Chapter 6 Engine Types and Classifi cations 129 Copyright by Goodheart-Willcox Co., Inc. A B C Injector Intake manifold Fuel spray into throttle body air horn Fuel in Cylinder head Cylinder head Air in Throttle body To computer Intake valve Intake manifold Intake manifold Fuel sprays into combustion chamber Fuel spray into intake port Only air passes through throttle body and inlet to intake Injector Injector Air in Fuel in Fuel in Air in Only air passes through throttle body and inlet to intake Figure 6-6. A—In a throttle body injection system, the fuel injec- tor is located in the throttle body. B—In a multiport fuel injection system, injectors are located in front of each intake valve. C—In direct injection systems, the fuel injector is located in the cylin- der head. B Pancake Wedge Hemispherical Pent-roof A C D Figure 6-7. There are four basic combustion chamber shapes. A—Pancake combustion chamber. B—Wedge combustion chamber. C—Hemispherical combustion chamber. D—Pent- roof combustion chamber. This type is common in four- valves-per-cylinder cylinder heads. (Chrysler) Combustion Chamber Shape There are four basic combustion chamber shapes for gasoline engines. These are pancake, wedge, hemispherical, and pent-roof, Figure 6-7. The pancake combustion chamber, also called bathtub chamber, has valve heads almost parallel with the top of the piston. The chamber forms a flat pocket over the piston head, Figure 6-7A. This is an older, less-common combus- tion chamber design. A wedge combustion chamber, also called a wedge head, is shaped like a triangle or wedge when viewed from the side, as in Figure 6-7B. Valves are placed side-by-side with the spark plug next to the valves.