Cooling Down the EJ
First, I admit I broke a critical rule of testing. I changed multiple things at once. Therefore, it is hard to say how much each of the following modifications contributed to the end results. However, the good news is that they collectively controlled my temps. With over 100 WHP added to the Subie, oil temperatures got to 270 F in the pan during a track day at Button Willow. Something had to be done, so I started with an oil cooler. With a cross-country move approaching and a limited window to run the car at Button Willow, I proceeded to do everything I could: ceramic coat the headers, water pump housing upgrade, and hood louvers. I already had an upgraded CSF radiator installed during the motor build.
Process West Oil Cooler
The first step I took was installing the Process West oil cooler. The quality of the product is excellent, and it comes with thorough installation instructions. The only downside is that the cooler mounts in front of the radiator. So it wasn’t shocking that on the next track day, my oil temps stayed around 230 F no matter how hard I pushed the car, but the coolant temps quickly got out of control (222 F). After more than a couple of hot laps in 70 F weather, I’d have to do a cool-down lap to keep my coolant temps under control. More needed to be done.
Ceramic Coating and Water Pump Housing
One thing I failed to appreciate about the stock headers was all the heat shielding. Though a great power adder, the Killer B header was shedding heat into the engine bay. With some downtime during the holidays, I sent off the headers to Jet Hot for ceramic coating. Great customer service and turnaround were as advertised. Of note, they offer different levels of coating for different applications. I went with their Ultra Extreme (2500). Swain Coating works with Killer B, and if you use them, Killer B will honor their warranty. Using Jet-Hot technically voids Killer B’s header warranty. I didn’t know this at the time, but I haven’t had any problems with the header or coating. Additionally, I upgraded the OEM water pump housing to Killer B’s water pump housing. As you can see above, it allows the coolant to flow out of the water pump much more efficiently.
Hood Louvers
To reduce air pressure under the hood and increase airflow through the radiator, I installed hood louvers from Racing Louvers. This was the most emotionally challenging modification. It hurt to cut up my perfectly good hood. My advice is to go slow and take your time. The templates that came with the louvers were spot-on accurate, and with lots of anxious measuring and triple-checking, I eventually began cutting into the hood. Overall, it's not a hard job but very intimidating. Once they were installed, I have to say I liked the way they looked. All that’s left to do is hit the track!
The Result: It Worked!
Though I changed multiple things at once, the temperature between the previous track day and my debut of the cooling mods was exactly the same! This made for a great comparison! Below is the cooling data between a hot lap from before the cooling mods and after the cooling mods. As you can see below, the coolant temp dropped 18 degrees! I found I could hammer on the car lap after lap, with the only limitation being traffic. Later in the spring, I took the car to some track days with warmer weather and found more still needed to be done. With ambient air temps in the 80s, I found that the oil and coolant temps will gradually build and eventually demand a cool-down lap, but the climb in temp is gradual and manageable. The next step will be some ducting in order to track the car hard in the summer heat.
