The Complete Series on Honda Gasoline Engines Part 16

: Inline-Four K Series Original: Honda誌 - JDM Car Fans Magazine - 2025-04-19 11:49:45

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Previously, we covered several inline-four engines from the 1990s. These included iconic B, H, and F series models that earned their place in Honda’s engineering history. 🚗 Now, in this chapter, we begin with three "post-2000" inline-four engines.

Before diving into the K series, let’s go over its heritage. The K series is positioned as the high-end lineup among Honda's inline-four engines, replacing the previous high-performance naturally aspirated engines such as the B18C Spec R, H22A, H23A, F20B, F20C, and F22C1. It also succeeded more moderately performing engines like the H22A, H23A, B20B, F22A, and F23A with 2.0L and 2.4L K variants.

Another hallmark of the K series is the change in crankshaft rotation direction to counterclockwise, meaning the engine is mounted on the right side when facing the direction of travel. ⚡ This reversed orientation benefits drivetrain packaging and enables a more optimal front-wheel-drive layout in certain platforms.

The ignition system also evolved. Traditional distributors and high-voltage wires were replaced with coil-on-plug electronic ignition. The ECU now controls ignition timing based on input from multiple sensors, enabling more precise and efficient performance.

Like the B series, K engines come in two block heights: K20 is 212mm, while K23 and K24 are 231.5mm.

K series engines debuted on October 26, 2000, and were first equipped in the 2001 Integra Type R (DC5). 🏁 In 2015, the K20C1 was introduced in the ninth-generation Civic Type R (FK2) and remains in production today.

The first engine in this lineup was the DOHC i-VTEC K20A. Its signature red valve cover leaves no doubt about its performance orientation—only engines with a specific output of 100hp per liter or more received this treatment.

The K series is most known for its i-VTEC system. It builds upon Honda’s legendary DOHC VTEC by adding a VTC (Variable Timing Control) unit to the intake camshaft. This system can adjust valve timing by up to ±30°, improving responsiveness and fuel efficiency. 🔧

Not all K series engines have VTEC on both camshafts. High-performance versions usually feature i-VTEC on both intake and exhaust. In contrast, lower-output versions like the K20A3 have i-VTEC only on the intake side. These engines operate as 12-valve at low rpm and switch to 16-valve at higher rpm for better efficiency and power.

The K20A, launched in 2000, immediately garnered attention, surpassing even the F20C of the S2000 in recognition. It formed the basis for future models like the Euro-R (CL7) and the eighth-gen Civic Type R (FD2). Its export version, the K20A2, also delivered a robust 200hp.

Lower-output K20 engines like the K20A1, A3, A4, and A6 were tuned for efficiency, with compression ratios below 10:1 and outputs between 150–160hp.

The K20Z line, introduced in 2005, also featured high- and low-performance variants. The K20Z1 produced 210hp, while K20Z3 and Z4 reached 200hp. Only K20Z2 was lower output, rated at 153hp.

In 2003, Honda introduced the K20B with i-VTEC and direct injection (indicated by the lowercase "i"). It achieved lean-burn performance with an air-fuel ratio of up to 65:1. It powered the Honda Stream (RN5) with 156hp and 188Nm torque.

FD2 Type R's K20A is considered the most powerful naturally aspirated K-series engine, delivering 225hp at 8000rpm and 215Nm at 6100rpm. 🔥

The red-letter K20Z3 engine, used in the US-market eighth-gen Civic Si (FG2), made 197hp and 188Nm.

The K23A1 was the first factory turbocharged K engine. Debuting in 2007 in the Acura RDX, it featured a Mitsubishi TD04HL turbo producing ~1.1 bar of boost, generating 240hp and 350Nm torque. 💨

The 2.4L K24 line includes K24A, K24Z, K24Y, and K24W, used in mid-size cars like Accord, CR-V, Odyssey, and Element. All share an 87mm bore and 99mm stroke.

The K24A2 in Japan's Odyssey Absolute made 200hp. In the US Acura TSX, it hit 205hp. The K24Z7 found in the ninth-gen Civic Si made 205hp with an 11:1 compression ratio and a 6-speed manual. 🇯🇵

The latest K20 variant is the K20C. Introduced in the FK2 Civic Type R in 2015, it pairs turbocharging with direct injection. The K20C1 remains in use today. 🏎️ K20C2 is a naturally aspirated version making 158hp, used in US-market Civics and Formula 4 race cars.

The K20C3 powers the Chinese-market Avancier and UR-V, with 272hp and 370Nm torque. Though heavy vehicles, the engine offers tantalizing tuning potential. Notably, only the exhaust cam in the K20C features VTEC.

K20A was retired in 2011, K20B in 2006, and K20Z in 2015. Currently, only the K20C line remains. The sole K23 ended in 2012. Some K24 variants remain, though the L series is gradually replacing them.

📌 Stay tuned for the next installment in our Honda engine series!

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