Catch Can Debate

[Coheed]

Originally Posted by ANTI_LAG

Also running our catch can will not cause any CELs to come on thus allowing full OBD2 Emission compliance.

The only downside is it will fail a visual inspection if they see it is vented to atmosphere. It's tough to stay compliant with all the laws, but I agree this is the most effective way to do this.

[wootwoot]

Originally Posted by ANTI_LAG

If you cruise out of boost which most people on the planet do then I am correct, the rest of what you have said in the above post is a bunch of jibberish and im not going to correct all of it.

This is what this thread is about. We can't simply call someone wrong and walk away because they are too wrong to correct. That doesn't make any sense and is a poor attitude in general. That's also how misinformation gets spread. I think we can figure this out if we take our time and work together.

Lets see if we can find some understanding here as to what we are disagreeing about. If I misrepresent you, please speak up:

What we seem to agree on:
1. The purpose of the PCV is to relieve crankcase pressure cased by blow-by gases.
2. Too much crankcase pressure is bad.
3. Blow-by gasses going into the engine is bad.
4. The stock system is not optimal as it is designed for emission reasons and not performance.
5. The system is comprised of two hoses. One from the block to the intake manifold (IM) and another from the block to the intake just before the throttle body.

What we seem to disagree on:

The front hose from the block to the intake just before the throttle body:

According to Calum, the hose from the block to the intake is sucking fresh air from the intake stream into the crankcase.

ANTI_LAG believes this hose pushes air out of the crankcase and into the intake stream. This would relieve the crankcase pressure and cycle it back into the engine, which is what the emission control system was made to do.

The hose from the block to the intake manifold:

According to Calum this hose pushes air out of the crankcase and into the intake manifold.

I think ANTI_LAG believes it does the same thing.

The PCV valve

It seems you both have a different idea of which way the PCV valve works because you have different ideas of which hose is doing what. But it seems we agree that it is a one-way valve.

Solution:

It seems Calum is recommending a filter to be placed on the front crankcase port (that goes to the intake) and a catch can being put on the rear port (that goes to the intake manifold). You then plug the holes in the intake and the manifold.

ANTI_LAG seems to think you need a breather on both lines coming from the crankcase. Again plugging the intake and IM holes.

It seems we are not agreeing on what the front hose does (crankcase to intake) and thus offering two dissimilar solutions to what is best.

So, can we debate a bit more on what the front hose is doing? Seems like a vacuum gauge would make fast work of this problem.

The two ports on the block are either an in and an out (Calum) or are two vents (ANT_LAG). Place your bets here and lets figure this out!

[ANTI_LAG]

Originally Posted by Calum

No, it wont. The venturi will require the exhaust header tube to be full in order to create a vacuum. Given the audience I'll use the example of a carburetor venturi. You can see the venturi tubes in the picture, they're there because if the full width of the throttle opening were used it wouldn't create sufficient vacuum under most driving conditions.

You would be surprised at how much exhaust flows even at idle, if you were running a 4 inch exhaust it would be different. We had this system on a old all motor car with a side exit header, I know it works but it does not have its place on this car, this is also the same way a recirculated dumptube can band-aid a boost creep issue. I feel we are way out of the reality of which options to use on this exact vehicle talking about this method.

I dont really want to keep going back in forth as I know we have went over alot of info, all I can say is look past the FRS/BRZ and subaru community and see how other cars are doing this, youll find the way we have ours is used alot and has many benefits.

It was fun having this discussion with everyone, this is a good thread and glad you made it OP, hope I didnt come off as an jerk, I just like to spread info we have ran across on our street and race cars. Even if you guys dont choose our catch can system I hope you find the one that meets your needs.
Later guys.

Dave

[Calum]

Originally Posted by wootwoot

It seems Calum is recommending a filter to be placed on the front crankcase port (that goes to the intake) and a catch can being put on the rear port (that goes to the intake manifold). You then plug the holes in the intake and the manifold.

First off, THANK YOU. That was very well put. I just didn't quote all of it for screen space.

The only correction I have is my recommendation wouldn't require a hole in the intake manifold to plugged. The air/oil separator would just be T'ed into the back hose.

Originally Posted by ANTI_LAG

You would be surprised at how much exhaust flows even at idle, if you were running a 4 inch exhaust it would be different. We had this system on a old all motor car with a side exit header, I know it works but it does not have its place on this car, this is also the same way a recirculated dumptube can band-aid a boost creep issue. I feel we are way out of the reality of which options to use on this exact vehicle talking about this method.

I dont really want to keep going back in forth as I know we have went over alot of info, all I can say is look past the FRS/BRZ and subaru community and see how other cars are doing this, youll find the way we have ours is used alot and has many benefits.

It was fun having this discussion with everyone, this is a good thread and glad you made it OP, hope I didnt come off as an jerk, I just like to spread info we have ran across on our street and race cars. Even if you guys dont choose our catch can system I hope you find the one that meets your needs.
Later guys.

Dave

This car is the first experience I have with the subaru community other then the 2.5i I owned before, and I wasn't modding that at all. Most of this doesn't come from any car community, it comes from my marine engineering technician courses. A hell of a long way from an engineer degree, but I still consider it much more reliable then most of what is on forums.

As for the venturi, I completely agree, that's for the .001% and doesn't belong here. I attempted to make that point when I first mentioned. Clearly I didn't put enough emphasis on that. Consider it dropped.

Dave, you didn't come off as being a jerk, and I hope I didn't either. We have a difference of opinion. If you can show me I'm wrong, I'd be glad to learn something. And I hope we can continue this without taking it personally. Despite the fact that this stuff has been well figured out by others, this is still science to us. Lets treat it as such.

wootwoot and I seem to understand what you've said in the same way. So, if you would, comment and/or make and corrections to wootwoot's post as applicable and we can use that as a jumping off point to continue from.

Hopefully we could bring this to a conclusion and a mod can clean it up. This could potentially be a lot of good information.

[wootwoot]

DON"T LEAVE US ANTI_LAG! You come across as a very knowledgeable guy and that is what we are after... KNOWLEDGE!

Lets try to keep it going to figure this out. If nothing else, this thread could PROVE to the rest of us that you have a superior catch can design. If not for us, do it for your sales... or just to prove your design to the community.

We are making good headway... we can't stop now!

[JoeBoxer]

Are the only application specific models the Crawford and Cusco? I would love the Saikou Michi if only somebody would get a car to them so they could get the correct measurements, they deal with a shop in Tucson so if anybody wants to go see them maybe they can get us one set up. I think pricing was only around $120.

[ANTI_LAG]

Originally Posted by wootwoot

This is what this thread is about. We can't simply call someone wrong and walk away because they are too wrong to correct. That doesn't make any sense and is a poor attitude in general. That's also how misinformation gets spread. I think we can figure this out if we take our time and work together.

Lets see if we can find some understanding here as to what we are disagreeing about. If I misrepresent you, please speak up:

What we seem to agree on:
1. The purpose of the PCV is to relieve crankcase pressure cased by blow-by gases.
Correct
2. Too much crankcase pressure is bad.
Any pressure is bad, but over pressure can cause valve stem leakage (smoke out exhaust), seals to push out, and dip stick to push out
3. Blow-by gasses going into the engine is bad.
Those gases are already burned combustion, to send it back into the engine is the same as a EGR system, except that a EGR system has a solenoid which opens it only at cruising which would not harm performance or idle, this does happen at a smaller scale though, thats why the engine does not run rough, but still dirty air is not what you want on a performance car.
4. The stock system is not optimal as it is designed for emission reasons and not performance.
YES
5. The system is comprised of two hoses. One from the block to the intake manifold (IM) and another from the block to the intake just before the throttle body.
This is correct, on most other cars you would have it off the back of the block and the valve cover or in the case of the EJ20/25 it comes from each valve cover and a center block exit.

What we seem to disagree on:

The front hose from the block to the intake just before the throttle body:

According to Calum, the hose from the block to the intake is sucking fresh air from the intake stream into the crankcase.

ANTI_LAG believes this hose pushes air out of the crankcase and into the intake stream. This would relieve the crankcase pressure and cycle it back into the engine, which is what the emission control system was made to do.

The hose from the block to the intake manifold:

According to Calum this hose pushes air out of the crankcase and into the intake manifold.

I think ANTI_LAG believes it does the same thing.
While maybe Calum might be right at some point of the rpms, the fact is that you pull the intake tube off any car with a pcv connected to it you can find oil residue coming from it and leading into the throttle body. Go pop the intake off your buddys car and run your finger across the thottle plate, crack it open a little and feel in there.

The PCV valve

It seems you both have a different idea of which way the PCV valve works because you have different ideas of which hose is doing what. But it seems we agree that it is a one-way valve.
The pcv valve is a one way check valve, depending on manufacturer some do have a spring inside to fight the amount it will release (controlling), but none the less, especially on a turbo app this valve will be shut under boost.

Solution:

It seems Calum is recommending a filter to be placed on the front crankcase port (that goes to the intake) and a catch can being put on the rear port (that goes to the intake manifold). You then plug the holes in the intake and the manifold.
This will result in a vacuum leak.

ANTI_LAG seems to think you need a breather on both lines coming from the crankcase. Again plugging the intake and IM holes.
This is the case if you run a open standalone pcv catch can like the one we offer.

It seems we are not agreeing on what the front hose does (crankcase to intake) and thus offering two dissimilar solutions to what is best.


So, can we debate a bit more on what the front hose is doing? Seems like a vacuum gauge would make fast work of this problem.
One does not need to do more than follow the oil residue
The two ports on the block are either an in and an out (Calum) or are two vents (ANT_LAG). Place your bets here and lets figure this out!

Hope that was what you guys were looking for

[ANTI_LAG]

Originally Posted by JoeBoxer

Are the only application specific models the Crawford and Cusco? I would love the Saikou Michi if only somebody would get a car to them so they could get the correct measurements, they deal with a shop in Tucson so if anybody wants to go see them maybe they can get us one set up. I think pricing was only around $120.

Ours is, bolt it in and go.

[wootwoot]

Well.... Here's what I'm thinking at the moment:

If Colum is right, a double breather set up like what ANTI_LAG has will not hurt anything. The hose that was connected to the intake would just sick air in through the breather and the hose that was connected to the intake manifold would just push air out the intake. The best thing in this situation may be two separate breather tanks so one can suck air in and one can push air out. A dual can set up would work if either one of you was correct. Also, at minimum, the kit ANTI_LAG sells shouldn't do any harm even if Colum is correct and ANTI_LAG is wrong.

If ANTI_LAG is correct and we do as Colum suggests I am not sure it will be safe. With one side pushing into the atmosphere and the other pushing into the manifold.... what would happen?

[JoeBoxer]

Originally Posted by ANTI_LAG

Ours is, bolt it in and go.

Yeah but it's $300 which although your weld quality is amazing i'm not paying that for a catch can especially since i'm NA anyways.

[Calum]

Originally Posted by ANTI_LAG

Hope that was what you guys were looking for

Nice, thank you.

I think we agree on another thing. The reason I recommend putting a filter on what I'm calling the air inlet to the crankcase is to vent the vapors from there as under some driving conditions there will be some vapors, namely when the PCV valve is closed. I didn't say to put a catch can there because the amount shouldn't be enough to even leave a mark. Though putting a catch can to separate the oil from the air in this line, then venting it to atmosphere wouldn't hurt anything.

With that in mind it might be that we're arguing in circles. Are you approaching this from a stand point of wide open throttle? I've been approaching this from the stand point of cruising, as I feel most of us spend more time under cruise then wot. Under wot, whether the engine is FI or NA the line going to the intake manifold will be sealed off by the PCV valve, leaving the other hose to passively vent blowby gases to atmosphere. But the point of the system is to positively or actively remove the blowby gases hense my approach.

[Calum]

Originally Posted by wootwoot

If ANTI_LAG is correct and we do as Colum suggests I am not sure it will be safe. With one side pushing into the atmosphere and the other pushing into the manifold.... what would happen?

https://www.google.ca/search?q=breat...w=1366&bih=705

There's plenty of cars out there running what I spoke of. Just be aware that most cars supply the air back to the crank case via a valve cover. It's easier for manufacturing and the air just runs through the oil drain back channels from the head(s) to the block.

[wootwoot]

Originally Posted by Calum

Nice, thank you.

I think we agree on another thing. The reason I recommend putting a filter on what I'm calling the air inlet to the crankcase is to vent the vapors from there as under some driving conditions there will be some vapors, namely when the PCV valve is closed. I didn't say to put a catch can there because the amount shouldn't be enough to even leave a mark. Though putting a catch can to separate the oil from the air in this line, then venting it to atmosphere wouldn't hurt anything.

With that in mind it might be that we're arguing in circles. Are you approaching this from a stand point of wide open throttle? I've been approaching this from the stand point of cruising, as I feel most of us spend more time under cruise then wot. Under wot, whether the engine is FI or NA the line going to the intake manifold will be sealed off by the PCV valve, leaving the other hose to passively vent blowby gases to atmosphere. But the point of the system is to positively or actively remove the blowby gases hense my approach.

A double breather would remove the gasses as well right?

[Calum]

Originally Posted by wootwoot

A double breather would remove the gasses as well right?

If you mean a system that blocks off both the intake manifold port and the intake duct port and just vents both crankcase ports to atmosphere, I'm sorry but I don't think it will.

With a kit that blocks off the intake manifold port there's nothing actively drawing the gasses out of the crankcase. It's just venting off through the baffles at the top of the crankcase. Add in the hoses supplied with most of these systems and the routing, the restriction may very well cause the crank case to go from a vacuum under most driving conditions, to a slight pressure. This is BAD.

The system I suggested will emulate this under WOT, as all OEM systems do to when the PCV valve closes. But under every other driving condition the system I suggested will cause a vacuum in the crankcase which will pull much more gasses during those conditions, and increase piston ring seating which will help to reduce the amount of blowby and increase efficiency.

The system I'm suggesting will stop the VAST majority oil from making it into the intake manifold by using an air/oil separator. It will let some oil into the intake system though, I wont deny that. But keeping the vacuum in the crankcase, helping the rings to seal better during most driving conditions, and actively removing the blowby gases, is more important for 99% of the users here.

For a track only car, one that sees wot for most of it's running time a double breather would be more effective then my suggestion or the OEM system. But for a car like that, a vacuum pump would be the way to go. They can cost about the same but can actually add a significant amount of power by increasing ring seating.