Does the LS Dry Sump Pull Vacuum?
Thread Starter
Racer
Joined: Mar 2007
Posts: 254
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From: Washington, D.C. District of Columbia
Does the LS Dry Sump Pull Vacuum?
I have done searches but can't find and answer. If I removed the PCV system and sealed the block would the dry sump on my LS3 pull any kind of vacuum? I'm wondering if I delete the PCV and vent the oil tank would it be a more effective (although non-emissions legal) way to clean out the crankcase and get the benefit of having vacuum in the block. As far as I can tell, the LS3 dry sump is a 2-stage pump that has one stage scavenge through two ports in the pan. Probably not enough to pull any kind of vacuum that would show performance gains, but would it clean out the block of PCV fumes?
Le Mans Master
Joined: Aug 2005
Posts: 5,375
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From: CA.
St. Jude Donor '13-'14-'15
A dry sumps picks up "everything" in the pan---The pan is a dynamic place where lots of things are changing at once--There is oil--air--oil vapor -- and a mixture of any of these being sucked up thru the pump---When it all settles into the tank--naturally all the air rises and separates to the top of the tank as does the vapor--leaving just oil to be pumped back into the motor--- The air is then released via a vent or PCV system
Running a vacuum pan system is primarily used in drag racing or short duration running engines-- On an engine used to run anything more than just a few seconds at once I would NOT gamble with a sealed engine or vacuum system---The HP gains are minimal at best and can create catastrophic results
PS: From my circle track racing (endurance engines) background --all the dry sump systems were vented---to atmosphere
Running a vacuum pan system is primarily used in drag racing or short duration running engines-- On an engine used to run anything more than just a few seconds at once I would NOT gamble with a sealed engine or vacuum system---The HP gains are minimal at best and can create catastrophic results
PS: From my circle track racing (endurance engines) background --all the dry sump systems were vented---to atmosphere
Race Director
Joined: Mar 2005
Posts: 10,399
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From: Austin Texas
There is no vacuum in the crankcase. The only vacuum involved in the PCV comes from the throttle body via the hose between the TB and the valley cover.
If anything there is pressure in the crankcase from blowby. The PCV system attempts to keep the crankcase neutral by removing pressure via the valley cover to TB and the allowing fresh metered air in via the valve cover lines.
If anything there is pressure in the crankcase from blowby. The PCV system attempts to keep the crankcase neutral by removing pressure via the valley cover to TB and the allowing fresh metered air in via the valve cover lines.
Race Director
Joined: Mar 2005
Posts: 10,399
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From: Austin Texas
Clean side would be the line from before the throttle body, it's filtered, measured air that travels from before the throttle body eventually to the crankcase. On an LS3 it's a line from one valve cover, on an LS7 it appears to be a line from each valve cover and from the oil tank.
Dirty side is the line from the valley cover (crankcase) to behind the throttle body, it's dirty air (blowby) that travels from the crankcase to the intake.
Dirty side is the line from the valley cover (crankcase) to behind the throttle body, it's dirty air (blowby) that travels from the crankcase to the intake.
Melting Slicks
Joined: Dec 2006
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You're going your engine more harm than good man; you do not want pressure in the crankcase. PLUS you want to get rid of those nasty fumes, that only vacuum can do. Just install a catch-can so your intake doesn't get oil (or at least not as much 
).
).
Thread Starter
Racer
Joined: Mar 2007
Posts: 254
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From: Washington, D.C. District of Columbia
That's the problem - overpressure. Undoubtedly caused by my supercharger. Whether it's simply blowing past factory ring gaps, or there is damage somewhere, I don't know. Compression and leak down tests have been inconclusive. I've already got two catch cans, one of them -12 AN. I realize that this is a bigger problem that requires an engine teardown, but I dont have the means to do that right now. So I am trying to figure out ways to vent off overpressure, flush the intake and block, and keep the cabin of my car from smelling like a dirty oil filter. I was thinking that if I capped all the PCV ports, used the suction of the oil pump to pull fumes out of the block, then route the dirty vent line from the oil tank directly to the PCV vacuum at the TB (with a catch can inline), then maybe that might work.
Thread Starter
Racer
Joined: Mar 2007
Posts: 254
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From: Washington, D.C. District of Columbia
When it's in tune, 700 at 14# (stock engine) This is a street car that gets driven hard, no track time. I've tried every combination I can think of to try to have my cake and eat it too. But if I vent to air, then i'm letting crap settle and accumulate in my oil - it also stinks up my cabin; if I try to hook up some sort of PCV - not enough flow to clear the block and I get oil out the pan bolts and everywhere else. There's no place to put a vacuum pump (I want AC - not that it works once the engine heats up...) I've even looked at the Racetronics - electronic pump but consensus is not enough vacuum and pump won't last long enough. So I started thinking about oil pumps to clear the block, but I doubt there's a solution there for me anyway. I'm likely just gonna have to live with frequent oil changes and oil stink, and start saving for a forged 418.
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Pro
Joined: Nov 2007
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any oil pump will not be enough volume to evacuate that block. I've never noticed any cabin smell, maybe you need a better filter(s) or change the vent locations (physical location of can). A properly vented block will outperform even a 5 stage vacuum pump. Put a boost gauge on one of your pcv lines and watch it. It might be rather alarming under full power haha.
thanks for the suggestions