This article details several unique and notable automobile engines.
Wikipedia has a short article on flat engines, below is an description regarding flat 12-cylinder motors. Flat engines are also referred to as boxer engines. However, Wikipedia makes a distinction between the 180 degree V12 engine and a true boxer motor:
“Flat-12 engines are generally not true horizontally opposed engines (boxer), but rather 180° V-engines. A true boxer has one crank pin per piston, while in the 180° V-engine, two opposing pistons share the same crank pin.”
“The flat-12 is wider (but significantly lower in height) than a V12 . Despite the advantage of having a lower center of gravity than a V12, that advantage can be somewhat offset by the need for a higher mounting height in the engine bay to provide clearance for the exhaust system (six runners on either side). Whereas a V12 can be used in front-engined or mid-engined applications, a flat-12 is used exclusively in mid-engined sports cars. In addition, because it has no advantage in terms of vibrations compared to the more commonly-used V-12, the design is rarely used on production cars.”
Subaru flat 12-cylinder boxer engine
from this Wikipedia article:
“Motori Moderni designed a 3.5 litre flat-12 engine for Subaru, which would be used in the 1990 Coloni Formula One car. The Coloni−Subaru was not competitive and did not start a Grand Prix. The Motori Moderni flat-12 engine also appeared in detuned form in the Jiotto Caspita supercar. This only appeared in a single prototype and was not put into production.”
“Subaru was briefly involved in Formula One circuit racing when it bought a controlling interest in the tiny Italian Coloni team for the 1990 season. The Coloni 3B’s 12-cylinder engine was badged as a Subaru and shared the boxer layout with the company’s own engines, but was an existing design built by Italian firm Motori Moderni.”
Specs from Steve Eta Tauri Site
“Engine con fig – flat 12
Bore x stroke – 84mm x 52.6mm
Capacity – 3498cc
Compression ratio – 11.5:1
Estimated power – 600bhp @ 12,500rpm (compare this to the Honda V10 in the McLaren which is quoted as 690bhp)
Max rpm – 13,000
Engine weight – 159kg”
Ferrari flat 12-cylinder Colombo engine
This motor was technically a 180 degree V12 and not a true boxer motor. It was created in multiple forms and designed by Giaoccino Colombo for both V12 and flat-12 applications. It first appeared as a flat engine in the Ferrari 365 GT4 BB of 1971 (according to Wikipedia).
Porsche flat 8-cylinder engine
There is a great page with detailed photos from many angles here by user 914-6 on Pbase.com. It appeared in the Porsche 907 race car. There seems to be very limited information on this engine on the internet outside of the pbase.com web page linked above. According to Wikipedia it was latery developed into a flat 12-cylinder engine for the Porsche 908 race car.
Porsche flat 6-cylinder engine
The Porsche flat-6 has been a long time component of the iconic Porsche 911 for many years in many revisions. It has also appeared in the 914-6, 959, Cayman and Boxster. The Porsche flat-6 cylinder engine was originally designed as an air-cooled motor when it appeared in the 1963 Porsche 911, and remained air-cooled until the type 996 was produced in 1998 when water-cooling was adopted instead. The original 2.0 liter 1963 motor produced approximately 128hp while recent editions from the 997 and 991 models produce between 350hp and up to 473hp in the turbocharged models. Higher power levels are achieved in the race applications of these motors.
Subaru flat 4-cylinder engines
Subaru designates these motors as EA and EJ models beginning in 1966 with the EA-52 55hp 977.2cc motor and progressing through the introduction of the EJ-15 in 1989. Subaru is known very well for it’s role in the World Rally Championship racing series for it’s Impreza WRX STI rally car which was sold to the general public with the turbocharged 2.5 liter EJ257. This motor produced approximately 300hp at the crankshaft (before drivetrain losses)
Mazda Wankel rotary engines
While it was not invented by Mazda, but rather by Felix Wankel, the Mazda Wankel engines have been present in one for or another since their first model 798cc 2-rotor L8A motor and later debuting in the 1968 Mazda Cosmo as the 982cc 110hp model 0810, generally referred to as the 10A series. In it’s modern production form it appears in the Mazda RX-8 as the 1.3 liter 13B-MSP Renesis. Rotary engines are known to consume a certain amount of oil, which needs to be replaced frequently. This is considered to be normal operation of the engine. A benefit of the engines is that they are very small and light. According to Wikipedia: “The unmodified 13B-MSP Renesis Engine has a weight of 122 kg (247 lbs), including all standard attachments (except airbox), but without engine fluids (such as coolant, oil, etc.).” It has appeared as fuel-injected and carbureted, as well as turbocharged and naturally-aspirated designs.
The inline or straight engine is described by Wikipedia:
“The straight-six engine or inline-six engine (often abbreviated I6) is a 6-cylinder internal combustion engine with all six cylinders mounted in a straight line along the crankcase. The single bank of cylinders may be oriented in either a vertical or an inclined plane with all the pistons driving a common crankshaft; in vehicles where this engine is installed inclined versus vertical, it is sometimes called a slant-six engine. The straight-six layout is the simplest engine layout that possesses both primary and secondary mechanical engine balance, resulting in relatively low manufacturing cost combined with much less vibration than engines with fewer cylinders.”
BMW inline 6-cylinder engines
BMW first produced the liquid-cooled inline 6-cylinder motor in 1933 for aviation purposes. It was created by starting with a model M10 4-cylinder engine and adding two cylinders. In 1968 the model M30 was produced as a native inline 6-cylinder design. Wikipedia also lists the 1.2 liter M78 as one of the first inline 6-cylinder motors to be produced by BMW but does not make it clear if this was the result of adding two cylinders to the M10, or if this was in fact a distinctly separate motor from start to finish. While the inline 6-cylinder engine generally requires a longer engine-bay than a V6, they are reported to be very smooth due to the piston movement all being in a single plane or axis (up and down, for example). With this arrangement there are fewer forces to balance than would be found in a V6 motor, which has pistons moving in two different planes (one plane for each cylinder bank).
Nissan inline-6 RB-series engines
“The RB engine is a 2.0–3.0 L straight-6 four-stroke petrol/gasoline engine from Nissan produced from 1980-2004.” Wikipedia states also on this page that the RB engine code exclusively refers to 6-cylinder inline models.
Here is a list of models :2.0/2.4/2.5/2.6/2.8/3.0 L — RB20E, RB20ET, RB20DE, RB20DET, RB20DET-R, RB24DET, RB25DE, RB25DET, RB26DETT, RB28DETT, RB30S, RB30E, RB30ET, RB30DE. Brought into popularity largely when it was introduced into the 1986 R31 Nissan Skyline. A concurrent line of RD series (diesel) inline-6 motors were also produced.
Here is a brief paragraph describing the R31’s engine:
“The R31 RB engines are often referred to as “Red Top” engines because of the red cam covers. There were three variants. The earliest series of DOHC RB engines used the NICS (Nissan Induction Control System) injection system with 12 very small intake runners, and a butterfly system to divide the intake ports in half for better low RPM performance. Later versions used ECCS (Electronically Concentrated Control System) engine management, discarded the twelve tiny runners for six much larger ones (though they retained twelve ports on the head, so there was a splitter plate), and received a slightly larger turbocharger. Nissan’s RD28, a 2.8 straight-6 engine, featured for a diesel option.”
The newest model of Nissan Skyline GT-R is not mentioned here since a new engine was adopted. The RB series was replaced in this case by the 485 – 530hp 3.8 liter V6 VR38DETT.