2002–2007 Subaru WRX/STI Top-Mount Intercooler, Part 1: Introduction and Goals

Interested in purchasing our WRX/STi top-mount intercooler? Check out our product page for more information!

Mishimoto Subaru WRX/STi Performance Top-Mount Intercooler Kit

The Bugeye, Blobeye, and Hawkeye Subarus have always been a prime choice for a fun daily driver or project vehicle. With a burbley turbocharged flat-four and a robust AWD system, it is hard to beat the overall value of these early models. Nonetheless, the performance aftermarket is massive with documentation available for building your car from mild to wild. Key components to the aftermarket success are the large enthusiast groups such as NASIOC and IWSTI that provide a great place for swapping information on repairs and modifications, and also general discussions about why these cars are so great! These Subarus provide a great base for entry into the racing world, whether it be rallycross, autocross, or track days. Reasonably inexpensive consumables make this a budget track car or fun car, similar to an older BMW or Mazda Miata. With all that praising out of the way, let’s move onward towards our target for this project.

After much debate our team decided to develop a top-mount intercooler specifically for the 2001–2007 WRX and STI. I can guess what you are thinking: this has been done before, the current offerings from other companies work fine, and why are we coming into this project so late. This is easily explained. We have seen firsthand what is currently available, and we think we can develop a better product. We can provide better details and substantiated data that will help tailor your purchasing considerations to the plans you have with your vehicle. We want to develop an intercooler to work with vehicles that are not quite ready for a front-mount intercooler but that are exceeding the capabilities of the stock tube-and-fin cooler. Obviously, we would not produce such an intercooler and recommend you use it on your 500 whp STI. Rather, we want to provide significant performance benefits for vehicles at stock horsepower, up to around 325 whp. (Past this point our engineers are finding that a front-mount intercooler would be more efficient at reducing air intake temperatures [AIT].) The basic goal is to produce the best-performing intercooler for this particular power range.

We already carry a great line of universal intercoolers of different shapes and sizes, as well as a selection of direct-fit units. Presently, we have direct-fit intercoolers for the Hyundai Genesis, Dodge Neon SRT-4, BMW E90, and Mitsubishi Lancer Evolution. These coolers were exciting projects that produced some great bolt-on performance and cooling benefits.

Back to this project! First we set up some basic goals. The Intercooler must:

  1.     support vehicles up to 325 whp
  2.     provide substantial benefits for AITs
  3.     be a direct fit and require minimal, if any, modification
  4.     produce bolt-on horsepower and torque for both stock and modified vehicles

Our primary goal is to provide an ideal core composition that will result in efficient heat transfer and lower AITs. Bolt-on power gains are a secondary objective, however our engineers are confident they can produce both of these benefits. Reduced AITs will result in a much happier engine, and we love happy flat fours.

We also intend to design this cooler with a larger volume than that of the factory core. This will allow for support with modified vehicles and allow for improved power/efficiency when properly tuned. I am confident that our team will have no problem squeezing out a few extra ponies over the WRX and STI coolers.

We did not intend to design a cookie-cutter top mount like the products already on the market. It is more difficult and time consuming to take a new and unique approach, and our team put a huge amount of effort and time into the development of this product. Are the results going to be worth it? Absolutely!

One easy thing about this project was the convenience of finding a test fit vehicle, which can be a challenge, but we are fortunate to have the perfect vehicle already in our shop:  a 2003 WRX wagon. The initial testing of this cooler will include dyno pulls, street use, repeated installation, and data logging.

The Mishimoto WRX wagon
The Mishimoto WRX wagon

So after taking a look at current offerings for top mounts, we decided to dive right into a few prototype designs. Check back next time for our second stage of product development!

Interested in purchasing our WRX/STi top-mount intercooler? Check out our product page for more information!

Mishimoto Subaru WRX/STi Performance Top-Mount Intercooler Kit