The following changes are applied based on the previous 4G63-SOHC engine.

    The cylinder head is made of an aluminum alloy that is lightweight and offers outstanding cooling efficiency.
The combustion chamber is of the pent-roof type. The two intake and two exhaust ports are in a cross-flow arrangement. There is a squish area provided in the combustion chamber which promotes turbulence, further mixing of the air-fuel mixture and more efficient combustion.
The spark plugs are located at the center of the combustion chambers.
The camshaft bearings are placed at six locations on intake side, and six on the exhaust side.

    A single timing belt drives both camshafts and the oil pump.
An auto tensioner absorbs changes in timing belt tansion for less noise and longer life of timing belt.
All sprockets are made of a sintered alloy.
All sprocket are made of a sintered alloy with the aligning mark for the timing.

    An oil jet to cool the piston is equipped at the main bearing between cylinder in the cylinder block. Oil jets out when the pressure of the oil led out of the oil opening of main bearing rises above 196 kPa.

    The cylinder head gasket is designed to improve the sealability by using a 5-layer type metal gasket.

    The counter balance shaft is designed to be lightweight by adopting the counter balance shaft shown in the figure below.

By applying ion plating on the oil ring surface, the piston ring is designed to reduce friction and to improve durability reliability.