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Discussion Starter · #1 ·
Hey Gang!

Nick here from Mishimoto, back with some more goodies in the works for the VB platform, this time in the form of regulating oil temperatures! That's right, we're kicking off the R&D process for our direct-fit oil cooler kit:

Steady On - 2022+ Subaru WRX Oil Cooler R&D, Part 1 - Design Plans and Prototyping


The WRX has been a long-standing namesake in the Subaru lineup, and for a good reason. Its rally-inspired heritage has evolved into a distinct, affordable sporty sedan that is a sucker for bolt-on modifications. However, even as the WRX grows and changes through each iteration, some things remain a constant theme – temperature management, specifically when it comes to oil.

Engine oil is the lifeblood of any vehicle, and maintaining its temperature is ideal for proper lubrication. Subaru knows this and keeps the FA24 T's engine oil temps in check with a liquid-to-liquid stacked plate cooler right at the oil filter housing. However, as the power increases or the driving conditions become more demanding, this stock cooler becomes less efficient and detrimental to the rest of the system, which can cause an isolated case of global warming under the hood. So basically, by giving the stock cooler some backup, it's easier to keep the engine oil at its proper operating temperature while not adding stress to the cooling system.

Reinforcements for the OEM oil cooler come in the form of an additional liquid-to-air cooler remotely mounted on the front of the vehicle. The extra cooler added to the team aids in dissipating excess heat from the oil before returning to the OEM cooler, mitigating the additional heat transfer to the coolant. By installing this cooler in conjunction with the OEM system, our design also avoids the risk of overcooling. As the oil cycles back into the stock system, it will absorb heat from the coolant to maintain operating temperature.




Keen observers and previous WRX owners alike may notice a striking similarity in the FA24's OEM oil cooler. That's because there's more than one common thread in the WRX's evolution. Not much was carried over from the VA WRX, but one component that survived the journey was this oil cooler. Given this, we already had a sandwich plate and filter adaptor on hand to kick off our development, and our design plans whittled down to devising mounts for our 19-row, stacked plate cooler.




With the help of our Faro Design ScanArm, our engineer, Mitch, creates a 1-to-1 scale replica of the VB WRX's front end to determine the perfect placement for our cooler. Mitch then used our modeling software to finalize our design.




As sophisticated as our scanner and modeling software are, nothing quite beats installing these designs on the vehicle. Using the finalized models, we quickly fabricate a pair of steel brackets that easily tie into the WRX's radiator support, providing our 19-row cooler with a secure home. Also, since we already had compatible components in the facility, this newly installed cooler was more than just a test fit but a working prototype.




The WRX might have changed and evolved over the years, but it still hasn't grown out of the need for improved oil cooling. So while this prototype may be functional, we still have our fair share of work to do before it's fully up to Mishimoto standards. Stay tuned for the first look at our completed kit coming soon!


As always, don't hesitate to reach out with any questions that you might have!

-Nick
 

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Discussion Starter · #3 ·
Without a thermostat, this should make warmup slower. How much difference did you see in warmup times?

Also since you have a double stack, any change in oil pressure/flow rate at filter outlet?
Great questions!

So we actually expect the oil warmup times to be about the same between our thermostatic and non-thermostatic kits which is due to how each of these kits installs. Our non-thermostatic kit retains the OEM liquid-to-liquid cooler that will maintain temperatures using coolant. Since it's constantly flowing to the cooler, there will be a slightly longer warm-up for the oil, but it shouldn't be much more than a typical warm up period. Our thermostatic kit on the other hand does not retain the OEM cooler, but will only flow when the oil is to temperature. Again, we don't expect to extend the warm-up time much longer than OEM.

As for the pressure and flow rate, we'll monitor those on additional road tests, but we expect a similar result as our VA oil cooler kit, which was a 5PSI pressure drop.

-Nick
 

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Great questions!

So we actually expect the oil warmup times to be about the same between our thermostatic and non-thermostatic kits which is due to how each of these kits installs. Our non-thermostatic kit retains the OEM liquid-to-liquid cooler that will maintain temperatures using coolant. Since it's constantly flowing to the cooler, there will be a slightly longer warm-up for the oil, but it shouldn't be much more than a typical warm up period. Our thermostatic kit on the other hand does not retain the OEM cooler, but will only flow when the oil is to temperature. Again, we don't expect to extend the warm-up time much longer than OEM.

As for the pressure and flow rate, we'll monitor those on additional road tests, but we expect a similar result as our VA oil cooler kit, which was a 5PSI pressure drop.

-Nick
Interesting that they both have similar warmup. Stock warmup is slow even in mild tropical winters, is it possible to add an electric heater in the adapter plate to warm up oil more quickly?

5psi sounds significant at low revs. FA20 is ~15psi at warm idle.

As an aside, the oil coolers on FA20 hold a lot of oil that doesn't drain out on oil change. Is is possible to have a Tee in the lower hose from oil cooler? A drain line could perhaps be added routed down to splash shield and ending in a drain plug? Hose brackets attached to lower rad support or turbo skid plate would keep it from flopping around.
 
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