FUEL INJECTION

VALVE AND CAMSHAFT PLACEMENT CONFIGURATIONS

Two basic valve and camshaft placement configurations of the four-stroke gasoline are used automobiles.

OVERHEAD VALVE (OHV)

As the name implies, the intake and exhaust valves on an overhead valve engine are mounted in the cylinder head and are operated by a camshaft located in the cylinder block. This arrangement requires the use of valve lifters, push rods, and rocker arms to transfer camshaft rotation to valve movement. The intake and exhaust manifolds are attached to the cylinder head.

OVERHEAD CAM (OHC)

An overhead cam engine also has the intake and exhaust valves located in the cylinder head. But as the name implies, the cam is located in the cylinder head. In an overhead cam engine, the valves are operated directly by the camshaft or through cam followers or tappets. Some engines have separate camshafts for the intake and the exhaust valves. These are called dual overhead camshaft (DOHC) engines.

Valve Arrangement

there are several valve arrangements. Most of these designs are not used in current automotive engines.

ENGINE DESIGNS

The gasoline-powered, internal-combustion piston engine has been the primary automotive power plant for many years and probably will remain so for years to come Present-day social requirements and new technological developments, however, have necessitated searches ways to modify or replace this time-proven workhorse. This portion of the chapter takes a brief look at the most likely contenders, and how they work.

Diesel engine

Diesel engines represent tested, proven technology with a long history of success. Invented by Dr. Rudolph Diesel a German engineer and first marketed in 1897, the diesel engine is now the dominate power plant in heavy-duty trucks, construction equipment, farm equipment, buses and marine applications. During the late 1970s and early 1980s, many predicted small diesel engines would replace gasoline engines in passenger vehicles. However stabilized gas prices and other factors dampened the enthusiasm for diesels in these markets. The use of diesel engines in cars and light trucks is now limited to a few manufacturers.

Diesel engines and gasoline-power engines share several similarities. They have a number of components in common, such as the crankshaft, pistons, valves, camshaft, and water and oil pumps. Both of them are available in four-stroke combustion cycle models. However, the diesel engine and four-stroke compression ignition engine are easily recognized by the absence of an ignition system. Instead of relying on a spark for ignition a diesel engine uses the heat produced by compressing air in the combustion chamber to ignite the fuel. The systems used in diesel-powered vehicles are essentially the same as those used in gasoline vehicles.