A buddy of mine checked his intake today to find it covered with oil. He's got a JRSC on there. I told him its most likely coming from the fresh air tube from the valve cover and told him to just take it off because the SC is probably sucking oil out of the valve cover under boost. Since the valve cover take IN air through this tube I said it would be okay to plug up the intake side and leave the tube from the valve cover hanging until he gets a chance to buy a breather. But he said he did that and like heavy amounts oil & vapors are coming out the tube when its running, like almost a quart he said??? Is there something else wrong else where with his crank case venting system that could cause this? Or is this actually normal? I personally don't think this is normal. But I'm at work and this is just what he's telling me over the phone. Any ideas guys?

 

PCV could be to blame.. but I would at least get a oil catch can on there asap. From what I know... its because of the boost. All that oil thats blowing by is causing a great loss in power.. oil is not as combustable as fuel.. hehe

 

Might need a new PCV valve. Breather filters are trash as they increase blowby considerably.

 

If it's not the PCV valve, it's blow-by. Easy way to tell is to pull the breather hose off the intake tube and push the throttle. If you see oil coming out, the engine is shot.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chris &raquo;</TD></TR><TR><TD CLASS="quote">PCV could be to blame.. but I would at least get a oil catch can on there asap. From what I know... its because of the boost. All that oil thats blowing by is causing a great loss in power.. oil is not as combustable as fuel.. hehe</TD></TR></TABLE>

Agreed, a catch can is nessessary with boost.

 

That tube coming out of the valve cover blows into the intake tube, not the other way around. Vacuum from the engine pulls air thru the intake tube and also thru that pipe out of the valve cover. Since the JRSC increases vacuum in the intake tube, that could be the reason for the increased amount of oil coming through, especially if the PVC is shot (the S/C might be making it worse).

When a turbo or centrifugal S/C is used, the intake pipe becomes subjected to positive pressure, in which case you have to remove the breather tube from the valve cover and use a catch can of some sort (since you don't want air to be blown back into the valve cover).

 

why not just put the breather filter on the end? how would that INcrease blow by?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PatrickGSR94 &raquo;</TD></TR><TR><TD CLASS="quote">That tube coming out of the valve cover blows into the intake tube, not the other way around. </TD></TR></TABLE>

I'm certain the tube from the intake tube to the valve cover is to allow fresh air INTO the valve cover. But back to my buddy's car, I took a quick look at it after work today and neither of us really had time tonight to mess with it. But when he revs the car there is a steady stream of whitish smoke coming out of the tube from the top of the valve cover. Our first guess would be to check the PCV valve, but its crammed in there pretty well with the SC setup so not tonight. But I just wanted to confirm that this continous cloud of white smoke coming out during revs is a agrred symtom of a bad PCV valve?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Black-LS &raquo;</TD></TR><TR><TD CLASS="quote">

I'm certain the tube from the intake tube to the valve cover is to allow fresh air INTO the valve cover. </TD></TR></TABLE>

*disregard this post, see below*

I'm pretty sure the tube is there to help relieve crankcase pressure that gets built up, and to also direct the blowby vapors back into the intake manifold for re-combustion, which helps with emissions. It's part of the PCV system, or Positive Crankcase Ventilation, which means it ventilates, or lets air or pressure out of, the crankcase. I was reading on Endyn's website about the massive crankcase pressures produced by a built high compression engine, which is why they offer valve covers with extra pressure relief openings welded onto it. I also looked inside my stock rubber inake pipe the other day and could see a slight oily residue where that tube enters the intake pipe, which means the vapors are blown out of the valve cover and sucked into the intake pipe.




Modified by PatrickGSR94 at 10:39 AM 4/17/2003

 

On a stock engine, the manifold vacuum sucks air out of the crankcase thru the PCV valve. Then air is sucked into the crankcase thru this breather tube to make up for what's sucked out. If the PCV valve is plugged, or there's enough blow-by to overwhelm it, then air flows backwards thru the breather hose, dragging a bunch of oil with it.

With boost, the manifold is still under vacuum when you're idling. But when the manifold pressure goes above atmospheric, it wants to blow back into the cranckase.

I don't know the plumbing details of a JRSC. Is the PCV hose connected upstream or downstream of the compressor? I suppose the best would be to have the PCV connected between the throttle & the compressor. And the breather should be upstream of the throttle.

 

Alright it seems I was actually wrong about the tube on the valve cover. Blow-by vapors are blown out of the engine block, through the PCV valve and into the intake manifold. Apparently that tube on the valve cover does suck in fresh air from the intake.

In that case I guess you would not want to use it w/ a JRSC since the increased vacuum in the intake pipe might pull air out of the valve cover, instead of air coming into the valve cover like it should.

I don't know, maybe I have no idea what I'm talking about and you should just ignore me.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PatrickGSR94 &raquo;</TD></TR><TR><TD CLASS="quote">... In that case I guess you would not want to use it w/ a JRSC since the increased vacuum in the intake pipe might pull air out of the valve cover, instead of air coming into the valve cover like it should...</TD></TR></TABLE>
Well... I'm the one who's never seen a Jackson SC in real life... There's still a throttle body, right? Upstream of the actual compressor?

So it should work just like stock if you put your PCV hose somewhere downstream of the throttle, but upstream of the compressor. Then your breather hose goes upstream of the throttle, in the air intake duct. There's always going to be some dP across the throttle body, even wide-open.

 

The JRSC is a roots-type supercharger which replaces the intake manifold. The throttle body is before the compressor, and the compressor pulls more air in through the intake tube (intake tube still under negative pressure or vacuum, like stock) and forces it into the cylinders. This is opposed to the turbo or centrifugal supercharger, both mounted before the throttle body, which push more air through the intake tube (positive pressure or boost).

 

OK, I wasn't sure if maybe the JRSC had throttles at the ports, downstream of the compressor. Also didn't know where the PCV fitting was located on the JRSC.

There's still gonna be more vacuum after the throttle & before the compressor; vs. the intake duct. So the PCV system should still work like its supposed to. If its plugged up, then that's the same as a plugged up system without a JRSC.

This shouldn't be as weird as a turbo. I know on Saabs they have to put check valves in there to avoid pressurizing the crankcase. And the breather (inlet tube) is still upstream of the compressor.