Catch cans and crank pressure
02-09-2015, 12:13 AM
#151
Drifting
No, catch line used to go to piping from filter to throttle body/intake is now capped. The line from catch - can to intake piping is now a simple K&N little filter venting under hood. The intake now isn't part of the oil vapor - catch can system, and is not emissions compliant.
I've got to draw this up to allow congruity. Sorry about the grammar/past posts, typed fast while wife saying, "Hey, we're late!"
G
I've got to draw this up to allow congruity. Sorry about the grammar/past posts, typed fast while wife saying, "Hey, we're late!"
G
Vent between air filter and turbo? Do you mean the original hose that runs from the top of the AOS to the J-boot? If so, and if you are venting the crank to atmosphere, then have you done anything to replace the scavenging effect/vacuum supplied by the J-boot connection? You want whatever scavenging effect you can get....
02-09-2015, 09:29 AM
#152
After this thread a change in approach was decided for my car. The AOS now have 1" opening. There will be two 1/2" hoses from the head going to a T, this have a 19mm hose connected to the AOS turbo breather port. The turbo breather port is blocked off at the engine mount. Hope this will work well, I am not in the mood to removed the turbo an redo this if it doesn't...
02-10-2015, 12:51 PM
#153
Drifting
Hey guys,
I asked Mario to review this post/comments/potential resolutions, etc.
I wanted to share exactly what was done to my car that worked (so far) as I wasn’t with him when the actual work was done. I’m too busy running my businesses and raising children with my wife to work on my cars at night, weekends, etc. We did the planning in my garage with my input. I do have over 20 years experience modifying these "nutty" cars and used to do most of the wrenching.
This solution likely won’t work with journal bearing turbo cars as Mario pointed out below. The car is currently at German Auto in Phoenix to diagnose the Drive Shaft Shop (LR) 968 axles that don’t fit, but the stock 968 axles fit as designed. They won’t honor the warranty until we measure the stock axle CV compression/expansion against the stock axles, and the balance shaft seal was seeping from the excessive crankcase pressure. Didn’t want to change out any more gaskets until we had the crankcase pressure under control.
Many of these cars are highly modified, and what worked for my car may not work for others. Hope this helps some of you towards remedy.
Below are Mario’s comments after reading the post/comments on excessive crankcase pressure issues:
If you don't have the restrictive barn door flow meter there is no crankcase vacuum (scavenging) provided by the j-boot connection. The crankcase is open to the atmosphere via the intake air filter. The engine ingests whatever the crankcase pushes out into the intake tract. There are other systems where this connection is made in a high vacuum area (after the throttle body with a PCV valve) but to the best of my knowledge the 944t is not one of them.
Vent to motor mount breaks the siphon effect that would otherwise draw oil out of the stock oil film bearing after shutdown. The stock bearing requires a high volume and pressure of oil to work. The motor mount vent also serves to release backpressure if the drain can’t flow fast enough. The ball bearing turbo does not rely on pressure, in fact it restricts the feed to just over 1mm before the ball bearing and flows oil over it for cooling purposes. We drain that 1mm pressurized volume into a 13mm hose. A sign that a turbo drain is not sufficient is turbo shaft seal failure.
Hope this helps some of you!
I asked Mario to review this post/comments/potential resolutions, etc.
I wanted to share exactly what was done to my car that worked (so far) as I wasn’t with him when the actual work was done. I’m too busy running my businesses and raising children with my wife to work on my cars at night, weekends, etc. We did the planning in my garage with my input. I do have over 20 years experience modifying these "nutty" cars and used to do most of the wrenching.
This solution likely won’t work with journal bearing turbo cars as Mario pointed out below. The car is currently at German Auto in Phoenix to diagnose the Drive Shaft Shop (LR) 968 axles that don’t fit, but the stock 968 axles fit as designed. They won’t honor the warranty until we measure the stock axle CV compression/expansion against the stock axles, and the balance shaft seal was seeping from the excessive crankcase pressure. Didn’t want to change out any more gaskets until we had the crankcase pressure under control.
Many of these cars are highly modified, and what worked for my car may not work for others. Hope this helps some of you towards remedy.
Below are Mario’s comments after reading the post/comments on excessive crankcase pressure issues:
If you don't have the restrictive barn door flow meter there is no crankcase vacuum (scavenging) provided by the j-boot connection. The crankcase is open to the atmosphere via the intake air filter. The engine ingests whatever the crankcase pushes out into the intake tract. There are other systems where this connection is made in a high vacuum area (after the throttle body with a PCV valve) but to the best of my knowledge the 944t is not one of them.
Vent to motor mount breaks the siphon effect that would otherwise draw oil out of the stock oil film bearing after shutdown. The stock bearing requires a high volume and pressure of oil to work. The motor mount vent also serves to release backpressure if the drain can’t flow fast enough. The ball bearing turbo does not rely on pressure, in fact it restricts the feed to just over 1mm before the ball bearing and flows oil over it for cooling purposes. We drain that 1mm pressurized volume into a 13mm hose. A sign that a turbo drain is not sufficient is turbo shaft seal failure.
Hope this helps some of you!
02-10-2015, 02:50 PM
#154
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02-10-2015, 02:59 PM
#155
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Thread Starter
Hey guys,
I asked Mario to review this post/comments/potential resolutions, etc.
I wanted to share exactly what was done to my car that worked (so far) as I wasn’t with him when the actual work was done. I’m too busy running my businesses and raising children with my wife to work on my cars at night, weekends, etc. We did the planning in my garage with my input. I do have over 20 years experience modifying these "nutty" cars and used to do most of the wrenching.
This solution likely won’t work with journal bearing turbo cars as Mario pointed out below. The car is currently at German Auto in Phoenix to diagnose the Drive Shaft Shop (LR) 968 axles that don’t fit, but the stock 968 axles fit as designed. They won’t honor the warranty until we measure the stock axle CV compression/expansion against the stock axles, and the balance shaft seal was seeping from the excessive crankcase pressure. Didn’t want to change out any more gaskets until we had the crankcase pressure under control.
Many of these cars are highly modified, and what worked for my car may not work for others. Hope this helps some of you towards remedy.
Below are Mario’s comments after reading the post/comments on excessive crankcase pressure issues:
If you don't have the restrictive barn door flow meter there is no crankcase vacuum (scavenging) provided by the j-boot connection. The crankcase is open to the atmosphere via the intake air filter. The engine ingests whatever the crankcase pushes out into the intake tract. There are other systems where this connection is made in a high vacuum area (after the throttle body with a PCV valve) but to the best of my knowledge the 944t is not one of them.
Vent to motor mount breaks the siphon effect that would otherwise draw oil out of the stock oil film bearing after shutdown. The stock bearing requires a high volume and pressure of oil to work. The motor mount vent also serves to release backpressure if the drain can’t flow fast enough. The ball bearing turbo does not rely on pressure, in fact it restricts the feed to just over 1mm before the ball bearing and flows oil over it for cooling purposes. We drain that 1mm pressurized volume into a 13mm hose. A sign that a turbo drain is not sufficient is turbo shaft seal failure.
Hope this helps some of you!
I asked Mario to review this post/comments/potential resolutions, etc.
I wanted to share exactly what was done to my car that worked (so far) as I wasn’t with him when the actual work was done. I’m too busy running my businesses and raising children with my wife to work on my cars at night, weekends, etc. We did the planning in my garage with my input. I do have over 20 years experience modifying these "nutty" cars and used to do most of the wrenching.
This solution likely won’t work with journal bearing turbo cars as Mario pointed out below. The car is currently at German Auto in Phoenix to diagnose the Drive Shaft Shop (LR) 968 axles that don’t fit, but the stock 968 axles fit as designed. They won’t honor the warranty until we measure the stock axle CV compression/expansion against the stock axles, and the balance shaft seal was seeping from the excessive crankcase pressure. Didn’t want to change out any more gaskets until we had the crankcase pressure under control.
Many of these cars are highly modified, and what worked for my car may not work for others. Hope this helps some of you towards remedy.
Below are Mario’s comments after reading the post/comments on excessive crankcase pressure issues:
If you don't have the restrictive barn door flow meter there is no crankcase vacuum (scavenging) provided by the j-boot connection. The crankcase is open to the atmosphere via the intake air filter. The engine ingests whatever the crankcase pushes out into the intake tract. There are other systems where this connection is made in a high vacuum area (after the throttle body with a PCV valve) but to the best of my knowledge the 944t is not one of them.
Vent to motor mount breaks the siphon effect that would otherwise draw oil out of the stock oil film bearing after shutdown. The stock bearing requires a high volume and pressure of oil to work. The motor mount vent also serves to release backpressure if the drain can’t flow fast enough. The ball bearing turbo does not rely on pressure, in fact it restricts the feed to just over 1mm before the ball bearing and flows oil over it for cooling purposes. We drain that 1mm pressurized volume into a 13mm hose. A sign that a turbo drain is not sufficient is turbo shaft seal failure.
Hope this helps some of you!
02-10-2015, 03:31 PM
#156
Drifting
Steve R Zemla
Applications Engineer
Marketing Manager
TiAL Sport
tialsport.com
(989)- 729- 8553
02-10-2015, 11:52 PM
#157
Three Wheelin'
Hey guys,
I asked Mario to review this post/comments/potential resolutions, etc.
If you don't have the restrictive barn door flow meter there is no crankcase vacuum (scavenging) provided by the j-boot connection. The crankcase is open to the atmosphere via the intake air filter. The engine ingests whatever the crankcase pushes out into the intake tract. There are other systems where this connection is made in a high vacuum area (after the throttle body with a PCV valve) but to the best of my knowledge the 944t is not one of them.
Vent to motor mount breaks the siphon effect that would otherwise draw oil out of the stock oil film bearing after shutdown. The stock bearing requires a high volume and pressure of oil to work. The motor mount vent also serves to release backpressure if the drain can’t flow fast enough. The ball bearing turbo does not rely on pressure, in fact it restricts the feed to just over 1mm before the ball bearing and flows oil over it for cooling purposes. We drain that 1mm pressurized volume into a 13mm hose. A sign that a turbo drain is not sufficient is turbo shaft seal failure.
Hope this helps some of you!
I asked Mario to review this post/comments/potential resolutions, etc.
If you don't have the restrictive barn door flow meter there is no crankcase vacuum (scavenging) provided by the j-boot connection. The crankcase is open to the atmosphere via the intake air filter. The engine ingests whatever the crankcase pushes out into the intake tract. There are other systems where this connection is made in a high vacuum area (after the throttle body with a PCV valve) but to the best of my knowledge the 944t is not one of them.
Vent to motor mount breaks the siphon effect that would otherwise draw oil out of the stock oil film bearing after shutdown. The stock bearing requires a high volume and pressure of oil to work. The motor mount vent also serves to release backpressure if the drain can’t flow fast enough. The ball bearing turbo does not rely on pressure, in fact it restricts the feed to just over 1mm before the ball bearing and flows oil over it for cooling purposes. We drain that 1mm pressurized volume into a 13mm hose. A sign that a turbo drain is not sufficient is turbo shaft seal failure.
Hope this helps some of you!
The KKK turbos used in Porsche turbo cars for decades are based on very old-school designs that are agricultural in origin. Therefore the center bearing sections require copious amounts of lubricating oil, and an effective means of evacuating said oil. All 911-based Porsche Turbos, from 930 to 991 and even the Cayenne/Panamera TT use an engine-driven mechanical oil scavenge pump to evacuate the turbo oil drain(s), which actually help to increase the effectiveness of the breather system.
The 951 simply uses a sewer-sized drain pipe that relies on the vacuum in the J-pipe to effectively evacuate the turbo and maintain a vacuum in the crankcase, which not only evacuates crankcase vapors but also helps ring sealing as I mentioned in a previous post.
Modern turbochargers with ball bearings do not require nearly as much oil as the plain bearings of KKK turbos, so the logical solution is to restrict the turbo oil feed to keep the center section from flooding. Unfortunately this affects Porsche's carefully designed breather system, and when combined with high boost pressures, it results in excessive crankcase pressure.
Porsche tends to design the best turbo breather systems in the business, so it would be instructive to look to their modern versions for inspiration.
These systems use check valves to change the flow path of the crankcase vent depending on whether there is vacuum or positive pressure in the intake manifold (downstream of the throttle plate). During light load/off-boost conditions, the crankcase vapors are routed to the intake manifold, downstream of the throttle plate. If boost pressure builds, it closes a check valve that blocks off the no-boost vent line, and opens a second check valve that allows crankcase vapors to enter upstream of the throttle plate (in the turbo inlet pipe, or J-boot of a 951).
The above quote is correct that not much of a vacuum will be present in the J-boot without a barn-door MAF during light load/off-boost scenarios, but there is plenty of vacuum there when there is boost and the turbo is spinning; the system needs to have check valves implemented as described above to take advantage of this . . . .
Implementing such a system in a 951 would require plenty of trial and error; I am merely a mechanic and not an engineer so I cannot calculate the required breather hose sizes, etc, but the system should flow through a quality catch can that incorporates some sort of mesh screen to allow for enhanced air/oil separation over that of the cyclonic chamber of the factory AOS
I will look into posting schematics of some of the Porsche systems that I am talking about; I am slightly worried about being smitten from above by the Porsche overlords for posting copyrighted images, but I will come up with something.
02-11-2015, 12:48 AM
#158
Drifting
Thanks for posting. You'll like what we've designed. Neat work/engineering towards my turbo of choice.
Like your post. Clean. Thanks for sharing.
G
Like your post. Clean. Thanks for sharing.
G
I was about to post that the restriction of the massive oil drain system for the factory turbo is the single largest factor of crankcase pressure issues for the guys with modern aftermarket turbos, but the above is the best explanation that I have seen about the issue so far.
The KKK turbos used in Porsche turbo cars for decades are based on very old-school designs that are agricultural in origin. Therefore the center bearing sections require copious amounts of lubricating oil, and an effective means of evacuating said oil. All 911-based Porsche Turbos, from 930 to 991 and even the Cayenne/Panamera TT use an engine-driven mechanical oil scavenge pump to evacuate the turbo oil drain(s), which actually help to increase the effectiveness of the breather system.
The 951 simply uses a sewer-sized drain pipe that relies on the vacuum in the J-pipe to effectively evacuate the turbo and maintain a vacuum in the crankcase, which not only evacuates crankcase vapors but also helps ring sealing as I mentioned in a previous post.
Modern turbochargers with ball bearings do not require nearly as much oil as the plain bearings of KKK turbos, so the logical solution is to restrict the turbo oil feed to keep the center section from flooding. Unfortunately this affects Porsche's carefully designed breather system, and when combined with high boost pressures, it results in excessive crankcase pressure.
Porsche tends to design the best turbo breather systems in the business, so it would be instructive to look to their modern versions for inspiration.
These systems use check valves to change the flow path of the crankcase vent depending on whether there is vacuum or positive pressure in the intake manifold (downstream of the throttle plate). During light load/off-boost conditions, the crankcase vapors are routed to the intake manifold, downstream of the throttle plate. If boost pressure builds, it closes a check valve that blocks off the no-boost vent line, and opens a second check valve that allows crankcase vapors to enter upstream of the throttle plate (in the turbo inlet pipe, or J-boot of a 951).
The above quote is correct that not much of a vacuum will be present in the J-boot without a barn-door MAF during light load/off-boost scenarios, but there is plenty of vacuum there when there is boost and the turbo is spinning; the system needs to have check valves implemented as described above to take advantage of this . . . .
Implementing such a system in a 951 would require plenty of trial and error; I am merely a mechanic and not an engineer so I cannot calculate the required breather hose sizes, etc, but the system should flow through a quality catch can that incorporates some sort of mesh screen to allow for enhanced air/oil separation over that of the cyclonic chamber of the factory AOS
I will look into posting schematics of some of the Porsche systems that I am talking about; I am slightly worried about being smitten from above by the Porsche overlords for posting copyrighted images, but I will come up with something.
The KKK turbos used in Porsche turbo cars for decades are based on very old-school designs that are agricultural in origin. Therefore the center bearing sections require copious amounts of lubricating oil, and an effective means of evacuating said oil. All 911-based Porsche Turbos, from 930 to 991 and even the Cayenne/Panamera TT use an engine-driven mechanical oil scavenge pump to evacuate the turbo oil drain(s), which actually help to increase the effectiveness of the breather system.
The 951 simply uses a sewer-sized drain pipe that relies on the vacuum in the J-pipe to effectively evacuate the turbo and maintain a vacuum in the crankcase, which not only evacuates crankcase vapors but also helps ring sealing as I mentioned in a previous post.
Modern turbochargers with ball bearings do not require nearly as much oil as the plain bearings of KKK turbos, so the logical solution is to restrict the turbo oil feed to keep the center section from flooding. Unfortunately this affects Porsche's carefully designed breather system, and when combined with high boost pressures, it results in excessive crankcase pressure.
Porsche tends to design the best turbo breather systems in the business, so it would be instructive to look to their modern versions for inspiration.
These systems use check valves to change the flow path of the crankcase vent depending on whether there is vacuum or positive pressure in the intake manifold (downstream of the throttle plate). During light load/off-boost conditions, the crankcase vapors are routed to the intake manifold, downstream of the throttle plate. If boost pressure builds, it closes a check valve that blocks off the no-boost vent line, and opens a second check valve that allows crankcase vapors to enter upstream of the throttle plate (in the turbo inlet pipe, or J-boot of a 951).
The above quote is correct that not much of a vacuum will be present in the J-boot without a barn-door MAF during light load/off-boost scenarios, but there is plenty of vacuum there when there is boost and the turbo is spinning; the system needs to have check valves implemented as described above to take advantage of this . . . .
Implementing such a system in a 951 would require plenty of trial and error; I am merely a mechanic and not an engineer so I cannot calculate the required breather hose sizes, etc, but the system should flow through a quality catch can that incorporates some sort of mesh screen to allow for enhanced air/oil separation over that of the cyclonic chamber of the factory AOS
I will look into posting schematics of some of the Porsche systems that I am talking about; I am slightly worried about being smitten from above by the Porsche overlords for posting copyrighted images, but I will come up with something.
02-11-2015, 01:30 AM
#159
Drifting
I am slightly worried about being smitten from above by the Porsche overlords for posting copyrighted images, but I will come up with something.
Hey Chris,
Chill towards copyrighted images, all shared is within published documented data shared from Owner's Manuals to any Google interaction. I'm a stickler towards compliance, and would never share anything that would jeopardize my business. Still like your post within merit shared.
Kindest Regards,
G
Hey Chris,
Chill towards copyrighted images, all shared is within published documented data shared from Owner's Manuals to any Google interaction. I'm a stickler towards compliance, and would never share anything that would jeopardize my business. Still like your post within merit shared.
Kindest Regards,
G
02-11-2015, 05:57 AM
#160
A while ago I installed a 968 AOS cover that features a nipple for a vacuum hose that goes straight to the intake on the stock 968 engine. I added a blue/black check valve in between, T'd it to one of the banjo plugs between runners 3 & 4, so that crankcase air would be sucked straight into the intake only when the engine ran under vacuum. We discussed this in length 3 or 4 years back in the "smoke at idle" thread.
It must have worked somehow as I could spot a slight oil film in the intake between runners 3 & 4, though lately I felt I did not need it anymore with my GT turbo and eventually removed it.
Increased crankcase vacuum could be obtained by T-ing the AOS hose back into the intake on the larger nipple for the hose going to the brake booster, with of course a PCV in between that would close when the engine runs under boost.
With that said, this is not going to help with Tom's issue where there is excessive crankcase pressure under boost (and also he uses a journal bearing turbo). How about simply trying a smaller cone filter to create back enough vacuum in the AOS line...
It must have worked somehow as I could spot a slight oil film in the intake between runners 3 & 4, though lately I felt I did not need it anymore with my GT turbo and eventually removed it.
Increased crankcase vacuum could be obtained by T-ing the AOS hose back into the intake on the larger nipple for the hose going to the brake booster, with of course a PCV in between that would close when the engine runs under boost.
With that said, this is not going to help with Tom's issue where there is excessive crankcase pressure under boost (and also he uses a journal bearing turbo). How about simply trying a smaller cone filter to create back enough vacuum in the AOS line...
02-11-2015, 09:36 AM
#162
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Here's a quick draw of the install of the can catch without venting from the camshaft cover with 2 check valves.
The check valve between the tee and the intake manifold prevents the camshaft from being under pressure on boost and the check valve between the tee and the MAF tree doesn't allow air to be sucked from the MAF tree under vacuum. Of course, a restrictor must be put in the line to the intake manifold to suck as little as possible.
The check valve between the tee and the intake manifold prevents the camshaft from being under pressure on boost and the check valve between the tee and the MAF tree doesn't allow air to be sucked from the MAF tree under vacuum. Of course, a restrictor must be put in the line to the intake manifold to suck as little as possible.
02-11-2015, 11:52 AM
#164
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However, the check-valve requires some pressure/vacuum to open. I doubt there is enough in the J-pipe to open the CV. Which equates to keeping the port closed all of the time.
A possible solution would be a 3-way solenoid valve in place of the "T". Then electronically (ex. pressure switch) you can route the flow to the intake or the J-pipe.
The correct PCV will work as a check-valve as well. Adding a second CV is an added precaution to keep the path closed under boost.
02-11-2015, 01:48 PM
#165
Rennlist Member
This after much pondering, like all the thoughts in this thread.
I even thought of a strong electrical vacuum pump that would have enough capacity to create decent crankcase vacuum even under high boost/rpm situations (might as well free up some power, if I'm gonna do this, I thought), and install a vacuum release valve for low load situations (can't have too much vacuum)
But, I don't think there's an electrical pump reliable enough for sustained use, and would also use up alot of electrical power.