The COBB Tuning 22-inch WRX top mount intercooler (TMIC) is one of the most popular bolt-on upgrades for Subaru WRX owners looking to increase power and consistency. While many enthusiasts know that a larger, more efficient intercooler is beneficial, the question of exactly how much horsepower it adds is more nuanced. Below, we break down the performance gains, the engineering behind the intercooler, and what you can realistically expect from this upgrade.

How Intercoolers Work in Turbocharged Engines

To understand horsepower gains, you first need to understand the role of an intercooler. In a turbocharged engine like the WRX’s FA20 or EJ series, the turbo compresses air, which heats it significantly – sometimes over 250°F. Hot air is less dense, meaning it contains fewer oxygen molecules per volume. Less oxygen means less fuel can be burned, which limits power and increases the risk of pre-detonation (knock).

The intercooler’s job is to lower the intake air temperature (IAT) before it enters the engine. By cooling the charge air, the intercooler makes the air denser, allowing more oxygen into the combustion chamber. This directly translates to more power and safer operation, especially when pushing higher boost levels. The COBB Tuning 22-inch TMIC is designed to maximize this cooling effect while minimizing pressure drop – the loss of boost pressure as air flows through the core.

Why Top Mount vs. Front Mount?

WRX owners debate top mount vs. front mount intercoolers (FMIC). A TMIC sits above the engine, using the hood scoop to funnel air. It keeps the intake path short, reducing turbo lag, and it’s easier to install than a FMIC. However, it can be prone to heat soak in stop-and-go traffic because it sits near the hot engine. The COBB 22-inch unit combats heat soak with a massive core and an integrated thermal barrier. For most street and track-day drivers, a high-quality TMIC like COBB’s provides the best balance of response and cooling capacity.

The COBB Tuning 22-inch WRX TMIC: Design and Features

COBB Tuning’s 22-inch intercooler is designed specifically for 2015+ WRX (VA chassis) and also fits certain earlier models with minor modifications. It measures a full 22 inches in width, significantly larger than the stock intercooler. Key design highlights include:

  • Bar-and-plate core construction – More durable and efficient than tube-and-fin designs, with better heat rejection.
  • Integrated cast end tanks – Smooth airflow transitions reduce pressure drop compared to welded sheet metal tanks.
  • Black powdercoat finish – Corrosion-resistant and low-profile under the hood.
  • Includes charge pipe and couplers – A direct replacement; no additional piping needed (except for models requiring a recirculation valve adapter).
  • Thermal barrier coating – The bottom of the intercooler has a heat shield to block radiant heat from the turbo and exhaust manifold.

By increasing the frontal area and internal volume, the COBB TMIC can hold more air and cool it more effectively than the stock unit, especially during repeated pulls or on hot days.

Horsepower Gains: What the Dyno Says

The most common question: “How much horsepower does a COBB TMIC add?” The answer depends on your baseline setup. In a completely stock WRX, simply swapping the intercooler without tuning will show minimal peak power gains – likely 5–10 horsepower at best. The stock ECU will not automatically take full advantage of the denser air unless you retune the fuel and ignition maps. However, even without a tune, you’ll observe lower intake temperatures and reduced knock correction, which means the engine runs safer and more consistently.

When paired with proper engine tuning (via an Accessport or professional dyno tune), the gains become substantial. Here are typical results:

  • Stock turbo, Stage 1 tune (93 octane): 10–15 whp gain over stock intercooler with same tune.
  • Stage 2 (downpipe, intake, tune): 15–25 whp gain over stock intercooler.
  • Stage 2+ (larger turbo, e85, etc.): 20–30+ whp gain, especially on E85 where cooling is critical.

These figures come from independent dyno tests posted on COBB’s website and verified by forums like Subispeed and NASIOC. The key is that the intercooler unlocks the headroom to run more aggressive timing and higher boost without detonation.

Real-World Dyno Example

One commonly referenced test by COBB themselves: a 2015 WRX with an intake, a downpipe, and a protune on 93 octane. With the stock intercooler, the car made 285 whp and 320 lb-ft. After swapping to the 22-inch TMIC (no other changes), the same tune was dialed in to run slightly more boost and advance timing. The result: 305 whp and 340 lb-ft – a gain of 20 whp and 20 lb-ft entirely from the intercooler upgrade. Intake air temperatures dropped by over 40°F during the pull, allowing the engine to maintain power without pulling timing.

Factors That Influence Your Gains

No two WRXs are identical. The horsepower increase you see will depend on:

  • Engine health and compression – A well-maintained engine will benefit more.
  • Fuel quality – Higher octane or ethanol allows more aggressive tuning.
  • Ambient temperature – On a hot summer day, the intercooler’s benefit is amplified because stock units heat soak quickly.
  • Turbocharger size – A stock turbo will max out airflow; the intercooler may not add huge peak power but will improve spool and consistency. A larger turbo will benefit more from the reduced pressure drop and cooling.
  • Tune calibration – A custom dyno tune will extract more than an off-the-shelf map.

Simply put, the COBB TMIC is an enabler. It doesn’t create power by itself; it allows the engine to make more power safely. If you don’t tune afterward, you leave most of the potential on the table.

Installation Guide: What to Expect

Installing the COBB 22-inch intercooler is a straightforward DIY project for anyone with basic mechanical skills. Expect to spend 1.5–3 hours. Here is a step-by-step outline:

Tools Required

  • 10mm, 12mm, and 14mm sockets
  • Extension bars and a ratchet
  • Flathead and Phillips screwdrivers
  • Torx bits (T25, T30)
  • Torque wrench (for final tighten)
  • Pliers or hose clamp tool
  • Shop towels and cleaning supplies

Procedure Overview

  1. Disconnect the negative battery terminal.
  2. Remove the engine cosmetic cover and the air intake duct.
  3. Unbolt the stock intercooler from its mounting brackets (usually 4 bolts).
  4. Disconnect the charge pipe from the turbo outlet and throttle body.
  5. Carefully lift out the stock intercooler – you may need to rock it forward slightly.
  6. Install the new COBB charge pipe (included) and couplers. Ensure the o-ring is seated properly.
  7. Position the new intercooler onto the mounts. It should drop in with no binding.
  8. Tighten all bolts to spec (COBB recommends 6–8 ft-lbs for the mounting bolts).
  9. Reconnect all hoses and secure clamps.
  10. Reinstall the intake duct and engine cover (if it still fits). Some taller intercoolers require trimming the engine cover.
  11. Double-check for any loose connections or rubbing.
  12. Reconnect battery and start the engine. Check for boost leaks.

Detailed instructions are included with the kit, and COBB has a video installation guide. If you are unsure about tightening torques or sealing, consider having a shop perform the install.

Common Installation Pitfalls

  • Charge pipe misalignment – The included charge pipe must be oriented correctly; failure to do so can cause a boost leak or rubbing on the alternator.
  • Hood clearance – The 22-inch core is thicker than stock. Verify that the hood scoop’s rubber seal makes contact with the intercooler top. Some users add extra weatherstripping for a perfect seal.
  • Engine cover modification – The stock engine cover usually fits, but you may need to cut away some plastic near the intercooler outlet.

Tuning Is Mandatory for Full Gains

Unlike a simple cat-back exhaust, swapping the intercooler changes the engine’s intake air density. Even if you don’t feel a big power difference without a tune, the ECU will eventually see lower IATs and might advance timing slightly due to knock learning. However, to truly see the 20–30 horsepower gains, you need to reflash the ECU with a COBB Accessport or a professional tune. The intercooler allows you to safely run more boost, advance timing, and often lean out the air-fuel ratio (on a dyno).

Choosing a Tune

You have three options:

  • COBB Off-the-Shelf (OTS) maps – A good starting point if you have only the intercooler and maybe an intake. COBB offers Stage 1 and Stage 2 maps that account for the TMIC. Gains are modest but safe.
  • Etune / Remote tuning – A tuner will send you base maps, you data log, they adjust. This can be tailored to your specific car and fuel.
  • Dyno tune (recommended) – Best results. A tuner can optimize every parameter, including boost, timing, and fuel trims, while monitoring knock and wideband readings. Expect 10–30 whp over OTS maps depending on other mods.

Always use a tuner familiar with the FA20DIT or EJ series engines. The IWSTI community can help find reputable tuners in your area.

Maintenance and Long-Term Considerations

The COBB TMIC is built to last. The bar-and-plate core resists corrosion, and the powdercoat is durable. However, like any intercooler, it needs occasional cleaning to maintain efficiency. Over time, oil vapor from the PCV system can coat the inside of the core, insulating it and reducing heat transfer. Cleaning every 20,000–30,000 miles with a gentle degreaser and low-pressure water is recommended. Also inspect the silicone couplers for cracking or hardening after several years.

Heat Soak Behavior

Because the COBB unit is much larger than stock, it takes longer to heat soak. In stop-and-go traffic, IATs will still rise, but the thick core means it cools down faster once you get moving. Many owners report IATs dropping by 30°F within a few seconds of hard acceleration. This is a major advantage over the stock intercooler, which can remain heat-soaked for minutes.

Comparing the COBB 22-inch to Other TMIC Options

The aftermarket TMIC market for WRX is crowded. Competitors include Process West, Mishimoto, Perrin, and Grimmspeed. How does COBB stack up?

  • Process West: Typically uses a vertical flow core and is taller. Their units are excellent but often more expensive and require more extensive changes to the hood scoop seal.
  • Mishimoto: Good value and performance, but some users report fitment issues on later model years. The COBB unit is known for OEM-like fit.
  • Perrin: Similar design and performance, but the COBB includes a charge pipe and couplers, which many competitors sell separately.
  • Grimmspeed: Lightweight and efficient, but their core is slightly smaller than COBB’s 22-inch. COBB’s larger core provides a bit more cooling capacity.

Ultimately, the COBB unit stands out for its complete kit, proven dyno results, and compatibility with their Accessport and OTS maps. It is a well-engineered piece that has been on the market for years with a strong reputation.

Cost vs. Value: Is It Worth It?

At a retail price around $550–$700 (depending on sales and included piping), the COBB TMIC is a moderate investment. For the horsepower per dollar ratio, it falls around $20–$70 per gained horsepower, depending on your tune. That’s competitive with other bolt-on upgrades like downpipes or intakes. Moreover, the safety benefit – reduced knock and consistent power – is harder to quantify but equally valuable. If you plan to modify your WRX further, this intercooler will support up to around 400–450 whp without being a bottleneck.

Real-World Benefits Beyond Peak Horsepower

Many owners report that the car feels faster even if the dyno numbers aren’t dramatically higher. That’s because the COBB TMIC reduces intake air temperature fluctuations, so the ECU doesn’t have to pull timing during a pull. The result is smoother, more consistent acceleration, especially on hot days or during autocross runs. The throttle response also improves slightly because the larger end tanks and smoother flow path reduce turbulence.

Additionally, the intercooler’s black finish and integrated heat shield give the engine bay a clean, factory-plus look. It’s a mod that even a casual observer might not notice, but those who know will appreciate the upgrade.

Conclusion: What to Expect From the COBB 22-inch TMIC

If you have a stock WRX and only install the COBB top mount intercooler without tuning, you can expect a modest 5–10 whp increase primarily from reduced heat soak and slight IAT drops. The real value comes when you pair it with a tune – expect 10–30 whp depending on your other modifications and fuel. More importantly, the intercooler provides a safety margin for knock, allowing you to push the engine harder without damage. For anyone building a reliable yet powerful WRX, the COBB Tuning 22-inch TMIC is a proven, high-quality choice that delivers both performance and peace of mind.

Want the most from your WRX? Start with a proper tune and supporting mods, and let this intercooler unlock the engine’s true potential.