The new "definitive catch can" thread
#41
Why doesn't anyone run the exhaust side VC port to their turbo inlet? I run mine that way so as boost builds, the PCV shuts, then the turbo is pulling a vacuum on the crankcase. By running a fresh air breather isnt the crankcase just going to atmospheric pressure and not staying in vacuum? The purpose of keeping the case in vacuum is to help pull the rings towards the walls.
Not to mention that when running a fresh air inlet style filter or tank on the valve cover you are essentially creating a vacuum leak at idle.
IMO the best option is to run two sealed cans. One on the intake side, the other on the VC to inlet side. This will keep moisture/oil trapped in the cans while preventing vacuum leaks.
Another option is the down draft style. Run a pipe from your exhaust/down pipe at an angle and a hose to your VC inlet. The exhaust will pull a vacuum if done properly but can cause some slight smoking and failing emissions.
Not to mention that when running a fresh air inlet style filter or tank on the valve cover you are essentially creating a vacuum leak at idle.
IMO the best option is to run two sealed cans. One on the intake side, the other on the VC to inlet side. This will keep moisture/oil trapped in the cans while preventing vacuum leaks.
Another option is the down draft style. Run a pipe from your exhaust/down pipe at an angle and a hose to your VC inlet. The exhaust will pull a vacuum if done properly but can cause some slight smoking and failing emissions.
#44
Boost Pope
Thread Starter
iTrader: (8)
Join Date: Sep 2005
Location: Chicago. (The less-murder part.)
Posts: 33,052
Total Cats: 6,615
And, not only do you not want oil mist hitting the compressor blades, you also don't want it getting into the intercooler, where it will condense into liquid and coat the inside of the tubes.
#47
Like nearly every single answer/comment on this website: it depends.
OEM (MSM) runs a type of catch can (ish) and drains the fluid back into the oil pan and returns that "cleaned" air back into line just before the MAF.
But in the case of higher horsepower (=more blowby) builds, you'll be sucking that poorly filtered air back into the turbo and everything else. Not saying it's impossible to clean it all out. But you'd need a really good catch can or maybe more. Twice now (different setups) I've had issues with blowing loads of crap into my intake. Until I can make a bullet proof catch can, I'm not going that path again.
Yes it helps to pull a little vacuum on the crankcase, but isn't anywhere near enough to make a difference in power. From what I've read, you need 12-14 inches of vacuum (a lot) to generate more power, but to truly take advantage of this pressure differential, you'd need to install thinner rings to reduce friction losses.
OEM (MSM) runs a type of catch can (ish) and drains the fluid back into the oil pan and returns that "cleaned" air back into line just before the MAF.
But in the case of higher horsepower (=more blowby) builds, you'll be sucking that poorly filtered air back into the turbo and everything else. Not saying it's impossible to clean it all out. But you'd need a really good catch can or maybe more. Twice now (different setups) I've had issues with blowing loads of crap into my intake. Until I can make a bullet proof catch can, I'm not going that path again.
Yes it helps to pull a little vacuum on the crankcase, but isn't anywhere near enough to make a difference in power. From what I've read, you need 12-14 inches of vacuum (a lot) to generate more power, but to truly take advantage of this pressure differential, you'd need to install thinner rings to reduce friction losses.
#50
Confused on the catch can setup for N/A track only conditions. Is the preferred option is to disconnect /block PCV and intake and run crankcase to can and back to intake ? Or is it better to have a dual setup like the Radium and run crankcase into one can and PCV into another can? I don't want my seals blown and since the car will be at WOT most of the time, Radium recommended that PCV could be deleted.
#52
Elite Member
iTrader: (15)
Join Date: Jan 2007
Location: Murfreesboro,TN
Posts: 2,052
Total Cats: 267
11:1 VVT motor. I run the stock setup on the intake side and a -06 hose from the exhaust side to a catch can. Small holes drilled in the covers and copper scrubbers. No issues with excessive oil in catch can.
#55
I was wondering if my car was worn beyond where catch cans and venting would help. It's an 01 with 160k 25k turboed. Check valve in the pvc line with a gtx pvc. The hot side has an 18' hose with a breather on it. It's blowing oil out the breather. About an ounce every hundred miles or so. Street use only. I had to stick the breather into a can, it was leaking oil all over. Compression test with Orilley's tester was 190-190-195-195. If it's rings I'll probably just replace engine when it gets too bad, but if it's in the head I have a somewhat fresh ported, CCed head I could use. What do you think. Do I try dual large vents or is it too late?
#56
Moderator
iTrader: (12)
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,664
Total Cats: 3,013
Joe, dual large vents will help, whether the extra blowby is caused by high boost or a tired engine. Either way there's an increased volume that needs to be relieved somewhere so it doesn't push oil out through the seals and gaskets.
#59
I haven’t modified your VC version but if that’s the port to the center chamber then that’s the one to enlarge. That small of a hole really adds an insignificant greater pressure relief if you make the IM side a -10AN + PCV delete VTA setup but I did it anyways like you are. I’m just thankful that my dipstick was loose enough to pop up rather than blow out seals before I did these VC mods.