Editing Flat-four engine (section)

=== Exhaust manifold ===
The typical firing order for a boxer-four engine is for the left bank of cylinders to ignite one after another, followed by the right bank of cylinders (or vice versa), with the [[Firing order#Even and uneven firing order|firing interval]] evenly spaced at 180 degrees. Traditionally, the exhausts from the two cylinders on each bank were merged, with the resulting uneven exhaust pulses causing a characteristic "flat-four burble" exhaust sound.

The other common exhaust configuration (such as used by Subaru since the mid-2000s) is to pair the cylinders with a firing interval offset of 360 degrees, in order to optimise the [[Exhaust manifold#Exhaust scavenging|exhaust pulses]].<ref>Announcement on Legacy exhaust in Japanese: {{cite web |title=Fuji Heavy Industries, Press Information |url=http://www.fhi.co.jp/news/03_04_06/03_05_23b.htm |date=2003-05-23 |access-date=2013-12-16 |archive-date=2016-05-15 |archive-url=https://web.archive.org/web/20160515173706/http://www.fhi.co.jp/news/03_04_06/03_05_23b.htm |url-status=dead }}</ref><ref>Announcement on Forester exhaust in Japanese: {{cite web |title=Fuji Heavy Industries, News Release |url=http://www.fhi.co.jp/news/05_01_03/05_01_27.html |date=2005-01-27 |access-date=2013-12-16 |archive-date=2016-03-04 |archive-url=https://web.archive.org/web/20160304084234/http://www.fhi.co.jp/news/05_01_03/05_01_27.html |url-status=dead }}</ref><ref>Announcement on Impreza exhaust in Japanese: {{cite web |title=Fuji Heavy Industries, News Release |url=http://www.fhi.co.jp/news/07_04_06/07_06_05_01.html |date=2007-06-05 |access-date=2013-12-16 |archive-date=2016-03-09 |archive-url=https://web.archive.org/web/20160309183635/http://www.fhi.co.jp/news/07_04_06/07_06_05_01.html |url-status=dead }}</ref> This configuration requires long exhaust manifolds, in order to pair the cylinders on opposite banks, and results in a less distinctive exhaust sound.