On Wed, 17 Aug 2016 14:04:28 -0500, Jon Elson
wrote:

Ed Huntress wrote:

The
"pseudo Atkinsons," like the engines in today's hybrids, have the
same-length stroke for all four parts of the cycle. But they open the
intake valve late so the cylinder is less-filled.
My only quibble is that the trick, at least on the Honda, is this also means
the intake valve CLOSES late, allowing some of the charge to be pushed back
into the intake manifold. So, the compression stroke starts with the piston
part way up the cylinder. This ends up with pretty low compression (or
cylinder pressure, if you prefer) at ignition.

I'm guessing the trick in the Nissan engine is they effectively reduce
displacement while still achieving a good cylinder pressure at low
horsepower settings. That ought to improve efficiency.

Jon

I've never paid much attention to Atkinson engines, so I don't know
what Honda is doing. BTW, the reason usually stated for *not* using
the Atkinson cycle in regular engines is that they're not very
tractable. I have read that they're slow to respond to the throttle,
but beyond that, I don't have a clue.

There must be a lot going on with the Nissan engine, combining the
turbocharger, the variable compression, and the Arkinson cycle. They
may have published a paper on it with SAE. That's where you get the
details.

--
Ed Huntress