PiP – the Marvelous Mountain Machine

I am glad the confusion got cleared.
Compression ratio - Wikipedia, the free encyclopedia

 

^^ keep looking down the page:

See also Atkinson cycle - Wikipedia, the free encyclopedia

Here is another definition:

compression ratio | Britannica.com

For this particular engine design, the two sentences contradict each other. I use the meaning of the first sentence.

Compression ratio - definition of compression ratio by The Free Dictionary

One can easily argue that compression begins when the intake valves close, not at BDC in this engine.

 

They are talking about real Atkinson cycle:

not the "modern" which is basically a Otto with fake variable compression/expantion in which difference btw intake and power cycles created using valve-train:

 

It is not the least bit clear to me that the modern Atkinson engine compression ratio can't be computed the same way as the original version. The first sentence of the Britannica quote above fits perfectly.

 

What I mean that on real Atkinson compression and expansion ratios did differ due to additional linkage. On modern modified Otto cycle engines (also incorrectly called Atkinson) the difference is simulated by using late valve closing. But this (or any other magic with valvetrain) does not really change compression ratio as "the ratio btw minimal and maximum volume on compression stroke"; if it did then the high revving motorcycle engines shouldn't really be rated at 12.5:1.

Here is more on Atkinson:
Atkinson cycle - Wikipedia, the free encyclopedia


With opposed pistons:

 

BTW modified Otto cycle engines much closer to Miller cycle than Atkinson cycle:
Miller cycle - Wikipedia, the free encyclopedia

 

Perhaps a simple 'compression ratio' is too ambiguous, and users should specify which of several kinds of compression ratio is being discussed. E.g. effective vs. geometric.

Here is a Toyota press release. Be sure to open up the full quote, showing "effective compression ratio is about 8:1".
Our Point of View: Atkinson Meets Otto: Why the Prius is So Efficient

 

They can say whatever they want but it is not Atkinson engine. His patent specifically calls out linkage design, as the way to eschew Otto patents.

Moreover delayed intake closing is common on high-revving engines (such as m/c engines) and it helps at higher RPMs.

If anything it more closely follows Miller patent:
Miller cycle - Wikipedia, the free encyclopedia

What does it make of "turbocharged Atkinson" Toyota is so proud of?

 

That piece became unnecessary when Otto's patents finally expired, a very long time ago.

So he didn't write is patent application very well, to separate that linkage from the differing compression and expansion ratio feature, a major contributor to his engine's improved efficiency. We continue to use that later feature.

 

So you are saying the inventor of the engine didn't know what he invented? uzzled:

It is a Miller cycle not Atkinson.

EDIT:
How Mazda's Skyactiv Fuel-Efficiency Technology Works | Vehicles & Technology content from WardsAuto

Thanks Mazda does not employ ignorant marketing idiots Toyota does.

 

To be called a Miller cycle, would not a supercharger or turbocharger be required on the engine?

 

So what about Toyota's "turbocharged Atkinson" engine?

I had edited previous post to include quote from Mazda people.. check it out. Mazda does call their non-super/turbo-charged SkyActiv Miller cycle.

If you re-read patent excerpt Miller was designed around turbocharger use, and at the start and light loads there is no turbo boost, so w/o that it would work exactly as Toyota's "modern Atkinson"

 

I agree with the physics. What I don't know is where the line between Atkinson and Miller gets drawn....or who decides.

 

Yes we are not arguing how it works, just whose patent it is closer to and how to name it.

It is basically the same thing; whatever you call it Dick or Rick or Rich

 

No, I said that he didn't write his patent application very well. He needed better Intellectual Property Law attorneys reviewing it.

 

Here is a text that gives both definitions of compression ratio. Mine matches equation 3.20 (cr = v7 / v2), while Cylcopathic's matches 3.21 (cr = v1 / v2).




From A Textbook of Internal Combustion Engines, R. K. Rajput, Laxmi Publications Pvt. Ltd, 2007.

 

Does anyone know where I can dig up the volume of the combustion chamber for the 1NZ and 2GR "Atkinson" engines? I'm wondering if Toyota actually did change the CR between the two, or if they just switched between using compression ratio as expansion ratio.

 

...following more on the beginning of the thread, Appalachia can have a similar effect: Pgh to DC, 68 mpg; DC to Pgh 62 mpg. The ability to coast downhill to reach a good cruising speed, and then maintain the speed while generating energy is satisfying.

 

Looks like in conditions like these you gain about 10%. On regular Gen3 you'd be looking 56-58 in similar conditions.

On many downhills battery fills up and ECU runs engine for braking.

 

Someone earlier in the thread asked about high mountain driving. Here is my experience. I live in a very hilly area at 9500 ft -- just W of the Eisenhower Tunnel in Colorado. PIPs were not for sale (and still are not I think), but I got one in Seattle (2013 model) and had it shipped. I am very happy with all aspects. I have 30000 miles on it and lifetime average is 71 mpg. Every drive here is hilly, and of course long drives (to Denver, or Grand Junction, or St Paul, MN, have a big impact on the mileage). The biggest thing -- one which I learned on my 2005 Prius -- is to use snow tires in winter. That makes a HUGE difference, and of course we have snow here from Oct to May.

The altitude itself is a nonissue. The big hills -- e.g., the 5000 ft drop to Denver -- are fun since one can do that 60 mi drive using almost no gas. Anyway, no problems and it all works well.