PCV System

**1ViciousGSX** · 08-10-2007

Quote:

Originally Posted by Andrew7dg

Not picking on you but the vent on the side sees lots of vacuum when the turbo is spooling. Thats when the engine needs vacuum under boost. When it is at idle (off boost) for example, is when it doesn't see much vacuum however that when the PVC valve works and is sucking air out.

The other reason that it is routed into the intake line is because it needs metered air.

So the people that have vents on the side of their valve cover are also pulling in unmetered air through the PVC system. Kind of like what I am dealing with using a GM MAFT

Not picking on you either, but the last thing I want on on my turbo inlet is vacuum. It doesn't really matter because once you go WOT there is no vacuum at the PCV.

Andrew7dg · 08-10-2007

Quote:

Originally Posted by 1ViciousGSX

Not picking on you either, but the last thing I want on on my turbo inlet is vacuum. It doesn't really matter because once you go WOT there is not vacuum at the PCV.

so, if you don't mind me asking, what do you have on the side of the valve cover. is that were you have your catch can? is it venting off to the atmosphere or is it sealed?

**1ViciousGSX** · 08-10-2007

Quote:

Originally Posted by Andrew7dg

so, if you don't mind me asking, what do you have on the side of the valve cover. is that were you have your catch can? is it venting off to the atmosphere or is it sealed?

Catch can breather venting to the atmosphere.

Andrew7dg · 08-10-2007

Quote:

Originally Posted by 1ViciousGSX

Catch can breather venting to the atmosphere.

A setup like your only take care of half of "crankcase ventilation", it will be enough to relief pressure in most cases but it will do nothing to ventilate crankcase due to lack of vacuum in the system, ventilation as in removing blow by and contaminates which will settle into your oil if not pulled out.

**1ViciousGSX** · 08-10-2007

Quote:

Originally Posted by Andrew7dg

A setup like your only take care of half of "crankcase ventilation", it will be enough to relief pressure in most cases but it will do nothing to ventilate crankcase due to lack of vacuum in the system, ventilation as in removing blow by and contaminates which will settle into your oil if not pulled out.

What do you think the PCV is for???

Here is how it works, at idle and cruise intake vacuum from the intake manifold is transfered thru the PCV hose, throught the PCV valve, thru the engine and on to the breather. All the breather does is supply incoming air to counter act the vacuum inside the engine which removes fumes and contaminants by sucking them into the intake to burn in the engine. So whether you get the fresh air from the intake pipe after the air filter, but before the turbo or from an external breather, it doesn't matter to the PCV system. At WOT there is no vacuum, so the PCV shuts closed and is not used.

So would you rather have the fumes and contaminants go out thru an external breather/catch can or feed it into your turbo at WOT?

Andrew7dg · 08-10-2007

It flows both ways. Under boost, the PCV closes, and blowby and other CC leaks need a way out - through the VC breather. It helps to have vacuum to pull gasses out or they stay in the oil.

If you look at my arrangement I do have a catch can but it is sealed and hooked up back to the intake tube. So get the best of both, vacuum and something to filter out the crud that comes out the VC breather so it doesn't go into the turbo.

**1ViciousGSX** · 08-10-2007

Quote:

Originally Posted by Andrew7dg

It flows both ways. Under boost, the PCV closes, and blowby and other CC leaks need a way out - through the VC breather. It helps to have vacuum to pull gasses out or they stay in the oil.

Yeah, I think I covered that already. The stock PCV system do not create a vacuum in the crankcase either, it only moves air thru the crankcase. You want a vacuum on the crankcase, block off the breather port. And then watch oil shoot out of every possible area under boost.

With the amount of blowby coming out of our engines under high boost, you'll never have a vacuum inside the crankcase. Even if you could put together a system to create a vacuum in the crankcase under full boost. the gains would not offset the effort.

Possitive Crankcase Ventilation. Not Positive Crankcase Vacuum, get it?

**1ViciousGSX** · 08-10-2007

Quote:

Originally Posted by Andrew7dg

If you look at my arrangement I do have a catch can but it is sealed and hooked up back to the intake tube. So get the best of both, vacuum and something to filter out the crud that comes out the VC breather so it doesn't go into the turbo.

When was the last time you looked at your compressor wheel to see if it's crud free?

blageo23 · 08-10-2007

Quote:

Originally Posted by 1ViciousGSX

Not picking on you either, but the last thing I want on on my turbo inlet is vacuum. It doesn't really matter because once you go WOT there is no vacuum at the PCV.

When at WOT the PCV system goes in reverse because of the boost. Thats why you get oil in the intake because the blowby goes through the breather side and into the intake.

**1ViciousGSX** · 08-10-2007

Quote:

Originally Posted by blageo23

When at WOT the PCV system goes in reverse because of the boost. Thats why you get oil in the intake because the blowby goes through the breather side and into the intake.

That's why I have a catchcan/breather, so that doesn't happen.

The system doesn't go in reverse, the PCV valve closes off the flow under boost, what comes out of the breather is blowby.