The Honda S2000 AP1 remains a benchmark for front-engine, rear-wheel-drive sports cars, celebrated for its razor-sharp handling and the naturally aspirated F20C engine that revs past 9,000 RPM. Enthusiasts seeking to sharpen the car's already lively character often turn to a lightweight flywheel and performance clutch upgrade. This combination reduces rotational inertia, improves throttle response, and increases torque capacity, transforming the driving experience. This article explores the technical benefits, practical trade-offs, and detailed cost breakdown for this popular modification.

Understanding the S2000 AP1's Drivetrain

The factory flywheel in the AP1 is a dual-mass unit designed to smooth out engine vibrations and provide a comfortable daily driving experience. Weighing approximately 18 to 20 pounds, it prioritizes refinement over outright performance. The stock clutch is adequate for the F20C's 237 horsepower, but as power levels increase—whether through bolt-on modifications, forced induction, or engine tuning—the factory setup can slip and fail under higher torque loads.

Upgrading to a lightweight flywheel and a performance clutch addresses these limitations. The flywheel reduces rotating mass, allowing the engine to accelerate and decelerate more freely, while the clutch provides a higher torque capacity and more positive engagement. Together, they unlock quicker acceleration, better engine braking, and improved shift feel.

Benefits of a Lightweight Flywheel

Reducing flywheel weight has a cascading effect on engine performance and drivability. The benefits go beyond simple acceleration improvements.

Reduced Rotational Inertia

The flywheel stores kinetic energy; lighter versions require less energy to spin up and down. This means the engine revs faster when you blip the throttle and drops RPM more quickly when you lift off. For the S2000 AP1, which lives at high RPMs, this makes the engine feel much more responsive. Gear changes become quicker and smoother because the engine speed adjusts more rapidly to match road speed.

Improved Acceleration

Less rotational mass means more of the engine's power reaches the wheels. In a chassis that thrives on momentum, a lightweight flywheel reduces the time spent accelerating between gears. On track days, this translates to earlier apex exits and better lap times.

Enhanced Engine Response

Throttle inputs feel immediate and linear. The car becomes more playful and connected, rewarding precise driving. This is especially noticeable during rev-matched downshifts, where the lighter flywheel allows the engine to spin up almost instantly.

Potential for Increased Engine Braking

A lighter flywheel allows the engine to slow down faster when you lift off the throttle, effectively increasing engine braking effect. This can help reduce brake wear during spirited driving and gives the driver more control entering corners.

The Performance Clutch Upgrade

A performance clutch is not just about handling more power—it also improves engagement feel and durability under stress. The AP1's stock clutch is designed for comfort; an upgrade offers more positive lockup and higher thermal capacity.

Higher Torque Capacity

Performance clutches use stronger pressure plate springs and friction materials with higher coefficient of friction. This allows them to hold more torque without slipping, even with forced induction or aggressive driving.

Positive Engagement

Unlike the often vague feel of a worn stock clutch, a performance unit provides a distinct engagement point. This improves confidence when launching the car or executing heel-and-toe shifts.

Material Options

Common friction materials include organic, ceramic (sintered iron), and carbon. Organic offers smooth engagement similar to stock, ideal for daily driving. Ceramic handles higher torque and heat but may be grabby and cause chatter. Carbon is lightweight and provides excellent heat dissipation but comes at a premium.

Durability and Heat Resistance

Performance clutches are built to withstand higher operating temperatures without fading. This is critical for track use, where repeated clutch engagements can generate significant heat.

Cost Breakdown for the Upgrade

Costs vary widely based on components chosen, labor rates, and whether you install yourself. Below is a detailed breakdown of typical expenses for an AP1 lightweight flywheel and clutch upgrade.

Lightweight Flywheel

Prices range from $350 to $900, depending on material and brand. Single-piece chromoly steel flywheels (common choices like ACT Prolite or Fidanza) cost around $400–$600. Aluminum flywheels with a replaceable steel friction surface run higher, up to $800–$900. Some options include the OEM-weight reduction flywheels that retain some mass for better daily comfort. Popular brands include ACT, Fidanza, and Spoon Sports.

Performance Clutch Kit

A complete kit includes the clutch disc, pressure plate, release bearing, and often alignment tools. Single-disc organic kits suitable for street use typically cost $400–$700. Stage 2 kits with ceramic discs for track/street use range $600–$1,200. Twin-disc clutches, which offer even higher torque capacity and smooth engagement, can cost $1,200–$2,500. Brands like Exedy, OS Giken, and Competition Clutch offer proven S2000 solutions.

Installation Labor

Professional installation at a reputable shop runs $300–$800. The S2000's transmission is not overly difficult to remove, but a lift and proper tools are required. Shops that specialize in Honda/Acura performance may charge a premium. Independent mechanics might be lower, but ensure they have experience with the AP1 drivetrain.

Additional Parts and Fluids

It's wise to replace the pilot bearing, throwout bearing, and rear main seal while the transmission is out—typically $50–$150 for all parts. Also factor in new transmission fluid (MTF4) and possibly engine oil if needed. Add $30–$60 for fluids and gaskets.

Total Estimated Cost

ComponentLow EstimateHigh Estimate
Lightweight Flywheel$400$900
Clutch Kit (single disc, organic or ceramic)$500$1,200
Installation Labor$300$800
Additional Parts/Supplies$80$200
Total Range$1,280$3,100

Most street-focused builds land between $1,500 and $2,200 for quality parts and professional installation. DIY installation can save $300–$800, but it's a moderately involved job requiring basic mechanical skills and a transmission jack.

Potential Downsides and Considerations

While the performance gains are significant, lightweight flywheels and performance clutches come with trade-offs.

Increased Noise Vibration and Harshness (NVH)

Reducing flywheel mass eliminates the damping effect of the dual-mass design. You may notice more transmission gear noise, especially at idle, and a slight rattle when the clutch is disengaged. Ceramic clutches can produce a chattering sound during engagement, which some find intrusive in daily driving.

Harder Clutch Engagement

Performance clutches often have a heavier pedal feel and a more abrupt engagement. This can make stop-and-go traffic less comfortable and may require adjustment for smooth takeoffs.

Stall Tendency

A lightweight flywheel reduces stored rotational energy, making it easier to stall the engine when starting from a stop. Drivers need to apply slightly more throttle and slip the clutch longer until they adapt. This is more pronounced on hill starts.

Daily Driving Trade-Offs

For a car used primarily on weekends or track days, the NVH and engagement changes are usually acceptable. For a daily commuter, a moderate-weight flywheel (12-14 pounds) and a sprung organic clutch can offer a good balance of performance and drivability. According to the S2000 community on S2Ki, many owners recommend the 13-pound Fidanza flywheel with an Exedy Stage 1 organic clutch for street use.

Installation Tips and Recommendations

Whether DIY or professional, attention to detail ensures long reliability.

  • Resurface or replace the flywheel friction surface: If reusing a flywheel, ensure it's properly machined. Most lightweight flywheels are new and ready to install.
  • Use new bolts and proper torque: Flywheel bolts are torque-to-yield; replace them. Use blue Loctite on pressure plate bolts.
  • Inspect the rear main seal: Replace if there is any leakage. Oil from a rear main seal can contaminate the clutch disc.
  • Bleed the clutch hydraulic system: After installation, flush and bleed the clutch master and slave cylinders to ensure firm pedal feel.
  • Bedding in the clutch: Follow the manufacturer's break-in procedure, typically 500–800 miles of gentle street driving with varied loads.

Conclusion

Upgrading the S2000 AP1 with a lightweight flywheel and performance clutch is one of the most effective ways to sharpen the car's dynamics without adding power. The reduction in rotational inertia yields quicker revving, better throttle response, and more engaging driving. A matched clutch provides the torque-holding capacity needed for modified engines or track use, while improving engagement feel. Costs range from roughly $1,300 for a budget-friendly DIY setup to $3,000+ for top-tier components and professional installation. For enthusiasts who prioritize connection and responsiveness, this modification is a rewarding investment that makes the AP1 even more thrilling to drive.