Subaru Impreza CS400: 75-Unit Rally-Bred Hot Hatch

The Subaru Impreza STI CS400 stands as a pinnacle of engineering collaboration between Subaru and Cosworth, delivering a limited-run supercar killer disguised as a practical hatchback. Launched in 2010, this model pushed the boundaries of the WRX STI platform with a Cosworth-overhauled engine producing 395 horsepower and 400 lb-ft of torque, making it one of the most ferocious production Imprezas ever built. Only 75 units were produced, each priced at around £50,000, targeting enthusiasts craving uncompromised performance.

Genesis of a Performance Legend

The CS400 emerged from Subaru’s desire to create the fastest road-going Impreza, enlisting Cosworth—the famed British tuner behind iconic Fords like the Escort Cosworth—for expertise in high-output engines. Building on the third-generation Impreza WRX STI’s 2.5-liter flat-four boxer engine, Cosworth introduced forged pistons, reinforced conrods, upgraded bearings, a robust head gasket, an enhanced oil pump, and a larger turbocharger. These modifications elevated output by over 30% compared to the standard STI’s 296bhp, achieving 395bhp at the crank and a torque peak of 400lb ft.

This wasn’t just about power; the drivetrain received carbon synchromesh on the first three gears of the six-speed manual for smoother, faster shifts under load. A free-flowing exhaust with larger-diameter pipes amplified the turbocharged growl, turning every rev into a symphony of mechanical aggression. The result? A 0-62mph sprint in 3.7 seconds and an electronically limited top speed of 155mph, figures that humbled many supercars of the era.

Chassis and Handling Mastery

Beyond the engine, Cosworth and Subaru transformed the CS400’s dynamics. The suspension featured Bilstein dampers paired with Eibach progressive springs, lowering the front by 15mm and widening the track by 24mm for sharper cornering. This setup dropped the ride height by 10mm overall, improving stability without sacrificing everyday usability. The ride quality impressed reviewers, balancing compliance on rough roads with taut control during high-speed runs.

Braking prowess came courtesy of massive 355mm AP Racing front discs with six-piston calipers, ensuring the CS400 could haul down from triple-digit speeds with confidence. Lightweight 18-inch alloys shod in sticky, DOT-approved semi-slicks expanded the track by 12mm, enhancing grip and poise. Visually, subtle enhancements like a revised front bumper, body-colored grille, fog lights, a discreet rear lip spoiler, and CS400 badging distinguished it from standard STIs without resorting to garish aero add-ons.

Driving Dynamics: Thrills and Quirks

Behind the wheel, the CS400 delivered immense cross-country pace, with turbo boost surging dramatically past 3500rpm, propelling the car through gears at alarming speed. The mechanical gearshift felt precise and engaging, rewarding skilled drivers with rapid progression. However, not all was flawless: some tests noted turbo lag below 3500rpm and overly short gearing that made top speed harder to reach without constant shifts. Straight-line stability suffered from lightness at the front, leading to wayward behavior and hints of understeer on corner entry—issues that dulled its point-and-shoot precision.

Despite these traits, the all-wheel-drive system shone on twisty B-roads, harnessing the flat-four’s unique boxer rumble and AWD traction for addictive momentum. In track comparisons, like Auto Express’s Performance Car of the Year tests, the CS400 dominated older Impreza specials with 119bhp advantages, posting the quickest laps thanks to its modern power and brakes. Videos from the era capture its explosive launches, with tires screeching amid a turbo chorus.

Interior Refinements and Practicality

The cabin retained the Impreza’s functional layout but gained Cosworth touches: Recaro sport seats trimmed in black leather with CS400 embroidery, a matching leather steering wheel, piano-black accents, and tinted glass. Rear seats accommodated adults reasonably, underscoring the hatchback’s versatility. Critics pointed out some cheap plastics lingered, feeling mismatched for the £50,000 price, but the overall ergonomics supported long hauls.

• Recaro seats: Bolstered for high-g cornering with supportive leather.
• Cosworth branding: Subtle plaques and stitching elevate the premium feel.
• Infotainment: Standard STI setup with basic audio and nav, functional but dated today.
• Boot space: Practical 340 liters, expandable for weekend duties.

Performance Benchmarks and Rivals

Claimed stats painted a hypercar picture: 0-60mph in 3.7 seconds, quarter-mile in the low 12s, and relentless AWD pull to 155mph. Real-world tests confirmed its dragstrip dominance over contemporaries like the Mitsubishi Evo X FQ-400 or Nissan GT-R entry models, though pricier rivals like the Audi RS3 offered more polish. Fuel economy hovered around 20mpg combined, thirstier than efficiency-focused hatches but par for the course in high-output turbos.

In group tests against classic Imprezas—like the WRX STI R205 or Prodrive P1—the CS400’s power edge secured victories, catapulting ahead with superior acceleration despite its hatchback form. Its rally pedigree, echoing World Rally Championship winners, added intangible allure for Subaru faithful.

Ownership Considerations and Legacy

With just 75 built (mostly UK-spec right-hand drive), the CS400 is a collector’s gem today, values holding strong above £40,000 for low-mileage examples. Maintenance demands expertise: the Cosworth engine thrives on premium fuel and regular servicing, while AWD components require vigilance. Forums note reliable longevity if maintained, though parts scarcity inflates costs.

Its legacy endures as Subaru’s boldest road car, bridging rally icons like the Colin McRae Edition with modern tuners. For 2026 buyers, it offers analog thrills in an EV-dominated world—raw, loud, and unapologetically fast.

Key Specifications at a Glance

Frequently Asked Questions (FAQs)

Is the Subaru CS400 street-legal?

Yes, it features DOT-approved tires and meets road regulations, blending track capability with daily drivability.

How rare is the CS400?

Only 75 units produced worldwide, primarily for the UK market, making it highly collectible.

What’s the CS400’s fuel economy?

Expect 18-22mpg combined; its high-output turbo demands 98-octane fuel.

Does it outperform standard STIs?

Significantly: 33% more power/torque, quicker acceleration, and superior brakes.

Is it reliable long-term?

With proper maintenance, yes—Subaru’s boxer durability shines, though specialist servicing is advised.