Oil Catch Can Setup - Help Needed
12-23-21, 10:19 AM
#26
A baffled oil neck should help along with its larger ports. The stock oil neck doesn't really do a good job keeping oil down, especially under cornering. https://www.irperformance.com/produc...l-filler-neck/
Run the -10 port to a vented catch can.
Make sure your PCV is eliminated. In your pictures it appears to be gone.
If a motor has worn parts of excessively loose clearancinng it can exhibit more blow by.
There should be no vacuum generated at the turbo inlet. The only way you would generate vacuum at the turbo inlet is if you were to block the air filter. The reason the stock venting system dumps there is so any oil that gets pushed oil gets burnt up by the motor. This is a bad idea as it coats the entire intake track and intercooler with oil, reducing efficiency.
If everything is set up correctly and you are still experiencing excessive blow by, a last resort is to weld a fitting onto the rear oil return blockoff plate and run a 2nd vent line to the catch can from there. This only works on single turbo cars however.
An aftermarket oil pan with better baffling will help keep oil down under cornering, but doesn't solve an actual blowby issue.
Run the -10 port to a vented catch can.
Make sure your PCV is eliminated. In your pictures it appears to be gone.
If a motor has worn parts of excessively loose clearancinng it can exhibit more blow by.
There should be no vacuum generated at the turbo inlet. The only way you would generate vacuum at the turbo inlet is if you were to block the air filter. The reason the stock venting system dumps there is so any oil that gets pushed oil gets burnt up by the motor. This is a bad idea as it coats the entire intake track and intercooler with oil, reducing efficiency.
If everything is set up correctly and you are still experiencing excessive blow by, a last resort is to weld a fitting onto the rear oil return blockoff plate and run a 2nd vent line to the catch can from there. This only works on single turbo cars however.
An aftermarket oil pan with better baffling will help keep oil down under cornering, but doesn't solve an actual blowby issue.
The following 2 users liked this post by IRPerformance:
DaleClark (12-24-21),
gracer7-rx7 (12-23-21)
10-04-22, 10:35 PM
#27
A baffled oil neck should help along with its larger ports. The stock oil neck doesn't really do a good job keeping oil down, especially under cornering. https://www.irperformance.com/produc...l-filler-neck/
Run the -10 port to a vented catch can.
Make sure your PCV is eliminated. In your pictures it appears to be gone.
If a motor has worn parts of excessively loose clearancinng it can exhibit more blow by.
There should be no vacuum generated at the turbo inlet. The only way you would generate vacuum at the turbo inlet is if you were to block the air filter. The reason the stock venting system dumps there is so any oil that gets pushed oil gets burnt up by the motor. This is a bad idea as it coats the entire intake track and intercooler with oil, reducing efficiency.
If everything is set up correctly and you are still experiencing excessive blow by, a last resort is to weld a fitting onto the rear oil return blockoff plate and run a 2nd vent line to the catch can from there. This only works on single turbo cars however.
An aftermarket oil pan with better baffling will help keep oil down under cornering, but doesn't solve an actual blowby issue.
Run the -10 port to a vented catch can.
Make sure your PCV is eliminated. In your pictures it appears to be gone.
If a motor has worn parts of excessively loose clearancinng it can exhibit more blow by.
There should be no vacuum generated at the turbo inlet. The only way you would generate vacuum at the turbo inlet is if you were to block the air filter. The reason the stock venting system dumps there is so any oil that gets pushed oil gets burnt up by the motor. This is a bad idea as it coats the entire intake track and intercooler with oil, reducing efficiency.
If everything is set up correctly and you are still experiencing excessive blow by, a last resort is to weld a fitting onto the rear oil return blockoff plate and run a 2nd vent line to the catch can from there. This only works on single turbo cars however.
An aftermarket oil pan with better baffling will help keep oil down under cornering, but doesn't solve an actual blowby issue.
03-01-23, 09:17 AM
#28
I am confused - read too many threads on this and some for 2nd gen may have threw me off too.
Also, my '95 has the hose going from the oil filler neck down to the turbo inlet as Dale mentioned, but it also has a capped nipple at the oil filler neck - basically 2 nipples on the filler neck (pics below).
So would I cap the nipple at the turbo?
Should I connect the outlet of the catch can to the UIM?
Or is that UIM connection even necessary if there is a vent filter on top of the catch can? i.e., if the purpose of the catch can is to collect residue from the vapor generated by PRESSURE so it doesn't make its way out onto the track as oil droplets, then vacuum isn't needed? Or should i switch to a non-vented catch can? If this works via pressure, it would seem you don't need vacuum so I can use the vented one I ordered (before thinking this through better :-( ) ? On the other hand, using a catch can with no filter vent doesn't allow the oil vapor to make its way out of the filter (such as if the can fills up and you don't catch that in time).
And further thinking: if the UIM is pressurized by the turbos when the engine is under boost then not only is there no vacuum, but the pressure could bleed out through the catch can vent?
Also, my '95 has the hose going from the oil filler neck down to the turbo inlet as Dale mentioned, but it also has a capped nipple at the oil filler neck - basically 2 nipples on the filler neck (pics below).
So would I cap the nipple at the turbo?
Should I connect the outlet of the catch can to the UIM?
Or is that UIM connection even necessary if there is a vent filter on top of the catch can? i.e., if the purpose of the catch can is to collect residue from the vapor generated by PRESSURE so it doesn't make its way out onto the track as oil droplets, then vacuum isn't needed? Or should i switch to a non-vented catch can? If this works via pressure, it would seem you don't need vacuum so I can use the vented one I ordered (before thinking this through better :-( ) ? On the other hand, using a catch can with no filter vent doesn't allow the oil vapor to make its way out of the filter (such as if the can fills up and you don't catch that in time).
And further thinking: if the UIM is pressurized by the turbos when the engine is under boost then not only is there no vacuum, but the pressure could bleed out through the catch can vent?
Last edited by MilesBFree; 03-01-23 at 09:44 AM.
03-01-23, 12:41 PM
#30
OK, after a bunch more reading including on turboed race cars, it seems most would simply put the catch can between the source of the fumes, in our case the nipple on the filler neck, and the location to which to vent it to (upstream of the turbo, which could be between the air filter and the turbo).
In our case (again), i think if the factory plumbed this into the primary turbo inlet, I will go with that. So pop the hose off the filler neck, attach it to the output of the catch can, and add a new length of hose between the oil filler nipple and the can's inlet.
I don't dispute the folks who are smarter than me that there may not be much vacuum there, but my thinking is that the stock setup works by crankcase pressure in the oil pan, not vacuum at the turbo inlet. In non-turbo cars (other than with huge cams and/or diesel where there isn't any real vacuum) there would be vacuum in the intake manifold. In turbo cars, there won't be when you are on boost (and there will be turbo pressure pushing against the pressure coming from the oil pan through the filler neck) when the catch can is most needed.
I decided against a vented can - using the hose to the turbo inlet makes me think it is not required. Also, air could be drawn into the turbo inlet through the vent filter, which is likely not going to be anywhere near as good as the K&Ns in the M2 filter box.
In our case (again), i think if the factory plumbed this into the primary turbo inlet, I will go with that. So pop the hose off the filler neck, attach it to the output of the catch can, and add a new length of hose between the oil filler nipple and the can's inlet.
I don't dispute the folks who are smarter than me that there may not be much vacuum there, but my thinking is that the stock setup works by crankcase pressure in the oil pan, not vacuum at the turbo inlet. In non-turbo cars (other than with huge cams and/or diesel where there isn't any real vacuum) there would be vacuum in the intake manifold. In turbo cars, there won't be when you are on boost (and there will be turbo pressure pushing against the pressure coming from the oil pan through the filler neck) when the catch can is most needed.
I decided against a vented can - using the hose to the turbo inlet makes me think it is not required. Also, air could be drawn into the turbo inlet through the vent filter, which is likely not going to be anywhere near as good as the K&Ns in the M2 filter box.
Last edited by MilesBFree; 03-01-23 at 12:54 PM.
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