Smoke at idle
09-19-2011, 05:39 PM
#106
Burning Brakes
Hi Nick,
Funny you mention you once had the line to the AOS plugged ahead of the throttle body, as I was wondering if it would provide more or less vacuum to the AOS. On your set up it shows it didn't provide enough and that you get more vacuum from the turbo inlet.
Now that oil is making its way out of the top of the turbo, perhaps it's time to do the plastic bag test and/or let the engine idle for several minutes watching closely for smoke coming out of the exhaust?
Funny you mention you once had the line to the AOS plugged ahead of the throttle body, as I was wondering if it would provide more or less vacuum to the AOS. On your set up it shows it didn't provide enough and that you get more vacuum from the turbo inlet.
Now that oil is making its way out of the top of the turbo, perhaps it's time to do the plastic bag test and/or let the engine idle for several minutes watching closely for smoke coming out of the exhaust?
09-19-2011, 06:55 PM
#107
My 3.2 4 valve turbo engine, like all of you on the smoking at idle club, smoked at idle and had been doing it even after being completelly rebuilt and capacity reduced from 3.4 to 3.2 liters. After reading this tread I did the plastic bag test and found some positive crankcase pressure. Installed, in series, two original one way (blue/black) one way valves fron the fitting in the 968 AOS to the intake and immediatelly the smoke at idle stopped. I still had some smoke when pulling away so I installed two bigger one way valves, in parallel( too increase vacuum at crankcase and positive pressure flow out of the AOS and safety reasons), between the AOS and the catch can(vented to atmosphere) and now I get no smoke whatsoever. I still have to measure restriction under boost to make sure I have enough positive crankcase pressure venting capacity from the two bigger one way valves in parallel. But so far so good. Finally!!!
Last edited by zagaone; 09-19-2011 at 11:47 PM.
09-19-2011, 07:10 PM
#108
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I'm back on the road again. I had to drive 15-20 miles to "clear the pipes" because the entire exhaust system had a coating of oil installed, but all is well for the next 15-20 miles. I haven't hit high boost yet, but I did do a few 12-13 psi 3rd & 4th gear pulls at 1/2 throttle or so... it feels nice and strong so far.
For the crankcase vent, I just ran a 1/2" hose from the AOS to the turbo inlet - no T at this point, and NO smoke at idle. I also replaced the turbo vent hose elbow (was hard as a rock!) with a new silicone elbow from LR. That could have been a contributor to the idle smoke since it may have limited vacuum going to the turbo drain.
For the crankcase vent, I just ran a 1/2" hose from the AOS to the turbo inlet - no T at this point, and NO smoke at idle. I also replaced the turbo vent hose elbow (was hard as a rock!) with a new silicone elbow from LR. That could have been a contributor to the idle smoke since it may have limited vacuum going to the turbo drain.
09-19-2011, 07:52 PM
#110
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My 3.2 4 valve turbo engine, like all of you on the smoking at idle club, smoked at idle and had been doing it even after being completelly rebuilt and capacity reduced from 3.4 to 3.2 liters. After reading this tread I did the plastic bag test and found some positive crankcase pressure. Installed two original one way (blue/black) one way valves fron the fitting in the 968 AOS to the intake and immediatelly the smoke at idle stopped. I still had some smoke when pulling away so I installed two bigger one way valves, in parallel( two increase flow and safety reasons), between the AOS and the catch can(vented to atmosphere) and now I get no smoke whatsoever. I still have to measure restriction under boost to make sure I have enough positive crankcase pressure venting capacity from the two one way valves in parallel. But so far so good. Finally!!!
09-19-2011, 08:20 PM
#111
What I did is basically the same concept as the drawing of zerMatt951 in page 5 of this tread with the variation of using two one way valves in parallel between the AOS and the catch can and using the additional port on the top of the 968 AOS to connect the hose going to the blue/black one way valve and then to the intake.
In my case I don't think venting to the turbo intake will make any significant difference to the turbo spooling with the drawback of maybe dirting the whole intercooler and intake tubing with an oil film and altering the fuel mixture by mixing it with oily air, specially now that some(hopefully very little) oily air will be introduced through the connection from the AOS and the intake.
In my case I don't think venting to the turbo intake will make any significant difference to the turbo spooling with the drawback of maybe dirting the whole intercooler and intake tubing with an oil film and altering the fuel mixture by mixing it with oily air, specially now that some(hopefully very little) oily air will be introduced through the connection from the AOS and the intake.
Last edited by zagaone; 09-19-2011 at 11:44 PM.
09-20-2011, 05:01 AM
#112
zagaone, thanks for your input.
If I understand correctly your set up, it's as described on the diagram below. Is this correct?
(It assumes that the crankcase will always be under pressure when the engine is running under boost)
If I understand correctly your set up, it's as described on the diagram below. Is this correct?
(It assumes that the crankcase will always be under pressure when the engine is running under boost)
Last edited by Thom; 09-20-2011 at 10:50 AM.
09-20-2011, 05:09 AM
#113
Matt, good to see you have this solved. Time to enjoy the car.
ETA : we may need a new president for the Smoking at idle club, as the founding member left the board
ETA : we may need a new president for the Smoking at idle club, as the founding member left the board
Last edited by Thom; 09-20-2011 at 06:17 AM.
09-20-2011, 08:03 AM
#114
Burning Brakes
One question for all the 3 litre owners....
I am assuming you are all using a 951 dipstick (as I am) as opposed to a 968 one. Is there any difference in the way they read full. Could we be over filling our oil if we read the level on a 951 dipstick as this is meant for a different oil pan?
I am assuming you are all using a 951 dipstick (as I am) as opposed to a 968 one. Is there any difference in the way they read full. Could we be over filling our oil if we read the level on a 951 dipstick as this is meant for a different oil pan?
09-20-2011, 08:20 AM
#115
Nick, I checked this recently - the same dipstick is used and pick up tubes are of the same length, if shaped slightly differently to suit the respective intake manifolds.
Using less oil may help (in my case it helped to a certain extent), but it remains a bandaid and doesn't address the actual issue which is lack of vacuum.
Using less oil may help (in my case it helped to a certain extent), but it remains a bandaid and doesn't address the actual issue which is lack of vacuum.
09-20-2011, 11:35 AM
#116
Thom that is exactly my set up with an additional blue/black 1-way valve in line with the other blue/black for safety. As clarification for those that may want to use this setup it is important to notice that out of the AOS is just one big hose that split into two smaller hoses for the parallel one way valves and downstream again joining into another one big diameter hose into the oil catch can.
Regarding the dipstick I had this same doubt a long time ago and what I did was left the oil go down until the oil level warning came on on the dashboard. Remeasured the dipstick and found out it was measuring correct. So overfilling because of the dipstick is not the issue.
Angel
Regarding the dipstick I had this same doubt a long time ago and what I did was left the oil go down until the oil level warning came on on the dashboard. Remeasured the dipstick and found out it was measuring correct. So overfilling because of the dipstick is not the issue.
Angel
Last edited by zagaone; 09-20-2011 at 11:51 AM.
09-20-2011, 12:04 PM
#117
Thom that is exactly my set up with an additional blue/black 1-way valve in line with the other blue/black for safety. As clarification for those that may want to use this setup it is important to notice that out of the AOS is just one big hose that split into two smaller hoses for the parallel one way valves and downstream again joining into another one big diameter hose into the oil catch can.
09-20-2011, 12:27 PM
#118
Not necessarily. The tube/hose diameter out of the AOS is bigger than the size of the parallel hoses for the 1way valves. The same afterward. The hose going into the catch can is a lot bigger that the 1way valve hoses. This is the reasons I put the 1 way valves in parallel since I could not find a 1 way valve with the in and out tubes diameter big enough.
Your drawing is the optimum design. Is just a lot more difficult to put together. You will need to modify the AOS and the Oil catch can to accept separate and independent "circuits".
I believe I have enough venting capacity this way without the complication:
Big hose out of AOS -> Two parallel smaller hoses with one way valves -> Big hose into catch can
Angel
Your drawing is the optimum design. Is just a lot more difficult to put together. You will need to modify the AOS and the Oil catch can to accept separate and independent "circuits".
I believe I have enough venting capacity this way without the complication:
Big hose out of AOS -> Two parallel smaller hoses with one way valves -> Big hose into catch can
Angel
09-20-2011, 04:42 PM
#119
Angel, thanks for the clarification, it makes sense.
I am interested to know if the line with the two blue/black check valves you have between the intake and the AOS is likely to get clogged over time. Please keep us updated.
I am interested to know if the line with the two blue/black check valves you have between the intake and the AOS is likely to get clogged over time. Please keep us updated.
