🚗 Honda Automobile Gasoline Engine Series Part Two: The Twin-Cylinder EH Series

Introduction

Honda engines are classified into four main categories: automobile series, motorcycle series, commercial power units, and aviation engines. This article focuses solely on the automobile engine series. Honda’s engines are typically categorized by the number of cylinders, with each type represented by an initial letter followed by two digits for displacement and a letter for the version. For example, the L15B7 VTC turbo engine in the 10th-gen Civic: “L” represents the four-cylinder L series, “15” indicates a 1.5-liter displacement, “B” stands for the subseries, and “7” denotes the version number. Honda has produced various mass-market engines, including inline twin-cylinder, inline three-cylinder, inline four-cylinder, inline five-cylinder, and V6 engines.

Development of the EH Engine

The previous article covered the N and EA series twin-cylinder engines, which were in production from 1967 to 1977. These were eventually replaced by a unique twin-cylinder engine derived from Honda’s 1000cc Gold Wing motorcycle engine—a horizontally opposed four-cylinder engine that was modified by removing two cylinders to create the EH engine.

Specifications:

Displacement: 545cc

Bore: 72mm

Stroke: 67mm

Compression Ratio: 9.5:1

Max Power: 28 HP at 5500 RPM (Acty), 31 HP at 5500 RPM (Today JA1)

Max Torque: 41 Nm at 4000 RPM (Acty)

Design Origin: The EH engine was developed from the Honda Gold Wing motorcycle engine and can be understood as an inline twin-cylinder machine derived from halving the 1000cc horizontally opposed four-cylinder engine. This engine powered the 1977-1988 Acty mini-truck and the 1985-1988 Today model. The Acty had 28 HP, while the Today achieved 31 HP, both fitting the requirements for Kei Car models at the time.

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Image Gallery:

1985 Today (JA1) with the EH inline twin-cylinder engine, producing 31 HP at 5500 RPM. (Image from Honda Collection Hall video)

Rare photo of an EH cylinder head, showcasing its compact layout, influenced by the horizontally opposed motorcycle engine design.

1977 Acty mini-truck, which succeeded the 1960s TN360 mini-truck, used the 545cc EH engine.

The first-generation Today (JA1) also featured the EH engine, with improved power of 31 HP and torque of 43 Nm, meeting the daily driving needs in Japan.

A Period of Growth

The 1980s in Japan were marked by significant economic prosperity, leading to advancements in both high-end and mass-market vehicles.

Transition to New Engines

In 1988, the EH engine was replaced by the three-cylinder E05A engine, which powered models like the Today and marked the beginning of a new chapter in Honda’s engine series.

Next Episode Preview

In the next installment, we will explore the E05A/E07A inline three-cylinder engines and their impact on Honda’s lineup. Thank you for reading!