This change allows the exhaust port velocity to more effectively scavenge the cylinder and reduce reversion pulses to enhance induction.

Later it was also available on low-end model 910 Bluebirds for the Japanese domestic market and some light Nissan commercial vehicles in a single-plug configuration.

Reference specifications (twin plug): Car models: The Z16E is an EFI version of the Z16S, fitted with Nissan's EGI system.

The Z18 was also available in some of the commercial vehicle engine lineups; those models were of a single plug cylinder head design.

Reference specifications: Car models: The Z18E is a 1.8 L (1,770 cc) fuel-injected engine produced primarily for the Japanese market.

Most specs were the same as those of the Z18, but maximum power increased to 115 PS (85 kW; 113 hp) (SAE) at 6,200 rpm in 1980 (Bluebird, Skyline).

All NAPZ engines sold in California reportedly had dual plug heads regardless of the year.

Beside the fuel-injection, a significant change for the Z24i was the addition of an optical crank angle sensor in the distributor rather than a vacuum advance and ignition module.

This allowed the JECS throttle-body injection system to identify the top dead center (TDC) of cylinder number one.