What's the deal with breathers?
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TECH Apprentice
Joined: Jan 2010
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What's the deal with breathers? So I see alot of guys running -10an lines from valve covers to catch can....why so big?
I currently have -6an mostly because I had so extra push lock hose laying around and the Valve covers already had nipples for that size hose(altho I did drill out small side one valve cover had) .
Is this something I should consider sealing to -10 and if so why?
I currently have -6an mostly because I had so extra push lock hose laying around and the Valve covers already had nipples for that size hose(altho I did drill out small side one valve cover had) .
Is this something I should consider sealing to -10 and if so why?
I would think what u have is fine. As long as its venting it should work as is. Stock pcv line on the truck intakes is the same size. I have no issues using the stock pcv with a check valve inline.
In forced induction applications the ideal way to setup PCV systems is by using a gauge/logger to monitor and record crankcase pressure (just like you would with other pressures, boost pressure, fuel pressure, oil pressure, etc... )
Then adjust as necessary to achieve desired pressure. Street/OEM seal engines (using OEM gaskets with no reinforcement) cannot tolerate high vacuum in the crankcase for risk of damaging an oil seal (so you wouldn't want a vacuum pump that draws 7" of Hg for example). A moderate amount of pressure drop (say 0.5" Hg) is reasonable, helps ensure crankcase vapors are being scavenged (cleaner oil), and protects the oil seals (keeps pressure from blowing oil past the engine's seals).
An evacuation setup that does not offer at least some pressure drop is considerably lacking, should not be used for a daily driver (high mileage expectancy).
Then adjust as necessary to achieve desired pressure. Street/OEM seal engines (using OEM gaskets with no reinforcement) cannot tolerate high vacuum in the crankcase for risk of damaging an oil seal (so you wouldn't want a vacuum pump that draws 7" of Hg for example). A moderate amount of pressure drop (say 0.5" Hg) is reasonable, helps ensure crankcase vapors are being scavenged (cleaner oil), and protects the oil seals (keeps pressure from blowing oil past the engine's seals).
An evacuation setup that does not offer at least some pressure drop is considerably lacking, should not be used for a daily driver (high mileage expectancy).
The larger size lines are to slow down the velocity of the oil vapor before it hits the can. this gives it a better chance at separating the air from the oil inside the can.
Launching!
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Verdad Gallardo On the pressure drop side (vacuum signal) we want a small line. This is to provide maximum vacuum signal (pressure drop) by minimizing volume. On a forced induction engine, both sides should be pressure drop sides (one goes to the intake manifold, one goes to the pre-compressor inlet which sees pressure drop during boost, provided a sufficient air filter is used) a restrictor is often used in this location (pre-compressor to crank case) on some OEM turbo engines to provide increased vacuum signal to the crankcase.
Think of the opposite- what is the largest line you can use? That would be NO line. The atmosphere can be seen as an enormous line of infinite diameter, which is what we are trying to avoid (the word PCV literally means "positive"CV, as in non-atmospheric pressure system). If oil is being picked up by any PCV related lines- the problem is with the baffle, not the line.
Think of the opposite- what is the largest line you can use? That would be NO line. The atmosphere can be seen as an enormous line of infinite diameter, which is what we are trying to avoid (the word PCV literally means "positive"CV, as in non-atmospheric pressure system). If oil is being picked up by any PCV related lines- the problem is with the baffle, not the line.