The 2.5 L (2497 cc) KL family uses an 84.5 mm (3.33 in) bore and 74.2 mm (2.92 in) stroke. It includes the Japan-only KL-ZE, which produced 200 bhp(149 kW) and 165 lb·ft (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 bhp 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 within the intake manifold. The valves actuate at particular engine frequencies (i.e. rpms) to produce optimal torque/horsepower output at any given engine speed. The valve operates to create three specific first-order resonant frequencies that increase cylinder air charge. All three resonances are used from 0 to 6250 rpm (6800 for the KL-ZE). Above that threshold, the first primary resonant chamber is again used, but at this engine speed the pressure wave from the second-order resonant frequency aids in charging the cylinder.