Currently, only two carmakers produce boxer engines – Porsche and Subaru. Normally, when you hear a six-cylinder boxer engine, the first to come to mind is the German automaker, famous for being the last brand to put an air-cooled engine in a high-performance sports car. Subaru is still sticking to flat-four engines for its models, but back in the golden era of Japanese sports cars, it introduced a six-cylinder boxer engine that could rival what Porsche had. The EG33 was the only flat-six Subaru engine to feature in a two-door coupe. It also served as a basis for future Subaru flat-six engines. In 2020, Subaru produced its last flat-six engine, but before that happened Subaru almost redefined the GT segment altogether, with a Porsche-sounding Subaru, powered by a flat-six.

Subaru’s last six-cylinder boxer for performance applications

Dubbed the EG33, this was at the time, the largest Subaru engine for road applications. It was only surpassed by the EZ36 - Subaru’s last flat-six engine – but that one was not ideal for performance applications due to thinner cylinder walls, potentially resulting in warped blocks. The EG33 design was based on the brand’s four-cylinder EJ engines, and more specifically, the EJ22 unit, later found in the Subaru STI 22B. The EG33 and EJ22 shared the same bore and stroke, with the main differences being the number of cylinders and the EG33’s DOHC valvetrain versus the EJ22’s SOHC.

What makes the EG33 great?

In addition to being one of the most powerful boxer engines of its time, the EG33 was also a robust unit, able to withstand a lot more than the factory power figures. This is due to the thick cylinder walls, making the engine ideal for tuning applications. This makes the EG33 a popular option for engine swaps, in various Subaru projects and Porsche replicas. At the same time, the EG33 was not much larger than the EJ22 flat-four engine, meaning it could fit in almost all engine bays that were originally intended for a flat-four unit.

Aside from some oil consumption issues, most prominent on early EG33 variants, this Subaru flat-six is a stout unit. It is also a non-interference engine with a belt-driven timing system. As a bonus, this lesser-known flat-six unit sounds like a Porsche and is often dubbed the Poor Man’s Porsche engine.

The Subaru Alcyon SVX was the only production car to feature the EG33 flat-six

When you think of 1990s JDM sports cars, you think of Supra, Skyline, or even Subaru Impreza STI. The SVX was one of the lesser-known Japanese sports cars, despite having a Porsche-sounding flat-six. The SVX was produced from 1991 to 1996 and was more of a grand tourer than an all-out sports car. It was more comparable to the JS-series Mazda Eunos Cosmo, which was a luxury counterpart to the FD RX-7.

The Subaru SVX design was done by Giorgetto Giugiarro at Italdesign and featured a few interesting design elements, such as the windows, which were partially fixed like on a Lamborghini Countach or McLaren F1. The SVX design was a lot more streamlined compared to its predecessor, the Subaru Alcyone XT. The SVX has a drag coefficient of 0.29. This allowed for a top speed of 154 mph, which was limited to 143 mph in later model years. The base-model Subaru SVX was front-wheel-drive only while all-wheel drive was optional.

Depending on the region, there were two different all-wheel-drive systems offered on the Subaru SVX - variable torque distribution (VTD) AWD, which typically split power 64/36 between the front and rear axles, with the possibility of 50/50 distribution when necessary, or ACT-4 (Active Torque Split) all-wheel-drive system, which split power 90/10 in normal conditions but would constantly calculate and split accordingly.

Why the car wasn’t as popular as the engine it came with

The Subaru SVX featured a lot of novelties, including keyless entry and automatic seatbelts. It also featured thin A-pillars, making for a seamless transition between the windshield and side windows, and improving visibility. Although the Subaru SVX was meant to be the Japanese brand’s flagship, the car was plagued by a few issues.

Unlike most other JDM sports coupes at the time, the Subaru Alcyone SVX came only in naturally aspirated form. No turbocharged variant was available from the factory, which meant Subaru’s grand tourer could only rival the "boring”, naturally-aspirated variants of other JDM sports cars. At that time, Subaru didn’t have a manual transmission that could handle the EG33’s torque, which is why the only available transmission was a four-speed, 4EAT automatic.

Meanwhile, other JDM icons like the Supra and Skyline GT-R featured manual transmissions sourced from German manufacturer, Getrag. Why Subaru didn’t employ this unit is a mystery. Moreover, Subaru’s four-speed automatic quickly developed a reputation for being unreliable. Due to defective torque converters, prone to overheating, the transmission would, often suffer catastrophic failure. Luckily, manual conversions are relatively easy to perform. The final nail in the coffin for the Subaru SVX was the steep asking price. When new, the SVX cost $24,000 to $28,000, which was similar to or more than some of its rivals including the Mitsubishi 3000 GT and Nissan 300ZX to name a few.

Why did Subaru stop making flat-six engines?

The reason is simple - engine downsizing. Instead of larger displacement and more cylinders, the Japanese carmaker decided to stick with turbocharged flat-four engines. Porsche of all brands went the opposite way by giving its first hybrid 911 a larger-displacement flat-six engine. These days, Porsche is the only one using six-cylinder boxer engines, due to their inherent advantages. Having said that, Subaru recently reminded us that it can still make high-performance cars with the Subaru STI Project Midnight, but will it take a similar approach with electrification? Time will tell.

GALLERY