to the reversion, it would be true if the engine used extremely short or no intake runners. While it is true that the engine breaths like a much smaller ICE, the loss of bottom end power is because of the standing wave in the intake at low rpm. These miller cycle engines would not be usable in a car without some kind of boost at lower rpms. In the hybrids this is the traction motor. In other uses they are a super charger to attenuate the reversion. As a stationary power plant that runs at a fixed rpm these would be a good application.

 

While they can be made to do so, clearly, SuperChargers need NOT supply boost at low throttle openings and low RPM. A proper design, SC speed variable independent of engine RPM, could easily act as a "reed/flap" valve to prevent reverse intake airflow. Given a proper/correct design the SC might just idle along only supplying enough "boost" airflow for normal "otto" cycle operation until an extraordinary level of power is desired.

 

...that's right, they use the turbo for boost instead of electric.

 

Mazda has or had a miller cycle engine in the Millenium. Subaru is experimenting with a turbo. Is it Miller Cycle? Atkinson? or ???

 

Miller cycle requires a supercharger as an integral part of the design.

So no, it isn't a Miller Cycle.

It's unlikely that any Atkinson Cycle engine implementation would have enough leftover energy in the exhaust to run a turbocharger.

So that leaves out the Atkinson Cycle.

 

Google: subaru "miller cycle"
Google: mazda "miller cycle"

 

First, my guess would be that if this is truly a turbocharger (exhaust gas driven "super" charger) then this "concept" vehicle is headed down a one-way dead end street.

But there is a slight indication that the engine might "transition" from a form of Atkinson cycle into a standard "otto" turbocharged engine as the driver "asks" for more and more performance, using variable valve timing, and as the turbocharger comes "online".

I don't remember if I ever really knew why but it seems to me that a Miller Cycle engine REQUIRES a positive displacement supercharger or the equivalent thereof. I don't see, readily, how a turbocharger could do that.