PCV question(s)

[Mud_]

With an LS6 style setup am I correct in thinking it's as simple as send the valley to vacuum (via a catch can in my case), and send clean air in through the driver's side valve cover?

Any benefit in giving clean air to both valve covers?

Any disadvantage to just putting a small filter straight on the valve cover(s) (smells?)? I see these referred to as breathers, but if I'm understanding correctly in the LS6 system it's an inlet, not an outlet...or will it potentially blow out some oil vapour?

This is all with a view to ITBs and I'm currently feeling thick...vacuum also goes to the brake booster, purge solenoid and HVAC, any potential pitfalls? I'm planning to put a non-return valve and a small reservoir on the brake booster, although I think my current cam shouldn't cause problems with lack of vacuum.

Is the small vacuum-operated thing underneath the ABS unit the doodad that disengages the AC clutch when pressing on?

[stevieturbo]

PCV generally tries to draw fresh air through the crankcase and then into the engine, to maintain a clean crankcase.

This is of course at the expense of clean air into the intake/engine, as you're drawing that dirty crankcase air into it. Hopefully a good can will ensure no oil gets by. And better still could be filtered too.

Or simple...just vent the heap into a suitable catch can ( which of course is vented too, not the usual sealed up cheap ebay ste )
This may not keep the hippies happy, but it works.

With ITB's, you'd probably need a few cylinders to pull enough vacuum for the servo, not sure one single cylinder runner would be enough ? Although it might.

Strangely, an awful lot of modern cars seem to have an electric vacuum assist pump for their brakes. I've seen the pumps listed for Mercs, VW/Audi, Mercedes, Jag, Volvo etc and not just diesel models.

[Mud_]

stevieturbo said:

PCV generally tries to draw fresh air through the crankcase and then into the engine, to maintain a clean crankcase.

This is of course at the expense of clean air into the intake/engine, as you're drawing that dirty crankcase air into it. Hopefully a good can will ensure no oil gets by. And better still could be filtered too.

Or simple...just vent the heap into a suitable catch can ( which of course is vented too, not the usual sealed up cheap ebay ste )
This may not keep the hippies happy, but it works.

With ITB's, you'd probably need a few cylinders to pull enough vacuum for the servo, not sure one single cylinder runner would be enough ? Although it might.

Strangely, an awful lot of modern cars seem to have an electric vacuum assist pump for their brakes. I've seen the pumps listed for Mercs, VW/Audi, Mercedes, Jag, Volvo etc and not just diesel models.

I've tee'd into each intake runner to make a vacuum manifold, this should give good vacuum and retains the IAC. I did wonder if there was a way of ensuring the vacuum manifold stayed clean (beyond just the catch can), since this goes straight to the intake runners. Pumps like the MES DEA are recommended, but a bit noisy and it's more expense and complication, so I'll avoid it if I can. An OE unit might be worth investigating.

The LS6 valley cover is my 'dirty out', this doesn't need a partial vacuum pulling on it then (going to a vented can)? I wasn't sure if this was necessary to keep the air moving in the right direction through the valve covers.

[Boosted LS1]

The valley cover is indeed the dirty air. It will need vacuum to draw it out. Meanwhile the rocker covers are where clean air's drawn in., hence the flow.

You can put a restrictor in the rocker covers or just use one breather with a restrictor. You probably only need a small amount of flow, mainly to get rid of explosive gasses in the crankcase. Less flow will give you more vacuum and cleaner itb's.

[stevieturbo]

This is the sort of pump.

http://www.ebay.co.uk/itm/BRAKE-BOOSTER-SERVO-AIR-...

Oddly some listings seem to refer to it as an aircon pump...probably just dumb sellers but it's fitted to loads of cars.

I'm sure how different makes trigger it will vary, but I found Volvo make a nice little T-piece that goes into the vac line with an inbuilt pressure switch.
So via a relay this triggers the pump to run

eg

http://www.ebay.co.uk/itm/VOLVO-S60-XC70-VACUUM-CO...

I've fitted one to my own car for use with anti-lag. That said, I havent yet tried it with an aggressive ALS setup where there is positive pressure in the intake at all times.

But it will certainly work as an assistance pump, even for the likes of say towing with the engine off, this little pump would keep the servo charged up so your brakes work which I'm guessing is maybe why OEM's are fitting them ? In case of engine stoppage and the brakes normally die with no vacuum.

[Mud_]

Boosted LS1 said:

The valley cover is indeed the dirty air. It will need vacuum to draw it out. Meanwhile the rocker covers are where clean air's drawn in., hence the flow.

You can put a restrictor in the rocker covers or just use one breather with a restrictor. You probably only need a small amount of flow, mainly to get rid of explosive gasses in the crankcase. Less flow will give you more vacuum and cleaner itb's.

Do you have a feel for what size restrictor would work well? It's 5/16" hose onto the valve covers, so starting with a little less than 8mm ID I suppose.

I've read anecdotally that the driver's side valve train often look cleaner than the passenger side (where the valve cover is usually blocked) - this may be reason-enough to open that side up. The passenger side is actually in a more convenient place too. If I used both valve covers as clean air in I could at least restrict the flow down to 1/2 on each side.

[Mud_]

stevieturbo said:

This is the sort of pump.

http://www.ebay.co.uk/itm/BRAKE-BOOSTER-SERVO-AIR-...

Oddly some listings seem to refer to it as an aircon pump...probably just dumb sellers but it's fitted to loads of cars.

I'm sure how different makes trigger it will vary, but I found Volvo make a nice little T-piece that goes into the vac line with an inbuilt pressure switch.
So via a relay this triggers the pump to run

eg

http://www.ebay.co.uk/itm/VOLVO-S60-XC70-VACUUM-CO...

I've fitted one to my own car for use with anti-lag. That said, I havent yet tried it with an aggressive ALS setup where there is positive pressure in the intake at all times.

But it will certainly work as an assistance pump, even for the likes of say towing with the engine off, this little pump would keep the servo charged up so your brakes work which I'm guessing is maybe why OEM's are fitting them ? In case of engine stoppage and the brakes normally die with no vacuum.

That Volvo unit may get around a major criticism of the MES DEA, that it's over-sensitive and basically runs all the time.

I'm hoping a non-return and a small reservoir will negate the need for a pump, but I'll think on packaging and whether it's worth the added complication to keep cack out of my intake!

Thanks both by the way

[robbyd]

stevieturbo said:

PCV generally tries to draw fresh air through the crankcase and then into the engine, to maintain a clean crankcase.

What I don't get (with my LS1) is that there seems to be no means by which the system can draw fresh air in...

Correct me if I'm wrong, but the oil filler cap is sealed and there are no other breathers. On closed throttle the PCV valve just makes vacuum in the crankcase, and given these engines can feed a lot of oil up top, is it any wonder they can suck it out through the TB on lift-off from high revs?

[Mud_]

robbyd said:

What I don't get (with my LS1) is that there seems to be no means by which the system can draw fresh air in...

Correct me if I'm wrong, but the oil filler cap is sealed and there are no other breathers. On closed throttle the PCV valve just makes vacuum in the crankcase, and given these engines can feed a lot of oil up top, is it any wonder they can suck it out through the TB on lift-off from high revs?

The LS6 valley cover PCV system is an upgrade for early engines: https://ls1howto.com/index.php?article=18

[stevieturbo]

robbyd said:

What I don't get (with my LS1) is that there seems to be no means by which the system can draw fresh air in...

Correct me if I'm wrong, but the oil filler cap is sealed and there are no other breathers. On closed throttle the PCV valve just makes vacuum in the crankcase, and given these engines can feed a lot of oil up top, is it any wonder they can suck it out through the TB on lift-off from high revs?

There will be a link to the intake manifold side and there will be one of the crankcase/valve cover pipes routed to say the airbox somewhere.

There will be restrictions placed where necessary to ensure only a small amount of air is drawn through, and usually mediocre oil/air separators to prevent oil being drawn in....which is why it usually is to some degree.

[robbyd]

this is basically the same PCV as I have:

http://i.ebayimg.com/images/i/231269372609-0-1/s-l...


both pipes come off the rocker covers and go straight into the TB (engine side I guess, without checking).

seems no pipework to inlet tract prior to TB, which I agree, would make sense...

[Boosted LS1]

Mud_ said:

Boosted LS1 said:

The valley cover is indeed the dirty air. It will need vacuum to draw it out. Meanwhile the rocker covers are where clean air's drawn in., hence the flow.

You can put a restrictor in the rocker covers or just use one breather with a restrictor. You probably only need a small amount of flow, mainly to get rid of explosive gasses in the crankcase. Less flow will give you more vacuum and cleaner itb's.

Do you have a feel for what size restrictor would work well? It's 5/16" hose onto the valve covers, so starting with a little less than 8mm ID I suppose.

I've read anecdotally that the driver's side valve train often look cleaner than the passenger side (where the valve cover is usually blocked) - this may be reason-enough to open that side up. The passenger side is actually in a more convenient place too. If I used both valve covers as clean air in I could at least restrict the flow down to 1/2 on each side.

On a rover v8 it's literally a pin hole on one valve cover. I'm guessing but maybe only a couple of mm's iirc. All you need is some flow, not masses of unmetered air.

[Mud_]

Boosted LS1 said:

On a rover v8 it's literally a pin hole on one valve cover. I'm guessing but maybe only a couple of mm's iirc. All you need is some flow, not masses of unmetered air.

Good to know