Critique this PCV setup
10-08-2012, 02:54 PM
#1
Critique this PCV setup Did some PCV thinking today and made some diagrams. In this setup, the catch can is filtering the air in and out of boost (I'm trying to use the 2-port unvented AMW can I already have). The air vented from the crankcase in boost goes back into the turbo so it's burned instead of smelling like ***. When out of boost, the air venting the crankcase is filtered w/o needing an extra small filter. Nothing is venting to atmosphere. The factory line on the TB is capped. This is the truck manifold so the PCV vents into the top center of the manifold.
Thoughts?
Issues with tuning?
Do we have to worry about the amount of air that is bypassing the MAF by going through the crankcase?
A small amount of oil will probably still get into the turbo in boost, is this an issue? I could run that crossover line to a small breather I guess.
Downsides I see... it's elaborate, needs three check valves.
There's still potential to get oil into the turbo catchcans aren't perfect.
The crossover line could be vented to atmosphere if needed.
Out of boost, the MAF isn't measuring the air being sucked into the passenger side valve cover.
In boost, the MAF is double counting the blowby since its going back in before the turbo.
I know I'm overthinking it... just trying to come up with a nice PCV system that covers all the bases.
Idle/out of boost:
In boost:
Thoughts?
Issues with tuning?
Do we have to worry about the amount of air that is bypassing the MAF by going through the crankcase?
A small amount of oil will probably still get into the turbo in boost, is this an issue? I could run that crossover line to a small breather I guess.
Downsides I see... it's elaborate, needs three check valves.
There's still potential to get oil into the turbo catchcans aren't perfect.
The crossover line could be vented to atmosphere if needed.
Out of boost, the MAF isn't measuring the air being sucked into the passenger side valve cover.
In boost, the MAF is double counting the blowby since its going back in before the turbo.
I know I'm overthinking it... just trying to come up with a nice PCV system that covers all the bases.
Idle/out of boost:
In boost:
10-09-2012, 12:41 PM
#3
Not sure what you got going on there with the valve cover going directly to the intake of the turbo?? Smoke machine? lol.
I built a similar setup. I used one of the check valves that went into the factory manifolds for the air pump and welded it in my down pipe just past the tranny.... Then ran a 3/4" hose from it to the top of my catch can.... eliminate the engine intake intirely. I have a 1/2" hose going from each valve cover to the catch can.
Before this running E85 my oil would be cream colored in a week... Now it stays clear and I can feel the exhaust pull the vacuum from it so I assume it works good.
I built a similar setup. I used one of the check valves that went into the factory manifolds for the air pump and welded it in my down pipe just past the tranny.... Then ran a 3/4" hose from it to the top of my catch can.... eliminate the engine intake intirely. I have a 1/2" hose going from each valve cover to the catch can.
Before this running E85 my oil would be cream colored in a week... Now it stays clear and I can feel the exhaust pull the vacuum from it so I assume it works good.
Last edited by pwrtrip75; 10-09-2012 at 02:12 PM.
10-09-2012, 02:45 PM
#6
The middle check valve keeps prevents the engine from sucking in fresh air that hasn't been through the engine yet when out of boost boost. If this valve wasn't here then it would basically be bypassing the PCV system.
The right-most check valve prevents boost from leaving the intake manifold when in boost.
The engine will be pulling more vacuum than at the turbo inlet, as per the 1st diagram. The vac at the turbo inlet should be relatively small unless the air filter is undersized or clogged. The catch can is in-line between the engine and any air that is going into the turbo inlet, as per the 2nd diagram. In boost the vac in the turbo inlet will help to draw blowby from the crank case. But, catch cans aren't perfect and I may just run this crossover line to a vent so I'm not fouling my intake piping with oil. This could also help the vent filter from getting clogged with oil vapor like it could if placed directly on the valve cover.
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10-09-2012, 04:34 PM
#8
yes, you will have very little vacuum at the turbo inlet at idle but when the rpms rise the vacuum will drop quickly, you will need a vent in the system to prevent "sucking" the engine seals in or move the PCV inlet further away from the turbo inlet.
10-09-2012, 04:44 PM
#9
I see what you're saying. My thinking was that the turbo inlet vacuum in boost wouldn't be great enough to damage seals, and that there would be enough blowby coming out of the crankcase to counteract this vacuum. I'm slowly considering running a vent filter now. This will also prevent oil from getting into the charge pipes.
10-09-2012, 09:01 PM
#11
It's similar to using only valve cover breathers, except he's running it through the catch can. He said he didn't want anything getting sucked into the engine. The blowby will push itself out through the valve cover tubes and through the catch can and out the vent.
I did some research and I guess the PCV system also helps reduce engine sludge. I like the idea of my crankcase being vented with clean air.
I did some research and I guess the PCV system also helps reduce engine sludge. I like the idea of my crankcase being vented with clean air.
10-10-2012, 05:25 AM
#12
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It's similar to using only valve cover breathers, except he's running it through the catch can. He said he didn't want anything getting sucked into the engine. The blowby will push itself out through the valve cover tubes and through the catch can and out the vent.
I did some research and I guess the PCV system also helps reduce engine sludge. I like the idea of my crankcase being vented with clean air.
I did some research and I guess the PCV system also helps reduce engine sludge. I like the idea of my crankcase being vented with clean air.
10-10-2012, 05:19 PM
#15
i used this setup and it seemed to work good for me and i know a few other people who have been doing it this way and had no problems. im not sure if it needs vacuum assistance or not but it seemed to work pretty good. what do you mean there should be fresh air going in? the engine pulls fresh air from the intake so i dont see why it would also need fresh air from the pcv system.
10-10-2012, 07:59 PM
#17
i used this setup and it seemed to work good for me and i know a few other people who have been doing it this way and had no problems. im not sure if it needs vacuum assistance or not but it seemed to work pretty good. what do you mean there should be fresh air going in? the engine pulls fresh air from the intake so i dont see why it would also need fresh air from the pcv system.
10-10-2012, 09:35 PM
#18
Ferocity -
I like where you're going with this man. I had thought of the exact identical setup as you posted, and had planned to do. People run both valve covers to a breather for some reason, I was concerned with the caustic crap in the crankcase in a street car with just using breathers with no PCV. I had also thought about hooking the exhaust evac setup up through a non vented catch can and have a breather on the other valve cover. I don't know what's right, or what's wrong. I don't want to be changing my oil every 500 miles because I just ran both covers to a vented catch can and have no part-throttle vacuum/pcv system.
I like where you're going with this man. I had thought of the exact identical setup as you posted, and had planned to do. People run both valve covers to a breather for some reason, I was concerned with the caustic crap in the crankcase in a street car with just using breathers with no PCV. I had also thought about hooking the exhaust evac setup up through a non vented catch can and have a breather on the other valve cover. I don't know what's right, or what's wrong. I don't want to be changing my oil every 500 miles because I just ran both covers to a vented catch can and have no part-throttle vacuum/pcv system.
10-10-2012, 09:59 PM
#19
Ferocity -
I like where you're going with this man. I had thought of the exact identical setup as you posted, and had planned to do. People run both valve covers to a breather for some reason, I was concerned with the caustic crap in the crankcase in a street car with just using breathers with no PCV. I had also thought about hooking the exhaust evac setup up through a non vented catch can and have a breather on the other valve cover. I don't know what's right, or what's wrong. I don't want to be changing my oil every 500 miles because I just ran both covers to a vented catch can and have no part-throttle vacuum/pcv system.
I like where you're going with this man. I had thought of the exact identical setup as you posted, and had planned to do. People run both valve covers to a breather for some reason, I was concerned with the caustic crap in the crankcase in a street car with just using breathers with no PCV. I had also thought about hooking the exhaust evac setup up through a non vented catch can and have a breather on the other valve cover. I don't know what's right, or what's wrong. I don't want to be changing my oil every 500 miles because I just ran both covers to a vented catch can and have no part-throttle vacuum/pcv system.
10-10-2012, 10:13 PM
#20
Fresh air goes into the intake yes, but not the crankcase in your setup. In your setup, air going into the crank case is purely from blowby, which is anything but fresh air. I'm not sure how important it is to have fresh air going through the crank case, but I've read that it has several benefits, already pointed out here.