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Three hundred horsepower. Three hundred pound-feet of torque. Thirty thousand dollars.
That’s probably enough to summate 90% of the winning formula for Fuji Heavy Industries Ltd.’s Subaru 2.5L turbocharged DOHC H-4. The only engine with a performance-per-dollar quotient like this is DaimlerChrysler’s 2.4L turbocharged DOHC 4-cyl., and it barely missed making the cut.
This is Subaru’s first-ever 10 Best Engines winner, and it’s not surprising given the company’s reputation for reliable, though usually unspectacular and unassuming powertrains. With the 2.5L turbocharged DOHC H-4, you can forget about that reputation: Subaru’s showing us why it’s won all those World Rally Championship trophies.
In the lightweight Impreza WRX STi, this engine exhibits truly violent performance. Sixty mph (97 km/h) arrives in 4.8 secs., so wave bye-bye to the Porsche 911 and stay neck-and-neck with Corvette. We told you this engine was strong.
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| Subaru 2.5L turbocharged H-4 |
The Subaru 2.5L turbocharged H-4’s most-direct competitor is the big-turboed 2L 4-cyl. that powers Mitsubishi’s own rally-car-for-the-street, the Lancer Evo-lution; the Lancer mill makes 271 hp and 273 lb.-ft. (370 Nm) of torque, for performance nearly identical to the STi’s. So why didn’t we even nominate the Evo engine? The reasoning is that if you’re going to be enamored of small 4-cyl. engines with lots of turbo boost, then why not go for the one with the best numbers? Moreover, Ward's judges believe the Subaru H-4 is smoother (thanks to its opposed-cylinder architecture), more flexible and more technically intriguing.
The turbocharged 2.5L DOHC H-4 marks Subaru’s first-ever use of variable-valve timing for its signature “boxer” opposed 4-cyl. Even if you resist the urge to stab the throttle to exploit the 300 lb.-ft. (407 Nm) of twist, the variable valve timing ensures the boxer 4-cyl. remains flexible and responsive. The intercooler for the wide-mouth turbo even sports its own gimmick: the driver has a switch that sprays the intercooler with water when that last kilowatt of power is required, presumably helping to cool the intercooler itself so that it can in turn deliver cooler intake air.
But this engine’s best trick is the one it’s bought for: otherworldy acceleration at almost any speed. Packing 120 hp/L, Subaru’s turbocharged 2.5L DOHC H-4 is one of the most exciting engines available in the U.S. at any price. Its relative affordability only underscores its brilliant performance and technical sophistication.
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| Fuji Heavy Industries Subaru 2.5L H-4 | |||||
| Engine type | 2.5L turbocharged DOHC H-4 | ||||
| Displacement (cc) | 2,457 | ||||
| Block/head material | aluminum/aluminum | ||||
| Bore x stroke (mm) | 99.5 x 79 | ||||
| Horsepower (SAE net) | 300 @ 6,000 rpm | ||||
| Torque | 300 lb.-ft. (407 Nm) @ 4,000 rpm | ||||
| Specific output | 120 hp/L | ||||
| Compression ratio | 8.2:1 | ||||
| Application tested | Subaru Impreza WRX STi | ||||
| Fuel economy for tested vehicle (EPA city/hwy. mpg) | 18/24 | ||||
