One Of The World's Only Twin-turbo Flat-four Engines Was Built By Subaru – And It Didn't Go As Planned

Although Subaru didn't invent level engines, and isn't nan only automaker still utilizing them, those motors person go a defining characteristic of nan brand. (The aforesaid tin beryllium said for all-wheel drive, of course, but we'll time off that for different day.) In fact, Subaru has relied connected level engines, besides called boxer engines, for astir each of its vehicles since nan Subaru 1000 reached nan roadworthy successful 1966. And each gas-powered personnel of nan existent lineup — moreover nan Subaru BRZ built together pinch Toyota — has one.

Naturally, Subaru's boxers person evolved since nan 1960s, complete clip trying retired galore of nan aforesaid refinements and upgrades arsenic accepted soul combustion motors, including substance injection, turbocharging, supercharging, and moreover diesel engines ne'er sold successful nan U.S. In 1993, Subaru doubled down connected forced induction by processing a four-cylinder boxer motor pinch 2 turbochargers, 247 horsepower, and 228 pound-feet of torque.

The mill was made mostly for Japan, wherever folks thrust connected nan right-hand broadside of nan road, and it really wouldn't fresh into cars pinch steering wheels connected nan left. Nor is this nan only typical Legacy from nan early '90s we missed retired on: There was erstwhile a Japan-only Legacy Touring Bruce version honoring "Die Hard"-era Bruce Willis.

Regardless, nan steering-wheel location wasn't nan logic things didn't spell arsenic planned. It turns retired utilizing a sequential twin-turbo setup, for illustration nan Legacy did, has an inherent weakness erstwhile it comes to powerfulness transportation and isn't truthful awesome successful position of emissions, either.

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First off, let's look astatine really a azygous turbocharger works. It's a reasonably elemental process, arsenic a accepted turbocharger is powered by nan motor itself and relies connected 2 mini fans mounted connected nan other sides of a short axle. One side, nan basking side, is driven by exhaust state that's routed done nan turbocharger earlier going done nan existent exhaust system. As that turbine spins, truthful does nan instrumentality connected nan different side, nan acold side, which sucks successful caller aerial to unit much of it into nan cylinders. More aerial mixing pinch nan substance intends much power. 

With today's emblematic twin-turbo engines, groups of cylinders person their ain abstracted turbocharger that runs successful parallel to nan other. Subaru's setup utilized sequential turbocharging, wherever nan aerial from nan first turbo past spins nan second, pinch nan mixed effort boosting each 4 cylinders together. In theory, nan statement helps destruct turbo lag: Subaru's first turbo was calibrated to present low-speed boost while waiting for nan 2nd to travel into play astatine higher motor speeds.

But you can't really hole turbo lag, and this only moved nan problem from 1 spot successful nan powerband to another. When AutoSpeed tested an Australian-market Legacy, known arsenic nan B4 successful that state — which, to beryllium sure, drives connected nan right-hand broadside of nan roadworthy — it noticed an "ugly 'hole' successful nan torque delivery" system that occurred while waiting for nan 2nd turbo to travel on.

Subaru's innovative motor had its issues, but it was conscionable a mini branch connected nan highly successful EJ20 family tree. Introduced successful nan Japan-only 1989 Subaru Legacy RS/GT, nan original EJ20 motor was portion of nan automaker's first foray into capacity engines and featured astir 2.0 liters of displacement and a azygous turbocharger originated from IHI. The centrifugal delivered astir 217 horsepower and astir 200 pound-feet of torque erstwhile mated to a five-speed manual transmission successful nan 1989 Legacy RS. By nan clip nan motor went retired of accumulation successful 2003, it could make 276 horsepower/253 lb-ft.

Perhaps much important for automotive history is that it was nan EJ20 that made nan WRX a legend. Subaru's iconic athletics compact welcomed a first-gen single-turbo EJ20 successful 1992, letting drivers negociate 236 ponies and 224 lb-ft pinch a five-speed instrumentality for rally-inspired on-road thrills. A decade later, Subaru began exporting nan Subaru WRX to nan United States, delivering nan aforesaid benignant of capacity arsenic a modern Audi S4 but for thousands of dollars less.

The aforesaid engines would go a halfway constituent of galore Subaru models complete nan years, and not conscionable caller ones. The EJ20 became plentifulness celebrated pinch tuners, too, who loved really easy it was to switch nan motors for their builds. The automaker yet stopped EJ accumulation successful 2019, but it remains a item of our comprehensive guideline to Subaru engines.