Cl engines induct only air during the intake process. Late in the compression process ,fuel is ejected directly in to the combusion a ^{relatively high temperature The high temperature of air serve to unite the fuel. Diesel engines are inherently stratified because of the nature of the fuel-injection. The fuel-air mixture is fuel-rich near the center of fuel-injection cone and fuci-lean in area of the combustion chamber that are farther from the filet injection cone. Unlike the combustion process in the SI engine, which occur at almost constant volume. The combustion process in the diesel engine ideally occur at constant pressure. That is, the combustion process in the CI engine is relatively slow, the fuel-air mixture continues to burn during a significant portion of the expansion stroke (fuel continues to be injected during this potion of the expansion stroke) and the high pressure that would normally result from combustion is relieved as the piston recede. After the combustion process is completed, the expansion process continues until the piston reaches BDC. Diesel may complete the five general engine process through either a 2•stroke cycle. Furthermore, the diesel may be subclassified as either an indirect injection diesel or direct injection diesel. Indirect injection (IDI) or divide chamber diesel are geometrically similar to divided chamber stratified charge SI engine. All IDI diesel operate on 4-stroke cycle. Fuel is injected in to the pre chamber and combustion is initiated by out ignition. A glow plug is also located in the prechamber, but is only used to alleviate cold start difficulties. In the I D diesel engines there is no prechamber, and fuel is injected directly in to the main chamber. The ID diesel may operate on 2-stroke or a -1-stroke cycle}