Why Upgrade to a Garrett 24-Inch Intercooler on Your Evo?

The factory intercooler on any Mitsubishi Evo works reasonably well for stock power levels, but it quickly becomes a bottleneck once you start turning up the boost. Heat soak, pressure drop, and restrictive core density all conspire to rob you of power exactly when you need it most. A Garrett 24-inch intercooler addresses these issues head-on with a larger frontal area, more efficient bar-and-plate core construction, and significantly better heat rejection. This upgrade lowers intake air temperatures by 30-50°F under sustained boost, which directly translates to more consistent power delivery and reduced risk of knock. For Evo owners running upgraded turbos, higher boost levels, or track days, this is one of the most effective cooling upgrades you can make. This guide covers every step of the installation process, from tools and preparation to final tuning considerations, so you can tackle the job with confidence in your own garage.

Understanding the Garrett 24-Inch Intercooler Design

Before diving into the installation, it helps to understand what makes the Garrett 24-inch intercooler a worthwhile investment. Garrett is a name synonymous with turbocharging, and their intercoolers are engineered to match the performance of their turbochargers. The 24-inch variant refers to the core width, which is designed to fit within the Evo's front bumper opening with minimal modification. The intercooler uses a bar-and-plate core design rather than the tube-and-fin construction found on many factory units. Bar-and-plate cores offer superior thermal efficiency and structural rigidity, meaning they resist deformation under high boost pressures. The internal fin density is optimized for both flow and heat transfer, and the cast end tanks feature smooth internal transitions to reduce turbulence and pressure drop. Typical pressure drop across this intercooler is less than 2 psi at flow rates exceeding 600 hp, which is excellent for a street-driven performance car.

Key Specifications

  • Core dimensions: 24 inches wide by 12 inches tall by 3.5 inches thick
  • Core construction: Bar-and-plate with louvered internal fins
  • End tanks: Cast aluminum with smooth internal transitions
  • Inlet/outlet: 2.5-inch or 3-inch diameter options depending on kit
  • Estimated flow capacity: 700+ hp
  • Weight: Approximately 18-22 pounds depending on configuration

These specifications make the Garrett 24-inch intercooler suitable for everything from a mild daily driver on pump gas to a serious track weapon running E85 and a larger turbo. The core size is large enough to make a real difference but remains manageable for a DIY installation without requiring extensive bumper beam modifications or cutting.

Tools and Materials You Will Need

Having everything ready before you start will save you multiple trips to the tool box and keep the installation moving smoothly. Here is a complete list of what you need:

  • Garrett 24-inch intercooler core and end tank assembly
  • Intercooler piping kit (hot side and cold side, typically 2.5 or 3-inch aluminum)
  • Socket set with metric sockets from 8mm to 19mm
  • Combination wrenches: 10mm, 12mm, 14mm, 17mm
  • Screwdriver set: flathead and Phillips
  • Hose clamps: heavy-duty T-bolt style preferred over worm gear (6-8 required)
  • Silicone couplers: 4-ply with embedded reinforcement (at least 4 standard, plus reducers if needed)
  • Heat-resistant tape or heat wrap for charge piping near exhaust components
  • Drill with step drill bit or hole saw (for mounting bracket holes if not pre-drilled)
  • Measuring tape or calipers
  • Safety goggles and mechanic's gloves
  • Jack and jack stands or ramps
  • Trim removal tools for bumper clips and fasteners
  • Penetrating oil (for stubborn bolts)
  • Shop towels and cleaning solvent
  • Anti-seize compound for bolts
  • Torque wrench (recommended for critical fasteners)

You may also want a helper for positioning the intercooler and aligning piping, especially if this is your first time removing the bumper on an Evo. The fitment is generally good, but having an extra set of hands makes the job significantly easier.

Preparation and Vehicle Setup

Proper preparation reduces the chance of damaging components and ensures the installation goes smoothly. Start by parking your Evo on a level, well-lit surface. If you have access to a lift, use it, but jack stands and a creeper will work fine for this job. Disconnect the negative battery terminal and secure it away from the battery post. This prevents any accidental short circuits and protects the ECU during the electrical disconnection of any cooling fans or sensors you may need to move. Allow the engine to cool completely if it has been running recently, as many of the components you will be working near get extremely hot.

Removing the Front Bumper

Getting to the intercooler area on an Evo requires removing the front bumper cover. This is a straightforward process if you take your time and work methodically. Locate the fasteners holding the bumper in place. These are typically a combination of bolts along the top edge near the hood latch, plastic push clips in the wheel wells, and screws along the bottom lip. Use a trim removal tool for the plastic clips to avoid breaking them. A few 10mm bolts secure the bumper to the crash bar or radiator support. With all fasteners removed, gently pull the bumper outward from the sides, working it free from the fender clips. You do not need to fully remove the bumper if you can support it out of the way, but removing it entirely gives you much better access and is worth the extra few minutes. Place the bumper on a soft surface like a blanket to prevent scratches.

Accessing the Factory Intercooler

With the bumper off, you will see the factory intercooler mounted directly in front of the air conditioning condenser and radiator. The factory unit is held in place by two or four brackets bolted to the radiator support or crash bar. There will also be charge pipes running from the turbocharger compressor outlet to the intercooler inlet, and from the intercooler outlet to the throttle body. Take a moment to inspect the condition of the factory piping and hoses. You may notice any existing boost leaks, cracked couplers, or loose clamps, which are common issues on higher-mileage Evos. This is also a good time to clean out any debris lodged between the intercooler and the condenser.

Removing the Factory Intercooler

Removing the factory intercooler is a direct process that involves a few specific steps. Begin by loosening the hose clamps on the charge pipes at both the intercooler and the throttle body/turbo ends using a socket or screwdriver depending on the clamp type. Gently twist and pull the charge pipes apart from the intercooler. If they are stuck, use a small pry bar or flathead screwdriver with caution to avoid damaging the intercooler or piping. Once the piping is disconnected, locate the mounting bolts securing the intercooler brackets. There are typically two on the top and two on the bottom, but some Evo models may have additional fasteners. Remove these bolts and carefully lift the intercooler out of the vehicle. Watch for any plastic shrouds or fans that may be attached to the intercooler frame, especially on later model Evos. With the intercooler removed, clean the area thoroughly, removing any dirt, oil, or debris that has accumulated behind the core. This is also an excellent opportunity to check the condition of the radiator and condenser fins and straighten any bent ones with a fin comb.

Installing the Garrett 24-Inch Intercooler

Now comes the centerpiece of the upgrade: fitting the Garrett intercooler into the car. Position the new intercooler in the factory location or slightly forward if you need additional clearance for the piping. The Garrett unit is larger than stock, so you may need to make small adjustments to the mounting points. Most Garrett intercoolers come with pre-drilled brackets that align with the factory mounting holes, but some require you to drill new holes or use supplied brackets. If drilling is necessary, measure twice before committing. Use a center punch to mark the hole location, then drill with a step bit or a sharp bit at a slow speed to avoid tearing the metal. Secure the intercooler using the supplied bolts and washers. Apply a small amount of anti-seize to the threads to prevent corrosion and make future removal easier. Torque the bolts to a moderate specification, around 15-20 ft-lbs for typical M8 fasteners, but check the instructions provided with your specific kit. The intercooler should sit level and square within the bumper opening. If there is any interference with the crash bar or bumper beam, you may need to trim or space the intercooler slightly. Many Evo owners find that the Garrett 24-inch intercooler fits with minimal trimming, often just a small notch on the lower bumper support.

Piping Considerations

The piping that comes with a quality intercooler kit is designed to route from the turbo to the intercooler and then to the throttle body with minimal bends. Fewer bends mean less turbulence and lower pressure drop. Before installing the piping, dry-fit all the sections to ensure they align properly. The hot side pipe from the turbo to the intercooler often runs close to the exhaust manifold or downpipe. Wrap this section with heat-resistant tape or use a heat shield to reduce heat soak into the intake charge. The cold side pipe from the intercooler to the throttle body is just as critical. Keep it as short and straight as possible. Trim the pipes to length using a hacksaw or pipe cutter if they are too long. Deburr the ends with a file to prevent the silicone couplers from being cut. Slide the silicone couplers and clamps onto the pipes, then connect them to the intercooler end tanks and the turbo or throttle body. Tighten the clamps evenly, ensuring the coupler is fully seated on both the pipe and the intercooler neck. Use T-bolt clamps rather than standard worm gear clamps, as they provide more consistent clamping force and are less likely to back off under vibration.

Final Connections and Piping Assembly

With the intercooler mounted and all pipes cut to length, finalize the piping connections. Start at the turbocharger compressor outlet. Slide a silicone coupler over the turbo outlet, then install the hot side pipe, ensuring it does not contact any hot engine components. Secure with T-bolt clamps at both ends. Route the pipe to the intercooler hot side inlet. The inlet is typically on the driver's side for a 24-inch intercooler, but confirm the orientation of your specific unit. Connect the cold side pipe from the intercooler outlet to the throttle body. This pipe often needs to clear the fan shroud and alternator, so check for clearance issues. If the pipe contacts the fan shroud, you may need to trim a small section of the shroud with a utility knife. Some kits include a blow-off valve or recirculation valve fitting on the cold pipe, so ensure any sensors or vacuum lines are reconnected correctly. Double-check every clamp and ensure the silicone couplers are not twisted or pinched. A small boost leak at any joint will cost you performance and may cause tuning issues.

Reinstalling the Front Bumper and Trim

Before reinstalling the bumper, verify that the intercooler is centered in the opening and that there is adequate airflow to the core. The Garrett 24-inch intercooler is designed to fill most of the front bumper opening, which maximizes air capture. If the bumper does not sit flush, check for any piping or brackets that are contacting the bumper skin. Adjust the position of the intercooler slightly or add spacers if needed. Once everything fits correctly, reinstall the bumper in reverse order of removal. Align the clips and slides carefully to avoid breaking them. Tighten all fasteners evenly. Reattach the wheel well liners and any undertray components. Reconnect the battery and verify that the cooling fans do not contact the intercooler or piping when they spin. If they do, adjust the piping routing or trim the fan shroud slightly.

Initial Startup and Leak Testing

After the installation is complete, perform a thorough check before starting the engine. Reconnect the battery, then turn the ignition to the ON position without starting the engine. Listen for the fuel pump prime and ensure no warning lights remain on that indicate a disconnected sensor. Start the engine and let it idle. Listen for any unusual noises such as whistling or hissing from the intake system. A boost leak test is highly recommended at this stage. You can build a simple leak tester from a PVC cap and a Schrader valve that fits the turbo inlet, or use a commercial boost leak tester. Pressurize the system to 15-20 psi and listen for leaks. Common leak points are at silicone coupler joints, the intercooler core itself, and the throttle body gasket. Soapy water sprayed on joints will bubble at any leak point. Fix any leaks before driving. If you do not have a boost leak tester, a careful visual inspection and a gentle throttle blip can reveal major leaks, but a proper test is far more reliable.

Test Drive and Performance Verification

With the engine running smoothly, take the car for a gentle test drive. Allow the engine to reach operating temperature before applying significant boost. Drive at low load for the first few miles, then gradually increase boost pressure. Pay attention to how the car pulls. Compared to the factory intercooler, you should notice that the car feels stronger in the mid-range and that power does not fall off as quickly during sustained acceleration. This is a result of lower intake air temperatures and reduced pressure drop. If you have a boost gauge or data logging capability, monitor boost pressure. You may see a slight increase in boost due to the lower restriction of the Garrett core. If you also have an intake air temperature sensor, watch the IATs during a pull. A well-functioning Garrett 24-inch intercooler should keep IATs within 10-15 degrees of ambient under normal driving, and well below 30 degrees above ambient under sustained full-throttle pulls. If your IATs are still high, check for heat soak from the piping or consider adding a heat shield for the hot pipe.

Tuning Considerations After Intercooler Upgrade

Installing a larger intercooler changes the air density and flow characteristics of your induction system. If your Evo is tuned on the factory ECU with a conservative calibration, the increased cooling may actually lean out the air-fuel mixture slightly at high boost because the air is denser. This is generally safe, as the intercooler prevents knock, but it is ideal to have the car re-tuned to take full advantage of the upgrade. A competent tuner can adjust the boost, timing, and fueling to maximize the benefits of the lower intake temperatures. On a modified Evo with an aftermarket ECU, this is a natural step. Even if you are not planning a full retune, it is worth logging your fuel trims and knock correction values after the install to ensure everything is within safe parameters. Many enthusiasts find that they can safely run a degree or two more timing advance with the Garrett intercooler, yielding noticeable power gains.

Common Challenges and How to Handle Them

No DIY installation is without potential pitfalls. One common issue is fitment interference with the air conditioning lines or radiator hoses. On some Evo models, the larger intercooler core may contact these components. If this happens, carefully bend the AC lines slightly away using a tubing bender, or add small spacers between the intercooler brackets and the mounting points to shift the intercooler forward. Another challenge is piping alignment. Aftermarket kits sometimes require you to cut the pipes, and getting the angle exactly right takes patience. If a pipe is angled awkwardly, the coupler will be stressed and may leak. Take the time to adjust the pipe orientation and, if necessary, cut a small amount off the pipe to change the angle. Finally, the bumper may not clip back on as easily as before. This is common with larger intercoolers. You may need to trim the bumper support or the inner lip of the bumper skin. Use a sharp utility knife or a Dremel tool, and remove material gradually until the bumper fits without binding.

Long-Term Maintenance and Care

A Garrett intercooler is built to last, but it does require some basic attention. The bar-and-plate core can trap debris such as leaves, bugs, and small stones. Periodically clean the face of the intercooler with a soft brush or low-pressure water. Do not use a pressure washer directly on the core fins, as high pressure can bend the delicate cooling fins and reduce efficiency. Check the silicone couplers and T-bolt clamps every few thousand miles. Silicone ages over time and can harden or develop cracks, especially near hot engine components. Replace any couplers that show signs of deterioration. Also, check the mounting bolts for tightness, as vibration can loosen them over time. With these simple checks, your Garrett intercooler will provide many years of reliable service.

Performance Gains and What to Expect

Upgrading to a Garrett 24-inch intercooler is not just about peak horsepower, though that does increase. The real benefit is consistency. On a hot summer day, a stock Evo intercooler will heat soak quickly, and you will feel the power drop after a few hard pulls. The Garrett core sheds heat far more effectively, so your intake air temperatures stay low for lap after lap or pass after pass. On a typical tuned Evo making 350-400 whp, you can expect a reduction in intake air temperature of 20-40°F at the end of a quarter-mile pass compared to the factory intercooler. On a more aggressively modified car making 500+ whp, the difference is even more dramatic. The lower temperatures also reduce the risk of detonation, allowing you to run more aggressive tuning or lower-octane fuel safely. In real-world driving, this translates to a car that feels stronger, responds better, and is more pleasant to drive hard.

Final Thoughts on the Garrett 24-Inch Intercooler Upgrade

Installing a Garrett 24-inch intercooler on your Evo is a straightforward project that delivers substantial rewards. The process is manageable for anyone with basic mechanical skills and a standard set of tools. The key is to prepare adequately, take your time with the fitment, and never compromise on the quality of the connections. A properly installed intercooler will transform how your Evo performs, especially in challenging conditions. Whether you are building a street car, a track day warrior, or a drag strip contender, this upgrade is one of the best investments you can make. If you want to learn more about the technical aspects of intercooler design, check out Garrett Motion's official charge air cooler knowledge center for detailed engineering data. For additional installation tips and community experience, explore the EvoM.net general discussion forum where many owners share their build threads and solutions. You can also refer to Road & Track's guide on intercooler installation fundamentals for general best practices. If you encounter specific fitment issues, the Mitsubishi Forums community is an excellent resource for model-specific advice, and EngineLabs has a comprehensive comparison of intercooler core types that can help you understand the engineering behind your new setup. Take your time, follow the steps in this guide, and you will be rewarded with a cooler, faster, and more reliable Evo.