The Complete Series on Honda Gasoline Engines: Part 18 – The Inline-4 R Series Original: Honda Magazine

The Complete Series on Honda Gasoline Engines: Part 18 – The Inline-4 R Series
Original: Honda Magazine | Date Updated: 2024-11-25

🌟 Hello, my friend...
Welcome to a hidden gem—OLD FISHER DISCOUNT, your one-stop online shop with 9,999+ unique finds waiting for you. 🎉
🛒 Explore a World of Discoveries
Dive into our collection and uncover special treasures that will delight and inspire.
🔗 Start Your Journey Here: www.fisherdiscount.com
Come and see why we’re more than just a shop; we’re a place of endless possibilities! ✨

Last time, we delved into the L series engines. Now, let’s wrap up this series with the R series—the penultimate chapter in Honda’s engine history, as the latest P series was already discussed during the 3-cylinder engines feature. The R series is designed for use in C-segment and D-segment vehicles, succeeding the D17A and B20B engine lines. Although the R series achieved massive sales, it has little association with high-performance tuning. Production in Japan ceased in September 2019, and other regions are also reaching the "end of the line."

Overview of the R Series Engines
The R series features an aluminum alloy cylinder block with SOHC 4-valve configurations. It integrates Honda’s i-VTEC system, which switches between the Miller and Otto cycles to achieve high power output and fuel efficiency. During low-load operation in the Miller cycle, the intake valve closes slowly using a high-lift cam profile. This pushes some of the air-fuel mixture back, reducing the compression ratio while maintaining the expansion ratio, thereby minimizing heat efficiency losses. This marked Honda’s first implementation of the Miller cycle in its engines.

The ignition system mirrors that of the K series, employing ECU-controlled individual ignition coils.

Key Features and Variants of the R Series

R18A2: Found in the European Civic FN1, its standout feature is the integrated exhaust manifold within the cylinder head, directly connecting to the catalytic converter.
Right-hand Orientation: The R series reversed the engine orientation and crankshaft rotation, positioning it on the right-hand side for better weight distribution in left-hand-drive vehicles.
Released on September 28, 2005, the first R18A engine powered the 8th-generation Civic (FD1 and FA1). Available in 1.6L, 1.8L, and 2.0L versions, all variants shared an 81mm bore. Stroke measurements were 77.4mm (1.6L), 87.3mm (1.8L), and 96.9mm (2.0L).

Performance and Applications

R16A: Primarily built for Singapore’s 8th-generation Civic FD4, this special edition engine produced 125 hp at 6,300 rpm and 15.4 kg-m of torque at 4,300 rpm.
R18A: Delivering 140 hp at 6,300 rpm and 174 Nm of torque, it powered models like the Civic, City, and Stream. Variants like R18A1 and R18A2 catered to specific regions, with the latter being a Europe-exclusive offering.
R20A: Launched on July 13, 2006, it powered models such as the Accord (CP1), CR-V (RM1), and Acura ILX (DE1). With a compression ratio of 10.6:1, it produced 156 hp at 6,300 rpm and 19.3 kg-m of torque.
The engine also incorporated balance shafts and a three-stage variable intake manifold.

The End of an Era

By 2019, the R series engines had ceased production in Japan, giving way to the turbocharged L series. While innovations like the Miller cycle were commendable, the R series was overshadowed by Honda's more advanced turbocharged K20C and L15B engines.