# Mitsubishi Orion engine
The Mitsubishi Orion engine, also called the 4G1 series, is a family of inline-four gasoline internal combustion engines produced by [Mitsubishi Motors](https://www.edgepedia.org/mitsubishi-motors), first fitted in the Colt and Colt-derived models in 1978, with displacements from 1.2 L to 1.6 L.[1](https://www.youtube.com/watch?v=5bvVnJtk1sY) It was introduced in the 1970s alongside the Astron, Sirius, and Saturn engine families, and was designed to replace the earlier Neptune (4G4x) series.[1](https://www.youtube.com/watch?v=5bvVnJtk1sY) • [2](https://mitsipedia.info/index.php/Orion)
| Key fact | Detail |
|---|---|
| Family | Inline-four gasoline engines, 4G1 series, introduced in the 1970s with the Astron, Sirius, and Saturn families[1](https://www.youtube.com/watch?v=5bvVnJtk1sY) |
| First application | Colt and Colt-derived models, 1978[1](https://www.youtube.com/watch?v=5bvVnJtk1sY) |
| Displacement range | 1.2 L to 1.6 L across the family[1](https://www.youtube.com/watch?v=5bvVnJtk1sY) |
| Predecessor | Replaced the Neptune (4G4x) series[2](https://mitsipedia.info/index.php/Orion) |
| Notable variant | 4G12 Modulated Displacement (MD), 1982, cylinder deactivation[2](https://mitsipedia.info/index.php/Orion) |
| Valve layouts | SOHC 12-valve, SOHC 16-valve, and DOHC variants[3](https://assets.website-files.com/65e87c59c173c4626d91c75a/67b3aed503f9c3d795d87fa1_38597566019.pdf) |
| Largest member | 4G18, 1.6 L, manufactured 1998 to 2012[4](https://engineguide.wiki/mitsubishi/engine-mitsubishi-4g18/) |
## Design and variants
The 4G1 series covers several displacements identified by engine codes, including the 4G13, 4G15, and 4G18, and was offered in SOHC 12-valve, SOHC 16-valve, and DOHC configurations.[5](https://cargeek.org/engines/mitsubishi-4g1) • [3](https://assets.website-files.com/65e87c59c173c4626d91c75a/67b3aed503f9c3d795d87fa1_38597566019.pdf) The 4G15 has a bore of 75.5 mm, and the 12-valve version, with two intake and one exhaust valve per cylinder, displaced 1,468 cc and entered production in 1989 for the third-generation Mirage and Lancer, available with either a carburetor or fuel injection.[6](https://manualzz.com/doc/60165077/mitsubishi-4g1-series--4g13--4g15--4g18-user-manual) The 4G15 is among the [Mitsubishi](https://www.edgepedia.org/mitsubishi) engines that use a timing belt rather than a timing chain.[7](https://faq.mitsubishi-motors.co.jp/faq/show/3448?back=front%2Fcategory%3Ashow&category_id=8&page=18&site_domain=default&sort=sort_access&sort_order=desc)
The largest member of the family is the 4G18, a 1.6-liter gasoline engine manufactured in Japan between 1998 and 2012.[4](https://engineguide.wiki/mitsubishi/engine-mitsubishi-4g18/)
## Modulated Displacement: early cylinder deactivation
**Cylinder deactivation.** In 1982 Mitsubishi developed the 4G12 Modulated Displacement (MD), which has been described as the world's first engine with cylinder deactivation technology.[2](https://mitsipedia.info/index.php/Orion) The system allowed a four-cylinder engine to run on two cylinders under light load, improving fuel economy at a time before the technique became widespread.[2](https://mitsipedia.info/index.php/Orion)
The engineering was documented in an SAE technical paper, "Mitsubishi Orion-MD: A New Variable Displacement Engine," presented by T. Fukui and colleagues at the Passenger Car Meeting & Exposition in [Dearborn, Michigan](https://www.edgepedia.org/dearborn-michigan), on June 6, 1983. The paper describes a 1.4-liter, four-cylinder variable-displacement engine developed as an optional powerplant for a subcompact passenger car.[8](https://saemobilus.sae.org/papers/mitsubishi-orion-md-a-new-variable-displacement-engine-831007)
## MVV lean-burn version
In October 1991, the new Mirage and Lancer models were fitted with the 4G15 engine using the MVV (Mitsubishi Vertical Vortex) system, a combustion design in which a vertical vortex, a tumbling flow aligned with the cylinder axis, organizes the air-fuel mixture for lean combustion.[9](https://www.mitsubishi-motors.com/jp/company/history/company/)
## Use in Proton vehicles
Malaysia's Proton used Orion-family engines in its cars. The Mitsubishi 4G91 1.5 DOHC engine became a popular halfcut transplant among Wira owners, but only a very small number of export-specification Wiras left Proton's factory with this engine installed.[10](https://www.carlist.my/news/orion-to-campro--a-brief-history-of-proton-s-engines-60684/60684/) Proton's engine history later moved from these Mitsubishi designs toward its own Campro engines.[10](https://www.carlist.my/news/orion-to-campro--a-brief-history-of-proton-s-engines-60684/60684/)
## Later developments
The family continued in production into the 2000s with multi-point injection versions such as the 4G13 and 4G18 16-valve MPI engines, which use a pressure-feed lubrication system with full-flow filtration.[11](https://www.valvulita.com/sites/default/files/manual_de_servicio_mitsubishi_4g13_4g15_4g18_0.pdf) Later 4G15 variants included MIVEC, Mitsubishi's variable valve timing technology, and the 4G15 MIVEC cylinder head has been used in engine swaps replacing the earlier SOHC 4G15.[12](https://www.api.motion.ac.in/jriunde/53I058B/milictk/78I7681B15/mitsubishi%2Blancer%2B4g15%2Bengine%2Bmanual.pdf)
## References
1. [Mitsubishi Orion engine, Audiopedia video description](https://www.youtube.com/watch?v=5bvVnJtk1sY)
2. [Orion, Mitsipedia](https://mitsipedia.info/index.php/Orion)
3. [4G1 Engine Series workshop manual, specifications section](https://assets.website-files.com/65e87c59c173c4626d91c75a/67b3aed503f9c3d795d87fa1_38597566019.pdf)
4. [Engine Mitsubishi 4G18, EngineGuide](https://engineguide.wiki/mitsubishi/engine-mitsubishi-4g18/)
5. [Mitsubishi 4G1 (Orion) engine: specifications, cars fitted and common faults, CarGeek](https://cargeek.org/engines/mitsubishi-4g1)
6. [Mitsubishi 4G1 Engine User Manual, Manualzz](https://manualzz.com/doc/60165077/mitsubishi-4g1-series--4g13--4g15--4g18-user-manual)
7. [Mitsubishi Motors FAQ: timing belt or timing chain by engine model](https://faq.mitsubishi-motors.co.jp/faq/show/3448?back=front%2Fcategory%3Ashow&category_id=8&page=18&site_domain=default&sort=sort_access&sort_order=desc)
8. [Fukui, T., Nakagami, T., Endo, H., Katsumoto, T., et al., "Mitsubishi Orion-MD: A New Variable Displacement Engine," SAE 831007, 1983](https://saemobilus.sae.org/papers/mitsubishi-orion-md-a-new-variable-displacement-engine-831007)
9. [会社の歴史（三菱自動車の歴史）, Mitsubishi Motors](https://www.mitsubishi-motors.com/jp/company/history/company/)
10. [Orion to Campro: A Brief History of Proton's Engines, Carlist.my](https://www.carlist.my/news/orion-to-campro--a-brief-history-of-proton-s-engines-60684/60684/)
11. [Mitsubishi 4G13/4G15/4G18 service manual, General Information](https://www.valvulita.com/sites/default/files/manual_de_servicio_mitsubishi_4g13_4g15_4g18_0.pdf)
12. [Mitsubishi Lancer 4G15 Engine Manual](https://www.api.motion.ac.in/jriunde/53I058B/milictk/78I7681B15/mitsubishi%2Blancer%2B4g15%2Bengine%2Bmanual.pdf)
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*Topic: Encyclopedia › Technology and the built world › Transport and spaceflight › Road transport › Automobiles › Automobile engines › Japanese engines*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 15, 2026 · Edited: Sep 30, 2026; Oct 15, 2026; Oct 25, 2026 · Last review: Oct 15, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license