Subaru CB engine

The CB engine was first introduced in August 2020 with the second-generation Levorg.{{cite news |url=https://www.autoblog.com/2020/08/20/subaru-levorg-official-reveal-wrx-preview/ |title=Subaru Levorg, also known as the WRX's wagon cousin, revealed in production form |author=Stocksdale, Joel |date=August 20, 2020 |website=Autoblog |access-date=2 September 2020}}{{cite news |url=https://paultan.org/2020/08/21/2020-subaru-levorg-officially-debuts-in-japan-sgp-platform-new-1-8l-turbo-boxer-engine-and-eyesight-x/ |title=2020 Subaru Levorg officially debuts in Japan – SGP platform; new 1.8L turbo boxer engine and EyeSight X |author=Lye, Gerard |date=August 21, 2020 |work=paultan.org |access-date=2 September 2020}} According to Subaru, CB stands for Concentration/Compact Boxer.{{cite news |url=https://car.watch.impress.co.jp/docs/news/1273449.html |lang=ja |title=スバル、新開発水平対向エンジン「CB18型」の疑問点を確認 「EJ20時代の強度剛性思想を採用」 |trans-title=Subaru answers questions about the newly developed boxer engine 'CB18': 'Adopts the strength and rigidity concept of the EJ20 era' |author=Tanikawa, Kiyoshi |date=August 28, 2020 |work=Car Watch |access-date=6 April 2021}} It is the fourth-generation boxer engine family from Subaru.{{cite web |url=https://www.subaru.jp/brand/technology/technology/driving_boxer.html |title=テクノロジー：DRIVING {{!}} 水平対向エンジン |trans-title= Technology: Driving {{!}} Horizontally opposed engine |lang=ja |publisher=Subaru of Japan |access-date=6 April 2021}} Compared to the preceding FB series, the CB is shorter; the bore pitch (centerline to centerline spacing between adjacent cylinders) has decreased from {{cvt|113.0|to|98.6|mm|abbr=on}} and the overall crank length has decreased from {{cvt|350.5|to|315.9|mm|abbr=on}}.{{cite news |url=https://car.watch.impress.co.jp/docs/news/1273157.html |lang=ja |title=スバル、新型レヴォーグのCB18エンジンは熱効率40％ λ＝2のリーン燃焼やオフセットシリンダー採用 |trans-title=Subaru's new Levorg CB18 engine uses lean combustion with a thermal efficiency of 40%, λ=2, and an offset cylinder |author=Tanikawa, Kiyoshi |date=August 27, 2020 |work=Car Watch |access-date=6 April 2021}}

For the first time in a Subaru engine, the centerlines of the cylinder bores do not intersect with the crankshaft axis; instead, there is a crank offset of {{cvt|8|mm|abbr=on}}. This offset reduces friction during the piston downstroke. Overall thermal efficiency is 40% due to the adoption of lean-burn combustion with an excess air ratio (λ) of 2. The injector is positioned next to the spark plug in the center of the combustion chamber to ensure the lean mixture will ignite reliably. A small single-scroll turbocharger was equipped to maintain charge air volume and improve throttle response.

The connecting rods in the CB engine are split horizontally, like those in the second generation EJ engines.{{cite web |url=https://www.subaruparts.com/oem-parts/subaru-connecting-rod-12100aa201 |title=Connecting Rod — Subaru (12100AA201) [EJ22] |website=Subaru Parts |access-date=6 April 2021}} The third generation FB/FA connecting rods are split diagonally{{cite web |url=https://www.subaruparts.com/oem-parts/subaru-connecting-rod-12100aa470 |title=Connecting Rod — Subaru (12100AA470) [FB25] |website=Subaru Parts |access-date=6 April 2021}} (also called an offset or asymmetrical connecting rod) to allow a longer piston stroke without increasing the width of the engine,{{cite web |url=http://www.caranddriver.com/news/subaru-fb-series-engine-subaru-flat-four-engines |title=Examining Subaru's New FB-series Flat-Four |last=Colwell |first=K.C. |date=January 2011 |work=Car and Driver |publisher=Hearst Corporation |access-date=15 April 2011}} but the horizontally-split connecting rods are stronger.

The first engine in the series is designated CB18, a 1.8 litre dual overhead cam 16-valve engine featuring dual AVCS with gasoline direct injection and a turbocharger.{{cite web |url=https://www.subaru.jp/levorg/levorg/content/spec/pdf/new_levorg_specifications.pdf |title=スペック |trans-title=Specifications |website=Subaru of Japan |access-date=2 September 2020}} Compared to the FB16 used in the previous generation of the Levorg, the CB18 offers decreased fuel consumption ({{cvt|16.6|km/L|mpgUS|abbr=on}} for the CB18 and {{cvt|16.0|km/L|mpgUS|abbr=on}} for the FB16, both using the JC08 mode) and increased torque ({{cvt|300|Nm|kgm lbft|abbr=on}} for the CB18 and {{cvt|250|Nm|kgm lbft|abbr=on}} for the FB16). In addition, the CB18 achieves its peak torque at a lower engine speed. Engine weight of the CB18 has been reduced by {{cvt|14.6|kg|abbr=on}} compared with the FB16.

In October 2020, Subaru announced the CB18 also would be fitted to the top-of-the-line 'Sport' trim of the 5th generation Subaru Forester in the Japanese market; other models of the Forester are equipped with the mild hybrid FB20D e-BOXER.{{cite press release |url=https://www.media.subaru-global.com/ja/news/3019 |title=ＳＵＢＡＲＵ 「フォレスター」改良モデルを発表 |lang=ja |trans-title=SUBARU 'Forester' improved model announced |date=October 22, 2020 |publisher=Subaru Global Media |access-date=6 April 2021}}

The CB18 engine is also fitted to the Subaru Legacy Outback for the Japanese market.{{cite press release |url=https://www.media.subaru-global.com/ja/news/3154 |title=SUBARU 新型「レガシィ アウトバック」を発表 |trans-title= SUBARU announces new 'Legacy Outback' |lang=ja |date=October 7, 2021 |publisher=Subaru Global Media |access-date=8 November 2021}}{{cite web |url=https://www.subaru.jp/legacy/outback/spec/index/ |title=Subaru Legacy Outback Main equipment list (Japanese) |access-date=9 September 2021}}

In April 2022, Subaru had to suspend production of Forester, Outback and Levorg after it discovered a sensor in CB18 engine malfunctioned.{{cite news |title=Subaru Suspends Shipment of Some Models Due to Engine Sensor Malfunction — Media |url=https://money.usnews.com/investing/news/articles/2022-04-14/subaru-suspends-shipment-of-some-models-due-to-engine-sensor-malfunction-media |access-date=15 April 2022 |agency=Reuters |date=14 April 2022}}

;CB18 specifications:

• Displacement: {{cvt|1795|cc|L|1|abbr=on}} DOHC, turbocharged
• Bore × stroke: {{cvt|80.6|×|88|mm|2|abbr=on}}
• Compression ratio: 10.4:1
• Power: {{cvt|177|PS|kW hp|0|abbr=on}} at 5,200–5,600 RPM
• Torque: {{cvt|300|Nm|kg.m lbft|0|abbr=on}} at 1,600–3,600 RPM

;CB18 applications:

• 2021–present JDM Subaru Levorg (VN5)
• 2021–present JDM Subaru Forester (SK5)
• 2021–present JDM Subaru Legacy Outback (BT5)
• 2025– JDM Subaru Forester (SL5)

{{Reflist}}

{{Commons category|Subaru CB engines}}

({{langx|ja|Subaru CB engine}})

• {{cite news |url=https://car.watch.impress.co.jp/docs/news/1271497.html |title=スバルの技術を極めた、新型「レヴォーグ」。SGPボディやCB18エンジンのカットモデル展示 |lang=ja |trans-title=The technology of Subaru's new 'Levorg'; cutaway model of SGP body and CB18 engine |author1=Tanikawa, Kiyoshi |author2=Yasuda, Tsuyoshi (photographer) |date=August 20, 2020 |work=Car Watch}}
• {{cite news |url=https://car.watch.impress.co.jp/docs/news/1272327.html |title=スバル新型「レヴォーグ」のデジタルコクピットや1.8リッターの採用理由が明らかに YouTubeLive「NEW LEVORG 徹底解剖」レポート |lang=ja |trans-title=Subaru's 'Levorg' digital cockpit and the reason for adopting 1.8 litres revealed in YouTube Live 'New Levorg thorough dissection' report |author=Tsubakiyama, Kazuo |date=August 24, 2020 |work=Car Watch}}

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Category:Subaru engines

Category:Boxer engines

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Category:Four-cylinder engines