Most research done to increase the fuel efficiency of vehicles, or more correctly internal combustion engines, has focused on the ability of the engine to efficiently burn the fuel. The focus has been on the development of high efficient vapor delivery systems. These are also the areas most often quoted or denounced by engineers.
Engineers typically note the low number of hydrocarbons in the exhaust as the evidence that the engine efficiency cannot be significantly improved. This general statement regarding the internal combustion engine is misleading because it assumes that the improvement in fuel efficiency gains are primarily related to unburnt fuel. In reality fuel efficiency gains are related to increasing the thermal efficiency of the engine, of which increasing the efficiency of the burn is part of the solution only. The real indicator of how efficient the engine is running is to examine the thermal efficiency.
Increasing the thermal efficiency of the engine takes many forms
Increasing the efficiency of the burn
Reducing the heat loss from the cylinder, which results in drop in the heat available to expand the gasses producing the pressure that drives the piston. Heat loss from the cylinder is the result of, incoming cool air, loss through the cylinder walls to the engine cooling system, loss of heat to the exhaust, loss of energy in friction, which shows up as heat in the oil and cooling water.
reducing the loss due to friction. This can be achieved by the use of low friction bearings such as ball or roller, and or the use of Teflon graphite or molybdenum based lubricants. High efficiency oils with low viscosities can help to reduce power loss loss in pumping oil.
Engine internal power consumption, pumps Oil, water, air (including the engin intake stroke which acts as a vacuum pump to draw air into the cylinder and as a compressor to pump air out of the cylinder..
It should also be noted that the lubricants in the engine itself, especially with the use of the "standard" wet sump, can also result in losses as the crank is continually splashing into the oil bath in the engine. This has been greatly reduced with the design and implementation of deep sump baffled or even dry sump engine designs.
Reducing the work required by the engine to produce power (lower intake vacuum, exhaust pressure), lowering the intake vacuum by the use of larger air intakes, properly designed intake manifolds which encourage laminar air flows and reduce turbulence, larger intake valves with efficient air flows designs. Reducing the exhaust pressure also helps to eliminate the work required by the engine by eliminating the need to "Pump" the exhaust gasses down the exhaust pipe. Such changes as high flow piping with minimal bends, larger pipes, tuned ports that use the velocity of gases from one cylinder to draw exhaust from the timing the exhaust into the header to avoid exhausting into a pressure wave from a previous cylinder.
Increase the efficiency of the transfer of heat energy to mechanical energy (engine design characteristics). A largely overlooked area by most engineers. reducing waste heat from the burn is of primary importance. This can be achieved in the field by creating an insulating block to the thermal transfer to the cylinder walls, utilize a high temp but very short burn, modify the fuel to burn more efficiently. increase the time required to or allowed to transfer power to the crank from the expanding gases.
Reduce or eliminate heat loss in the burn process (energy absorbing products of combustion such as nitrous oxides. The combustion process has two major energy periods. when the burn starts energy is required to start the breakdown and recombination of molecules. Heat is gained because the breakdown of some molecular chains produce a net release of energy, that exceeds the energy required to create the new molecules being formed. Modifying the fuel can result in production of molecules that will produce a net gain in heat released rather than a loss.
If the problem of increasing fuel efficiency is taken as the combination of all factors than vaporizing the fuel, while necessary to create a satisfactory burn, is only a single part of the overall requirement.
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