Yet another catch can post
#11
Awesome explanation rmerchant. I appreciate it.
I got 2 ADD W1 baffled cans in hand. One just happens to have a breather and the other is closed loop, so I'm ready to rock.
Ill repost my findings once complete, with pics.
Thanks
I got 2 ADD W1 baffled cans in hand. One just happens to have a breather and the other is closed loop, so I'm ready to rock.
Ill repost my findings once complete, with pics.
Thanks
#13
Registered User
The stock closed loop system has the front vent connected to the intake pipe between the air filter and the throttle plate. The pressure in this part of the pipe is atmospheric minus the small pressure drop due to air being pulled through the air filter. This hose is much larger than the PCV hose. Even when the vacuum in the intake manifold is strongest, the smaller PCV hose cannot flow more air than the vent hose. Therefore, the inside of the valve cover (and the crankcase) is always at atmospheric pressure. Having the vent line open to the atmosphere or connected to the intake pipe upstream of the throttle plate or compressor does not change the operation of the system since the vent tube sees atmospheric pressure either way.
At part throttle or idle, the PCV check valve opens due to the vacuum in the intake and the blow by gasses are sucked directly into the intake manifold. If the PCV line flows more air than the blow by produced by the engine, the extra air is provided by the vent line into the valve cover.
On a boosted car, the PCV check valve is closed under boost (or full throttle for NA) and the blow by gasses go out of the valve cover using the only opening available - the vent line. The closed system recirculates these gases back into the intake air stream (boosted or not). They become compressed with the intake air and when the BOV opens they spray around the engine compartment if the BOV is open to the atmosphere, or recirculate if the BOV is plumbed back to the intake.
Having the vent open to the atmosphere keeps these gasses and oil vapor from entering the intake system to be burned and vents them directly to the atmosphere, aversely effecting emissions.
Having a recirculating system in a boosted car puts these gasses back into the intake system in front of the compressor and intercooler to be burned. Of course, it really isn't a true closed system if the BOV (or a waste gate on a SC car) opens to the atmosphere. The down side is that the oil vapor in the blow by gasses may affect the compressor blades and pool in the intercooler over time.
At part throttle or idle, the PCV check valve opens due to the vacuum in the intake and the blow by gasses are sucked directly into the intake manifold. If the PCV line flows more air than the blow by produced by the engine, the extra air is provided by the vent line into the valve cover.
On a boosted car, the PCV check valve is closed under boost (or full throttle for NA) and the blow by gasses go out of the valve cover using the only opening available - the vent line. The closed system recirculates these gases back into the intake air stream (boosted or not). They become compressed with the intake air and when the BOV opens they spray around the engine compartment if the BOV is open to the atmosphere, or recirculate if the BOV is plumbed back to the intake.
Having the vent open to the atmosphere keeps these gasses and oil vapor from entering the intake system to be burned and vents them directly to the atmosphere, aversely effecting emissions.
Having a recirculating system in a boosted car puts these gasses back into the intake system in front of the compressor and intercooler to be burned. Of course, it really isn't a true closed system if the BOV (or a waste gate on a SC car) opens to the atmosphere. The down side is that the oil vapor in the blow by gasses may affect the compressor blades and pool in the intercooler over time.
The following users liked this post:
RolanTHUNDER (01-02-2017)
#18
The stock closed loop system has the front vent connected to the intake pipe between the air filter and the throttle plate. The pressure in this part of the pipe is atmospheric minus the small pressure drop due to air being pulled through the air filter. This hose is much larger than the PCV hose. Even when the vacuum in the intake manifold is strongest, the smaller PCV hose cannot flow more air than the vent hose. Therefore, the inside of the valve cover (and the crankcase) is always at atmospheric pressure. Having the vent line open to the atmosphere or connected to the intake pipe upstream of the throttle plate or compressor does not change the operation of the system since the vent tube sees atmospheric pressure either way.
At part throttle or idle, the PCV check valve opens due to the vacuum in the intake and the blow by gasses are sucked directly into the intake manifold. If the PCV line flows more air than the blow by produced by the engine, the extra air is provided by the vent line into the valve cover.
On a boosted car, the PCV check valve is closed under boost (or full throttle for NA) and the blow by gasses go out of the valve cover using the only opening available - the vent line. The closed system recirculates these gases back into the intake air stream (boosted or not). They become compressed with the intake air and when the BOV opens they spray around the engine compartment if the BOV is open to the atmosphere, or recirculate if the BOV is plumbed back to the intake.
Having the vent open to the atmosphere keeps these gasses and oil vapor from entering the intake system to be burned and vents them directly to the atmosphere, aversely effecting emissions.
Having a recirculating system in a boosted car puts these gasses back into the intake system in front of the compressor and intercooler to be burned. Of course, it really isn't a true closed system if the BOV (or a waste gate on a SC car) opens to the atmosphere. The down side is that the oil vapor in the blow by gasses may affect the compressor blades and pool in the intercooler over time.
At part throttle or idle, the PCV check valve opens due to the vacuum in the intake and the blow by gasses are sucked directly into the intake manifold. If the PCV line flows more air than the blow by produced by the engine, the extra air is provided by the vent line into the valve cover.
On a boosted car, the PCV check valve is closed under boost (or full throttle for NA) and the blow by gasses go out of the valve cover using the only opening available - the vent line. The closed system recirculates these gases back into the intake air stream (boosted or not). They become compressed with the intake air and when the BOV opens they spray around the engine compartment if the BOV is open to the atmosphere, or recirculate if the BOV is plumbed back to the intake.
Having the vent open to the atmosphere keeps these gasses and oil vapor from entering the intake system to be burned and vents them directly to the atmosphere, aversely effecting emissions.
Having a recirculating system in a boosted car puts these gasses back into the intake system in front of the compressor and intercooler to be burned. Of course, it really isn't a true closed system if the BOV (or a waste gate on a SC car) opens to the atmosphere. The down side is that the oil vapor in the blow by gasses may affect the compressor blades and pool in the intercooler over time.
#20
Community Organizer
is it possible the seals in your supercharger are leaking oil and that's what's blowing out your bov? Had the same thing happen to mine, replaced the seals and problem solved.
Thread
Thread Starter
Forum
Replies
Last Post