New RB2's. Rear turbo is slowly dripping from housing V-ban area onto DP's. Rob has been super supportive in my troubleshooting, we both agree that there is little chance that it is a problem with the turbo itself.
Suspected PCV issue: plugged head ports, changed VC/gasket, external PCV kit to OCC to intake. Still dripping.
I have tracked the potential problem to not having enough crankcase vacuum. This will not allow the turbo oil return to drain properly, this allows oil to sit against the seal and slowly weep out. BMW spec is -17 mBar at the valve cover. Seems some people run more...... all the way up to 100ish mBar which seems to be when engine seals start howling.
Most recent troublshooting
Lowered idle to stock: 650 Vacuum at intake went up to 19 psi (yay)
Removed drain line foil cover, no kink (yay)
No oil found at the front turbo housing vband (yay)
Rear turbo leaking at vband after about 15 minutes at idle
Made a fill cap with a fitting, hooked up to manometer.
Bmw spec: -17 mBar
Cold engine at idle reading: -1.7ish (booooo)
Warm engine at idle: -3.0ish (booooo)
So, it appears that just the rear turbo is not draining due to crankcase pressure being about 15ish mBar higher than oem spec. Not sure why the front is not leaking..... maybe it drains just a bit easier?
Removed flapper (30k miles on it). Appeared in working order. Closes when blowing into far end (inlet side), orifice seemed to be the only air flowing. While flapper was removed I blocked off the flapper hole on the VC with a conical thingy. I was able to get crank case pressure to hover around -17 to -25 mBar by modulating the seal of the cone in the VC hole. Closing the hole completely, as expected, caused the crank case vacuum to rocket up, last reading I saw before it started whistling was about -90 mBar. I then removed the cone and concluded the test. This tells me that I do not have a VC/gasket leak. I replaced the flapper hose, no change in the -2ish oil cap vacuum measurement.
Measured vacuum at pcv valve nipple: -17ish psi
While doing that test (hose removed from pcv valve) the crankcase pressure: -2.0ish mBar, not sure why it didnt change?
A test I just thought to do: Cap the flapper hose and remove vacuum and see how much pressure builds in crankcase over 10, 20, 30 seconds. Would that offer any insight?
Current thoughts/questions:
I have not done a leakdown test. I am dreading the results (every engine I've done a leakdown on showed bad results) and it is more comforting to me to eliminate everything else first. But I do recognize that I should do a leakdown test to rule out blowby concerns….. I’m just being stubborn/hopeful.
Will cracked ringlands, worn rings, valve seals, trashed engine cause much much higher positive pressure (>+50 mBar)? My crankcase readings are low but still vacuum, not positive pressure.
Can/should I restrict the flow through the flapper hole/orifice to bring pressure up to -17 to 20 mBar at idle? I know more vacuum can help with rings sealing and such.....that would help under boost. But that is not the case with most of our systems (using intake as vacuum vs using a pump as source) since there is zero vacuum under boost. So what would be the advantage of running higher than stock (-17 mBar) vacuum in the crankcase? Why are some people running vacuum up to just about seals whistling (70-100 mBar)? I know that there are more elegant ways to dial in the CC pressure....... but I like the stockish look and Im cheap whenever I can be.
Sorry for the long winded post, it is a summary of my recent email to Rob.
Suspected PCV issue: plugged head ports, changed VC/gasket, external PCV kit to OCC to intake. Still dripping.
I have tracked the potential problem to not having enough crankcase vacuum. This will not allow the turbo oil return to drain properly, this allows oil to sit against the seal and slowly weep out. BMW spec is -17 mBar at the valve cover. Seems some people run more...... all the way up to 100ish mBar which seems to be when engine seals start howling.
Most recent troublshooting
Lowered idle to stock: 650 Vacuum at intake went up to 19 psi (yay)
Removed drain line foil cover, no kink (yay)
No oil found at the front turbo housing vband (yay)
Rear turbo leaking at vband after about 15 minutes at idle
Made a fill cap with a fitting, hooked up to manometer.
Bmw spec: -17 mBar
Cold engine at idle reading: -1.7ish (booooo)
Warm engine at idle: -3.0ish (booooo)
So, it appears that just the rear turbo is not draining due to crankcase pressure being about 15ish mBar higher than oem spec. Not sure why the front is not leaking..... maybe it drains just a bit easier?
Removed flapper (30k miles on it). Appeared in working order. Closes when blowing into far end (inlet side), orifice seemed to be the only air flowing. While flapper was removed I blocked off the flapper hole on the VC with a conical thingy. I was able to get crank case pressure to hover around -17 to -25 mBar by modulating the seal of the cone in the VC hole. Closing the hole completely, as expected, caused the crank case vacuum to rocket up, last reading I saw before it started whistling was about -90 mBar. I then removed the cone and concluded the test. This tells me that I do not have a VC/gasket leak. I replaced the flapper hose, no change in the -2ish oil cap vacuum measurement.
Measured vacuum at pcv valve nipple: -17ish psi
While doing that test (hose removed from pcv valve) the crankcase pressure: -2.0ish mBar, not sure why it didnt change?
A test I just thought to do: Cap the flapper hose and remove vacuum and see how much pressure builds in crankcase over 10, 20, 30 seconds. Would that offer any insight?
Current thoughts/questions:
I have not done a leakdown test. I am dreading the results (every engine I've done a leakdown on showed bad results) and it is more comforting to me to eliminate everything else first. But I do recognize that I should do a leakdown test to rule out blowby concerns….. I’m just being stubborn/hopeful.
Will cracked ringlands, worn rings, valve seals, trashed engine cause much much higher positive pressure (>+50 mBar)? My crankcase readings are low but still vacuum, not positive pressure.
Can/should I restrict the flow through the flapper hole/orifice to bring pressure up to -17 to 20 mBar at idle? I know more vacuum can help with rings sealing and such.....that would help under boost. But that is not the case with most of our systems (using intake as vacuum vs using a pump as source) since there is zero vacuum under boost. So what would be the advantage of running higher than stock (-17 mBar) vacuum in the crankcase? Why are some people running vacuum up to just about seals whistling (70-100 mBar)? I know that there are more elegant ways to dial in the CC pressure....... but I like the stockish look and Im cheap whenever I can be.
Sorry for the long winded post, it is a summary of my recent email to Rob.
