Turbochargers have become very popular on passenger cars since the first mass-produced turbocharged passenger cars were put on market in Japan in 1979. Turbo lag is one of the most serious problem since the first mass-production started.Several new technologies such as a variable geometry turbocharger, ceramic turbocharger, etc. have been introduced to improve acceleration performance. A variable geometry turbocharger changes the area of gas flow passage and increases exhaust gas speed at low engine speed. A ceramic turbocharger reduces inertia moment of a turbine wheel and shaft.Turbocharger mechanical efficiency has equal importance as compressor efficiency and turbine efficiency.This paper describes the test results of ball bearing turbochargers developed at our company.