a PCV layout for a boosted engine
01-22-2008, 03:46 PM
#1
a PCV layout for a boosted engine After blowing the dipstick out of my engine yesterday, I decided to come up with something fairly bulletproof and functional. I've seen a couple of threads floating around, but it seems like most of those had a lot of description and covered some aspects of the overall system but not others.
I like the idea of using the turbo inlet as an alternate vacuum source. But I didn't want blowby to get out around an unrestricted breather on the valve cover. A fresh air source is still needed to support a pcv system that works at idle to keep fuel and water vapor out of the oil.
Sketched out the idea on a yellow sticky today, then made a quick diagram to post up, since a picture shows it so much easier than a long description. Should provide an escape path for crankcase pressure at all times, control oil from getting out around the breather, and keep the turbo inlet and the manifold isolated from each other at all times.
The one-way valves in the diagram are going to be brake booster check valves. I ended up with a handful of them somehow, and this setup needs three of them.
I like the idea of using the turbo inlet as an alternate vacuum source. But I didn't want blowby to get out around an unrestricted breather on the valve cover. A fresh air source is still needed to support a pcv system that works at idle to keep fuel and water vapor out of the oil.
Sketched out the idea on a yellow sticky today, then made a quick diagram to post up, since a picture shows it so much easier than a long description. Should provide an escape path for crankcase pressure at all times, control oil from getting out around the breather, and keep the turbo inlet and the manifold isolated from each other at all times.
The one-way valves in the diagram are going to be brake booster check valves. I ended up with a handful of them somehow, and this setup needs three of them.
02-07-2008, 08:10 PM
#2
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so did you just connect your PCV vac line to the intake piping for the air filter on the turbo? does it matter where, as long as it is getting suction? thanks for the draw-up btw. i've been going at this for weeks....
02-08-2008, 11:02 AM
#5
I don't have a line going to the turbo yet, and I don't have a check valve in the breather line since I still need that open to relieve the crankcase pressure until I do run that other line.
Some folks go with just a line from the PCV to the turbo intake.
I didn't think the turbo intake would pull enough vacuum at idle to do the job. (the job of really cleaning the water vapor out of the crankcase) That's why there's a T to still run to the original vacuum source on the side of the intake throat, and to also run to the turbo intake.
With check valves to make sure everything is flowing the right way. (so I don't have a vacuum leak at idle, and so boost isn't blowing back around to the turbo intake)
02-08-2008, 12:52 PM
#6
I haven't implemented it yet, just thought it out and drew it up.
I don't have a line going to the turbo yet, and I don't have a check valve in the breather line since I still need that open to relieve the crankcase pressure until I do run that other line.
Some folks go with just a line from the PCV to the turbo intake.
I didn't think the turbo intake would pull enough vacuum at idle to do the job. (the job of really cleaning the water vapor out of the crankcase) That's why there's a T to still run to the original vacuum source on the side of the intake throat, and to also run to the turbo intake.
With check valves to make sure everything is flowing the right way. (so I don't have a vacuum leak at idle, and so boost isn't blowing back around to the turbo intake)
I don't have a line going to the turbo yet, and I don't have a check valve in the breather line since I still need that open to relieve the crankcase pressure until I do run that other line.
Some folks go with just a line from the PCV to the turbo intake.
I didn't think the turbo intake would pull enough vacuum at idle to do the job. (the job of really cleaning the water vapor out of the crankcase) That's why there's a T to still run to the original vacuum source on the side of the intake throat, and to also run to the turbo intake.
With check valves to make sure everything is flowing the right way. (so I don't have a vacuum leak at idle, and so boost isn't blowing back around to the turbo intake)
You are correct on the turbo line not pulling enough at idle.
02-08-2008, 01:03 PM
#7
Aesome thread, I really like your idea and I have to get something in plan b/c I'll be doing my project soon. Say what exactly will you be using on your breather to make it more or less a relief valve and curious where to get a nice one way valve from? Thank for the great info!
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02-08-2008, 02:19 PM
#8
At this point I plan on using check valves out of a brake booster.
They're secure (the booster holds vacuum under different conditions, for days at a time), last a long time (how many times have you heard of someone needing to replace their braker booster check valve?), and are made to hold up to the correct level of boost/vacuum. (people running boost are not blowing out their brake boosters)
The downside is that the inlet is big and the outlet is even bigger, and they're L-shaped...
I may look into something else later, but I have 3 spare booster valves sitting here on a bench, so they're it for now.
02-08-2008, 03:21 PM
#10
what i have run for my vortech blower is a air/water seperator. i kept the pvc breather hose (LT1 car) attached to the valve cover,connected the hose to the seperator,then tapped into my intake tubing with a npt thread and connected the other end of the hose to that. works perfect.
02-08-2008, 03:24 PM
#11
what i have run for my vortech blower is a air/water seperator. i kept the pvc breather hose (LT1 car) attached to the valve cover,connected the hose to the seperator,then tapped into my intake tubing with a npt thread and connected the other end of the hose to that. works perfect.
02-08-2008, 08:10 PM
#13
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I haven't implemented it yet, just thought it out and drew it up.
I don't have a line going to the turbo yet, and I don't have a check valve in the breather line since I still need that open to relieve the crankcase pressure until I do run that other line.
Some folks go with just a line from the PCV to the turbo intake.
I didn't think the turbo intake would pull enough vacuum at idle to do the job. (the job of really cleaning the water vapor out of the crankcase) That's why there's a T to still run to the original vacuum source on the side of the intake throat, and to also run to the turbo intake.
With check valves to make sure everything is flowing the right way. (so I don't have a vacuum leak at idle, and so boost isn't blowing back around to the turbo intake)
I don't have a line going to the turbo yet, and I don't have a check valve in the breather line since I still need that open to relieve the crankcase pressure until I do run that other line.
Some folks go with just a line from the PCV to the turbo intake.
I didn't think the turbo intake would pull enough vacuum at idle to do the job. (the job of really cleaning the water vapor out of the crankcase) That's why there's a T to still run to the original vacuum source on the side of the intake throat, and to also run to the turbo intake.
With check valves to make sure everything is flowing the right way. (so I don't have a vacuum leak at idle, and so boost isn't blowing back around to the turbo intake)
thanks for the reply! now i just need to find a good check valve... i had one from McMastercarr, but the car wont run with it on.
Also, are you still keeping the factory PCV valve in there?
02-09-2008, 11:46 AM
#15
I am. I haven't tested it to prove this, but I suspect it restricts the flow somewhat, so the pcv line isn't a big vacuum leak at idle, but a more controlled/restricted flow.
(on a maf car it would be even more important since that air is unmetered with a breather setup, but on my maf-less speed density tune technically it wouldn't matter)
(on a maf car it would be even more important since that air is unmetered with a breather setup, but on my maf-less speed density tune technically it wouldn't matter)
07-08-2008, 10:27 PM
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Your diagram looks fairly straight forward. Did you just eliminate the pcv on the driver valve cover and keep it on the passenger side?
Imagine you just kept the pcv line (took out the actual pcv valve) and ran it to the catch can and "T" fitting?
Imagine you just kept the pcv line (took out the actual pcv valve) and ran it to the catch can and "T" fitting?
07-09-2008, 08:21 AM
#18
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I tried a similar set-up and it didn't work at wot. One hose couldn't vent enough crankcase pressure. All depends on how much power you are making. I had to delete the oneway valve at the fresh air inlet and take two hoses to the turbo air filter (one from the back of each valve cover). Used the valley cover tap to pcv to catch can to intake vac for part throttle evacuation.
