Subaru six-cylinder engines

Created as a refined luxury engine with improved power over the EA82T, Subaru introduced the ER27 engine in November 1985 for the Subaru ACX-II concept car, shown at the Tokyo Motor Show and billed as the 'concept car of the near future.' The concept went into production as the Subaru Alcyone VX (Subaru XT6 in North America) in August 1987, the exclusive application for the ER27. When the ER27 was introduced, it was the only water-cooled flat-6 automobile engine on the market. sharing similar bolt patterns and design to the EA82, but being of a higher flow in both cases. The intake manifold uses a two-piece design with a lower section bolting to the heads containing the coolant bridge, injectors and various vacuum lines. The upper intake manifold then bolts to the lower section and is unlike the EA82 or EJ22 "spider" manifold designs in that there is no central plenum chamber. The valve timing system is belt-drive using two individual timing belts, curiously one belt uses a spring tensioner (like the EA82) whilst the other uses a hydraulic tensioner (like the EJ22). Both JDM and USDM versions of the ER27 used multi-point electronic fuel injection. In North America, the ER27 was slightly derated to at 5,200 RPM and at 4,000 RPM. ==EG33==

Similar to how the six-cylinder ER27 is related to the earlier four-cylinder EA82, the EG33 shared bore and stroke dimensions with the contemporary four-cylinder EJ22. The EG33 was exclusively fitted to the Alcyone SVX, where it was paired with the 4EAT automatic transmission in both front- and all-wheel-drive configurations. After the SVX was discontinued, Subaru did not offer a six-cylinder engine until the EZ30 was developed and released for the Subaru Outback. Design Unlike the SOHC EJ22 it shared some dimensions with, the EG33 featured dual overhead cams; both engines used four valves per cylinder. The EG33 used a single toothed timing belt which drove the exhaust camshafts on each bank in addition to the water pump (mounted on the right bank); the intake camshaft on each cylinder bank was driven in turn by a set of helical gears via the belt-driven exhaust camshaft. At the time, the EG33 was the largest naturally aspirated engine that Subaru had ever made for regular production; in the 1990s, Subaru branded the Subaru 1235, a 3.5 L flat-12 engine designed by Carlo Chiti and Motori Moderni, intended for Formula 1 racing, although Christian von Koenigsegg reportedly was later interested in the engine for his supercar. For the 2026 Super GT season, Subaru is fitting a heavily modified EG33 into its BRZ GT300 racecar. This version of the engine has had its displacement reduced to 3.0 liters, but features twin turbochargers. ==EZ30 and EZ36==

In the United States, the EZ30 was introduced in the Outback H6-3.0 in November 2000 for the 2001 model year. In Japan, the EZ30 was introduced in the equivalent Lancaster 6 wagon in May 2000. A twin-turbo version of the EZ30 was produced for the Subaru B11S concept car, unveiled at Geneva in 2003. The EZ30 was refreshed in 2003, and when the Tribeca was introduced for the 2006 model year in January 2005, the EZ30 II was the sole engine option. The EZ36 was introduced with the restyled Tribeca for the 2008 model year, and replaced the 3.0 L EZ30 in the Legacy and Outback starting in 2009 for the 2010 model year. Starting with the 2020 model year, the six-cylinder EZ36 was dropped as the uplevel engine option for Subaru Legacy and Outback automobiles and instead the premium engine offered was the turbocharged four-cylinder FA24F, which was previously introduced for the 2019 model year as the sole engine option for the Subaru Ascent, the successor to the Tribeca. ;Notes Design EZ30D mk I The design of the EZ30 is credited to Noriaki Sekine. Unlike prior Subaru flat-6 designs, the EZ30 has a significantly smaller bore pitch (the distance between adjacent cylinder centerlines on each bank of the engine block) than the contemporary flat-4 EJ-series. The bore pitch of the EZ30 is , compared to a bore pitch of in the EJ series. The EZ30 also used a timing chain to drive the camshaft, while the earlier flat-4 EJ series uses a timing belt instead. These changes resulted in a more compact block; the external dimensions of the EZ30 are similar to the EJ25 four-cylinder engine, with length increasing by less than , A butterfly valve in the intake manifold opened at higher engine speeds, shortening the intake length and providing a passive supercharging effect through resonance. In North America, the EZ30 was derated slightly to and . instead of the single exhaust port used in the original EZ30D mk I, which gathered the exhaust from each cylinder bank into a single port. Other detail improvements included a new block casting and a reduction in overall weight by , achieved through the use of hollow-journal camshafts, reducing the number of bolts in the timing chain cover, and switching to a plastic intake manifold. A revised cooling system and variable valve timing (AVCS was now fitted to both intake and exhaust valves) allowed the EZ36 to run on regular unleaded fuel, instead of the premium unleaded required by the EZ30. ==References==