Why Upgrade the 4B11T Intercooler

The 4B11T engine, found in vehicles like the Mitsubishi Lancer Evolution X and some high-performance variants, is a turbocharged four-cylinder that responds exceptionally well to cooling upgrades. The factory intercooler is designed for moderate power levels but becomes a bottleneck as boost pressure and ambient temperatures rise. Installing a Greddy intercooler directly addresses heat soak, reduces intake air temperatures (IAT), and helps maintain consistent air density for combustion. Lower IATs mean the engine control unit (ECU) can retain more aggressive ignition timing and avoid pulling timing due to knock, resulting in a measurable power increase. Greddy intercoolers are engineered with bar-and-plate cores and efficient end tanks that offer better flow and thermal exchange than many OEM units. This upgrade is a foundational step before any additional engine modifications because it stabilizes the air charge, protecting the engine from detonation while allowing tuners to extract more power safely.

In this guide, we provide a professional, shop-level walkthrough for removing the factory intercooler and installing a Greddy unit. We cover the tools, preparation, step-by-step mechanical procedures, and post-installation testing. Whether you are a seasoned DIY mechanic or a first-time turbo upgrade installer, these instructions will help you complete the job correctly and avoid common pitfalls.

Tools and Materials Needed

Before beginning, assemble all necessary tools and components. Having everything on hand prevents mid-job interruptions and ensures a clean installation. The Greddy intercooler kit is typically designed as a direct-fit replacement, but some minor trimming or bracket adjustments may be required depending on your specific vehicle variant.

  • Greddy intercooler kit – Includes core, end tanks, and mounting hardware. Verify you have the correct kit for the 4B11T platform (e.g., Greddy V-Spec or Trust GRX series).
  • Metric socket set – 8mm, 10mm, 12mm, and 14mm sockets. A ratchet with extensions and a universal joint will help reach tight bolts.
  • Combination wrenches – Same sizes as sockets, especially for hose clamp hardware.
  • Intercooler piping kit – Often included with the Greddy kit or purchased separately. Verify hot and cold side pipes provide proper routing.
  • Silicone couplers and T-bolt clamps – High-quality 4-ply silicone resists blow-offs under high boost. T-bolt clamps distribute clamping force evenly.
  • Hose removal tool – For separating stubborn OEM hose connections.
  • Torque wrench – For tightening mounting bolts to manufacturer specifications. Over-tightening can crack plastic end tanks or brackets.
  • Trim tool or Dremel – For removing plastic shroud tabs or trimming the crash bar if required.
  • Safety glasses and gloves – Mandatory when working under the vehicle or with cutting tools.
  • Shop vacuum or compressed air – To clean debris after cutting or removing stock components.

Preparation and Safety

Work in a well-ventilated, level area. If possible, raise the front of the vehicle on jack stands or a lift to access the lower bumper area. Ensure the engine is completely cool – a hot engine can cause burns from coolant or contact with exhaust components. Disconnect the negative battery terminal to prevent any electrical shorts or accidental activation of fans while your hands are near the intercooler. Let the vehicle sit for at least 30 minutes after driving to allow the intercooler and piping to cool down.

Vehicle-Specific Considerations

The 4B11T intercooler is located in the front bumper area, below the radiator support. On many models, removing the front bumper cover or grille provides direct access. Check your vehicle’s service manual for bumper removal procedures – typically this involves unscrewing plastic fasteners and unclipping fog light connectors. Some owners prefer to remove only the lower grille or undertray, but full bumper removal gives you the space needed for careful pipe routing and bracket alignment.

Removing the Stock Intercooler

Start by removing any plastic shrouding or bumper pieces that block access. On the Evo X, for example, you will need to remove the inner fender liners partially and the factory intercooler duct. With the area exposed, locate the two brackets holding the stock intercooler – one on each side near the crash bar. Use a 10mm socket to remove these bolts.

Disconnecting the Piping

The stock intercooler has a hot side pipe from the turbo compressor outlet and a cold side pipe leading to the throttle body. Loosen the factory worm-gear clamps and gently twist the hoses to break them free from the intercooler inlets. If the hoses are stuck, use a hose removal tool or carefully pry with a flathead screwdriver – but be cautious not to puncture the silicone. Once all four clamp points are loose, pull the intercooler forward and tilt it to slide it out from under the crash bar. Set the stock unit aside; you may keep it as a spare or sell it.

Note: Some vehicles have an intercooler spray system or temperature sensor. Document the wiring and hose routing before disconnecting. The Greddy kit may require relocating the sensor housings – refer to the instructions.

Inspecting and Prepping the Installation Area

With the stock intercooler removed, take time to clean the area with a solvent or brake cleaner. Look for any oil residue, debris, or bent fins in the vicinity. This is also an excellent opportunity to inspect the condition of the turbo outlet hose and throttle body connection for cracking or leaks. Replace any damaged OEM hoses before proceeding – high boost will find weak points.

Mounting Bracket Modifications

Most Greddy intercoolers come with bracket adapters that bolt to the factory mounting points. Some vehicles require minor trimming of the plastic undertray or crash bar. Measure twice: if the new intercooler is thicker (bar-and-plate vs. tube-and-fin), the bumper cover may need to be trimmed slightly to accommodate the increased depth. Use a Dremel with a cutting wheel for plastic; deburr edges afterward. Test-fit the intercooler before finalizing any cuts.

Installing the Greddy Intercooler

Positioning the Core

Slide the Greddy intercooler into place from below. Align it with the factory mounting holes. Install the brackets loosely first; you may need to adjust the vertical position so the intercooler sits level and centered behind the bumper opening. Tighten the bolts to the torque specified in the kit – typically 8-12 ft-lbs for small bolts. Do not over-torque, as the brackets can flex.

End Tank Orientation

Greddy intercoolers often feature cast end tanks with inlet/outlet positions optimized for the 4B11T. Confirm that the hot side (from turbo) connects to the bottom or side inlet as marked. The cold side outlet should point toward the throttle body. If the end tanks are interchangeable, ensure the hose connections line up correctly with the stock pipe routing.

Securing the Intercooler

After positioning, tighten all mounting hardware in a cross pattern to prevent distortion. Verify there is no contact between the intercooler and the condenser or radiator – vibration can cause premature wear. Some users insert thin rubber strips as a buffer. Reinstall any plastic shrouds that were removed, as they help direct airflow through the core.

Connecting the Piping and Hoses

Hot Side Pipe

Start with the pipe from the turbo compressor outlet. If the Greddy kit includes its own hot side pipe, remove the factory pipe completely. Apply a thin film of silicone lubricant inside the silicone couplers to ease assembly. Slide a T-bolt clamp onto the pipe, then the silicone coupler, then the pipe’s end. Tighten the clamp just enough to hold the pipe from slipping but not so tight that it distorts the coupler. Repeat for the cold side pipe.

Cold Side Pipe

The cold side pipe runs from the intercooler outlet to the throttle body. On many 4B11T applications, this pipe passes near the radiator fan shroud. Ensure there is sufficient clearance; zip-tie the pipe away from moving parts if needed. Use the provided silicone reducers if the pipe diameters differ from the stock throttle body inlet. Double-check all clamps after the initial engine run.

Bov Recirculation

If your kit retains the factory blow-off valve (BOV), ensure the recirculation hose is properly connected to the cold side pipe. Greddy often includes a dedicated BOV flange. Leaks at this point will cause poor idle and stalling. Use a high-quality worm-gear clamp for the rubber hose.

Reassembly and Leak Testing

Before reinstalling the bumper and covers, perform an initial leak test. Reconnect the battery negative terminal. Start the engine and let it idle. Listen for hissing sounds around the intercooler connections. A common method is to use a boost leak tester – a cap that pressurizes the intake system. If you don’t have one, a soapy water spray on all joints while someone revs the engine can reveal bubbles. Tighten any clamp that shows leakage.

Reinstalling the Bumper

Carefully reattach the bumper cover or grille, ensuring no wiring or hoses are pinched. Check that the intercooler is not rubbing against the bumper. Some owners trim the inner bumper support slightly for clearance. When reinstalling plastic fasteners, hand-tighten to avoid stripping.

Final Inspection

With everything back together, inspect the radiator fan operation – the fan should cycle when the engine reaches operating temperature. Also verify that the intercooler fins are not dented during reassembly. Use a flashlight to look through the grille to ensure the intercooler is visible and unobstructed for airflow.

Performance Testing and Tuning Considerations

After installation, a test drive is essential. Start with gentle driving to allow the system to stabilize. Gradually increase boost under load in third or fourth gear. Monitor intake air temperatures using a OBD2 scanner or aftermarket gauge. You should see a significant drop in IAT compared to the stock intercooler, especially after repeated pulls. A 20-40°F reduction is common.

Boost Pressure and Knock Monitoring

Lower IATs mean the ECU will likely adapt timing. If you have an aftermarket tune or access to a reflash, adjust the boost targets slightly upward – the Greddy intercooler reduces pressure drop, so you may see a natural increase in manifold pressure. However, always check for knock via a wideband sensor and logging. Greddy’s official site recommends a retune when changing intercoolers, especially if you are running larger turbos or higher boost levels.

Further Upgrades

Consider pairing the intercooler with a larger intake pipe and high-flow filter to maximize airflow. Many 4B11T owners also install an oil catch can or crankcase ventilation system to keep the intercooler free of oil vapor buildup. Evo X tuning forums are a valuable resource for specific dyno results and real-world tips.

Maintenance and Long-Term Care

Aftermarket intercoolers require periodic inspection. Check the fins for debris or insect buildup, especially in warmer months. Gently wash the core with a low-pressure hose and mild detergent. Avoid using a pressure washer directly on the fins, as they can bend. Inspect silicone couplers for cracking or hardening every 6 months. Replace T-bolt clamps if they show rust. The Greddy anodized finish is durable, but road salt and gravel can chip it – consider installing a mesh rock guard behind the bumper.

If you track the vehicle, consider using a heat shield or reflective wrap on the hot side pipe to reduce radiant heat soak on the intercooler core. Road & Track’s guide on intercooler efficiency explains the science behind heat rejection rates – a clean, well-positioned core is key.

Common Installation Pitfalls to Avoid

  • Overtightening clamps – T-bolt clamps can crush silicone if torqued excessively. Use a torque wrench or feel; tighten until the coupler firms up but does not bulge.
  • Forgetting the rubber grommets – The kit includes vibration isolators between the bracket and core. Skipping them transmits vibration to the welds.
  • Incorrect pipe routing – Some Greddy kits offer multiple pipe configurations. Double-check that the cold side doesn’t contact the serpentine belt or fan.
  • Leaving OEM BOV recirculation line disconnected – This causes a massive vacuum leak. Connect it or cap it securely.
  • Not bleeding the cooling system – If you disturbed the radiator mounting, air pockets can form. Run the engine with the radiator cap off to purge air.

Conclusion

Installing a Greddy intercooler on the 4B11T is one of the most effective single modifications for improving engine performance and reliability. The bar-and-plate core technology reduces air intake temperatures dramatically, allowing for consistent power delivery in all driving conditions. By following this detailed guide, you have ensured a clean, leak-free installation that will serve you for many miles. The step of verifying fittings and performing a boost leak test cannot be overstated – even a small leak undermines the gains. With the intercooler in place, you are now ready to explore further tuning options, knowing the engine is well protected against heat-related detonation. For additional technical data, refer to Engine Basics’ overview of intercooler matching to optimize airflow for your specific power goals.

Enjoy the sharper throttle response and sustained power – your 4B11T will thank you on every gear pull.