The 2.5 L (2497 cc) KL family uses an 84.5 mm bore and 74.2 mm stroke. It includes the Japan-only KL-ZE, which produced 199 hp (149 kW) and 165 ft·lbf (224 Nm). Another variant, the KL-DE (also known as the KL-03 outside the USA, and fitted to 2.5 litre Ford Probes) was the worldwide version, with 164-174 hp in various applications. In 1998 a revised version of the KL known as the KL-G4 was used in the 626. It featured solid lifters, a cast crankshaft to reduce rotating mass and a reworked intake system. The distributor was replaced with a Ford EDIS coil-pack ignition.

Mazda introduced a key technology with these engines, known as the Variable Resonance Induction System (VRIS). A series of two butterfly valves coupled with electronically controlled actuators varied the volume and length of a resonant chamber attached to the intake manifold, producing 4 resonant frequencies. The valves actuate at particular engine frequencies (i.e. RPMs) to produce optimal torque/horsepower output at any given engine speed.