For Honda S2000 enthusiasts, the exhaust system is more than just a path for spent gases—it's a crucial component that can unlock the engine's true potential. Among the aftermarket upgrades that deliver tangible gains, the HKS S2000 headers stand out as a refined choice, blending race-proven materials with a distinctive, sporty exhaust note. Whether you're chasing every last horsepower on the track or simply want a more visceral driving experience on back roads, these headers offer a durable foundation that transforms the way the F20C or F22C engine breathes and sounds.

What Are HKS S2000 Headers?

HKS S2000 headers are aftermarket exhaust manifolds designed specifically for the Honda S2000 (AP1 and AP2 models). They replace the restrictive factory cast-iron or tubular manifold with a carefully engineered system that optimizes exhaust flow. HKS, a Japanese tuning powerhouse with decades of motorsport involvement, brings its expertise to these headers, crafting them to improve engine efficiency and throttle response. Unlike some budget options, HKS headers are developed with a balance between street usability and track performance, making them a favorite among owners who daily drive their S2000s while still pushing the car on weekends.

These headers are typically a key component of a "stage" upgrade, often paired with a high-flow catalytic converter and cat-back exhaust for maximum effect. But even as a standalone modification, an HKS header provides noticeable gains in mid-range torque and top-end horsepower, all while emitting a sharper, more aggressive exhaust note that announces your arrival without being obnoxious.

Durable Materials Used in Construction

Longevity is a hallmark of HKS engineering, and the S2000 headers reflect that commitment through their material choices and fabrication techniques. The construction is not just about resistance to heat and corrosion—it's about maintaining structural integrity under the high temperatures and vibration loads of a high-revving four-cylinder engine. Here's a closer look at the materials that make these headers durable:

  • 304 Stainless Steel: This is the most common material used in HKS S2000 headers. Grade 304 stainless offers excellent corrosion resistance, can withstand continuous temperatures up to 870°C (1600°F), and is easily welded. Its chromium-nickel content also gives it a bright, clean appearance that looks great under the hood.
  • 321 Stainless Steel (selected models): For even higher heat resistance, some HKS header variants use 321 stainless, which adds titanium for stabilization. This material resists scaling and intergranular corrosion at extreme temperatures, making it ideal for forced-induction applications or track cars that see sustained high RPMs. It remains strong and resists thermal fatigue cracking better than 304.
  • High-Grade Alloy Flanges and Hangers: The flanges that bolt to the cylinder head and the hangers that support the header are often cut from thick, CNC-machined stainless or mild steel with an anti-corrosion coating. This ensures a leak-free seal and prevents warping over time.
  • TIG Welding and Mandrel Bends: HKS employs precision TIG welding to create smooth, contamination-free joints. The tubing is mandrel-bent to maintain a consistent inner diameter, eliminating restrictions that reduce flow. The welds are visually inspected and sometimes X-rayed for quality assurance.

Beyond the base metals, many HKS headers are available with optional thermal coatings, such as ceramic or HKS's own "Kansai Service" heat barrier. These coatings reduce under-hood temperatures, protect the header from thermal cycling damage, and help maintain lower intake air temperatures, which can contribute to power gains.

Performance Benefits of HKS S2000 Headers

Installing an HKS header does more than just change the sound—it fundamentally alters how the engine produces power. The factory exhaust manifold on the S2000, while adequate for normal driving, creates a bottleneck that limits the engine's ability to expel exhaust gases efficiently. By replacing it with a freer-flowing header, you reduce backpressure and improve scavenging. Scavenging is the process where the outgoing exhaust pulse creates a low-pressure wave that actually pulls the next cylinder's exhaust out, and also helps draw in fresh air during the intake stroke. High-quality headers like those from HKS are engineered to maximize this effect.

Specific performance gains depend on the engine's condition, supporting modifications, and tuning, but dyno results from reputable sources consistently show:

  • +8 to +15 horsepower at the wheels (typically around 10 hp gain across the mid-range and top end).
  • +5 to +10 lb-ft of torque gain, often peaking between 4,000 and 6,000 RPM. This improvement makes the car feel more responsive during daily driving and corner exit.
  • Faster throttle response due to reduced exhaust restriction. The engine can rev more freely and feel less "choked" above 7,000 RPM.
  • Wider powerband—especially with equal-length header designs, the torque curve can be broadened, reducing the need to keep the engine constantly at redline.

It's worth noting that these gains are often amplified with an ECU tune. The factory ECU may run slightly rich or retard timing when it detects a free-flowing exhaust, so a proper flash or standalone ECU can unlock the header's full potential (see Tuning section below).

Sporty Exhaust Note: Sound Characteristics

The sound of an HKS-equipped S2000 is distinctive and addicting. The header changes the fundamental timbre of the engine, adding a sharper, more metallic edge without becoming harsh or raspy. The tone is often described as "race-inspired" with a deep growl at low RPMs that transitions into a high-pitched scream at full throttle. Compared to some other aftermarket headers, HKS units tend to have a slightly refined sound—less drone on the highway but more aggression when you're on the gas.

The sound signature also depends on whether you choose an equal-length or unequal-length header design:

  • Equal-length headers produce a more consistent, smooth tone since each cylinder's exhaust travels the same distance. This often results in a higher-pitched, "F1-like" sound at high RPMs with less combustion interference.
  • Unequal-length headers create a slightly more aggressive, choppy idle note and a deeper exhaust tone overall, with a bit more low-frequency rumble.

HKS offers both designs depending on your preference and goals, but their most popular S2000 header uses an equal-length primary tube configuration for maximum power and that iconic screaming sound.

Installation Considerations

Installing an HKS S2000 header is a moderate DIY job for someone with mechanical experience, but there are several critical factors to get right.

Tools and Equipment Needed

  • Socket set (10mm, 12mm, 14mm, 17mm), plus a torque wrench.
  • Breaker bar for stubborn manifold nuts.
  • Penetrating oil (e.g., WD-40 or PB Blaster) to loosen corroded fasteners.
  • New exhaust gaskets (header-to-head and header-to-cat or header-to-test pipe).
  • Anti-seize compound on nuts and studs.
  • Jack and jack stands (or a lift) to access the underside.

Step-by-Step Installation Overview

  1. Disconnect the battery (negative terminal) to avoid accidental shorts.
  2. Remove the factory exhaust manifold—this usually involves unbolting the heat shield, disconnecting the O2 sensors, and loosening the manifold from the cylinder head. On AP1 cars, the stock manifold is a cast iron piece; AP2 models had a tubular stainless steel manifold, but both require careful work to avoid breaking studs.
  3. Clean the cylinder head surface—any old gasket material must be removed to ensure a proper seal.
  4. Install new gaskets on the header flanges. HKS typically supplies high-quality gaskets, but using OEM or aftermarket metal gaskets is recommended for longevity.
  5. Position the header from below the car. Some HKS headers have a tighter fitment and may require manipulating the back of the engine (loosening engine mount bolts) to slip the header in.
  6. Bolt the header to the head—start all nuts by hand before tightening to torque specifications (usually 18-20 ft-lbs in a crisscross pattern).
  7. Attach the header to the exhaust system using the provided spring bolts or flanges. Make sure the O2 sensor bung is oriented correctly for wiring.
  8. Reinstall the heat shield if possible. Many aftermarket headers require removal of the stock heat shield or using HKS's own heat wrapping.
  9. Reconnect the battery and check for exhaust leaks on startup.

Potential Fitment Issues

While HKS headers are known for excellent fitment, there are a few common issues to be aware of:

  • Clearance with aftermarket engine mounts: Stiffer mounts can shift the engine position slightly, causing the header to contact the frame rail or steering shaft. In such cases, adjust engine mount placement or install header spacers.
  • O2 sensor wiring length: The factory O2 sensor harness may be too short to reach the new bung location. Extensions are available from HKS or aftermarket suppliers.
  • Exhaust system compatibility: Some HKS headers are designed to mate directly with HKS cat-back systems, so if you have a different brand's mid-pipe, you may need an adapter.

Given these variables, many owners opt for professional installation at a reputable shop that has experience with S2000 header swaps. The cost is modest compared to the risk of broken studs or a poor seal.

Choosing the Right HKS S2000 Header

HKS produces multiple header models for the S2000, each tailored to different performance goals and budgets. The key specifications to consider are:

Primary Tube Diameter

  • 1.5" – 1.625" (38–41mm) primary tubes are best for naturally aspirated street cars that prioritize low-to-mid-range torque. They keep exhaust velocity high, improving throttle response.
  • 1.75" (44mm) or larger primary tubes are suited for high-horsepower builds or forced induction. They flow more at high RPM but can soften low-end torque if the engine isn't built to make use of them.

Equal-Length vs. Unequal-Length Design

Equal-length headers (sometimes called "4-1" in S2000 context) are the most common for performance. They allow the exhaust pulses to reach the collector at evenly spaced intervals, which greatly improves scavenging and top-end power. Unequal-length headers (often "4-2-1" or varying primary lengths) can offer a broader torque curve but may sacrifice peak horsepower.

Coating Options

HKS offers headers in bare stainless, polished stainless, and occasionally with a ceramic coating (such as HKS's "Kansai Service" coating). Ceramic-coated headers reduce under-hood temperatures by up to 50% compared to bare metal, protect against rust, and look great. The trade-off is additional cost and sometimes a slightly different appearance (matte gray vs. shiny metal).

Model Specificity

While all HKS S2000 headers are designed to fit both AP1 and AP2 chassis, there are differences in O2 sensor placement and flange size. Always verify with HKS or your dealer that the part number matches your model year. The most common part numbers include the 14002-AT001 (early AP1) and 14002-AT002 (later models with larger flanges).

Tuning Your S2000 After Header Installation

To fully realize the benefits of an HKS header, an ECU tune is highly recommended. The stock ECU relies on closed-loop feedback from the O2 sensors to maintain a specific air-fuel ratio, but it cannot adjust the ignition timing or fuel maps to take advantage of the improved exhaust flow. Without tuning, you might only see modest gains, and in some cases the car may run slightly lean at high RPM due to the reduced backpressure.

Popular tuning options for the S2000 include:

  • Hondata FlashPro – A dealer-based or mail-order flash that modifies the stock ECU's maps. Many tuners offer pre-made basemaps for header-only setups, which can then be fine-tuned on a dyno.
  • K-Pro – A standalone ECU replacement that offers full control over fuel, ignition, and VTEC engagement. This is ideal for track cars or those with further engine modifications.
  • AEM EMS or Elite – High-end standalone for custom engine builds.

Even a basic flash can net an additional 5–8 horsepower over the header alone, with the added benefit of smoother idle and improved throttle response. Budget for approximately $400–$800 for tuning, which includes both the hardware (if needed) and dyno time.

Maintaining Your HKS S2000 Headers

With proper care, an HKS header can outlast the lifespan of the car. However, the extreme heat cycles and vibration of a high-revving engine require periodic attention. Here's how to keep your headers in peak condition:

  • Inspect for cracks or discoloration every few thousand miles, especially at welds near the flanges and collector. Hairline cracks are rare but can develop on track cars subjected to repeated thermal shocks.
  • Check and retorque header nuts after the first heat cycle. The gaskets compress and studs can loosen slightly. Use a torque wrench and the manufacturer's specification (typically 18-20 ft-lbs on M8 studs).
  • Clean the header surface to prevent carbon buildup and rust. A gentle degreaser and a soft brush are sufficient. Avoid abrasive pads that could damage stainless steel's protective oxide layer.
  • Inspect O2 sensor and wiring for heat damage. Moving the sensor location closer to the cylinder head can expose it to higher temperatures; heat shields or bung extensions may be needed.
  • Watch for bolt loosening on the collector flange. Vibration can cause the spring bolts to back off—apply threadlocker or use locking nuts if persistent.

If you live in an area with harsh winters or salted roads, consider applying a ceramic coating or using a stainless steel cleaner/protectant to guard against surface corrosion. Unlike mild steel headers, HKS's stainless construction is highly resistant to rust, but salt can still cause pitting over many years.

Common Issues and Troubleshooting

While HKS headers are well-engineered, no aftermarket part is perfect. Here are some frequent concerns reported by S2000 owners and how to address them:

  • Header hitting the frame or steering shaft: This can occur if the engine mounts have sagged or if aftermarket mounts shift the engine. Solution: double-check mount condition, and if clearance is tight, use an additional flex joint in the exhaust system or opt for a header with a slightly different collector angle. HKS's design is generally one of the best for clearance, but older cars with worn mounts may need attention.
  • Exhaust leak at the head flange: Usually caused by a warped flange or reused gasket. HKS uses thick flanges, but over-tightening can cause warping. Always use new gaskets and torque evenly. If a leak persists, have the flange resurfaced at a machine shop.
  • O2 sensor error codes (P0133, P0134, P0172): These can indicate that the O2 sensor is seeing different exhaust flow or is too hot. Extend the sensor wire and use a bung extension to move the sensor away from the direct heat. Some tuners also disable the secondary O2 sensor in the ECU if you are running a test pipe.
  • Raspy or metallic sound at high RPM: This is sometimes mistaken for a crack, but it may be caused by the header vibrating against the heat shield or chassis. Check for contact points and use heat shield tape or rubber isolators where possible.

Most of these issues can be avoided with careful installation and a bit of preventive maintenance. The HKS community is active, and forums like S2Ki.com and Honda-Tech have dedicated threads with detailed write-ups for specific header part numbers.

External Resources for Further Reading

  • HKS Official Website – For product specifications and dealer locator.
  • S2Ki Forums – Detailed owner reviews, installation guides, and dyno charts.
  • Hondata FlashPro – Information on ECU tuning for the S2000.
  • Ballade Sports – A reputable retailer offering HKS headers and associated tuning components.

Conclusion

HKS S2000 headers represent a proven upgrade that delivers on multiple fronts: they increase horsepower and torque, improve throttle response, and produce an exhaust note that transforms the character of the car without becoming tiresome on long drives. The use of high-grade stainless steel, mandrel bends, and precision welding ensures these headers stand up to years of spirited driving, whether your S2000 sees street or track duty.

When choosing a header, consider your performance goals, engine modifications, and budget. Pair your HKS header with a quality tune and a complementary exhaust system for the best results. With proper installation and maintenance, these headers will not only enhance your driving experience but also become a lasting part of your S2000's identity.

For owners seeking a durable, well-engineered exhaust upgrade that doesn't compromise on sound or power, HKS headers are an investment that continues to deliver smiles per mile.