Talk:Miller cycle

message: The patent that most clearly describes the Miller cycle is "US Patent 2,773,490, High expansion, spark ignited, gas burning, internal combustion engines. Ralph Miller (1956)". The difference between an ordinary Otto cycle and the Miller cycle is asymmetric valve timing. This decreases the effective volume change of the compression stroke without affecting the expansion stroke — thus the phrase "High expansion" in US patent 2,773,490. The section headed "Summary of the patent" is for "US Patent 2817322, Supercharged engine". This is a different thing altogether.  — Preceding unsigned comment added by 2604:2000:CFC0:1:7D70:BE49:DC2A:5E58 (talk) 18:37, 23 March 2014 (UTC)
thread_title: Description based on wrong patent

message: Apparently, the combustion engine in the Toyota Prius also uses the Miller cycle? Can anybody confirm this and, if so, add it to the page? Lio 07:17, 29 December 2005 (UTC)
thread_title: Untitled

message: It appears to be the Atkinson cycle and was already mentioned on that page Lio 07:22, 29 December 2005 (UTC)
thread_title: Untitled 2

message: I'm curious about something, and maybe somebody here can answer my questions.
If the Miller Cycle engine forces air/fuel mixture back out of the piston and into the intake manifold, won't that decrease fuel efficiency?  Won't the charge return to the intake manifold, mix with the clean air, and when it goes back into the piston, have more fuel injected into it?
This portion of the Miller Cycle, I felt, was not explained very clearly, only that the A/F Mixture was forced back out of the cylinder.
: Simple. You adjust your carburettor or injection system to operate in what would otherwise be a "lean" mode. What you describe is basically the production of an over-rich FA mixture by drawing too much fuel into it (basically, you end up with as much going in as would normally be needed for a 25% larger engine, in a typical Miller engine with an effective capacity ~80% of its maximum capacity), and how do we fix an engine that's running too rich? We lean out the mixture. Adjust it for the effective capacity (how much air is moved in a full cycle), not the maximum (how much air is drawn into the cylinder at BDC).
: Of course, in the modern world, we just use direct injection instead. Much easier. We know how much air has gone into the engine, and how much fuel we want to burn for the best power or efficiency, and just squirt that much in, with the valves already closed. 193.63.174.112 (talk) 14:25, 27 October 2015 (UTC)
thread_title:  Fuel Efficiency 

message: Hello
I guess someone got this wrong here!
The information on this site describes an Atkinson-Cycle Engine. In the Miller-Cycle the intake port is not closed later but earlier! Bernd
::I second that, this article is factual wrong. The original patent from Miller clearly states "Figure 3 is a crankshaft valve timing diagram illustrating an application of my system to a four-cycle engine in which the inlet valve closes before the end of the suction stroke" - Please read the whole thing for a better understanding
::Also the SAE says so. Wiki-pages in other languages have it right too, as English is not my native I wouldn't want to try to write this version new. Someone to the rescue, please!  — Preceding unsigned comment added by 2001:9E8:8AB0:C800:B4CC:E363:AC90:52C (talk) 23:44, 20 February 2023 (UTC)
replies: text: No, both cycles leave the intake valve open during part of the compression stroke so that the engine is compressing less against (or none at all?) the pressure of the cylinder walls. That's what increases efficiency. The Automotive Engineering International Online do not distinguish between the two in this page saying  "The engine employs the Atkinson/Miller high-expansion principle by means of late intake-valve closing...". There must be some minimal difference between the two, maybe about supercharging vs. normal aspiration. We must ask some engineer in the wiki community. 85.107.29.61 07:37, 25 October 2006 (UTC)

text: Two things:howstuffworks.com has a whole two paragraphs on the Miller Cycle engine.  Those two paragraphs are accurate.  However, they are the equivalent of describing a tsunami as a humongous wave:  technically correct, but somewhat less than what one would expect from an "encyclopedia".If the description here is wrong, then so is the one on howstuffworks.com.  Have you read this in its entirety?  What would you say is incorrect (other than "this article is so flawed in discribing the Miller Cycle that it can't be fixed with a few corrections", that is)?Andy Nguyen 19:49, 19 January 2007 (UTC)
thread_title:  Wrong information! 

message: Hey Aqn, Artmario2001. I kind of have to agree that the explanation is incorrect/misleading. Think about it. The limit of the mechanical advantage of the crankshaft, as the cylinder aproaches TDC or BDC is infinity. As the crankshaft moves 90 degrees from there, it actually has the least mechanical advantage. So, basically, that section does nothing to explain why compressing near BDC is inefficient. I'm not even convinced it is any less efficient than the rest of the compression stroke. It is, however, the easiest part of the compression stroke to remove, which is what causes the other efficiency gains to apply. Aij (talk) 19:14, 15 February 2008 (UTC)
thread_title: Mechanical Advantage

message: Here is the scoop on the miller cycle.  A combustion chamber is a fixed size.  Look at only intake and combustion strokes.  Intake draws in air and fuel.  Power expands air and fuel.  Both strokes happen in the same size chamer.  The important fact to consider is the fixed chamber.  Ask yourself this.  Is the combustion chamber the ideal size for power (combustion) stroke or does it need to be a little larger to make use of more of the expanding gas.  The expanding gas is still expanding and is capable of doing more work before the exhaust valve opens.  The miller cycle maintains compression ratio but takes in less air and fuel relative to the intake cycle.  The combustion stroke volume is in effect larger relative to the intake stroke volume.  More air and fuel is burned (less need for catalytic converter) before it is expelled by the exhause stroke.  The miller cycle sacrifices power for efficiency and that is the reason it has been used on stationary engines.  The amount of power loss is minimal and the miller cycle is the best option for a series hybrid automobile.
Anoziracs (talk) 17:26, 13 August 2008 (UTC)
thread_title:  The Miller Cycle 

message: First, the article is titled Miller cycle yet the article speaks only indirectly about the miller cycle. Instead the article speaks primarily about Miller cycle engines; that is, devices attempting to implement the thermodynamic cycle known as the Miller cycle. This is okay in that the implementation is important but perhaps the article could be split into two sections, one dealing with the cycle itself and one with engines. The second confusing thing is the lack of distinction between power and specific power (or power density) both in terms of volumetric and mass densities. This is especially important when the miller cycle is implemented, as is commonly done, using delayed intake valve closing as this technique reduces effective engine displacement in the same size and weight of engine.
Of course, a clear explanation of the Miller cycle as contrast to the Atkinson cycle is probably another required section in the article.
I don't have the time to rewrite the article right now but hopefully someone can make use of the above ideas. 205.189.151.15 (talk) 00:05, 17 March 2009 (UTC)
thread_title:  Suggestions for an improved article 

message: "Efficiency is increased by raising the compression ratio."
I'd dispute that.  The compression ratio, as correctly stated in the article, is typically limited by knock, and so is no greater than a regular Otto-cycle engine running similar boost.  To the above poster: the article describes a drop in power (due to a smaller volume of air being compressed per stroke, for a given cylinder size) not a loss in energy.
This cycle as described allows an increase in expansion ratio, without a similar increase in compression ratio - for an Otto cycle, the two are equal.  Thus more energy is extracted by allowing the combustion gases to expand more, giving higher efficiency (less energy remaining in the exhaust gases due to lower pressure/temperature).
Also agree with the poster of March 2009 that the cycle itself should be discussed as much as the engine type - an indicator diagram would help greatly.
There are other engine designs which similarly decouple the compression ratio from the expansion ratio - Gomecsys springs to mind.  — Preceding unsigned comment added by 80.4.149.253 (talk) 08:52, 23 June 2011 (UTC)
thread_title:  Compression vs expansion 

message: The article claims hybrid cars to use the Atkinson Cycle Engine, which they don't. They use an Otto engine and use the Atkinson Cycle Process modeled after the Atkinson Utilite Engine.
:Yes, I agree. Unfortunately Atkinson has become a marketing term so when an engine is described as Atkinson, they just mean 'over expanded' in Heywood's telling phrase. Unfortunately wiki relies on sources, and these days there are plenty of ignoramii and weasels who use the term in its new sense. Greglocock (talk) 08:39, 6 December 2016 (UTC)
thread_title:  About the Atkinson Engines 

message: Reading the 30 June 1945 interview with Helmut Caroselli, an engine designer at DVL, Deutsche Versuchsanstalt für Luftfahrt, in the wonderful "The Secret Horsepower Race: Western Front Fighter Engine Development - Calum E. Douglas" I learned how long it takes for inventions to be implemented. Caroselli was a Russian prisoner at the time. His expertise was invaluable, instead of being sent to a gulag he was interrogated by Prof. Dr. Polikovski, an aeronautical engineer from the Klimov company.
Polikovsky:
What developments do you foresee for the Otto cycle engine?
Caroselli:
My position is that the Otto engine will remain current. The critical aspect of its development is the compression ratio.....
In this regard it is necessary to include, as a development of the classic Otto process, the option of "prolonged expansion". To achieve this, the intake valve is closed later than usual, so that some of the air charge flows back into the intake system during the first part of the compression stroke. The expansion in the cylinder therefore takes place in a higher volume than the compression one, with a consequent increase in thermodynamic efficiency.
One of the criteria I adopted recently in choosing a car was the inclusion of the Atkinson cycle, i.e. the "sustained expansion" mentioned above.
The efficiency of this contemporary commercial Otto exceeds 40% and the specific solution adopted is not Atkinson's cumbersome original proposal but precisely the one suggested by Caroselli in 1945. And I thought it was a recent Toyota invention! Omblauman (talk) 23:55, 2 April 2024 (UTC)
thread_title:  Caroselli suggested it in 1945