Should You Go With A TMIC Or FMIC?

We discuss the pros and cons of the top mount intercooler vs a front mount intercooler setup. The answer is broad but what it boils down to is how much power are you planning on making?

For those of you who may be novices to the world of Subaru modification, you might have read on social media posts or articles about what mods you should do to your WRX. After weeding through all the different comments and opinions, you will have a pretty good idea of what mods are highly recommended among enthusiasts.

The basic performance upgrades aka BPU for lingo purposes, will include a cold air intake, cat-back exhaust system, and a COBB Accessport to lock in a required tune. But then there is the intercooler. All turbocharged Subarus will include a factory top mount intercooler which is the objective of this article. We will try to help make a clearer choice when it’s time to upgrade the intercooler on your WRX, STI, or other turbo Subaru models.

WHAT DOES THE INTERCOOLER DO? HOW DOES IT WORK?

So, your turbocharger has 3 main components. You have the compressor side, the middle cartridge which are the blade wheels attached to a shaft with bearings, then you have the exhaust housing. The job of the compressor side is to force air into your intake. The exhaust side pulls exhaust gases out. The air that is forced out of the compressor housing will pass through the intercooler which will lower the intake charge temperatures before entering the intake manifold. The cooler the intake charge temperatures, the higher the efficiency of your turbocharger and the rest of the modifications you have on your Subaru will be fully optimized. And this is true for turbocharged vehicles in general. What happens when those intake charge temperatures aren’t cool enough? Then you do the opposite which is putting a performance limit on your turbocharger and the rest of your mods. This is when your performance experiences heat soak.

WHAT IS INTERCOOLER HEAT SOAK?

Heat soak can occur if you are driving bumper to bumper on a 100-degree day, or if you are driving your Subaru hard on a weekend track day, and your engine is staying in the upper RPM range for longer periods of time. What happens is that your intercooler can get so hot from the engine bay temps, that it cannot cool those intake charge temperatures, forcing hot air into the intake driving up the intake air temperatures. Performance vehicles like the Subaru WRX/STI or even the MazdaSpeed platforms are more subjected to heat soaked intercoolers because they come from the factory with a top mount setup. In a Subaru WRX, the turbocharger sits right beneath the intercooler, so the intercooler must absorb the heat generated by the turbocharger’s exhaust housing along with the surrounding engine bay temps. The factory hood scoop can mitigate the heat allowing air to pass through the surface of the intercooler. But also know that the more modifications you have that generate more power and more boost, the top mount is further vulnerable to heat soak as the engine bay temps increase due to your heavy right foot.

Here is a photo of a stock bug eye engine bay where you can see how small the factory top mount is, and how it is vulnerable to heat in the engine bay:

HOW TO COMBAT HEAT SOAK

The natural cure is a larger intercooler. A larger and thicker core provides more surface coverage and volume to lower those intake charge temperatures before entering the intake. But choosing the right intercooler option is up to your modifications, driving style, and ultimate power goals. With that being said, let’s discuss what option will work best for your application.

A LARGER TOP MOUNT INTERCOOLER

For the majority of enthusiasts, a larger top mount intercooler should provide plenty of cooling support for the average modified Subaru. We carry a great selection of quality top mount options vs front mount intercooler options which we will discuss further down. For now, let’s highlight some of the main benefits of upgrading to a larger top mount intercooler setup:

DIRECT BOLT-ON INSTALLATION: Many of the aftermarket options we carry are direct bolt-on with minor revisions that will include all the required hardware to complete the installation. When compared to a front-mount intercooler setup, you need to install the piping, or have some fabrication needed depending on if you have a rotated turbo setup or a reverse intake manifold.
EFFECTIVE FOR UP TO 400 WHP: The majority of modified Subaru WRX or STI models on the road will have less than 400-wheel horsepower. Anything above that you should probably have built internals, have a proper built fuel system, along with the rest of the main components to take your power to the next level. But if you have an upgraded turbo and larger injectors and are making about 350 to the wheel on pump gas, you are going to surpass the thermal limits of your factory top mount setup and you should upgrade to a larger core.
FASTER SPOOL: Because a top mount intercooler connects right to the throttle body, there is less distance for the air to travel to the intake when compared to a front mount intercooler setup. A FMIC will have a larger core, along with all the routed piping that the air has to travel through before entering the intake. Now there is only a slight difference between a TMIC and a FMIC setup, but there are those of you who want less turbo lag as possible.
BETTER ENGINE COOLING EFFICIENCY VS A FMIC SETUP: There is some give and take when comparing a front mount setup to a top mount unit. Now a FMIC setup offers better cooling efficiency in terms of intake charge temps. However, it blocks the radiator therefor, a top mount intercooler will help to maintains normal coolant temps during warmer summer months.
MAINTAINS PERFORMANCE FOR THOSE IN WARMER AREAS: Applies to both FMIC setups and TMIC units. But for those of you in Arizona or an area that has a high volume of traffic with higher temps like a Southern California, a good aftermarket top mount intercooler setup will reduce the chances of heat soak to allow you to maintain peak performance in higher temps.

OR A FRONT MOUNT INTERCOOLER SETUP

A front mount intercooler setup is a standard modification on any turbocharged vehicle making decent power. The larger the core, the cooler the temps will be to the intake. And getting cooler temps to the intake is the main goal with intercoolers to optimize the performance out of your engine, and other modifications. When autumn hits and we get that first cold day after summer and your Subaru feels like it’s got a little more pep, those are the cooler temps getting fed into the intake. Because of these reasons, a front mount intercooler setup is the overall better choice if you’re worried about heat soak.

PROVIDES A LOWER INTAKE CHARGE TEMPERATURE VS A TOP MOUNT: The front mount will always have surface contact with incoming air while in motion vs a top mount that has to rely on that small window coming from the hood scoop. Front mount intercoolers will install in front of the radiator and have an overall larger core to absorb all the incoming air.
WORKS WELL WITH THE FACTORY, OR UPGRADED TURBOCHARGERS: This is a great option to have if you decide to build your Subaru further down the road. Front mount setups are highly effective on your factory turbocharger from mild upgrades, or if you have maximized all the basic performance upgrades. And it will be required when you have an upgraded turbocharger that is pushing a lot more air at a higher volume into the intake, or when you start making substantial horsepower numbers.
HIGHLY VERSATILE TO WORK WITH ALL POWER LEVELS: You want all the power, and you want it right now. Unfortunately, modifying Subarus or any vehicle for that matter, can be quite expensive. But that’s okay you can climb the ladder of power gradually. A front mount intercooler kit will provide lower intake charge temps throughout all power levels whereas, the top mount intercooler does have a limiting factor.
THAT RACECAR LOOK: When you see another Subaru coming at you on the opposite lane, what grabs your attention more than anything else? It’s going to be that front mount intercooler, and then you know they mean business. Additionally, when the hood is popped, you see the intercooler piping in polished or in a powder-coated finish. Plus, with the intercooler piping, you will either have a provision to add an aftermarket blow-off valve, or you can have your fabricator custom mount your BOV to your preferred location.
THE INSTALLATION IS A LITTLE MORE INVOLVED: Front mount intercooler setups are a little more time consuming and labor-intensive to instal when compared to a top mount setup. You have to remove the front bumper, mount the core behind the bumper bar, install all the piping and silicone couplers, and put everything else back together. It’s not too terrible to do, but the toughest part about removing or installing the top mount is accessing the clamps on the throttle body coupler due to limited space.

THE CONCLUSION?

A top mount intercooler is a key ingredient that is required on the path of modification. The factory unit works fine with mild bolt-ons. However, when you add a cat-back exhaust system this adds horsepower. A downpipe really adds power. An Intake adds a good amount of horsepower. A tune maximizes the modifications to make the smoothest powerband under load. Any modification increases boost which makes your turbocharger work harder. When the turbo works harder it’s pushing more air. If you’re pushing a higher volume of air through a hot or heat-soaked OEM top mount, you are forcing warm air into the intake. A larger top mount intercooler will reduce these temperatures up to a certain power level which can be argued up to 500, but after 400 you really could benefit from a front mount setup.

If you just want to have a turbo-back exhaust, intake, tune, and injectors, an upgraded top mount intercooler setup will be plenty. And a top mount is still a great option for those of you who have upgraded turbos and are keeping it around 350 on pump or upwards to 400 on E85.

A front mount intercooler setup will work with all power levels. On lower levels, you will experience just a little bit of more lag as the air has to travel through the pipes and a larger core before getting to the intake. However, it is mandatory if you are running 500 wheel or above. It is a good idea if you have a purpose-built track car where the engine is always in the upper RPM-range, and you are driving faster to receive the benefits of all the incoming air hitting the surface of the intercooler core. A front mount intercooler setup will also be ideal for enthusiasts who will eventually make it to those higher power levels. In a nutshell? TMIC is a great upgrade on power levels up to 400 wheel, is easier to install as a direct replacement for your OEM unit. A front mount is good from stock to beyond, a little more difficult to install, and offers cooler intake charge temperatures. It really depends on your power goals, but also consider your driving style, and how much heat you may experience where you live.

TOP MOUNT INTERCOOLER CHOICES:

SUBISPEED LIMITED RELEASE TOP MOUNT INTERCOOLER 2002-2007 SUBARU WRX / 2004-2021 STI

GRIMMSPEED TOP MOUNT INTERCOOLER 2022-2024 SUBARU WRX

PERRIN TOP MOUNT INTERCOOLER 2008-2021 SUBARU STI

COBB TUNING TOP MOUNT INTERCOOLER 2022-2024 SUBARU WRX

PROCESS WEST KHANACOOLER 2015-2018 SUBARU WRX

MISHIMOTO PERFORMANCE TOP MOUNT INTERCOOLER + CHARGE PIPE 2015-2021 SUBARU WRX

ETS TOP MOUNT INTERCOOLER 2008-2014 SUBARU STI

FRONT MOUINT INTERCOOLER CHOICES:

GRIMSPEED FRONT MOUNT INTERCOOLER 2015-2021 SUBARU WRX

ETS FRONT MOUNT INTERCOOLER 2015-2021 SUBARU STI

MISHIMOTO FRONT MOUNT INTERCOOLER 2015-2021 SUBARU STI