Improve charge-air cooling, reduce heat soak and give your Subaru STI’s turbocharged engine a more efficient intercooling system with the Mishimoto Performance Top-Mount Intercooler Kit for the Subaru WRX STI 2008–2021.

The factory top-mount intercooler must deal with increasingly high intake temperatures as boost, engine load and performance levels rise. This can be particularly noticeable during spirited road driving, repeated acceleration or track use. The Mishimoto STI TMIC has been engineered as a larger, more efficient direct-fit replacement for drivers looking to upgrade the cooling system without immediately converting their car to a front-mount intercooler setup.

At the heart of the system is a dense bar-and-plate aluminium intercooler core measuring 3.75 inches thick with a total core volume of 584 cubic inches. Cast aluminium end tanks are TIG-welded to the core to provide the strength and durability required in a turbocharged performance application.

Tested Cooling and Performance Improvement

Mishimoto subjected the STI top-mount intercooler to performance testing against the factory intercooler. During testing, Mishimoto reported a 10°F reduction in intake temperature and recorded a 5 wheel-horsepower and 7 wheel-torque increase on its stock test vehicle.

These figures make the Mishimoto TMIC an attractive upgrade for both standard and tuned Subaru WRX STI models where improved charge-air cooling and resistance to heat soak are priorities. Actual power and temperature results will vary depending on vehicle specification, tuning, ambient temperature, boost pressure and other modifications.

Key Features & Benefits

• Direct-fit performance TMIC for Subaru WRX STI 2008–2021
• Mishimoto-tested 10°F intake-temperature reduction compared with the stock intercooler
• Mishimoto-tested +5 whp and +7 wtq on its stock test vehicle
• Large 3.75-inch-thick intercooler core
• 584 in³ core volume
• Efficient dense bar-and-plate core design
• 100% aluminium construction
• Strong cast aluminium end tanks
• Precision TIG-welded construction
• Designed for standard and modified Subaru STI applications
• Works with the factory intercooler Y-pipe
• No modification required to the standard A/C line
• Supplied with replacement gaskets, PCV hose and throttle-body transition coupler
• Manufacturer states installation can be completed in under 30 minutes
• Choice of Stealth Black or Sleek Silver intercooler finishes depending on variation
• Backed by the Mishimoto Lifetime Warranty.

Available Intercooler Options

Mishimoto UK currently lists three configurations within this Subaru STI TMIC product family.

All three versions use the same performance-focused intercooler design; the primary difference is the intercooler finish and hose colour, allowing you to choose the appearance that best suits your Subaru WRX STI.

Subaru WRX STI Fitment

Vehicle application: Subaru WRX STI, model years 2008–2021. Mishimoto lists EJ257 and EJ255 engine codes for this product and GR/GV chassis codes in its technical information.

For SEO and vehicle-search purposes, this product may also be relevant to searches for Subaru Impreza WRX STI intercooler, particularly for earlier-generation STI models.

Because Subaru specifications can vary between UK, European, Japanese and other market vehicles, customers should confirm vehicle compatibility using the vehicle registration, VIN or existing intercooler configuration before ordering.

Important: This listing is specifically for WRX STI applications. Do not assume compatibility with a standard/non-STI Subaru WRX simply because the model year is the same.

Technical Specifications

Manufacturer: Mishimoto
Product: Performance Top-Mount Intercooler Kit
Product family: MMTMIC-STI-08
This variation SKU: MMTMIC-STI-08BKBK
Application: Subaru WRX STI 2008–2021
Engine codes listed by manufacturer: EJ257 / EJ255
Construction: Aluminium
Core type: Bar-and-plate
End tanks: Cast aluminium
Core thickness: 3.75 in
Core length: 21 in
Core height: 7.25 in
Overall length: 24.5 in
Overall height: 11.5 in
Overall width: 4.25 in
Core volume: 584 in³
Installation difficulty: Medium.

Power and Boost Guidance

Mishimoto describes the 584 in³ intercooler core as providing heat-transfer performance suitable for applications from stock power levels to approximately 400 whp. In its detailed technical notes, Mishimoto separately rates the kit for approximately 250–450 whp, with maximum limits of approximately 500 whp or 30 PSI of boost.

For builds exceeding those limits, Mishimoto advises that a larger front-mount intercooler may be more appropriate.

This makes the MMTMIC-STI-08 range particularly suitable for fast-road cars and moderately modified STI builds where retaining a top-mount intercooler configuration is preferred.

Direct-Fit Installation

One of the major advantages of this Mishimoto Subaru STI intercooler is its direct-fit design. It works with the factory intercooler Y-pipe and does not require modification to the standard A/C line.

Mishimoto states that installation can be completed in under 30 minutes, although actual installation time will depend on vehicle condition, existing modifications and installer experience.

What’s Included?

The Mishimoto MMTMIC-STI-08 kit includes the bar-and-plate top-mount intercooler, intercooler-to-throttle-body transition coupler, PCV hose, bypass-valve gasket, two Y-pipe-to-intercooler gaskets, a 3/4-inch I.D. black nylon hose fitting and a 3/4-inch I.D. black nylon tee hose fitting.

The inclusion of the required couplers, hose fittings and replacement gaskets helps provide a more complete installation package rather than requiring these components to be sourced separately.

Why Upgrade Your Subaru STI Top-Mount Intercooler?

Turbochargers compress intake air, which raises its temperature. The intercooler’s job is to remove as much of this heat as possible before the charge air enters the engine.

A larger and more efficient performance intercooler can help maintain lower and more consistent intake temperatures during demanding driving conditions. This is particularly useful on modified Subaru STI models running increased boost or where the vehicle regularly experiences repeated hard acceleration.

By combining a substantial aluminium bar-and-plate core with direct-fit installation, the Mishimoto Performance TMIC provides an upgrade path for Subaru owners who want increased cooling capacity while retaining the factory-style top-mount intercooler layout.

Ideal For

This intercooler is particularly well suited to Subaru WRX STI road cars, fast-road builds, tuned EJ-series engines, track-day cars and owners upgrading supporting modifications while wanting to retain a top-mounted intercooler.

For extremely high-power applications, however, customers should consider Mishimoto’s stated power and boost limits and determine whether a larger front-mount intercooler would be more suitable.

Frequently Asked Questions

Does the Mishimoto MMTMIC-STI-08BKBK fit the Subaru WRX STI?

Yes. Mishimoto lists this intercooler as a direct-fit application for the 2008–2021 Subaru WRX STI.

Will it fit a normal Subaru WRX?

This product is specifically listed by Mishimoto for the WRX STI. Compatibility with a non-STI WRX should not be assumed. Check your exact vehicle before ordering.

What is the difference between MMTMIC-STI-08BKBK, MMTMIC-STI-08SLBK and MMTMIC-STI-08SLBL?

The main difference is appearance. MMTMIC-STI-08BKBK uses a black intercooler with black hoses, MMTMIC-STI-08SLBK uses a silver intercooler with black hoses, and MMTMIC-STI-08SLBL uses a silver intercooler with blue hoses.

How thick is the Mishimoto STI intercooler?

The performance TMIC uses a 3.75-inch-thick core with a total stated core volume of 584 in³.

Does this intercooler increase power?

During Mishimoto’s testing on its stock test vehicle, the company recorded increases of 5 whp and 7 wtq together with a 10°F reduction in intake temperature compared with the stock intercooler. Results on individual vehicles will vary.

Do I need to modify the A/C line?

Mishimoto states that the intercooler installs without modification to the factory A/C line and works with the standard intercooler Y-pipe.

Is this suitable for a modified STI?

Yes, within the manufacturer’s recommended operating limits. Mishimoto’s technical information rates the kit for approximately 250–450 whp, with approximate maximum limits of 500 whp or 30 PSI. Cars exceeding those levels may be better suited to a larger front-mount intercooler.

Does it come with a warranty?

Yes. Mishimoto lists this product with its Lifetime Warranty