Life is all about balance. It may be cliché, but it’s true, especially when modifying cars. Attention must be paid to balancing power with handling, air with fuel, and most importantly, parts on your car with money in your wallet. That same balancing act applies to our catch can kits. We spend a lot of time balancing the cost of a catch can kit with its benefits.
Many engines have a “clean” side of the crankcase ventilation system and a “dirty” side. Some engines produce just as much worrisome blow-by from their clean side as their dirty side. We usually develop a two-can kit for these engines, one for each side of the system. Other engines’ clean sides don’t really produce much blow-by, so adding another can would drive up cost with no benefit to the customer.
Then, there are the engines whose clean-side blow-by production is borderline. Their clean side may not produce much blow-by, depending on driving style, power output, age, and a multitude of other factors. Or, the clean side might be just as troublesome as the dirty side. Subaru’s boxer engine falls into this category. For years, owners of Subarus equipped with turbocharged EJ series motors have been dumping blow-by out of their intercoolers on a regular basis. More recently, Subaru’s introduction of the direct-injected FA series has meant that owners now have even more reason to fear blow-by.
With each generation of the EJ series, and now the introduction of the FA series, Subaru’s crankcase ventilation systems have become more effective, but they’re still not perfect. In the case of the 2015+ WRX, the FA20DIT CCV system isn’t quite effective enough to prevent blow-by from building up on the back of the intake valves. In our testing, we saw a significant amount of blow-by from both the PCV (dirty) side and the CCV (clean) side, which is why our engineers at Mishimoto developed the 2015-2016 WRX catch can kit. Like our other dual-can kits, this design removes oil, fuel, and other by-products of combustion from both the clean side and the dirty side of the CCV system, letting only truly clean air glide over the intake valves of your FA20.
In the time since the 2015 WRX catch can kit’s release, we’ve gotten a mountain of feedback from the Subaru community. We’ve seen owners whose clean-side can catches a significant amount of blow-by and they’re happy to have it protecting their valves. Others’ clean sides only receive the occasional misting of blow-by. That’s why we’ve decided to release a catch can kit that solely targets the PCV system. Now, those of you who would like to protect your valves from the majority of blow-by, but can’t justify the cost of the full kit, have an effective solution.
So, how do you know if you need the full kit or just the PCV side? Probably the easiest way to find out would be to check the CCV line of your WRX for blow-by residue. The CCV line runs from a port on the driver’s side cylinder head, right behind the A/C compressor, to the turbo inlet pipe on the passenger side of the engine bay. To check if you may need a CCV-side catch can, pull this line where it connects to the cylinder head and inspect it for blow-by residue. It’s likely that you will see some residue no matter what, but if the line looks like somebody dunked it in your oil pan, you need the full kit. Of course, if you’re finding that your intercooler is cooling as much blow-by as it cools intake air, you probably need the full kit.
In the end, keeping your WRX’s engine happy is just as important as keeping your wallet happy. In fact, a happy engine often means a more reliable, and thus cheaper, engine. With the PCV-side WRX catch can kit you’ll be able to maintain that balance, or maybe, spend some more money on going faster. The choice is yours.
Thanks for reading,