help needed with pcv route

[bellswf]

wuz up guys. im looking for a little help. i installed a oil catch. and wanting to make sure i have pcv hoses correct.. someone told me that i didnt need 2 pcv valve connection.. i have one in rear of intake and one in left side valve cover. i have trick flow intake and lower. aftermarket cai that has a stem for hose to connect in with pcv system. also a connection in elbow between bbk trottle body and upper intake. then hose connects to underside of upper intake with a T that connects to supple tree. i

 

[vristang]

You should be fine with one connection to the intake, just cap off the others...
But won't hurt anything to make more connections either.

I would tie the PCV in at the intake manifold, not at the TB or CAI. The latter options can contaminate the TB and MAF with oil over time.

 

[JD1964]

The pcv system has a suction point which we all should recognize as obvious. Usually it's the tube coming off the underside of the upper manifold. That tube sucks air out of the crankcase, usually through the hole in the back of the lower manifold.

Theres another important connection. It's the supply route. By supply I mean the air thats getting sucked out of the crankcase has to be replaced by incoming air. Ford puts that connection at the throttle body. They do it for a reason. The reason is to make sure all ingested air is measured by the MAF. So, if you need to clean your throttle body now and then, so be it. But if you slap breathers in the valve covers and call it a day, you are ingesting un-metered air which can mess with the ECU's ability to manage things.

 

[JD1964]

I should mention that in a boosted application there would be an exception since the intake gets placed under pressure at times, rather than always under a vacuum such as in NA applications. Anyway, who can give me a good reason why the pcv air volume should not be measured by the MAF in just about any NA application? It's getting ingested into the combustion chambers so it should be measured.

What are the alternatives to connecting at the TB while still being measured by the MAF? How about in the intake tube downstream of the MAF but upstream of the TB, rather than directly at the TB?

 

[bellswf]

thanks for the help. so what im getting is that i should only use the underside connection on upper intake to pcv in back of lower intake. then cap off the other openings. im sure these valve covers are not stock, so is it best to remove the filter element in the left side valve cover and plug tue vc hole or just keep the filter? i was gonna try and put stock covers back on, but from having tfs twisted wedge heads, i must use tall vc where as stock arent tall enough.. im running megasquirt so im no longer using MAF it is a MAP sensor setup now..

 

[JD1964]

I had assumed you were equipped with MAF. With your setup I’m not exactly sure what would be best. Hopefully someone else will chime in and help out

 

[General karthief]

It should be a closed system. One vacuum line to the pcv from the intake, lose the valve cover filter and any other lines for the pvc.
You really don't want the pvc pulling air before the tb, not really a good source of vacuum and you are sending all the vapor through the tb and can coat it with oil residue.

 

[JD1964]

It should be a closed system. One vacuum line to the pcv from the intake, lose the valve cover filter and any other lines for the pvc.
You really don't want the pvc pulling air before the tb, not really a good source of vacuum and you are sending all the vapor through the tb and can coat it with oil residue.

If you have a vacuum line pulling air out of the crankcase, how is that displaced air replaced? Replacement air has to come back in to the crankcase somewhere. Factory is TB to oil filler neck on the valve cover.

 

[General karthief]

That is how you do it.
if you wish to leave the breather in the valve cover then thats fine, a speed density would be less effected by unmetered air than a mass air. The mass air computer will 'see' a certain amount of incoming air through the maf and adjust the fuel trim, if the pcv pulls air from the breather then you basically have a vacuum leak.

 

[vristang]

If you have a vacuum line pulling air out of the crankcase, how is that displaced air replaced? Replacement air has to come back in to the crankcase somewhere. Factory is TB to oil filler neck on the valve cover.

Why does air in the crankcase need to be replaced? Rings don't seal 100%...
Short answer, it doesn't. Ford had an inlet to allow fresh metered air from the TB to the crankcase, probably more for idle stability than anything else?

Plenty of engines out there with a sealed crankcase, and a vac pump...

thanks for the help. so what im getting is that i should only use the underside connection on upper intake to pcv in back of lower intake. then cap off the other openings.

That should work just fine. Have you been able to implement this, and test drive a couple times now?