[Christ]

You're also still not comparing apples to apples. I've read both of those papers before.

You're comparing a gas/electric hybrid to a "clean diesel" which is not a hybrid. The city efficiency of the Prius comes from the e-motor driving it when power from the gas engine isn't necessary.

If you want to compare apples to apples, you need to compare the Prius's gas engine ALONE to the Jetta's "Clean diesel", no hybrid action at all.

I'm also very familiar with the Atkinson Cycle engine and it's concepts. Saying that there are no pumping losses while the engine is pushing air back out of the cylinder and into the plenum so that another cylinder can draw it in is completely false. Yes, there are less pumping losses, but they're not gone.

Instead, what you now have is an engine that is pumping air back into the plenum, already mixed with fuel, so that another piston's intake valve can open, draw in under vacuum the pre-mixed air and fuel, with a little more air, and a little more fuel, so that cylinder can pump some of that mix back into the plenum, so another cylinder.... blah blah blah. The engine really isn't that hard to understand. Comp Cams built a package for race engines in the 70's and 80's that allowed people to run 19:1 compression on leaded gas, which followed that same principal. This is also where dynamic compression and dynamic displacement come into play.

19:1 static compression means literally nothing when designing an engine. You can build an engine to a MUCH higher tolerance than that, drawing in a full cylinder (100%VE), as long as you're not compressing a full cylinder. This is where the Atkinson Concept camshaft comes into play. If the camshaft allows part of the air charge back out of the cylinder, you can run an insanely high compression ratio, with better efficiency per unit of fuel used, than a traditional Otto Cycle engine.

So sure, your Toyota's Atkinson Concept engine (It's still not a true Atkinson Cycle engine) might have less pumping losses per unit used, but it's also making MUCH LESS power per pound (both pounds of engine weight, and pounds of air drawn) by having to process that air in a non-linear fashion, several times, without actually making any power from it.

Guess what? Diesel engines could use (probably not benefit from, but use) an Atkinson Concept camshaft design as well.