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Discussion Starter · #1 ·
Looking to avoid carbon deposits on the valves of my new WRX base model (FA20). Car will not be modified, or taken to the track.

Should I install dual catch cans, an AOS, or just leave it alone, given how it will be used?

Thanks!
 

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I'm not a professional but I think something is better than nothing. Get the cheaper option keep it installed for a year. So you get all season use and see if they actually do anything. If they don't remove and now you know:)
 

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I would install at least a dbl catch can (usually cheaper option) so you can get best of both world. I don’t think you need more expensive aos because like you said you wont track or mod the car so I can’t justify the expense. The double cans should act as a “filter” within the existing stock system. It can’t be worst than nothing so to me its a go.

Good to note that it’s not an invasive mod too


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Discussion Starter · #5 ·
If I choose to try a catch can...from what I've seen on the net, the PCV side has much more oil in it than the CCV side, to the point where a CCV catch can is not really necessary.

If true, is installing a single catch can sufficient?
 

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Discussion Starter · #7 ·
Before you piss money away.

What result are you expecting?
I'm expecting a) less oil vapor into the intake to reduce carbon deposits on intake valves and b) cleaner air for combustion.

My primary goal is a). I don't want to have valves walnut blasted as general maintenance.
 

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I'm expecting a) less oil vapor into the intake to reduce carbon deposits on intake valves and b) cleaner air for combustion.

My primary goal is a). I don't want to have valves walnut blasted as general maintenance.
This won't achieve that.
 

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Direct injection isn't new and people have bent over barrels trying to solve it.

You may have extended the interval 10%.

It's not just oil from the engine, it's oil from everywhere. In the air, in egr systems, in pcv systems, vacuum systems, losses from seals and bearings in things like turbos.

If you want to solve it, install dual injection.
 

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Discussion Starter · #11 ·
Direct injection isn't new and people have bent over barrels trying to solve it.

You may have extended the interval 10%.

It's not just oil from the engine, it's oil from everywhere. In the air, in egr systems, in pcv systems, vacuum systems, losses from seals and bearings in things like turbos.

If you want to solve it, install dual injection.
Thanks for your opinion, but I'd still like to see evidence, if you have any.
 

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Ive ran catch cans on all my DI cars. They tend to catch quite a bit. I just got my WRX sat(2021) and picked up a radium dual catch set up real cheap locally. Installing that tomorrow. AOE sounded cool but I didnt want to drop 500bucks on it and I have no problem draining the cans. Like said it wont directly solve the issue but will def help prolong the need to blast them. Ive actually never had to blast my other DI engines but may be different on the FA.
 

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@feh, I recommend a quality AOS. I agree with XJman in that it will not eliminate all deposits as there are many other sources of contamination that these devices will not solve for, but I respectfully disagree that it’s a waste of money as it will lengthen the time/miles one will go before needing major service. I’m basing this on personal experience. Before adding catch cans or AOS, I had A LOT of oil in my intake. I also inspected the valves and they too were coated with a lot of oil. Added a set of dual catch cans and found the intake and valves to be dry without new buildup after about a year of driving. I then removed the catch cans for about 6 months, reinspected, and found the intake and valves covered in a lot of oil – again. Long story short: Catch cans/AOS’s are helpful. And they certainly don’t hurt.

If you chose to go the single catch can route, then definitely do the PCV side. I rarely found anything noticeable on the CCV side.

As a personal preference, I recommend an AOS over the catch cans because it does not have to be emptied. Some people like to be able to see how much water/oil is getting trapped, but that got old with me. I also had an unfounded concern that one of the catch cans would fill up between services and block the system -which BTW never came close to happening.

Good luck with your decision and enjoy your new WRX!
 

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Discussion Starter · #17 ·
@feh, I recommend a quality AOS. I agree with XJman in that it will not eliminate all deposits as there are many other sources of contamination that these devices will not solve for, but I respectfully disagree that it’s a waste of money as it will lengthen the time/miles one will go before needing major service. I’m basing this on personal experience. Before adding catch cans or AOS, I had A LOT of oil in my intake. I also inspected the valves and they too were coated with a lot of oil. Added a set of dual catch cans and found the intake and valves to be dry without new buildup after about a year of driving. I then removed the catch cans for about 6 months, reinspected, and found the intake and valves covered in a lot of oil – again. Long story short: Catch cans/AOS’s are helpful. And they certainly don’t hurt.

If you chose to go the single catch can route, then definitely do the PCV side. I rarely found anything noticeable on the CCV side.

As a personal preference, I recommend an AOS over the catch cans because it does not have to be emptied. Some people like to be able to see how much water/oil is getting trapped, but that got old with me. I also had an unfounded concern that one of the catch cans would fill up between services and block the system -which BTW never came close to happening.

Good luck with your decision and enjoy your new WRX!
Thanks CoolMike. What you write here is a pretty good summary of what my research indicates: these devices are not a cure-all, but they definitely help.

I'll be installing a single AddW1 catch can at the PCV.
 

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Thanks CoolMike. What you write here is a pretty good summary of what my research indicates: these devices are not a cure-all, but they definitely help.

I'll be installing a single AddW1 catch can at the PCV.
Post pic of your diy, I tend to always get so focused in the job I always forgets to take pictures of it lol


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Discussion Starter · #19 ·
Installed the PCV catch can yesterday. Pretty straight forward...removing the existing hose from the crank case to the manifold was a little tedious. as the space is pretty cramped. Not real easy to get at the clamps...long needle nose pliers helps here.

Had to trim the hoses, which was a bit of a surprise since this kit is specifically for 15-21 WRXs. Had to go buy a hose cutter, as I wanted to do it right.

Pretty happy with the engineering of the ADD W1 kit. They were also responsive to the couple questions I had.
 

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Thanks for your opinion, but I'd still like to see evidence, if you have any.
Listen to logic here.

If carbon deposits were so simple to resolve, OEMs would include this type of system from the factory.

XJ is correct -- there may be a marginal improvement from capturing oil vapors and windage within the intake, but it's just that - marginal.

I'd expect the burden of proof should be on those pushing a product that is questionably necessary. You are asking the right question to the wrong people. You should be asking for studies with a population of multiple cars, all run identically with the same fuels and in the same climate, 50% with an AOS and 50% without investigating the valves at different intervals.
 
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