I've been considering adding a catch can to my car to help keep the IM clean. Been doing some reading and there's something I'm scratching my head at.

First off, I can understand that some people who are running open loop setups, where both the breather and PCV outlets from the crankcase are piped to a catch can that's vented to atmosphere, are finding the can quickly fills with oil on the track. Makes sense since the PCV valve is deleted in that configuration, so nothing stops the sloshing liquid oil from entering the tube. (Unless you have a baffle mod to prevent it collecting on top of the baffle.)

What I don't understand is, I've read several people saying their catchcans are collecting 500ml+ of oil in a single session despite being in a closed loop configuration. I would think a closed loop config would maintain the PCV valve in its normal spot at the crankcase outlet, and then route from there, through the can, and to the manifold. And so the valve should normally be closed except when the throttle is off, just like in the stock config. Sure, some oil might still get in there, but it should be the same amount as would be going into the IM if you were stock. In other words if you're catching 500ml per session with a closed loop setup, you would have been burning that 500ml with the stock setup, right?

I'm not burning any significant amount of oil on the track (in STR trim with 100tw tires [edit: clarification - 100tw on the track, not for autox obviously], keeping the oil about halfway between the min and max on the dipstick), so I would think if I run a can in a closed loop setup I shouldn't have any issues with it filling up quickly. But I want to check if I'm missing something. Are people putting the PCV valve between the can and the manifold, instead of between the crankcase and the can? If so, why? If not, is there something else I'm missing that would cause you to collect a ton of oil in the can but not burn the same amount in a stock setup?

 

Have you done the RainH8R mod to your VC? I think that is worth it if you are at tracks that fill up the catch can. I've found that it's very track dependent on if you need one or not.

I had mine with the PCV and crankcase both going to the catch can, then venting to atmosphere. I did not get a drop of oil in it at any track besides Gingerman. Then at Gingerman I overflowed my catch can and spilled oil everywhere. Did the RainH8R mod shortly after and then didn't get a drop of oil anywhere.

 

I don't have a catch can yet, but I'm not burning any noticeable oil at the tracks I frequent, or at autocross. I don't have the mod mostly because I try to stick to the letter of the rules for STR, and I don't know if that would be accepted. But regardless, I don't see how a closed loop setup that maintains the PCV valve would be any worse than the stock setup I have now. Open loop like you have is different because the valve isn't there anymore to block oil sloshing out while under power.

 

" 2020 SCCA® National Solo® Rules — 13. Street Category ....oil catch tanks or oil separators is allowed provided the function of the PCV system remains functional."

Legal for street and thus legal for STR if you keep the PCV. What is not legal for STR are the 100TW tires you said you are running. 200tW is the rule for street or st classes

I run a closed can on my AP1. Do not see anything on the street. At track nights, I see oil in the can. About 1/4 full or maybe 1/3 sometimes. I run a single small can so that is not a lot. I actually tend to see more at some autox events depending on the course, but likely due to the sloshing effect. I had one instance where I forgot about checking it, ran a track night and a 2 day autox and filled the can on the 2nd day of that event, creating quite a smoke screen til I emptied it

You can run a vented can with the PCV in place. Thought that is what most were doing to be honest. I do not like vented cans because I do not see a reason to dump more pollution than I need to out of the car for no reason and do not want to smell fumes from the catch can all the time.

As mentioned, I run a fairly small can, so never burning near the half quart some say they do, but this will be very track dependent. My can is set up like below

 

Thanks for the info on the can filling you're seeing. Before you installed the can were you burning a similar amount of oil to what you're now collecting?

Just to clarify what I meant earlier, I realize that catch cans are legal; that's why I'm looking to add one. It's the rainh8r baffle I'm not sure about.

And I run 100tw on the track, not for autox.

Re vented cans in closed loop, I'm not sure how that would work, as you'd have an unrestricted air path into the intake manifold.

Also it looks like the hose from the crankcase to the can has a bit of a dip where it goes under the brace there, just before the fuse box. Tough to tell from the picture how far down it dips, but you might want to reroute that to avoid the line getting blocked with oil.

 

yeah I noticed that but it is a smaller dip than it looks like. Have not had any issue with it so far. I think most of the oil stays in the air until it hits the baffle in the can. I do pull the line every now and then and see if I can drain any oil out of it and have not seen any yet so have not bothered re-routing.

 

Look into the rainh8r mod, and the issue that causes its necessity. I agree that it is pretty course dependent, that said the mod has stopped nearly all oil consumption on my ap1, even for normal, non smokescreen driving. Regardless of the catch can method, if you are hitting that rainh8r-solving left-right combo that sucks major amounts of oil, it will fill up the can very fast. Based on your 1/4-1/2 can filling you would probably benefit from rainh8r.

If you have oil consumption/smoke screen issues, catch cans are a waste of your time until you rainh8r. I have rainh8r, no catch can on my track car and have zero oiling issues after having smoke screening issues.

As far as STR legality, it's not worth worrying about. If you are placing at the pointy end of Tour events, talk to your competitors and any reasonable individual will have zero issues. Locally i wouldn't even address it.

 

F24, Rainh8r mod, dual catch cans VTA with breather filters. normally empty at the end of each track day.

 

IMO the reason for a catch can isn't to deal with major oil consumption. As you said it's going to be a pain if you haven't solved any oil consumption issues first. But that doesn't mean it's not valuable. The oil vapors going into the IM will foul things up over time. Really every car would be better off with a catch can; they just don't have them because of the cost and because most car owners aren't going to want an additional regular maintenance task. I had to replace my map sensor after it completely stopped working a while back, and I expect the fact that it's continuously getting coated in PCV vapors isn't helping its longevity, for instance.

The 1/4-1/2 can filling was engifineer.

And you're probably right about the baffle fix and STR. If I were having smokescreen issues I'd do it. As a side note, one other nice thing about a closed loop can setup is that if I ever did hit a track where I got significant oil sloshing, it'd just get burnt as usual once the can filled up rather than spraying all over the engine bay.

 

Not having the RainH8r mod does not make the can less useful. The catch can is not there to prevent oil usage as all it does is catch the oil that makes it out of the pcv. The catch can helps prevent all of that from going into the intake and causing the smoke screen these cars are famous for out of hard right hand corners. And it works pretty well for that.

On the comment of how much oil is in my can, as I noted, my can is pretty small so that amount is not much oil in reality. And of course some of that liquid is condensation as the air hits the can, which is cooler than where the air came from.