Monday, September 24, 2018

AOS - Every turbocharged Subaru should have one

When I bought my first turbocharged Subaru, I started learning all sorts of things to better understand my car.  From maintenance to modifications, there was a lot I needed to know so I could properly care for my car.  I'm still learning things as I take each step with modifying my WRX STI to my liking but when I noticed a puff of blue smoke coming from my exhaust on startup, I ran back to the drawing board and realized I had been holding off on a modification that I probably should've done the second I got the car: an Air-Oil Separator.


While common on modified cars, an Air-Oil Separator (AOS) can still be beneficial.  Even in stock form, oil can still make it's way through the intake system.  Boxer engines, or horizontally opposed engines, have pistons that move side to side. When running, the G-Forces push excess oil to the tops of the pistons. Because oil is just as combustible as fuel, this causes irregularities with the controlled explosions in the engine, subsequently creating multiple explosions or "detonation".  This can lead to causing the ever-popular "ringland failure" problem.  Installing an AOS eliminates the oil vapors in an intake system thus eliminating the loss of octane.  Without oil being burned off and the octane levels up, the engine can make more power!

On a stock turbocharged boxer engine, that oil getting through the intercooler doesn't make its way back to the engine.  As it is subsequently burned off, your oil levels start to drop a little.  It's not a significant amount, but over a long period of time it can be detrimental to the piston rings if the engine oil level isn't kept up.  Tie in the fact that the detonation and oil buildup in the engine are already wreaking havoc on those same rings and it's an accident waiting to happen.  Again, this can still happen on a bone-stock WRX, so even those who have been careful with their cars run the risk.

I've not noticed a single issue since installing the AOS on my car.  No loss in power, no puff of blue smoke, nothing but good things to report.  If you've got a turbocharged Subaru and you enjoy getting after it like I do, an Air-Oil Separator may not be the most glamorous modification you can spend your money on.  However, it'll certainly allow you to to have more fun and more peace-of-mind as you push your car further!

Will the Turbo Forester return?

Well, I can't avoid the facts anymore.  The Forester XT has joined the mausoleum of fun turbocharged Subarus that I loved like the Outback XT and Legacy GT.  Sure, the new 2019 Forester has a "Sport" model, but there's only so much you can do with 182 horsepower and some fancy trim.  While their overall lineup seems to be heading in the vanilla direction, we might still have some hope from our friends at Subaru Tecnica International - STI.


In years past, the US market has been largely ignored for the the Fast and Furious models that guys like me crave.  Look through just about any imported model and you'll find cool variations and homologation models that we've never had on US soil... and the STI lineup from Subaru is no exception.  However, that trend has been starting to change with a few limited production units we've managed to snag in recent years.  Subaru has brought over some STI fun with the BRZ tS and the WRX STI Type RA before, so is a quicker turbocharged Forester a possibility for us in the future?


Foresters have never worn the STI badge here in the states before, but there have been STI versions made in Japan before.  Much like the tweaked BRZ they made, the Forester tS has brought Subaru's racing boys to their family-sized crossover SUV before.  Improved aero, revised suspension, and interior and exterior tweaks to make it feel special.  These features have graced the Forester tS models in Japan before... but those have also been built around the existing turbocharged Forester XT to begin with.  One could say if the US were to get a Forester with STI treatment that it would still only come in the form of aero and handling and leave the naturally aspirated Boxer engine under the hood alone.

Still the possibility of more STI models in the US isn't out of the question.  As part of Subaru's "Prominence 2020 Plan", the STI Brand is charged with bringing more racing support, more performance parts, and more complete cars to the US market.  While the year 2020 is bearing down on us quickly, we've already seen a spike in special edition and limited production performance models coming to the states.

The possibility exists for Subaru to bring a Turbocharged Forester back to the US Market, but it's uncertain if they recognize enough of a demand in the market for something like this.  Don't hold your breath, as Subaru seems to lean more on the WRX and BRZ as their options for performance-minded customers.  Even the 6-cylinder Outback and Legacy have their days numbered and it's uncertain if those models will go back to a single engine option like the Forester has for 2019.  As 2020 approaches with the new Outback and Legacy design, the new WRX and WRX STI design, and the target point for their plans, we'll have to wait and see if STI will deliver us anything more than they already have.  Dear Forester... I'll be waiting.