Here's how you do Atkinson Cycle - Honda ExLink

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Shannow

Shannow

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Have mentioned before that Nissan were messing with a series of levers and rods to give a greater expansion ratio/exhaust stroke than intake/compression back in the 80s but it sounded like an overly complicated mechanical nightmare...Smokey played with offset bores which give a shift away from traditional piston displacement/degree changes, but only tiny compared to what is needed.

Honda appear to be commercialising a similar set-up

http://world.honda.com/powerproducts-technology/exlink/

Expansion ratio 1.4 times compression (BDC to TDC) offers great efficiency improvements, and would make an appropriately sized turbo really work.

Actually looks like the way that the Nissan engine was described back in the 80s
 
I have been trying to learn more about the Toyota 2.5L 4-cyl DOHC 16V w/ VVT-i engine. As near as I can determine, Toyota gets Atkinson type results with electronic valve timing. Coupled with the electric motors through the planetary gears set to handle the low torque of the Atkinson cycle, this engine/power train seems to be a dream come true.

It seems Honda is moving toward a mechanical implementation vice electronic. Perhaps aimed at smaller engine applications such as generators, compressors, etc.
 
Toyotas drivetrain is pretty flash, but it's not related to the Atkinson cycle, which is a technique that they use to get small engine economy (and output) out of a larger engine, by restricting the intake volume via valve timing and then expanding it "normally"...when the original Atkinson was mechanical, with actual difference in compression/expansion...as is the '80s Datsun, and now Honda.

To show that nothing is new under the sun, here's something 80 years old or so that's a mechanical/hydraulic

"synergy drive"

http://i16.photobucket.com/albums/b42/akashafamily/scan0004.jpg

As to the low torque, I was chauffeured in a hybrid lexus 4WD, and they are anything bu low torque.
 
'yota (and ford) does achieve basically an atkinson cycle by leaving the intake valve open significantly longer, so that some of the intake charge is pushed back out of the cylinder. this means that only partial (2/3?) of the compression stroke is used, while all of the power stroke is used. that is what defines the atkinson cycle.

while there are some losses in this process, it does couple nicely in hybrid use.

@shannow-- the torque you felt in that lex included the power from the electric side, teamed with the gas. Pretty cool!
 
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Leave it to Honda to figure out an elegant way to implement a complicated technology. I have a lot of respect for Honda's innovative engine designs. Most current methods of implementing Atkinson or Miller cycles involves radically early or late intake valve closing timings, which may lead to higher pumping losses.

OK, here's a philosphical question:

How would one calculate the displacement of the engine; based on the length of the intake stroke, or the expansion stroke?
 
if i were an authority on the subject, intake stroke length. reason being: displacement implies volume of air drawn into the engine, not how much it is compressed.

then again, i'm not an authority on it.
 
Originally Posted By: RobertISaar
if i were an authority on the subject, intake stroke length. reason being: displacement implies volume of air drawn into the engine, not how much it is compressed.


I agree. I think at best you might average the intake and power stroke ('cuse me, the "expansion" stroke) if you wanted to calculate a swept volume. I don't think I'd see the logic in using only the power/expansion stroke to calculate displacement.
 
In a purist sense, you would take the volume of air that it could consume (intake volume), as that's the maximum amount of fuel that you could mix into the thing...is also consistent with GTs and other power producing devices that way.
 
Ah, that is quite clever and 'course it would be small-engines-guru Honda to make an otherwise impractical theory work, albeit a single cyl.
I'm actually curious about the kind of harmonics and sound characteristic that an alternating stroke-length introduces- something not often heard before in an ICE
 
I just thought about the problem in engine balance that has been created by having the trigonal link oscillating at half-engine speed. I don't think this is a system that can be balanced perfectly, only optimized to vibrate as little as possible.
 
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