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krank vents or open athmosphere ?

16K views 57 replies 23 participants last post by  Hard AttacK 
#1 · (Edited)
I cant deside I got rid of the stock leaking pcv valve and I was wondering would I use krank vents (creates greater vacuum to the crankcase only @ idle) or just put some filters to the valvecover breathing lines and run open athmosphere ?


 

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#2 ·
subscribed... From what i know more vaccume in the crankcase means greater efficiency due to reduced rotational loss'..

Thats why when you put a dry sump system on a motor the output increases. With a constant vaccume in the crankcase the blowby gasses cant accumulate..
 
#3 ·
While crankcase vacuum is a good thing (helps your VSS seal, probably some negligible efficiency gains) I think PCV and krank vents are overrated. Especially if you're running them like stock (one to the intake, one to the manifold). The one time when you want to evacuate case gases as quickly as possible (boost) the manifold valve is closed. Personally I'd rather open all the ports and let the crankcase vent as much as possible.
 
#4 · (Edited)
My valvecover and cam seals started leaking because of the leaky pcv valve I dont want that to happend again and adding krank vent (just an another pcv valve) doesnt make me feel secure.

I would like to know how could I create more vacuum to the crankcase under boost. I´m planning to do vacuum reduction soon and I´m going to try to run both breather lines to the air intake through filters Im planning run the pcv hose to the intake pipe egr line.Allthough there will not be much vacuum at the intake because I have K&N filter but vacuum will be greater then running open athmosphere.
[air intake - filter/catch can - rear valve cover]
[air intake - filter/catch can - front valve cover]
and maybe use filters instead of cross pipe beetween valve covers

I see no reason to use krank vents if I do this I use only filters or a catch can There cant be presssure at the airintake right?

I see no reason have greater vacuum @ crankcase when I´m not boosting and if I just add krank vents that will happen.
 

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#6 · (Edited)
English isnt my native language so by excessive I mean greater than using stock pcv valve. So great that if I remove oil dip stick or oil cap I can hear it sucking air in and lean out at idle.
My pcv started leaking @ 14psi!



Would you suggest to run krank vents like [ valve cover - stock pcv valve - a catch can - krank vent - manifold ]
[valve cover - krank vent - intake]
 
#7 ·
The PCV valve doesn't create vacuum nor do Krank Vents. Krank Vents are just a PCV valve that can support higher amounts of boost. They're overpriced IMO. Just run the stock PCV valve. This will allow excessive blow by past the PCV valve, reducing crankcase pressure, and will not allow boost to get past the PCV valve that would normally pressurize your crankcase. This is what the breather hose is for on the rear VC. It lets pressure escape when the PCV wont allow air out.
 
#11 ·
No, the krank vent does not give you more air flow than stock. I think you have some misconceptions about what the krank vents actually do.

The stock pcv valve and the krank vents are one-way valves. That is ALL they are. The only difference between a stock pcv setup and krank vents is that you have an additional one-way valve preventing air from flowing in from the intake to the crankcase. The idea is that by preventing this air from entering, you maintain a little vacuum in the case.
 
#14 ·
I suppose you could do it that way although I would think that having it at atmospheric pressure isn't going to help crankcase vacuum at all. At least with vacuum in the intake manifold it is PULLING blowby from the crankcase. With it venting to atmosphere there is absolutely no vacuum going on at all.
 
#16 ·
i use to run open (through a catch can) but have since switched to KV. Like mentioned above, the 2nd valve off the rear cover just closes off the system. Which creates crank case vacuum as it doesn't have any place to get air to neutralize. Now, when the car is running I have to fight the vacuum to remove the oil cap now. With the KVs installed i also no longer overrun the stock pcv and pop my dip stick nor leak oil from the cap on high boost. When vented atmosphere sometimes oil would push. Perf wise, no diff IMO just person choice.
 
#17 ·
With the KVs installed i also no longer overrun the stock pcv and pop my dip stick nor leak oil from the cap on high boost. When vented atmosphere sometimes oil would push.
Why would that be the case? Under boost one KV is closed, so you're venting out the rear tube only. With no valves you're venting out both ports. I'm not sure I understand what's going on there.
 
#20 ·
underboost the front is closed = no pressurized air enters into the crankcase. I am sure the pcv valve use to leak, a new one may have resolved this but kv went on instead. So i guess i can't technically say KV fixed that :D
The 2nd valve is open and under vacuum (likely minimal as it is pre turbo) while boosting.
Prior catch can would catch oil (from booth finding its way into my crank case), after I have no oil in my intake lines(no longer going to atmos). Make sense?
 
#25 ·
So your saying the route to go is to buy the krank vents but instead of attaching the line that runs from the rear cover to the intake bubble, just run it to a catch can? I do plan on pouring 30 psi to my system and heard the stock pcv setup has issues with this much boost hence the kv. Ive been following these krank vent posts for a while also.

Terry
 
#26 ·
So justin, how about we run a hose from the rocker covers to a catch can. Then on the other side of the catch can we run a Y with one hose going to manifold vacuum, and the other to the intake, pre turbo. We install check valves in each of those hoses so you get some positive forced ventilation during on and off boost driving conditions? You will have manifold vac off boost and EVOIII suction during boost........
 
#27 ·
I personally wouldn't was EVOIII suction sucking oil vapors thru my turbos.

-Chris
 
#28 · (Edited)
^What you use ? Other people too with custom setups how does your crankcase breathe ?
I´ve been reading lot about this subject and it seems everybody is entitled to their own opinions.
Honda guys tell this is the best way to go
just a open crank case vent w can

Just talked with a guy who drives r33 gtr he told me you should have the motor sucking crankcase pressure out as it being made and your good to go valvecover->catch can->air intake pre turbo. but I however think keeping it from the intake the intake charge will be less contaminated.
 
#33 ·
I vote for krank vents, but don't go name brand, those are ridiculous expensive. Just get a barbed 3/8 1-way valve. I found some good to 100psi for about $7 each, I've got them on all my cars with no problems. I love this mod, it has stopped smoking on both my SLs, and I had good success on a previous VR-4 that had an oil drain issue when I went TD05. I also put one on our 270,000 mile tow truck...it doesn't burn oil anymore :)
 
#35 ·
Krank vents on an N/A are a whole different story. They make a lot more sense to me there. I don't understand all these supposed fixes that are attributed to them though. If they "fix" anything your car has some issues.

Agreed, i just didnt want to be the one to say it online. haha
I'll take the fall when the green police come knocking. ;)
 
#38 ·
^Nice signature!! :)

Eric
 
#41 ·
Yeah, most places sell the particular valve I've been using for $19.95...I paid $7.95 when I bought mine...you get raped on shipping though, so maybe we should put together a group buy and I could send them out individually?
 
#43 ·
Been there, done that. That one whistles, IIRC. It was made for use with liquids. The one I'm using is an "ozone check valve". The white ones are crap, don't last any time at all, it's a black one. They range in price from around $6-25 depending on where you shop for the exact same valve. Minimum shipping at most places is like $9 though so it only makes sense to buy a bunch of them at a time.

I literally tried probably 4 or 5 different valves before settling on the ones I'm using now.
 
#44 ·
I capped the lower intake, connected the rear valvecovers with a T that goes to a catch can and from there to the front pre-turbo intake tube. I Also capped the port on the intake bubble. I'm running 11:1 comp. and 12psi. and getting a max knock of 3 dataloging. I'm getting no oil at all in the intake system with this set up and before with the pvc valve I was getting oil in the intake, not much, but was also getting random knock readings much higher.
 
#46 ·
Would you be willing to illustrate that? I don't quite understand how you have the 4 breathers from the valve covers plumbed.
 
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