High Quality Content by WIKIPEDIA articles! The Toyota ZZ engine family is a straight-4 piston engine series. The ZZ series uses an aluminum engine block and aluminum DOHC 4-valve cylinder heads, a first for Toyota. The camshafts are chain-driven. The two 1.8 L members of the family, the 1ZZ and 2ZZ, use different bore and stroke. The former was optimized for economy and torque, while the latter is a "square" design optimized for high-RPM power. The ZZ family replaced the extremely popular cast-iron 4A engines.