Mazda K engine

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The Mazda K-series automobile engine is a short stroke 60° 24-valve V6 with belt-driven DOHC and all-aluminium construction. Displacements range from 1.8 L to 2.5 L. They all use a 27-degree DOHC valvetrain with directly actuated hydraulic bucket lifters. The K-series also features a highly rigid aluminum split-crankcase engine block design with 4-bolt mains with additional bolts securing the lower block, an internally balanced forged steel crankshaft with lightweight powder forged carbon steel connecting rods. They were designed with the intent of being as compact as possible for short-hood front-wheel drive applications. One unique innovation of the K-series was the introduction of Variable Resonance Induction System (VRIS). Based on the Helmholtz resonance principle, the intake manifold is equipped with 3 chambers tuned to a specific resonant frequency. The computer dynamically switches between each resonant chamber to achieve the appropriate resonant frequency for the engine's rpm. This effect optimizes volumetric efficiency over a given rpm range to provide maximum torque over the entire rpm range. VRIS is used on the K8, KF, and KL but nearly all modern Mazda V6s are now using this technology. The K-series all have a 7,000 rpm redline with 7500-7800 rpm limiter, which given the engine design is conservative. The KJ-ZEM Miller cycle engine had a 6,000 rpm redline, but was only available with an automatic transmission.