Straight-nine engine

{{Short description|Piston engine with nine cylinders in a straight configuration}}

{{notability |date=January 2025}}

The straight-nine engine (also referred to as an inline-nine engine; abbreviated I9 or L9) is a piston engine with nine cylinders arranged in a straight line along the crankshaft. The most common application is for large diesel engines used by ships.

Examples of straight-nine engines include:

• Rolls-Royce Bergen B, C and K series{{cite web |url=https://archive.today/20120730153647/http://www.ffklubben.com/Om%20bedriften/Om%20bedriften.htm |title=Historie om bedriften |trans-title=Company history |language=Norwegian |access-date=2025-01-24}}
• Wärtsilä RT-flex60C-B,{{cite web |url=https://www.dieselduck.info/machine/01%20prime%20movers/rt_flex/2004%20Wartsila%20RT%20Flex%20desc.pdf |title=The Sulzer RT-fl ex Common-Rail System Described |page=2 |publisher=Wärtsilä |via=Martin's Marine Engineering Page |access-date=2025-01-24 |year=2004}} RT-flex82C, RTA84T-D, RTA84C, RTA96C, 20, 26, 32, Wasa32LN, 38, 46 and 46F series