Revised catch can setup - thoughts oh wise ones?

[ozbilt]

By the way - can't believe nobody commented on my elite mspaint skills.

Some things are beyond description.

[boofhead]

Thinking about how a PCV valve works as this is bugging me and I am not sure why.

Now the PCV is spring loaded so
1) Idle = high vacuum so it over comes the spring and there is very low to no flow.
2) Accelerating = low vacuum but enough to slightly overcome the spring hence high flow.
3) Pressure = no vacuum so no flow.

So boost assuming it seals well enough should be ok though the issue is your looking for high vacuum to flow but it does not flow by design. I think that line do not hurt but equally does not contribute to the set up. A special one way valve would be different.

EDIT: Drawing is a master piece.

[hybrid]

Boof, are you mean the top PCV line?
I don't see how it's any different to a factory setup.
That one is not required to flow any more than a factory car would. It's only going to work within the vacuum range that it always would have.
It doesn't have to overcome blow by associated with boost or anything like that. It's going to be closed when all that's happening.

The supercharger side will have to cope with the most work, but that side will not be a PCV. It will just be a check valve, so it should take very little vacuum to make it move.
One of the ones I was looking at was 4hg.

[boofhead]

This is right the top line will only be of any value in non-boosted area of the map.
But then the other line will as work as well because of the air flow shear. Both doing the job while the top line providing extra vacuum when in the sweet spot. As I said - all good but not adding much value.

[lukep6470]

I was trying to find a diagram on how they do it on C32 and E55 MBs. They both run the same supercharger @ 16lb.

Might be worth some research.

[hybrid]

This is right the top line will only be of any value in non-boosted area of the map.
But then the other line will as work as well because of the air flow shear. Both doing the job while the top line providing extra vacuum when in the sweet spot. As I said - all good but not adding much value.

The only reason I'm using the top one is to try and keep the supercharger cleaner.
At idle and low throttle areas (which is where it will be most of the time, lets face it), the PCV should provide more vacuum than the supercharger inlet.
So the contaminants should flow into the manifold rather than the supercharger.

I've bought two check valves. They say they should only need 0.3Hg to operate, so I will put one in line with the PCV to help fight against boost leak. The PCV helps stop that manifold opening being just a massive vacuum leak, so I don't want to use just a check valve. The other one I will put inline with the supercharger, so if the PCV provides even 0.3Hg more vacuum than the supercharger inlet, that check valve should close (theoretically), stopping any of the flow into the supercharger.

Only one way to find out I guess! A glass section in each hose would be cool so you could watch exactly what's happening.

Edit: now that I think about it... the check valve in the supercharger line will not be to stop flow TO the supercharger if the PCV is pulling more vacuum. It will be to stop flow out of the supercharger intake, and make sure we only pull from the crankcase.

I've had so many iterations of this in my head, they're all getting mixed together.

[Husky65]

Hybrid, are you trying to keep this thing emissions compliant?
If not, I would try to keep those vapors from going back into the intake full stop.

I have seen this on another forum, where one valve cover had a breather, and the other had a dash fitting to a catchcan, and then stainless hose from the catch can that went down the back and connected to a fitting on the exhaust collector.

I am thinking of ditching my pcv system as I have noticed the idle is better without it, even though it is meant to be metered air. Problem is a little fresh air is entering the crankcase via the oil filler cap, so it's not really a closed system.
Just trying to figure out the best way to evacuate the crank vapours without only just using breathers

[hybrid]

Hybrid, are you trying to keep this thing emissions compliant?
If not, I would try to keep those vapors from going back into the intake full stop.

No, it doesn't need to be emissions compliant.

You don't want a bunch of oil going back into the intake, but that's what the catch can is for. It should only be fumes going back into the intake.
If you had a bunch of oil vapour gushing out then it might be an issue going back in your intake, but you've also got a bigger problem to worry about too.
Collector is an interesting one... you wouldn't want much back pressure in your exhaust in that setup.

But I'm going to try this method for a while and see how it goes.
PCV could affect your idle because it's letting air in, but you should be able to tune that properly as well. Unless you are using MAF and your crank case breather is not pulling it's air post MAF.

[Husky65]

Yeah you're right, with a good catch can it should be fine. No point re-inventing the wheel.
Didn't think of the back pressure of the exhaust.

I like your system. Saves you running 2 cans.

[hybrid]

It's yet to prove it's worth anything yet.. but we shall see.
I could have done some work on it this weekend (aside from the heat), but VPW sent me rocker cover breathers instead of the PCV grommet I asked for.

Edit: the venturi effect in the exhaust might overcome any pressure in there. I don't know. Maybe boof would know... he's done a lot on research on flow etc to come up with his tech zone articles.

[boofhead]

Using an exhaust evac system is quite common. Moroso sells one which is popular but there are others.

https://www.summitracing.com/int/search ... on-systems

The system is simple which is nice. It is simply a tube (tubes for dual system) that are installed on an angle so the exhaust flowing past the tube creates a sheer force hence causing vacuum. The air flowing is the key so unless the flow is stopped then back pressure will not be an issue.

[Husky65]

Great video.
Shows you how effective using the intake manifold is in terms of utilizing its vacuum if this system is only pulling 4-5in of vacuum(which I'm still impressed by). Although I guess at high vacuum the pcv is not flowing that much, so perhaps there is more flow through this than the pcv at higher engine vacuum??

[hybrid]

Doesn't pull a whole lot of vacuum does it.
I wonder how much volume it moves - that's more important really.

[boofhead]

You only want a low vacuum as it is as much to save the seals and in this case shoot the oily crankcase air out the exhaust system. Unless you filter it first with a catch can.

[gbx78]

This is the video boof showed me a while ago when i was building my catchcan system together. I think i meant to look into buying it but forgot and ended up with just the catchcan. Good video though i wonder for a side pipes car will all that crap thats sucked out burn in the exhaust before it exits or will it end up all over my rear quarter and more importantly will cool flames come out

Is this not the same principle as what hybrid is suggesting using the sc intake as a vaccuum?