Upgrading your vehicle's intercooler is one of the most effective bolt-on modifications for reducing intake air temperatures and reclaiming lost horsepower. The Mishimoto EVO Intercooler Kit is engineered specifically for Mitsubishi Lancer Evolution models (VIII, IX, and X) and delivers consistent 3–4 PSI gains in boost pressure while dramatically improving charge air cooling. This comprehensive guide walks you through every stage of the installation, from preparation to final testing, so you can complete the job safely and correctly.

What You’ll Need for the Installation

Before you begin, gather the following tools, equipment, and supplies. Having everything on hand will prevent unnecessary interruptions and help you work efficiently.

  • Mishimoto EVO Intercooler Kit (includes intercooler core, aluminum piping, silicone couplings, T-bolt clamps, and mounting hardware)
  • Socket set (metric: 8mm, 10mm, 12mm, 14mm, 17mm)
  • Combination wrenches (same metric sizes as sockets)
  • Torque wrench (capable of 10–50 ft-lb range)
  • Screwdrivers (flathead and Phillips head)
  • Trim removal tools (plastic pry tools to avoid scratching paint)
  • Jack and jack stands (or a lift, for extra clearance if needed)
  • Heat-resistant gloves
  • Safety glasses
  • Coolant (OEM-spec or equivalent – check your owner’s manual)
  • Shop rags and a drip pan
  • Penetrating oil (if fasteners are rusty – optional)
  • Digital camera or phone to take reference photos before disassembly

Preparation Steps

Proper preparation is critical for a smooth installation. Park the vehicle on a level surface, allow the engine to cool completely (at least 2 hours after operation), and disconnect the battery as your first active step.

Safety First: Disconnect the Battery and Relieve System Pressure

Begin by disconnecting the negative (black) terminal from the battery. This eliminates the risk of short circuits or accidental airbag deployment. Next, remove the oil filler cap and release the pressure cap on the coolant reservoir slowly to relieve any built-up pressure in the cooling system. Never remove a hot radiator cap – wait until the system is cool to the touch.

If you need additional access underneath the front bumper, safely raise the front of the car using a jack and support it on jack stands placed at the designated lift points. Ensure the vehicle is stable before crawling underneath.

Step 1: Remove the Front Bumper Cover

The front bumper cover must be removed to access the factory intercooler and piping. The process varies slightly between EVO models, but the general steps are as follows.

Location and Removal of Fasteners

  1. Remove the screws securing the upper grille (usually 4–6 Phillips-head screws).
  2. Remove the plastic push-clips along the top edge of the bumper cover (use a trim removal tool or small flathead screwdriver to pop the center pin, then pry the clip out).
  3. Remove the screws inside the wheel wells – there are typically 2–3 per side. Turn the steering wheel to each lock position for better access.
  4. Remove the bolts underneath the bumper (usually 2–4 10mm bolts) connecting the bumper to the under-tray.
  5. Carefully pull the bumper cover forward, starting at one side. Disconnect any fog light or turn signal connectors by pressing the release tab. Set the bumper aside on a soft surface to avoid scratching the paint.

Tip: Take a photo of the wiring connectors before disconnecting them to simplify reassembly.

Step 2: Remove the Factory Intercooler and Piping

With the bumper removed, you will have clear access to the stock intercooler, all intercooler pipes, and the blow-off valve (if equipped).

Disconnect Piping and Hoses

  1. Loosen the clamps on the silicone couplers connecting the intake pipe and throttle body using an 8mm socket or flathead screwdriver.
  2. Pull the stock intercooler piping free. Some connections may be tight – twist gently while pulling to break the seal.
  3. If your EVO has a factory blow-off valve (BOV), disconnect its vacuum line from the intake manifold or BOV nipple.
  4. Remove the rubber hose that connects the intercooler to the turbo outlet (typically a large-diameter hose with a spring clamp).

Remove the Stock Intercooler Core

  • Locate the four mounting bolts (two on each side) that attach the stock intercooler to the core support – typically 10mm or 12mm.
  • Support the intercooler from below while removing the last bolts – it can fall if left unsupported.
  • Carefully tilt the intercooler forward and maneuver it out of the vehicle. Pay attention to the A/C condenser lines; bending them can cause expensive damage.
  • Set aside the stock intercooler and any rubber hangers or brackets that you may reuse.

Note: For EVO X models, the factory intercooler is mounted very snugly. You may need to unbolt the crash bar (4 large bolts) to provide enough clearance. The Mishimoto kit includes optional spacers if you choose to retain the crash bar – refer to the included instructions.

Step 3: Pre-Installation Checks and Modifications

Before fitting the Mishimoto intercooler, perform a few preliminary checks to ensure a trouble-free installation.

  • Inspect the Mishimoto core: Ensure there are no shipping dents or bent cooling fins. If you see deep fin damage, return the unit before installation.
  • Test fit the piping: Lay out the new aluminum pipes and silicone couplers on a clean surface. Identify which pipe goes to the turbo outlet, throttle body, and blow-off valve. The Mishimoto kit is application-specific, but it never hurts to confirm routing.
  • Trim the factory fan shroud (if needed): On some EVO models, the Mishimoto intercooler is slightly taller than stock and may contact the lower edge of the cooling fan shroud. If your kit includes shroud trimming instructions, mark and cut a small section using a Dremel or utility knife. Only trim what is necessary – over-trimming can reduce fan efficiency.

Step 4: Install the Mishimoto Intercooler Core

Position the Core

Slide the Mishimoto intercooler into the opening, aligning it with the factory mounting points on the crash bar and core support. The intercooler should fit snugly. If the kit uses provided brackets or spacers, attach them now.

Secure the Core

  1. Install the supplied bolts (typically M8 x 1.25 flange bolts) into the mounting tabs.
  2. Hand-tighten the bolts until they are snug, then use a torque wrench to torque them to 18–22 ft-lb (24–30 Nm). Overtightening can crack the plastic mounting tabs or strip the threads.
  3. Double-check that the intercooler is level and centered relative to the fascia opening. Slight adjustments can be made by loosening and repositioning the rubber bushings (if applicable).

Tip: Apply a small amount of thread locker (blue Loctite) to these bolts to prevent them from loosening over time due to vibration.

Step 5: Route and Connect the New Intercooler Piping

The Mishimoto kit replaces the restrictive factory plastic piping with smooth, mandrel-bent aluminum sections and high-quality silicone couplers. Follow the routing you confirmed earlier.

Turbo-Outlet to Intercooler Charge Pipe

  • Slide a silicone coupler onto the turbo outlet flange (or compressor outlet if you have an upgraded turbo).
  • Fit the corresponding aluminum pipe into the coupler. Use the supplied T-bolt clamps – hand-tighten them only at this stage to allow pivoting and final adjustment.
  • Attach the opposite end of the pipe to the intercooler inlet (driver's side for most EVOs). Secure with another coupler and clamps.

Intercooler-Out to Throttle Body Pipe

  • Connect the second aluminum pipe from the intercooler outlet (passenger side) to the throttle body inlet.
  • If the kit includes a blow-off valve flange, install your BOV on that pipe before tightening the clamps. Use a new gasket or O-ring if provided.
  • Connect the vacuum line from the BOV to the intake manifold (usually a 3/16" or 1/4" vacuum hose). Secure with a small zip tie to prevent blow-off.

Final Pipe Alignment and Clamp Tightening

  1. Visually inspect all pipes to ensure they do not rub against the radiator, fans, hoses, or frame. Rotate each pipe slightly if clearance is tight.
  2. Once satisfied with the alignment, tighten all T-bolt clamps to 35–45 in-lb (4–5 Nm) using a small torque wrench or a nut driver. Overtightening can deform the silicone couplers or crack the aluminum pipes.
  3. Re-check the intercooler mounting bolts one final time.

Pro Tip: Apply a very thin film of silicone grease or dish soap to the intercooler beads and pipe ends before sliding on the couplers. This reduces friction and ensures a leak-free seal.

Step 6: Reassemble the Front End

Reinstall the Crash Bar and Under-Tray

If you removed the crash bar, reinstall it now using the original bolts. Torque them to 70–80 ft-lb (95–108 Nm) – do not guess; use a torque wrench. Reattach any under-tray panels or splash shields.

Install the Bumper Cover

  1. Carefully guide the bumper cover back into place, reconnecting the fog light and turn signal connectors.
  2. Align the cover with the wheel well side and lower mounting points. Press firmly to seat any push-clips.
  3. Install all screws, bolts, and push-clips in the reverse order of removal. Use a Phillips screwdriver to ensure an even tightening – do not overtighten to avoid cracking the plastic.
  4. Reinstall the upper grille and any trim pieces.

Step 7: Reconnect the Battery and Perform a Leak Check

Reconnect the negative battery terminal and tighten it securely. Start the engine and let it idle for a few minutes. Listen for any hissing sounds indicating a boost leak. A quick visual inspection of all couplers and hoses for movement or moisture is also recommended.

For a more thorough check, perform a boost leak test using a shop air compressor with a boost leak tester to pressurize the system to 15–20 PSI. Spray soapy water on all connections – bubbles indicate a leak that must be fixed before driving.

Step 8: Coolant Bleeding (If Required)

If you drained or disturbed the cooling system (e.g., when trimming the fan shroud or moving radiator), bleed the coolant. Run the engine with the radiator cap off until the thermostat opens and no more air bubbles escape. Add coolant as needed to maintain proper level.

Testing Your Installation

With everything reassembled and leak-free, take the vehicle for a test drive. Start with gentle driving to allow the ECU to adapt to the increased airflow and denser charge. Monitor your boost gauge (factory or aftermarket) – you should see a 3–4 PSI increase at wide-open throttle compared to the stock intercooler. Also keep an eye on intake air temperatures (IAT) using a scan tool or OBD-II logger; a quality intercooler will show a significant reduction in IAT during extended pulls.

Common Post-Installation Issues and Solutions

  • Boost creep or surge: If you experience unstable boost, check for a stuck wastegate or misrouted vacuum lines. The Mishimoto kit itself does not affect wastegate operation, but disturbed lines can cause issues.
  • Check engine light: If the CIL comes on, scan the code. Most commonly, it’s a lean code due to unmetered air leaks. Re-check all intercooler connections.
  • A/C warm at idle: If the A/C condenser is blocked by the larger intercooler core, the condenser fan may struggle. Ensure there is at least 1/2" gap between the intercooler and condenser. Some EVOs benefit from a slim fan upgrade.

Tuning Considerations for Maximum Gains

While the Mishimoto intercooler provides a mechanical improvement, the 3–4 PSI boost increase is a result of reduced pressure drop – not an actual increase from the turbo. To take full advantage of the denser air, consider a custom ECU tune (via ECMTuning or other tuning platforms). A tune will optimize ignition timing and fuel delivery for the colder intake charge, often yielding an additional 15–25 wheel horsepower on top of the intercooler gains.

For EVO enthusiasts, the AMS Performance forum offers extensive threads on intercooler tuning, and Mishimoto’s product page provides the latest fitment notes and technical support.

Conclusion

Installing the Mishimoto EVO Intercooler Kit is a rewarding DIY project that delivers tangible performance improvements: consistent 3–4 PSI higher boost pressure, lower intake air temperatures, and more reliable power on hot days. By following this detailed guide and taking the time to ensure proper fitment, secure connections, and leak-free operation, you can unlock the full potential of the kit. Whether you drive your EVO on the street or track, a well-installed intercooler remains one of the best investments for both performance and engine longevity.