Tuesday, August 14, 2018

Subaru WRX Cooling Mods - Upgraded Radiator, Fans, & Oil Cooler

A good client of ours has brought his 2013 Subaru WRX in to our shop a handful of times over the last couple years.  It started out stock, and has progressed with a Stage 2 setup, to full-bolt-ons, to an upgraded turbo and accoutrements.  Now making 400whp, and at the safe limit of the engine and transmission, the owner wanted to make sure it was going to be safe and hold-up in the Florida heat.  We recommended a handful of modifications to ensure the cooling system would be able to keep up with 100+ degree summer temps.  Read on to see what what we did to improve this WRXs cooling capabilities!





First up on the list, and one of the most common cooling system upgrades, is an all aluminum radiator. Commonly called a "racing radiator", these units will typically increase cooling capacity over a stock radiator by adding more cores, capacity, and efficiency.  The stock WRX radiator uses a single core, plastic end-tank radiator. This does it's job for the most part on a stock vehicle, but on a modified car it can be overwhelmed and can cause coolant temps to rise. The plastic end-tanks are also known to get brittle with age and crack, causing a leak, and creating a potentially bad situation for the vehicle.  All of this is remedied with an aluminum radiator, as it uses aluminum end-tanks and in most cases is a dual-core unit, with some radiators offering and extra thick triple-core. The extra cores provide more passages for the coolant to flow through and shed heat, while the end-tanks provide a stronger setup over plastic, while providing more coolant capacity.  These features add up to a more efficient radiator and can lower overall temps, and/or provide extended cooling capacity under extreme conditions. 




To go along with the radiator we added an aluminum fan shroud, and super high-flow SPAL fans in place of the OEM shroud and fans.  The fan shroud bolts onto the radiator and allows the fans to work much more efficiently by pulling hot air from across the entire inner surface of the radiator by creating a small vacuum.  An un-shrouded radiator/fan is moving air only through the portion of the radiator equal to the surface area of the fan.  So having a properly fitting fan shroud will increase the cooling efficiency of the fans when they are on, especially in idling or slow-moving conditions. Equally as important are the fans themselves, in this case we opted to use Italian made SPAL high flow fans mounted to the shroud.  There are a lot of aftermarket fans out there for cheap, many of them from China, and while they boast CFM and voltage ratings, the fact is that they do not move as much air as they want you to think. In short, they are junk.  The appropriate SPAL fans move serious amounts of air, way more than stock, and you can tell just by putting your hand around the radiator area when they are moving.  This air flow is important to pull air through the thicker aftermarket radiator, and to generally move enough air to keep the car cool when stationary.  



We start the process by draining the coolant and removing the stock radiator and fans.  We then mount the aluminum fan shroud to the new aluminum radiator and make sure there are no fitment or clearance issues.  The fan shroud in this case comes with fans, but we ditch those in favor of mounting the SPAL fans in their place. Before we toss the cheapo fans away, we clip the OEM style fan harness plugs off, this allows us to wire these to the SPAL wires, in place of the standard plug they come with. We then plug the SPAL fans right into the stock fan clips for an OEM look and ease of removal.  The whole assembly gets installed into the car, and we use new silicone radiator hoses in place of the stock rubber hoses.  We do this because the silicone hoses are slimmer and do not expand like the stock rubber hoses.  This is important because the engine bay is very tight on these cars, and we have seen the stock rubber hoses come in contact with a pulley or fan, split open, and bleed the coolant out all over the engine bay....Not a good thing.  The install is finished by adding coolant to the system and bleeding it of air bubbles.




Next up on the list is an external air-to-air oil cooler.  Performance engines are generally pretty hard on oil, as the tolerances are tight and this heats up the oil.  Add in forced induction and the oil temps continue to rise into dangerous territory when the engine is pushed hard. An oil cooler is an excellent way to bring those oil temps back down into a more reasonable temperature range, and potentially save yourself from an engine failure due to oil that has become to thin to properly lubricate. In this case we used a kit that mounts an oil cooler core right in front of the radiator, and runs the lines to the factory oil filter location. The install is very straightforward; requiring removal of the oil filter in order to install a sandwich plate, and the front bumper to install the core and mounts. This plate allows the installation of the "in" and "out" lines, which run oil to and from the cooling core.  The oil flows from the engine into the core, which is cooled down by the air moving over it (like an engine radiator), and the cooler oil is then returned to the engine. We ran the oil cooler lines and secured them to the chassis with rubber lined clamps, and zip ties.  The core gets mounted in place and bolted down, and then the bumper is replaced and checked for clearance.





The last mod installed on this car is the "Cylinder 4 Combustion Chamber Cooling kit" by Dom. This mod increases coolant flow in the left-hand cylinder head which improves reliability by reducing detonation causing hot spots. Basically, it Tees into the heater core coolant tube and pulls coolant around cylinder 4, which improves cooling for that cylinder, which is typically the hottest cylinder in the engine.  This is often why you see cylinder 4 failures more than any other cylinder on the Subaru EJ engines.  The install requires removing a plug on the back of the cylinder head and then installing the assembly into that now empty threaded hole.  Sealant is used to ensure the fitting does not back out or leak.  We then cut the lower heat core hose, install the T-fitting, clamp it in place, and then tighten it all up. Coolant is then bled to make sure there are no bubbles in the system, and it is ready to do it's job!  



With all of these mods in place this WRX is now ready for the Florida heat.  The above mods may not be flashy, or add horsepower, but they are a great way to maintain horsepower and are just as important as a shiny new intake. Ensuring your car runs well and doesn't overheat, or stress is lubrication system to the point of failure, is money well spent in any regard. This rings true for a Subaru WRX, STI, or any other performance vehicle. Stay cool out there!



Circuit Motorsports is a performance auto shop located in Orlando, Florida.  We specialize in performance upgrades, ECU tuning, engine builds, and fabrication.  If you are interested in performance upgrades or a full build consultation contact us today!


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