Setting the Stage for 500+ Horsepower

Building a Honda S2000 that reliably lives above the 500‑wheel‑horsepower mark is a serious undertaking. The F20C and F22C engines are known for their high‑revving character and strong bottom ends, but doubling or tripling factory power requires a carefully matched forced‑induction system. Among the turbocharger options available today, the BorgWarner EFR (Engineered for Reliability) series has earned a strong following for its combination of aerodynamics, spool characteristics, and durability. This article walks through the key decisions when selecting an EFR‑based turbo kit for a 500+ horsepower S2000, covering everything from turbo model choice to supporting modifications and tuning.

Why the BorgWarner EFR Series Stands Out

The EFR series was developed to bridge the gap between race‑bred response and street‑friendly drivability. Several engineering choices make these turbochargers particularly well‑suited to a high‑output S2000.

  • Gamma‑Ti turbine wheel: A titanium‑aluminide wheel that is roughly 40% lighter than a comparable Inconel wheel. Lower rotational inertia means the turbo spools faster without sacrificing flow capacity.
  • Integrated wastegate: The wastegate is built directly into the turbine housing, eliminating external dump tubes and simplifying the exhaust manifold design. This also reduces the chance of boost creep and keeps under‑hood temperatures lower.
  • Fully divided twin‑scroll housing: Many EFR models come with a twin‑scroll turbine housing that keeps exhaust pulses separated. On the S2000’s four‑cylinder engine, a divided housing with a proper twin‑scroll manifold improves spool time and reduces reversion.
  • High‑flow billet compressor wheel: The compressor wheel uses a patented aerodynamic design for high pressure ratio at lower shaft speeds, giving the S2000 both low‑end torque and top‑end horsepower.
  • Ceramic ball bearings: EFR turbos use a dual ceramic ball bearing center section that reduces friction compared to conventional journal bearings. This helps oil flow requirements stay manageable and improves transient response.

These features make the EFR series a natural fit for a street‑driven S2000 that sees track days or aggressive daily driving. You can read the full technical overview at BorgWarner Turbo Systems.

Key Factors in Selecting the Right Kit

Choosing a turbo kit isn’t as simple as picking a turbo size. The kit’s completeness, engine management compatibility, and physical fitment all affect the final result.

Power Goals and the Realistic Limit

500 wheel horsepower is a major milestone for any S2000. At this level, the stock internal engine components become marginal. While the F20C can handle 450–500 whp with a conservative tune, pushing past that almost always requires forged pistons, stronger rods, and head studs. Your turbo selection must match the fuel system and the engine’s ability to handle the airflow. If you plan to run 93‑octane pump gas, 500 whp is near the ceiling. With E85 or race fuel, 600+ whp becomes achievable but demands more careful part selection.

Engine Management and Tuning Complexity

Once you add a turbo, the factory ECU cannot properly manage fuel and ignition. A standalone engine management system (e.g., Haltech Elite 2500, AEM Infinity, or MoTeC) is mandatory. Many turbo kits bundle a piggyback or a basic reflash, but for 500+ hp you want full control over boost targeting, fuel trims, and knock prevention. Confirm that the kit you select is compatible with your chosen ECU and that a reputable tuner in your area knows the platform. Professional tuning is not optional; poor tuning is the fastest way to destroy an S2000 engine.

Installation Complexity and Hardware Quality

Some turbo kits are designed for a simple bolt‑on experience, while others require significant modification. For a 500‑hp build, expect to relocate the battery, upgrade the radiator hoses, and possibly modify the engine hanger. Look for a kit that includes: – A properly jig‑welded stainless steel exhaust manifold with a divider for twin‑scroll flow. – A full downpipe and front pipe to match your exhaust system. – All necessary gaskets, oil feed and drain lines, and silicone couplers. – A high‑capacity intercooler core (at least 3″ thick) with polished piping. – A blow‑off valve (preferably recirculated to avoid intake air‑metering issues).

Kits from established vendors such as SpeedFactory Racing or Ballade Sports have been proven on many S2000s at this power level.

Budget Beyond the Kit

A complete EFR turbo kit typically costs $4,000–$6,000. But that’s only the starting point. Supporting modifications—fuel system, cooling, clutch, and engine management—usually double the total investment. Plan for $10,000–$15,000 to do the job correctly and safely. Cheap is expensive in the long run.

Choosing the Right EFR Model for Your Build

The BorgWarner EFR lineup includes compressor sizes from 6258 to 9180. For an S2000 targeting 500+ whp, three models stand out. Below is a comparison of their key specs and real‑world behavior.

Model Compressor Wheel (Inducer/Exducer) HP Range (whp) Spool Characteristics Best For
EFR 7670 67mm / 70mm 400–550 Fast spool, full boost ~3500 RPM Responsive street car with track use; 500 whp ceiling
EFR 8374 70mm / 74mm 500–750 Moderate spool, full boost ~3800 RPM 500–600 whp with headroom; good for pump gas or E85
EFR 9180 75mm / 80mm 650–900 Later spool, full boost ~4200 RPM High‑compression, track‑only builds; extreme power levels

EFR 7670 – The Balanced Street Performer

The 7670 uses a 67mm inducer compressor wheel and a 70mm exducer. In the S2000, it reaches full spool (around 20 psi) by 3500–3600 RPM when paired with a proper twin‑scroll manifold. This turbo delivers a broad torque curve that pulls hard to 8,000+ RPM. It is an excellent choice if your power goal is 480–510 whp on pump gas and you want minimal lag. Many owners report that the car still feels responsive part‑throttle and has no “light switch” power delivery. The 7670 can support up to about 550 whp on E85 with a built motor.

EFR 8374 – The Sweet Spot for 500–600 Whp

With a 70mm inducer and 74mm exducer, the 8374 is the most popular EFR size for S2000 builds aiming for 500+ wheel horsepower. It flows enough air to comfortably make 550–600 whp while still spooling quickly enough for a weekend track car. Full boost arrives around 3800 RPM, and the power continues past 8,500 RPM. The 8374’s compressor map shows a wide efficiency island, meaning it can handle high boost levels without overspeeding. If your goal is exactly 550 whp on E85, this turbo will likely be your best match.

EFR 9180 – When More is Not Enough

The 9180 uses a massive 75mm inducer and an 80mm exducer. This turbo is for owners who are chasing 650+ wheel horsepower and are willing to trade low‑end response for top‑end top end. Full boost on an S2000 is typically not seen until 4200–4400 RPM. Below that boost threshold, the car drives like a naturally aspirated engine—which some find frustrating. The 9180 requires a built engine (forged pistons, rods, main studs) and a high‑flow fuel system (e.g., dual Walbro 525s or an external pump with surge tank). It’s best reserved for rolling‐‐race builds or time‑attack cars where mid‑range response isn’t critical.

For a detailed look at compressor maps and installation notes, check the BorgWarner EFR product page.

Supporting Modifications – Doing the Job Right

A turbocharger alone cannot make reliable horsepower. Every component in the path from air intake to exhaust tailpipe must be upgraded to handle the increased flow and heat.

Fuel System Upgrades

At 500 whp, the stock fuel pump and injectors are dangerously inadequate. You need at least a fuel pump capable of 500+ lph (e.g., Walbro 525) and injectors with 1000–1300 cc/min flow. On E85, up the injectors to 1500 cc/min. A return‑style fuel system with an adjustable fuel pressure regulator is highly recommended. The factory returnless system can cause pressure drops under high flow. Also, upgrade the fuel lines to ‑6 AN or larger.

Cooling System Enhancements

Forced induction adds enormous heat load. The factory radiator is barely sufficient for a naturally aspirated S2000 on a hot track. Use an aluminum radiator with at least a 2‑row core (e.g., Mishimoto or Koyo). Add an oil cooler (a Setrab or Mocal 19‑row cooler with thermostat is common). Consider a water‑to‑air intercooler if packaging is an issue, though air‑to‑air cores generally offer more thermal mass. Ensure the intercooler piping uses smooth bends and silicone couplers to minimize pressure loss.

Exhaust System

A turbo system is only as efficient as its exhaust path. Use a 3‑inch downpipe and a 3‑inch exhaust from the turbo back. A high‑flow catalytic converter can be fitted if local emissions laws require it, but many builders opt for a catless downpipe. The exhaust should be built with mandrel‑bent tubing and quality mufflers to reduce backpressure. Avoid excessive length or sharp contractions that will raise turbine outlet pressure and hurt spool.

Internal Engine Components

For 500 whp on pump gas, the stock F20C rods and pistons can survive with a conservative tune and careful boost control. But reliability improves dramatically with forged components. A set of forged pistons (9:1 compression or lower) and forged H‑beam rods (e.g., Manley or Carrillo) are standard. Install ARP head studs to prevent head lift. Consider a boundary Engineering oil pump gear upgrade to handle the extra RPM and turbo oil drain demands. These modifications are the difference between a fragile 500 whp car and a reliable one.

Clutch and Drivetrain

The stock clutch begins to slip around 350 whp. For 500+ whp, you need a twin‑disc clutch (e.g., ACT, OS Giken, or Competition Clutch) that can handle high torque without excessive pedal effort. The differential should be upgraded if you plan to launch the car hard—a Boss 600 or a smaller OS Giken LSD is common. Rear axles may also need upgrading if you start making 550+ whp with sticky tires.

Tuning – The Final Piece of the Puzzle

No turbo kit, regardless of quality, produces safe power without proper tuning. The S2000’s F20C/F22C is sensitive to ignition timing and knock. Work with a tuner who has experience with the EFR series and the Honda platform. Tuning parameters include: – Base fuel map: calibrate for the new injectors and fuel pressure. – Ignition timing map: typically reduce timing under boost to prevent detonation. – Boost control: set wastegate duty cycles to target boost pressure without overshoot. – Fuel trims: adapt for the MAF or MAP sensor, ensuring a smooth transition from idle to wide open throttle. – Knock management: set a safe aggressive spark table for high load areas.

A dyno tune using a load‑based system (e.g., Dynojet or Mustang) is recommended. Expect to pay $600–$1,200 for a complete tune, and budget for a follow‑up session after a few thousand miles to inspect the data logs. Avoid the temptation of “off‑the‑shelf” tunes—every combination of turbo, exhaust, and fuel needs a custom calibration.

For a deep dive into S2000 tuning strategies, S2KI forums have extensive threads from seasoned builders.

Conclusion – Building the Right 500+ HP S2000

The BorgWarner EFR series offers a clear path to 500+ wheel horsepower in the Honda S2000. By matching the correct turbo model—7670, 8374, or 9180—to your power goals and driving style, you can create a turbocharged S2000 that is both fast and reliable. But the turbo is just one component. Equally important are a properly selected kit, a robust fuel system, upgraded cooling, reinforced internals, and professional tuning. When all these pieces come together, the result is an unforgettable driving experience: an S2000 that pulls hard from 3500 RPM to the 9,000 RPM redline, delivering the kind of power that makes every on‑ramp feel like a race track. Take the time to plan your build, consult with experts, and invest in quality parts. Your engine—and your right foot—will thank you.