Calling experts on AOS/breather
09-02-2016, 04:16 PM
#16
Rennlist Member
Thread Starter
I drilled my AOS because at high-output, my motor would produce excessive crankcase pressure, which would cause oil leaks, push the dip stick up, etc. Drilling the AOS lowers the crankcase pressure under heavy boost, and eliminates the oil leaks, dip stick issues, etc. As V2 says, however, it also reduces the effectiveness of the Air-Oil-Separator (AOS), allowing more oily mist to escape out the top of the AOS. Because of that, most people who drill the AOS also install a closed-loop catch can, where the hose from the top of the AOS is routed to the catch can, to trap the oil, and another hose from the catch can is routed to the j-boot to vent the pressure. If you use a breather that is not routed back to the j-boot, you'll get a burning oil smell that can be annoying for a street car.
Not sure what you are referring to when you say the turbo might "suck oil" through the AOS, but there are two related issues there. First, when you alter the pressure/vacuum in the crankcase, the oil lubricating the turbo sometimes can't drain fast enough back into the oil pan. That's usually solved by controlling the oil feed to the turbo and reducing pressure in the crank. The other issue is when too much oil vapor spits out the top of the AOS and gets sent to the j-boot, resulting in noticeable amounts of oil in the j-boot and turbo inlet. That is why people use a catch can -- to trap the oil in the can instead of sending it straight into the turbo. A breather vented to atmosphere will also prevent oil from getting to the j-boot, but makes for a smelly car as all that oily pressure fills the air.
Not sure what you are referring to when you say the turbo might "suck oil" through the AOS, but there are two related issues there. First, when you alter the pressure/vacuum in the crankcase, the oil lubricating the turbo sometimes can't drain fast enough back into the oil pan. That's usually solved by controlling the oil feed to the turbo and reducing pressure in the crank. The other issue is when too much oil vapor spits out the top of the AOS and gets sent to the j-boot, resulting in noticeable amounts of oil in the j-boot and turbo inlet. That is why people use a catch can -- to trap the oil in the can instead of sending it straight into the turbo. A breather vented to atmosphere will also prevent oil from getting to the j-boot, but makes for a smelly car as all that oily pressure fills the air.
So please fill in but to sum it up. Since my car is a -89 Turbo Cup car which naturally I use mostly on track and only occasionaly on the street a set up to a breathercan sounds the best considering that my AOS opening has been opened up. And since the car is registered for the street I will when time comes for the annual MOT, attach the hose from the AOS to the j-boot to help scrutineers happy!?
09-02-2016, 09:12 PM
#17
Rennlist Member
Actually your combustion will be cleaner when you dont push oilmist trough the engine. But on a normal healthy engine i guess it cant be noticed "measured"
09-02-2016, 10:33 PM
#18
Rennlist Member
Thanks guys for the clarification!
So please fill in but to sum it up. Since my car is a -89 Turbo Cup car which naturally I use mostly on track and only occasionaly on the street a set up to a breathercan sounds the best considering that my AOS opening has been opened up. And since the car is registered for the street I will when time comes for the annual MOT, attach the hose from the AOS to the j-boot to help scrutineers happy!?
So please fill in but to sum it up. Since my car is a -89 Turbo Cup car which naturally I use mostly on track and only occasionaly on the street a set up to a breathercan sounds the best considering that my AOS opening has been opened up. And since the car is registered for the street I will when time comes for the annual MOT, attach the hose from the AOS to the j-boot to help scrutineers happy!?
09-03-2016, 04:43 AM
#19
Rennlist Member
Thread Starter
Thanks guys for youre input!
09-03-2016, 06:24 PM
#21
Rennlist Member
Thread Starter
Thanks Jay. I have thought about that but I have heard of people having issues with that setup (drilled AOS routed back before turbo)
Issue has been that they experience the turbo "sucking" exessive oil through that enlarged opening and filling the catch can pretty quick. Dont know if that was due to the enlarged opening or other engine related issues though. I like the Idea of the catch can to eliminate any oil that might get back in through the intake though. Maybe I should put in a restriction to make the AOS opening like stock again and use that setup.
But then I think why is it good too hook it back in like stock exept to help the environment and pass annual inspection? I am trying to find out the pros and cons of the stock kind of setup and pros and cons of just attaching it to a breather a la lindsey.
However I still feel I am not sure which is best.
Issue has been that they experience the turbo "sucking" exessive oil through that enlarged opening and filling the catch can pretty quick. Dont know if that was due to the enlarged opening or other engine related issues though. I like the Idea of the catch can to eliminate any oil that might get back in through the intake though. Maybe I should put in a restriction to make the AOS opening like stock again and use that setup.
But then I think why is it good too hook it back in like stock exept to help the environment and pass annual inspection? I am trying to find out the pros and cons of the stock kind of setup and pros and cons of just attaching it to a breather a la lindsey.
However I still feel I am not sure which is best.