Daihatsu Develops 658cc Ammonia Engine for Kei Cars

The Daihatsu 658cc ammonia engine is an experimental internal combustion engine developed by Daihatsu Motor Co. under parent company Toyota Motor Corporation's Multi-Pathway emissions strategy. Designed around a three-cylinder kei car displacement architecture, the prototype addresses automotive carbon emissions by using carbon-free liquid ammonia fuel alongside onboard-cracked hydrogen to sustain combustion. For the Malaysian automotive ecosystem, where Daihatsu acts as technical partner and shareholder in national carmaker Perodua (Perusahaan Otomobil Kedua Sdn Bhd), this research offers a direct preview of potential zero-carbon alternatives to battery electric vehicles for compact, mass-market city cars navigating tropical urban centres such as Kuala Lumpur.

Key Facts

The technical specifications and developmental attributes of the Daihatsu ammonia engine define its displacement class, operational mechanics, and current research milestones as showcased to the automotive industry.

The prototype 658cc inline-three powerplant relies on a single ammonia fuel tank and onboard conversion hardware rather than an independent high-pressure hydrogen cylinder.

How Does the Daihatsu Ammonia Engine Generate Hydrogen?

The Daihatsu 658cc engine operates by storing liquid ammonia in a standard vehicular tank and converting a fraction of it into hydrogen gas during vehicle operation. This eliminates the requirement for heavy, specialised secondary hydrogen storage tanks by using a combined square plasma reactor and a catalytic converter unit positioned directly atop the engine cylinder block.

According to technical documentation reported by Motor Fan Japan and cited by Autoblog, cold starts rely on electrical power to generate initial hydrogen from ammonia via the compact square plasma reactor. Once the assembly achieves required operating temperatures, thermal production transitions to the larger catalytic converter unit to supply higher volume hydrogen flow rates into the combustion chamber to burn alongside the ammonia.

Ammonia is better known as a raw material for producing agricultural fertiliser. However, the substance is also gaining attention as a hydrogen carrier because it is easier to store and transport than hydrogen itself.

Careta (reporting on Daihatsu technical exhibits at Japan Mobility Show 2026 Bizweek)

Daihatsu integrates an engine-mounted plasma reactor and catalytic cracking converter to generate combustible hydrogen gas directly from stored ammonia during operation.

What Are the Primary Technical Challenges of Ammonia Combustion?

The primary developmental challenges confronting Daihatsu's ammonia engine involve toxic exhaust emissions and physical packaging limitations. Burning ammonia generates nitrogen oxides (NOx), while incomplete combustion risks releasing unburnt ammonia and nitrous oxide (N₂O)—a potent greenhouse gas—alongside packaging assemblies that currently exceed the standard dimensional confines of compact passenger vehicles.

Daihatsu engineers note that while the core 658cc block fits kei vehicle specifications, the auxiliary plasma reactor, catalytic converter, and emissions abatement hardware add substantial physical bulk. Commercial viability requires significant reduction of these secondary assemblies to fit compact engine bays, such as those found in sub-1.0-litre Asian commuter vehicles, alongside advanced selective catalytic reduction to neutralise harmful N₂O and NOx emissions before commercial vehicle rollouts.

Incomplete combustion of ammonia produces dangerous greenhouse emissions including nitrous oxide (N₂O) alongside toxic unburnt ammonia, necessitating advanced exhaust abatement systems.

How It Compares for Malaysian Users

For Malaysian motorists residing in high-density urban settings such as Klang Valley apartments or condominiums, ammonia-fuelled combustion engines offer an alternative zero-carbon path that circumvents domestic electric vehicle charging constraints. Landed homes frequently accommodate private wallbox chargers, but high-rise residents facing shared infrastructure bottlenecks could theoretically utilise existing liquid fuel distribution networks adapted for ammonia.

Malaysia's year-round ambient temperatures averaging 32°C and humidity exceeding 80% impose severe thermal stress on high-voltage battery powertrains. Ammonia contains zero carbon molecules, producing zero tailpipe carbon dioxide (CO₂) without relying on imported rare-earth battery packs. However, because ammonia retail distribution, Sirim safety standards for passenger-grade ammonia tanks, and local pricing in RM (Ringgit Malaysia) do not yet exist, the technology remains strictly developmental for domestic road users.

Ammonia fuel technology provides a zero-carbon combustion route that circumvents the residential charging and grid-capacity hurdles common across Malaysian high-rise condominiums.

Common Questions

Does the Daihatsu ammonia engine require a separate hydrogen fuel tank?

No, the vehicle does not require a standalone hydrogen storage tank. The engine carries only liquid ammonia in its fuel tank, extracting the necessary hydrogen onboard through a small plasma reactor and catalytic converter while the vehicle operates.

Can this 658cc ammonia engine fit inside current compact cars?

Not yet. While the 658cc engine block itself is sized for compact kei cars, the developmental hydrogen-cracking reactors and catalytic units are currently too bulky to fit standard subcompact engine bays, requiring further miniaturisation.

Does burning ammonia produce zero harmful exhaust emissions?

No. While burning ammonia releases zero carbon dioxide (CO₂), it can generate harmful nitrogen oxides (NOx). Incomplete combustion can also produce toxic unburnt ammonia and nitrous oxide (N₂O), which is a potent greenhouse gas.

Sources and Methodology

This technical analysis synthesises reporting from the automotive publication Careta ("Daihatsu Bangunkan Enjin 658 cc Guna Ammonia", published by Qalif Latif on 15 October 2026), alongside referenced technical disclosures from Motor Fan Japan and Autoblog regarding the Japan Mobility Show 2026 Bizweek. All non-English technical descriptions were translated into British English, preserving official automotive terminology and Japanese kei car classification metrics. No commercial retail prices in RM (Ringgit Malaysia) or local warranty details have been established by Malaysian distributor networks, as the powertrain remains a pre-commercial prototype. This article was last updated on 15 October 2026. Information specific to Malaysia was verified against local automotive regulatory classifications and housing infrastructure contexts.