Technology Run Amok? - Part 1
Today, vehicles of all types are coming under attack from “less than informed” (to put it politely) pundits, ranging from the US Congress, to the man on the street, as not being “efficient” and “advanced enough.” “Enough” for what, no one ever specifies-which is symbolic of the average consumer’s ignorance and aversion to true understanding of these complex issues and technologies. Quick fixes, such as hybrids, of any type or functionality, are now paid more lip service as “the solution“, along with E85 (ethanol based alcohol fuel), VVT (variable valve timing), GDI (gasoline direct injection), and other acronyms that are spouted with abandon, and even less understanding.
In this entry, and the following series of weblog entries, I will examine some of these fallacies and their proponents, as well has how the consumer is going to pay for it all in the end.
MAGIC- The “magic” of sound engineering and the costs of ignorance in application.
A few years ago, DCX demonstrated a version of the 4.7L, overhead cam, 2 valve per cylinder, truck engine which had some seemingly innoculous additions and changes to the production design. These changes, none costing more than a few pennies per engine, allowed the experimental engine to attain approximately 12% better fuel economy across its powerband, when compared to the standard 4.7 v8 engine. What happened? Keep reading as I bring some of the detail of what was accomplished to light in less than technical terms….
What causes engine losses? Basically, there are 3 items that affect engine efficency:
FRICTION:Friction is the resulting drag on free movement by material type and finish, lack of lubricant, molecular collision (vicosity of lubricants, as an example), and many other conditions. In a perfect world, a friction free bearing would be a uniform gap between components that move relative to each other that neither increases in size, nor decreases in size. Unfortunately, no possible in the world we live in today. Even a maglev (magnetic levitation) has friction between its non-contacting surfaces.
Volumetric efficiency of an engine is the ability to move air and fuel charge into and out of a combustion chamber of an engine. Unless supercharged by either a positive displacement pump (Rootes type or centrifical that is direct driven) or a turbo-supercharger (original and proper name for a “turbocharger”) a naturally aspirated engine cannot achieve 100% efficiency.
“Volumetric efficiencies can be improved in a number of ways, but most notably the size of the valve openings compared to the volume of the cylinder and streamlining the ports. Engines with higher volumetric efficiency will generally be able to run at higher RPM, and thus power, settings as they will lose less power to moving air in and out of the engine.”
-from http://en.wikipedia.org
Uneven fuel burn can result in several issues with ICEs (Internal Combustion Engine), not the least of which is pre-ignition and detonation. When either occurs in a modern engine as the 4.7 litre, the ECU (Engine Control Unit or “computer”) will dump in more fuel and air to extinguish the explosion in the combustion chamber. NO, fuel/air does NOT normally explode-this is Myth #1 to remove from the public psyche- it burns in an even pattern across the combustion chamber from the spark plug to the farthest reaches of the combustion chamber.
HOW IS FRICTION OVERCOME?
Simply put, friction cannot be overcome 100 percent, but REDUCED to single digit percentages and less, by the careful application of lubricants, material selection, and fit/finish of the components.
Lubricants:
Every moving part has a mate of some type to apply its motion against. For example, a piston on a connecting rod travels in a linear motion within a bored cylinder, pivoting on a wrist pin fitted to the upper end of the connecting rod. The connecting rod lower end encompasses the rod journal of the crankshaft, which is in turn restrained by the main journals of the cylinder block.
The points of friction in this mechanism are:
- Cylinder block bore walls to piston
- Piston rings to cylinder walls
- Piston rings to piston
- Piston to wristpin
- Wristpin to connecting rod
- Connecting rod to crankshaft rod journals
- Crankshaft main journals to cylinder block main journals
9.0L John Deere Diesel Engine Cutaway-courtesy of John Deere & Company
Detrimental effects of Friction:
Lubrication is required to prevent metal to metal contact in the reciprocating and rotary motion components. Friction causes heat, wear, and fatigue in the component, generally speaking (there are other effects, outside the scope of this discussion).
Lack of lubrication will lead to such failures as:
Note galling on ends of pin, which rides in piston bore
(photo courtesy of Tim Gilles)
Worn main bearing half
(photo courtesy Tim Gilles)
