<div class="htmlview paragraph">This paper describes the progress of IDI diesel engine for passenger car.</div> <div class="htmlview paragraph">There are two options of direct-injection(DI) and indirect-injection(IDI) type for diesel engines.</div> <div class="htmlview paragraph">IDI-engines have been mainly used for diesel passenger car for a long time. In recent years, in order to reduce CO₂ and fuel consumption, DI engine for passenger car have been developed. Convential IDI engine have, generally speaking, 15 percent worse fuel economy while it has better potential of exhaust emissions, combustion noise and cabin heater performance than DI engines for passenger car.</div> <div class="htmlview paragraph">The possibility of fuel economy (CO₂) improvement in IDI diesel engine has been persued in a single cylinder engine.</div> <div class="htmlview paragraph">It was found that high pumping rate of injection system gives excellent fuel economy at high engine speed because of shorter injection duration without increase of exhaust emissions, though it gives a slightly worse fuel economy and HC at low speed.</div> <div class="htmlview paragraph">From cylinder pressure analysises the better SFC level by use of high pumping rate is proved to be more rapid combustion.</div>