Talk:Engine efficiency

message: "road legal cars are only about 20% to 35% when used to power a car"
This statement is an important fact and has no substatiation.  It needs a reference.  I can find nearly any number cited on the Internet that I wish, so it would be good to find a truly athoritative source, not a web equivalent to a magazine. 
The statement is also poorly formed.  It says "cars" are xxx efficient when used to power "a car".  This should clearly state if the efficiency rating is for the engine, or for the car as a whole.  Gnuarm (talk) 14:09, 3 April 2022 (UTC)
thread_title: Gasoline (petrol) engines

message: "Gasoline engines also suffer efficiency losses at low speeds from the high turbulence and head loss when the incoming air must fight its way around the nearly-closed throttle; diesel engines do not suffer this loss because the incoming air is not throttled" - This HAS TO BE incorrect. Moving air is what takes energy.  Not moving air (Maintaining the intake manifold vacuum) doesn't take energy.  The inefficiencies of nearly closed throttle operation doesn't come from pumping losses but rather ineffeicient fuel/air combustion  —Preceding unsigned comment added by Timmbacher (talk • contribs) 19:26, 30 September 2010 (UTC)
thread_title: misc

message: This really doesn't seem to be an article about engine efficiency in general.  It's about the efficiency of engines in particular applications configured with other equipment.  That is, the efficiency of engines being used to drive automobiles via a mechanical drive train (as opposed to, say, driving the generator of a serial hybrid) and without the benefit of ISG, etc.
I'd like to see another article that compares engine efficiency in a more general way.  People are interested in energy efficiency of engines for other applications like running generators.
In the mean time it might help to break down some characteristics that are being lumped together.  The efficiency of gasoline fueled piston engines are given after the losses to supporting equipment (which can vary).  It would be helpful to know the efficiency of the engine both with and without that equipment.  
Any other simple changes that would make the article a bit more general and useful would be appreciated. 
Thanx,  -ef  —Preceding unsigned comment added by 68.80.95.189 (talk) 23:51, 3 March 2009 (UTC)
thread_title:  Title change? 

message: A regular table is best also made (in a new article). I made a stub at appropedia: http://www.appropedia.org/Comparison_of_engines When finished, we can upload it here aswell
KVDP (talk) 10:16, 8 June 2010 (UTC)
thread_title: Engine eficiency table

message: http://www.bekkoame.ne.jp/~khirata/academic/kiriki/begin/general.html
The thermal efficiency of Stirling cycle that is used for Stirling engine is equal to that of Carnot cycle which is theoretical higiest efficiency. Expression of Carnot efficiency is follows.
1-Tc/Th
Where
Th : Higher temperature in the cycle
Tc : Lower temperature in the cycle
This means as to be large for a temperature difference, theoretical heat efficiency are higher. Among Stirling engine developed, the engine to achieve a thermal efficiency 40 % exists.
From: Prof. Iwamoto, Department of Mechanical Engineering, Faculty of Engineering, Saitama University
~~ Andy from Workshopshed ~~  —Preceding unsigned comment added by 212.125.73.242 (talk) 15:28, 18 January 2011 (UTC)
thread_title:  Stirling Engine Efficiency 

message: If someone wants to edit the section on gasoline engine efficiency, the following .gov website would be great: http://www.fueleconomy.gov/feg/atv.shtml. It cites three sources that could be used to re-write some of the more technical components of the section that are currently completely uncited. 128.12.48.61 (talk) 22:28, 30 November 2011 (UTC)
thread_title:  Source for Gasoline Engine section improvement

message: I've just finished reading Hunter's Steam power and have some interesting material to add here.  It is a bit too technical for the Steam engine article.  Lots of interesting figures on actual operating parameters of different types of piston steam engines.  It's going to take me a while to get it organized and figure out how to best present it.  Perhaps I will have it ready in 10 days or so.Phmoreno (talk) 03:28, 5 June 2012 (UTC)
thread_title:  Planned update of steam engine efficiency 

message: In the section entitled "Compression ratio" the first thing it mentions is expansion.  Someone may wish to edit this to actually make some sense.  If expansion is the most important, that it should be entitled as such. - KitchM (talk) 22:43, 20 January 2017 (UTC)
thread_title:  Compression or Expansion Ratio? 

message: "Engines using the Diesel cycle are usually more efficient, although the Diesel cycle itself is less efficient at equal compression ratios."  More efficient that what?
What does this sentence mean "Since diesel engines use much higher compression ratios (the heat of compression is used to ignite the slow-burning diesel fuel), that higher ratio more to air pumping losses within the engine."?
"Modern turbo-diesel engines use electronically controlled common-rail fuel injection to increase efficiency. With the help of geometrically variable turbo-charging system this also increases the engines' torque at low engine speeds (1200-1800RPM)."  But isn't a diesel engine a low speed engine which produces its power at low speed to begin with?
"The gas turbine is most efficient at maximum power output in the same way reciprocating engines are most efficient at maximum load."  Are you sure?
"The difference is that at lower rotational speed the pressure of the compressed air drops and thus thermal and fuel efficiency drop dramatically."  That is no comparison because they are different cycles and rotational speed versus air pressure do not coincide.
"...is under 10% load or not having any useful output on the driveshaft."  What?
Maybe this can be made a little easier to understand. - KitchM (talk) 23:07, 20 January 2017 (UTC)
thread_title:  Grammar Problems 

message: This particular statement in the gasoline section needs to be disputed: "However, modern tweaks like exhaust gas recirculation and fuel injection can slightly improve efficiencies upwards of what is predicted by the carnot theoretical construct. It’s possible to add exhaust gas heat energy back to the engine, slightly increasing its thermal efficiency, which isn’t part of the carnot cycle’s predicted best case scenario."  Carnot engines are the most efficient ideal engines. The sentence suggests that "modern tweaks" can somehow violate the 2nd law of thermodynamics. 2601:1C2:4D01:6750:88B6:1178:1264:D792 (talk) 15:50, 17 May 2023 (UTC)
thread_title:  Gasoline Section & 2nd Law of Thermodynamics