144 Auto Engine Repair Copyright by Goodheart-Willcox Co., Inc. Throttle body Intake manifold Hydraulic rocker arm Camshaft Camshaft sprocket Timing belt cover Oil pan Timing belt Balance shaft Exhaust valves Exhaust manifold Valve cover Figure 6-39. This is a modern, inline, four-cylinder, 16-valve engine. It has hydraulically controlled rocker arms that can shift to use different camshaft lobes on the intake camshaft. One set of camshaft lobes has profiles for low-speed efficiency, the other set has profiles for high-speed power and fuel economy. Note the use of a balancer shaft in this engine. (Honda) chemicals are combined or altered to produce water and electrons (electrical energy). The electrical energy from the fuel cell can then be used to operate large electric motors that propel the vehicle. Theoretically, fuel cells can convert hydrogen into electricity with very high efficiency. A fuel cell is made of a plastic, gas-permeable membrane coated with a catalytic foil, usually made of platinum. This membrane is sandwiched between two electrode plates. Hydrogen gas flows through the anode plate (negative electrode) and the membrane while compressed air flows the other way. The catalyst causes the hydrogen gas to separate into positive hydrogen ions and electrons. This causes a potential difference of elec- trical energy across the anode and cathode (positive elec- trode). When current is drawn out of the fuel cell, oxygen molecules separate and combine with hydrogen ions to form water and heat. Note: Some fuel cell designs derive the needed hydrogen from gasoline. Engines Figures 6-39 through 6-44 show several typical auto- motive engines. Study each carefully. Note the design varia- tions between the different types. Also, study the names of all of the parts. This will help you in later chapters as you continue to learn more about engines. Summary Cylinder arrangement refers to the position of the cylinders in the engine block in relation to the crankshaft. The four common cylinder arrangements are inline, V-type, W-type, and opposed. An inline engine has cylinders positioned one after the other in a straight line. A V-type engine looks like the letter V when viewed from the front or rear. A W-type engine is similar to a V-type engine, but with staggered cylinders. An opposed engine has two banks of cylinders that lay flat or horizontal on each side of the crankshaft.