Oil pressure without PCV
Thread Starter
Racer
Joined: Jul 2013
Posts: 351
Likes: 24
From: New York
Oil pressure without PCV
Hello. I use my LS3 for track events and got very small amounts of oil in the throttle body with the stock PCV system. I then capped the PCV nipple on the passenger valve cover and replaced oil fill cap with the Elite Engineering oil cap that vents to the srock location on the air filter housing. This works great with no oil at all making it into throttle body.
To pass state inspection I just left cap on PCV valve cover nipple, put on the stock oil filler cap, and installed the stock hose on the air filter housing. I drove a few miles to dealership and it passed inspection. I noticed the oil pressure was about 7 to 8 psi lower than normal and there was a lot of vacuum on the oil filler cap while idling. When I cracked open the oil filler cap, the vacuum released and oil pressure jumped back up to normal.
I am back to my Elite Engineering set up and everything is normal again.
Does anyone fully understand the reason for the stock plumbing and why the oil pressure was lower without any venting on the valve cover?
To pass state inspection I just left cap on PCV valve cover nipple, put on the stock oil filler cap, and installed the stock hose on the air filter housing. I drove a few miles to dealership and it passed inspection. I noticed the oil pressure was about 7 to 8 psi lower than normal and there was a lot of vacuum on the oil filler cap while idling. When I cracked open the oil filler cap, the vacuum released and oil pressure jumped back up to normal.
I am back to my Elite Engineering set up and everything is normal again.
Does anyone fully understand the reason for the stock plumbing and why the oil pressure was lower without any venting on the valve cover?
Drifting
Joined: May 2012
Posts: 1,623
Likes: 51
From: Gastonia North Carolina
Hello. I use my LS3 for track events and got very small amounts of oil in the throttle body with the stock PCV system. I then capped the PCV nipple on the passenger valve cover and replaced oil fill cap with the Elite Engineering oil cap that vents to the srock location on the air filter housing. This works great with no oil at all making it into throttle body.
To pass state inspection I just left cap on PCV valve cover nipple, put on the stock oil filler cap, and installed the stock hose on the air filter housing. I drove a few miles to dealership and it passed inspection. I noticed the oil pressure was about 7 to 8 psi lower than normal and there was a lot of vacuum on the oil filler cap while idling. When I cracked open the oil filler cap, the vacuum released and oil pressure jumped back up to normal.
I am back to my Elite Engineering set up and everything is normal again.
Does anyone fully understand the reason for the stock plumbing and why the oil pressure was lower without any venting on the valve cover?
To pass state inspection I just left cap on PCV valve cover nipple, put on the stock oil filler cap, and installed the stock hose on the air filter housing. I drove a few miles to dealership and it passed inspection. I noticed the oil pressure was about 7 to 8 psi lower than normal and there was a lot of vacuum on the oil filler cap while idling. When I cracked open the oil filler cap, the vacuum released and oil pressure jumped back up to normal.
I am back to my Elite Engineering set up and everything is normal again.
Does anyone fully understand the reason for the stock plumbing and why the oil pressure was lower without any venting on the valve cover?
Subscribed
Instructor
Joined: Feb 2012
Posts: 223
Likes: 14
From: West Chester Ohio
I might be having the same situation. I recently installed the Mighty Mouse catch can, upgrading from the EE can. The EE can, I had between the valley port and intake port. On the MM setup, they instruct to cap the valley port and instead run the fresh air source to the driver valve cover port. This, I suspect, has caused issues for me. I am having lower oil pressure and smoking at decel from redline.
Thread Starter
Racer
Joined: Jul 2013
Posts: 351
Likes: 24
From: New York
So far I have figured the reason for the vacuum at idle. At idle there is a vacuum in the intake manifold which pulls a vacuum on the crank case thru the dirty side PVC hose from the intake manifold to the engine valley cover. The clean side PCV hose from the passenger side valve cover to the air filter housing supplies fresh air to the crank case to replace the air the intake manifold vacuum is taking. This keeps a movement of air to relieve pressure and keep fumes from leaving the engine. My vented oil filler cap keeps all this working and without the fresh air supplied to the passenger valve cover, there is a vacuum in the crank case and valve cover.
But I still don't know how this affects oil pressure? I guess the vacuum in the crank case (when the fresh air isn't being supplied to the valve cover) causes the oil pressure to drop?
But I still don't know how this affects oil pressure? I guess the vacuum in the crank case (when the fresh air isn't being supplied to the valve cover) causes the oil pressure to drop?
Drifting
Joined: Nov 2011
Posts: 1,843
Likes: 330
From: western NY
As a quick test, pop off the oil filler cap to vent the crank case & see if your oil pressure goes up. Each inch of vacuum = approx. .49 psi.
Thread Starter
Racer
Joined: Jul 2013
Posts: 351
Likes: 24
From: New York
JFT69Z, that makes sense. Thanks. When the oem oil fill cap is removed or I have my vented Elite Engineering oil fill cap the oil pressure reads where it should at idle so I think you're right.
It's good to know the oil pressure wasn't actually lower but just the reading on the gauge.
It's good to know the oil pressure wasn't actually lower but just the reading on the gauge.
Supporting Vendor
Joined: Aug 2013
Posts: 1,374
Likes: 298
From: Virginia
i remember the customer question on this.
there is merit to the thought that the oil pressure sensor is exposed to oil which is also influenced by crankcase pressure.
so if for example you had one psi of oil pressure but two psi of crankcase pressure, you perhaps would see something other than 1psi on the gauge.
think of it as just a pressure gauge attached to the engine, reading whatever the highest or lowest number may be
now say we put the crankcase on a vacuum. we are not lowering how much oil the pump produces, or at what pressure, but relatively speaking we could indeed show less on the gauge.
this can be exaggerated as the OP accidentally did by blocking fresh air to the pcv system. if no air can get in, only air leaves, and the crankcase begins to move toward manifold vacuum, offset only by the blow-by made proportionate to load.
there is merit to the thought that the oil pressure sensor is exposed to oil which is also influenced by crankcase pressure.
so if for example you had one psi of oil pressure but two psi of crankcase pressure, you perhaps would see something other than 1psi on the gauge.
think of it as just a pressure gauge attached to the engine, reading whatever the highest or lowest number may be
now say we put the crankcase on a vacuum. we are not lowering how much oil the pump produces, or at what pressure, but relatively speaking we could indeed show less on the gauge.
this can be exaggerated as the OP accidentally did by blocking fresh air to the pcv system. if no air can get in, only air leaves, and the crankcase begins to move toward manifold vacuum, offset only by the blow-by made proportionate to load.
