Introduction: Why Upgrade to a HKS Racing Exhaust?

The Mitsubishi Lancer Evolution X (Evo X) is a turbocharged all‑wheel‑drive legend, respected for its raw performance and rally‑bred handling. However, the factory exhaust system is restrictive; it muffles the engine’s natural voice and creates a bottleneck that limits horsepower gains from other modifications. Upgrading to a HKS Racing Exhaust is one of the most popular first steps among enthusiasts because it delivers a noticeable power increase across the rev range while unleashing a deep, aggressive exhaust note that complements the Evo X’s character.

HKS exhausts are engineered with mandrel‑bent piping, high‑flow resonators, and lightweight materials such as stainless steel or titanium. These features reduce back pressure, improve exhaust gas scavenging, and drop significant weight from the rear of the car. In many cases, a cat‑back HKS system can add 10–15 horsepower at the wheels when paired with a tune. The sound is distinctive—a smooth, deep growl at idle that builds into a purposeful howl under full throttle, without being obnoxiously loud inside the cabin.

This guide provides a thorough, step‑by‑step walkthrough of installing a HKS Racing Exhaust on your Evo X. Whether you have basic mechanical experience or are a seasoned DIYer, you will learn the tools needed, safety precautions, removal techniques, installation best practices, and post‑installation checks to ensure a leak‑free, durable setup.

Tools and Materials Needed

Before you begin, gather everything required. Having the right tools on hand saves time and prevents frustration. Below is a comprehensive list:

  • HKS Racing Exhaust System – confirm that the kit is specific to your Evo X model year (2008–2015) and includes all hardware (gaskets, bolts, springs, and hangers).
  • Socket set – metric sockets from 8 mm to 18 mm, including a long extension for hard‑to‑reach bolts.
  • Wrench set – combination wrenches (10 mm, 12 mm, 14 mm, 17 mm) for flare nuts and tight spots.
  • Jack and jack stands – a low‑profile floor jack works best; two sturdy jack stands rated for at least 3 tons are essential for safety.
  • Penetrating oil – apply to exhaust flange bolts and hanger studs to ease removal of rusted fasteners (e.g., WD‑40 or PB Blaster).
  • Exhaust hanger removal tool – a dedicated tool or a long flat‑head screwdriver with a bent tip helps pry rubber hangers off the metal studs.
  • Safety glasses and gloves – protect your eyes from falling debris and your hands from sharp edges and hot metal.
  • Torque wrench – for tightening flange bolts to manufacturer specifications (typically 25–30 ft‑lb).
  • Rubber mallet or dead‑blow hammer – useful for aligning stubborn sections of the exhaust.
  • Anti‑seize compound – apply to threads and slip joints to prevent future corrosion and ease disassembly.

Optional but recommended: a creeper (to lie on), a shop light, and a friend to help position the heavy exhaust sections.

Preparation Steps

Proper preparation ensures a safe installation and prevents damage to your vehicle or the new components.

Work Area and Vehicle Setup

  • Park on a level, solid surface – concrete or asphalt is ideal; avoid gravel or dirt.
  • Engage the parking brake and chock the rear wheels to prevent movement.
  • Raise the vehicle using the jack at the designated rear jacking point (the differential housing). Place jack stands under the subframe just behind the rear suspension. Lower the car onto the stands and give it a gentle shake to confirm stability.
  • Allow the exhaust to cool completely if the engine has been running. Hot exhaust components can cause severe burns.
  • Disconnect the negative battery terminal – this is a good habit when performing any under‑car work to avoid accidental sensor shorts.

Inspecting the Existing Exhaust

Before removal, inspect the factory exhaust for rust, missing bolts, or damaged hangers. Note the orientation of the rubber hangers and any clips. Take a few reference photos—this helps during reinstallation, especially if you are fitting a second‑hand HKS system that lacks detailed instructions.

Removing the Stock Exhaust

Removal is straightforward but requires patience, particularly with corroded fasteners. Work from the rear of the vehicle toward the front.

Step 1: Loosen the Flange Bolts

Starting at the rear, locate the two large bolts connecting the rear axle section to the mid‑pipe. Apply penetrating oil and let it soak for five minutes. Use a socket and breaker bar to break them loose. Do not remove them yet—just crack them so they are easier to spin later.

Move forward and loosen the bolts at the front flange (where the mid‑pipe connects to the catalytic converter / downpipe). On the Evo X, there are two 12 mm bolts and two spring‑loaded studs. Be careful not to strip the nuts; use a six‑point socket.

Step 2: Detach the Exhaust Hangers

The stock system uses four to five rubber hangers. Using an exhaust hanger removal tool (or a lubricated flat‑head screwdriver), gently pry the rubber loops off the metal studs. It helps to slide the tool between the rubber and the metal, then twist. If the rubber is stubborn, apply a soap‑water solution or silicone spray. Work on one hanger at a time from rear to front.

Step 3: Remove the Exhaust Sections

With all bolts loose and hangers freed, remove the fasteners completely. The rear section (muffler and pipe) will drop down; support it with one hand to avoid damaging the rear bumper. Slide it out from under the car. Next, remove the mid‑pipe section. If the system is split into three pieces (rear, mid, front pipe on some HKS kits), repeat the process.

Tip: Have a helper support the heavy muffler section while you work on the front bolts—it prevents stress on the remaining hangers.

Installing the HKS Racing Exhaust

Preparation of the new hardware is key. Lay out all HKS components and verify the packing list. The kit should include gaskets, bolts, and sometimes replacement hangers.

Step 1: Dry‑Fit and Align

Before tightening anything, loosely assemble the exhaust sections under the car. Start at the front (catalytic converter flange) and work backward. Engage the slip joints and slide the rubber hangers onto the HKS‑provided studs. Do not install the gaskets yet—dry‑fitting lets you see how the pipes hang. Make sure the muffler tips are centered in the bumper cutout and that there is no contact with the chassis, suspension, or heat shields. If needed, slightly rotate the pipes at the slip joints to adjust clearance.

Step 2: Apply Anti‑Seize and Install Gaskets

Once alignment is satisfactory, disassemble the dry‑fit sections. Apply a thin layer of anti‑seize to all flange threads and to the inside of slip‑joint collars. Install the new ring‑type or multi‑layer steel gaskets between each flange. HKS typically supplies high‑quality gaskets; reuse them only if damaged.

Step 3: Tighten Flanges and Hangers

Reassemble the exhaust, this time with gaskets. Start at the front flange and torque the bolts to 30 ft‑lb (or per HKS instructions). Use a crossing pattern to ensure even sealing. Then work rearward: tighten the mid‑pipe to rear section flange, then the rear axle connection. Finally, attach the rubber hangers. Apply a drop of dish soap to the hanger holes to make installation easier—push them onto the metal studs until they click into the groove.

Step 4: Final Adjustments

After all bolts are snug, go back and torque each one again. Wiggle the exhaust to check for contact. Many HKS systems include a brace that connects the mid‑pipe to the transmission; install that brace now if included. Verify that the hangers are not twisted and that the muffler sits level. If the tips are crooked, loosen the rear section’s clamp, rotate the pipe, and retighten.

Post‑Installation Checks and First Start

A careful inspection after installation prevents annoying rattles and potential damage.

  • Verify all fasteners are tight – double‑check the flange bolts, the muffler hangers, and any clamps.
  • Check clearance – rotate the steering wheel lock‑to‑lock (if the system runs near the steering rack) and bounce the suspension to ensure nothing contacts.
  • Reconnect the battery – if you disconnected it earlier, now is the time.
  • Start the engine – let it idle and listen for exhaust leaks. A hissing or ticking sound near a flange indicates a poor seal. If you suspect a leak, use a gloved hand to feel for escaping air (be careful—exhaust gets hot fast).
  • Perform a road test – drive gently for the first few miles, then check for rattles at different RPMs and load conditions. Listen for drone inside the cabin; moderate drone is normal with a performance exhaust, but excessive vibration may indicate contact with the underbody.

After a few heat cycles, re‑tighten the flange bolts (the gaskets compress). Torque them to specification again to maintain a leak‑free seal.

Performance Gains and Sound Character

The HKS Racing Exhaust transforms the Evo X. Below is a summary of what you can expect:

Power and Torque

Without a tune, the exhaust alone yields a modest 5–10 hp increase, mainly in the mid‑range and top end. The freer‑flowing design allows the turbo to spool slightly quicker because the engine does not have to push against as much back pressure. When combined with a quality ECU tune (e.g., from a reputable shop like Cobb or Ecutek), gains of 15–25 hp are common, along with a broader torque curve.

Weight Reduction

The stock Evo X exhaust weighs approximately 40–45 lb. A HKS titanium back box or a stainless‑steel system typically shaves off 10–20 lb. This reduction in unsprung weight enhances suspension response and overall agility.

Sound Profile

HKS exhausts are known for their refined tone—deep, aggressive, but not raspy. At idle, it is a low rumble; under hard acceleration, it becomes a purposeful roar with minimal drone. The sound is particularly pleasing when the turbo spools, giving the car a motorsport character that turns heads at meets and track days.

If the exhaust is too loud for your daily commute, consider adding a HKS silent mid‑pipe or a resonated test pipe. Alternatively, keep the stock catalytic converter in place—the HKS cat‑back system is compatible with both OEM and aftermarket downpipes.

Tuning Considerations After Installation

Installing a HKS exhaust alters the airflow characteristics, which can affect the air‑fuel ratio. While the factory ECU will compensate to a degree, a custom tune unlocks the full potential.

  • Re‑tuning is strongly recommended – even a conservative tune will improve throttle response, smooth out idle, and add power. Many owners pair the HKS exhaust with a Cobb Accessport or an Ecutek flash.
  • Monitor boost and knock – with increased exhaust flow, boost levels may drop slightly (the turbo does not have to work as hard). A tune can restore or increase boost safely. Use a data logger to ensure knock counts stay low.
  • Consider a high‑flow cat or test pipe – if you are emissions‑compliant, a high‑flow catalyst further reduces restriction. For track use, a test pipe saves weight and improves spool, but it will increase exhaust volume.

Always choose a tuner experienced with Evo X and HKS products. A poor tune can lead to dangerous lean conditions. For reference, check community forums like EvolutionM.net for dyno charts and tuning advice.

Long‑Term Maintenance and Care

A HKS exhaust is built to last, but a little maintenance keeps it looking and sounding great for years.

  • Inspect bolts and hangers every oil change – road vibration can loosen fasteners. Retorque if necessary.
  • Clean the tips regularly – road grime and carbon buildup dulls the finish. Use a non‑abrasive chrome or metal polish. For titanium tips, use a specialty cleaner (e.g., SimiChrome).
  • Watch for corrosion – if you drive in salted roads, rinse the undercarriage frequently. Stainless steel is resistant, but weld joints can be vulnerable. Apply a light coat of CorrosionX or similar to flanges and slip joints.
  • Replace gaskets if leaks develop – a minor leak at a flange can be fixed by tightening; if that fails, replace the gasket. HKS gaskets are available from dealers or on HKS USA’s website.

The exhaust note may mellow slightly as the packing material in the muffler settles—this is normal and typically takes a few hundred miles.

Common Mistakes and Troubleshooting

Even experienced installers can run into issues. Here are solutions to frequent problems:

  • Exhaust hitting the rear sway bar – adjust the hanger orientation or add a spacer between the hanger and the chassis. Some HKS systems include a clearancing bracket; ensure it is installed.
  • Muffler tips too far inside or outside the bumper – loosen the rear clamp and slide the pipe in or out. Mark the ideal position before tightening.
  • Leak at the front flange (catalytic converter connection) – the HKS gasket may be thicker than OEM. Use two gaskets or apply high‑temperature silicone gasket maker (e.g., Permatex Ultra Copper) to the flange face.
  • Drone at 2000–3000 RPM – this is characteristic of many cat‑back systems. Adding a resonated mid‑pipe or a Helmholtz resonator can cancel drone frequencies.
  • Hardware not included with the HKS kit – some HKS systems are sold as “cat‑back only” without flanges. Verify the kit includes all necessary hardware; if not, you can purchase OEM‑style spring bolts from any auto parts store.

If you encounter persistent fitment issues, consult the HKS installation manual (available on HKS’s global site) or reach out to a certified HKS dealer.

Conclusion: Experience the HKS Difference

Installing a HKS Racing Exhaust on your Evo X is a rewarding project that yields immediate, tangible benefits—more power, a lighter car, and a sound that stirs emotion. The installation process is manageable for a DIY enthusiast with basic tools, provided you take the time to prepare and perform careful alignment. After a weekend of work, your Evo X will sound and feel like the performance machine it was always meant to be.

Remember to pair the exhaust with a proper tune to maximize gains and ensure reliability. Whether you use your Evo X as a daily driver, a weekend track toy, or a show car, the HKS Racing Exhaust is an upgrade that will bring a smile to your face every time you press the throttle.