Installing an HKS intake system on your Mitsubishi Eclipse is one of the most popular and rewarding performance upgrades you can make. Whether you drive a second-generation (2G) GS-T, GSX, or a third-generation GT, a high-flow intake improves engine breathing, unlocks horsepower, and sharpens throttle response. This guide covers everything you need to know: the costs involved, the installation process step by step, and the real-world results you can expect — with no fluff or overblown promises.

Understanding the HKS Intake System and Why It Works

HKS is a Japanese performance engineering company with decades of experience in turbo and naturally aspirated applications. Their intake systems are engineered to replace the restrictive factory airbox and intake tract with a smooth, low-restriction path for incoming air. The result is higher volumetric efficiency, which translates to measurable power gains — especially on turbocharged Eclipse models.

The HKS intake for the Eclipse typically includes a high-flow conical air filter (usually oiled cotton or dry synthetic), a mandrel-bent aluminum or carbon-fiber intake tube, silicone couplers, and all necessary hardware. The design reduces turbulence and heat soak compared to the stock plastic intake. Many kits also include a heat shield to keep ambient engine bay temperatures from robbing power.

Unlike generic “short ram” intakes, HKS tunes each system for a specific engine platform. For the 4G63 turbo engine found in Eclipse GS-T and GSX models, the intake tube is shaped to maintain proper air velocity and allow the mass airflow (MAF) sensor to read accurately. On later 4G64 and 6G72 engines, similar care is taken to avoid check-engine lights and idle issues.

Cost Breakdown: What You’ll Spend on an HKS Intake System

The total cost of an HKS intake installation varies by model year, engine type, and whether you do the work yourself or hire a shop. Here’s a realistic look at the numbers:

  • HKS intake kit (new): $250 – $600
  • Used kit (eBay, forums): $150 – $350 (if you can find a genuine one)
  • Professional installation labor: $100 – $300 (1–2 hours shop time)
  • Additional parts (couplers, clamps, MAF adapter): $0 (kit usually includes everything) to $50 if upgrading hardware
  • Required tools if you don’t own them: $50 – $150 (socket set, torque wrench, screwdrivers)

All told, you should budget $400 – $1,000 for a complete installation. Doing it yourself on a weekend saves the labor cost and gives you valuable hands-on experience. If you plan to install other upgrades later (like an HKS exhaust or blow-off valve), buying the tools pays for itself.

For reference, a cold-air intake from HKS for the 2G Eclipse typically retails around $350 new. The 3G (2000–2005) models often see kits priced closer to $280–$400. Always verify fitment for your exact year and engine code — HKS part numbers differ between turbo and non-turbo variants.

Preparing for Installation: Tools, Parts, and Safety

Before you touch your Eclipse, gather everything. Skipping a step can cause frustration mid-install or even damage your engine.

Tools You Will Need

  • Standard socket set (metric, 8mm–14mm)
  • Combination wrenches (10mm and 12mm most common)
  • Phillips and flathead screwdrivers
  • Torque wrench (for MAF sensor screws and throttle body bolts)
  • Pick tool or trim removal tool (for clips on airbox)
  • Safety goggles and mechanic’s gloves
  • Shop vacuum (to clean any debris from the intake tract)

Before You Start

  • Disconnect the negative battery terminal. This prevents shorts and resets the ECU for learning the new airflow.
  • Work in a well-ventilated area. If using a lift or jack stands, ensure the car is stable.
  • Read the HKS instruction manual thoroughly. It will have specific torque values and sensor locations.
  • Inspect your existing intake hoses and vacuum lines for cracks. Replace any damaged rubber before installing the new system.

Step-by-Step Installation Process

These steps are general — always defer to the included HKS instructions for your specific kit. The process is nearly identical for 4G63, 4G64, and 6G72 Eclipse engines, with minor differences in sensor placement.

Step 1: Remove the Factory Intake System

  1. Disconnect battery: Remove the negative terminal and tuck the cable out of the way.
  2. Disconnect MAF sensor: Unplug the electrical connector from the mass airflow sensor. It’s usually on top of the stock airbox or in the intake tube.
  3. Remove the airbox lid and filter: Unclip or unscrew the lid. Remove the old filter and discard it.
  4. Loosen the intake tube clamps: Use a socket or flathead to loosen the clamp at the throttle body and any intermediate brackets.
  5. Extract the stock intake: Wiggle the tube out of the rubber coupler at the throttle body. On turbo models, you may also need to remove the small resonator pipe and the recirculation hose from the blow-off valve.
  6. Unbolt the airbox base plate: Remove the three or four bolts holding the factory airbox to the chassis. Set the base aside.

Pro tip: Clean the throttle body opening and MAF sensor bore with a lint-free cloth and alcohol. Avoid getting dirt into the intake manifold.

Step 2: Install the HKS Intake System

  1. Mount the HKS heat shield (if included): Position it in the stock airbox location. Some kits use the original mounting holes, others require rivnuts or self-tapping screws.
  2. Attach the MAF sensor to the new intake tube: Use the supplied gasket and screws. Torque to factory spec (usually around 35 in-lbs). Do not overtighten — the plastic housing can crack.
  3. Connect the intake tube to the throttle body: Slide the supplied silicone coupler onto the throttle body neck. Then slide the HKS metal tube into the coupler. Tighten the clamp snugly but not enough to deform the tube.
  4. Position the filter: Clamp the HKS pod filter onto the end of the intake tube. Orient it so it sits inside the heat shield if you have one, or in an area with cool airflow (e.g., behind the headlight).
  5. Reconnect electrical connectors: Plug the MAF sensor harness back in. If your kit includes a secondary air inlet (for turbo models), connect that hose.
  6. Double-check clearance: Ensure the tube does not rub against the hood, radiator hose, or alternator belt. If it touches anything, rotate the couplers or use supplied zip ties to adjust.

Step 3: Final Checks and Reassembly

  • Tighten all clamps and bolts to the values in the HKS manual. A loose clamp can cause vacuum leaks and lean conditions.
  • Reconnect the battery negative terminal.
  • Start the engine and let it idle for a minute. Listen for any whistling or hissing — that indicates an air leak. If you have a scan tool, check for fuel trims; they should stabilize within a few driving cycles.
  • Inspect the MAF sensor reading (if possible) to ensure it’s not pegging or reading erratically.

    • Important safety note: After any intake change, the ECU needs time to adapt. Drive the car normally for about 50 miles before evaluating performance. Do not immediately take it to redline — let the learning happen gradually.

    Expected Performance Results

    What can you realistically feel after installing an HKS intake on your Eclipse? The gains vary by model, but here are the most common outcomes:

    Turbocharged 4G63 (GS-T/GSX)

    • Horsepower: +8–15 whp on a stock tune. With a remap or boost controller, gains can exceed 20 whp.
    • Turbo spool: Reduced restriction means the turbo can spin up faster. Expect to see boost arrive 200–400 RPM sooner.
    • Throttle response: Noticeably sharper, especially when transitioning from cruise to acceleration.
    • Sound: The turbo blow-off and intake whoosh become much more audible. Many owners describe it as a “deep growl” under load.

    Naturally Aspirated 4G64 or 6G72 (RS/GS/GT)

    • Horsepower: +5–10 whp. The gain is modest but still measurable.
    • Fuel economy: Some drivers report a 1–2 mpg improvement under light throttle, as the engine doesn’t have to work as hard to pull air.
    • Sound: A deeper intake note, but less dramatic than turbo models.

    These numbers come from real-world dyno tests on Mitsubishi Eclipse forums and HKS’s own data. For example, a 2G Eclipse GSX with just an HKS intake and 3-inch exhaust dynoed 235 whp (up from 210 stock) — a full 12% gain. Your results may vary based on engine condition, altitude, and tuning.

    Long-Term Considerations and Maintenance

    An HKS intake is not a “set and forget” part. To keep it performing, follow these tips:

    • Clean the filter every 15,000–20,000 miles (more often in dusty climates). Use HKS cleaning solution or a generic recharge kit for oiled filters.
    • Inspect silicone couplers for cracks or oil residue. Silicone can degrade if exposed to excessive engine heat or oil vapor.
    • Check MAF sensor health every few months. An oiled filter can coat the MAF wire, leading to incorrect readings. Dry filters avoid this issue.
    • Avoid water crossings. A pod filter sits low in the engine bay on some kits — driving through deep puddles can soak the filter and hydro-lock the engine. Consider a splash guard or heat shield that offers protection.

    Potential Downsides and How to Mitigate Them

    No performance part is perfect. Be aware of these common issues:

    • Heat soak in traffic: A short ram intake (without a heat shield) pulls hot air from the engine bay. In stop-and-go traffic on a hot day, the HKS intake may actually reduce power compared to stock. Solution: Always use the supplied heat shield, or wrap the intake tube with reflective tape.
    • Check engine light: On some 3G Eclipse models, the MAF sensor can throw a code if the intake tube diameter or bend radius is too far from stock. HKS designs their tubes to avoid this, but if you buy a generic knockoff, you might trigger codes. Always buy genuine HKS.
    • Increased intake noise: Not everyone wants to hear their engine or turbo at every throttle blip. If you prefer a quieter cabin, stick with the stock airbox or add a resonator silencer.

    Comparison: HKS vs. Other Eclipse Intake Options

    HKS is a premium brand, but it’s not the only choice. Here’s how it stacks up against competitors:

    • Injen: Similar quality, often cheaper ($200–$350). Injen uses a different filter shape; some drivers prefer HKS filter design for better flow.
    • AEM: Offers both short ram and cold-air variants. AEM’s DryFlow filter requires no oiling. Both brands are solid, but HKS typically has superior silicone and clamp quality.
    • K&N: Very affordable ($150–$250) but lacks a true cold-air heat shield. Works fine on a budget build.
    • eBay generic: Cheap ($50–$100). But you risk poor fitment, leaking MAF adapters, and low-quality filter media. Stick with HKS if you value reliability.

    For most Eclipse owners who want a balance of performance and build quality, HKS is the sweet spot. It’s not the cheapest, but it’s one of the best-engineered systems you can bolt on without touching the engine management.

    Final Verdict: Is the HKS Intake Worth It?

    Absolutely — if you’re realistic about the gains. The HKS intake system for a Mitsubishi Eclipse delivers better airflow, sharper throttle response, and a more exciting driving experience. The cost is moderate, the installation is doable for a home mechanic, and the parts are built to last. Combined with a simple cat-back exhaust or a boost controller (on turbo models), it’s the first step toward a much quicker car.

    For the most accurate pricing and fitment, check the official HKS website. You can also find detailed installation threads on DSMTuners (for 1G/2G) or EclipseForums — these communities are full of real-world dyno sheets and troubleshooting tips. And if you ever plan on bigger upgrades (bigger turbo, cams, standalone ECU), the HKS intake will support them without needing replacement.

    Grab your tools, take your time, and enjoy the process. Your Eclipse will thank you with every rev.