The Honda K-series engine is a line of four-cylinder four-stroke car engine introduced in 2001. The K-series engines are equipped with DOHC valvetrains and use roller rockers on the cylinder head to reduce friction. The engines use a coil-on-plug, distributorless ignition system with a coil for each spark plug. This system forgoes the use of a conventional distributor-based ignition timing system in favor of a computer-controlled system that allows the ECU to control ignition timings based on various sensor inputs. The cylinders have cast iron sleeves similar to the B- and F-series engines, as opposed to the FRM cylinders found in the H- and newer F-series engines found only in the Honda S2000. Similar to B series, the K-series car engines have two short blocks with the same design; the only difference between them being the deck height. K20 uses the short block with a deck height of 212 mm where K23 and K24 block has a deck height of 231.5 mm. Two versions of the Honda i-VTEC system can be found on a K-series engine, and both versions can come with variable timing control (VTC) on the intake cam. The VTEC system on engines like the K20A3 only operate on the intake cam; at low rpm only one intake valve is fully opened, the other opening just slightly to create a swirl effect in the combustion chamber for improved fuel atomization. At high engine speeds, both intake valves open fully to improve engine breathing. In engines such as the K20A2 found in the Acura RSX Type-S, the VTEC system operates on both the intake and exhaust valves, allowing both to benefit from multiple cam profiles. A modified K20C engine is used in motorsport, as the Sports Car Club of America Formula 3 and 4 series that run in North America both use a K20C engine, with the Formula 4 engine not having a turbocharger. These are gaining a following in the import scene, but also among hot rodders and kit car enthusiasts, because they can be put in longitudinal rear wheel drive layouts. Another significant difference between K-series engines is the alignment of the crankshaft to the center line of the bore. The K20C1 engine block has an offset alignment. Engines that do not have their crank shaft aligned to the bore are known as Desaxe engines. On the K20C1 engine this allows the power stroke to have more leverage and less thrust waste on sidewalls.

K20

K20A (i-VTEC)

K20A Spec R engine (FD2 Civic Type R)

K20B (i-VTEC I)

K20Z (i-VTEC)

K20Z3 (as fitted to Ariel's Atom 3.5)

K20C (Earth Dreams VTEC Turbo)

K20C & K20Z (Earth Dreams i-VTEC)

K23

K23A (i-VTEC Turbo)

K24

K24A (i-VTEC)

K24A2 and K24A3 (2006-2008 Acura TSX)

K24Z & K24Y (i-VTEC)

K24W & K24V (Earth Dreams i-VTEC)

Direct Injection, i-VTEC (intake camshaft & valvetrain) Please note: The K24W1 in the 2013-2017 Honda Accord had a raised power output of 189 hp and 182 lb•ft in the Sport Trim due to a different exhaust setup.

Legacy

The Honda K-series engines have built a significant legacy, widely regarded as some of the most influential and celebrated four-cylinder engines in automotive history. The engine’s reliability and performance, coupled with its lightweight aluminium construction and chain-driven timing system, solidified its reputation as a benchmark in engine design. This engineering excellence made the K-series a revered engine amongst people, setting a new standard for four-cylinder engines. As a result, it gained widespread praise for being durable and tuneable, quickly becoming a favourite among car enthusiasts and professional tuners alike due to its potential to handle both everyday driving and high-performance applications. The K-series engine’s impact extends beyond factory specifications, with its wide adoption in the aftermarket scene. The K20 and K24 variants, in particular, are often used in engine swaps and high-performance builds due to their ability to handle and withstand significant power upgrades. This adaptability, coupled with their success in motorsports like time attack and drag racing, cemented the K-series as one of the greatest four-cylinder engines of all time. The engine remains a benchmark from its long production run to this day, continuing to influence modern engine design and tuning practices.