Catch Can Setup Problem

[DonVaughnS13]

Hello fellow Zilvians,

I've searched and been through much of the catch can setup threads. Because of their age most have missing photos/broken links/scattered information.

I currently have a stock SR20DET setup with a new ISR air intake. I'm looking to add a catch can setup however there is no bung for the return line from the catch can after the MAF in the piping. I read this is where the line should go from the catch can.

Is there an alternative solution to successfully setting this up? I'm already aware of how to set much of it up, I just seem to have difficulty figuring this out.

Thank you in advance.

[S14rebuild]

Add a fitting to the intake... hose barb or an fitting......

[DonVaughnS13]

Add a fitting to the intake... hose barb or an fitting......

Thanks. That is my first idea. However I read there is a restrictor on the stock intake piping. I have not been able to find this fitting online. Is this restrictor required?

[S14rebuild]

Some will say yes, so will say no. Not to hard to add a fitting in the hose to act as a restrictor.

[DonVaughnS13]

Some will say yes, so will say no. Not to hard to add a fitting in the hose to act as a restrictor.


Thank you for your help!

[SupaDoopa]

Thanks. That is my first idea. However I read there is a restrictor on the stock intake piping. I have not been able to find this fitting online. Is this restrictor required?

That's a subjective question. Like S14 said, some do it as a precaution while others swear by it and then there is the crowd that doesn't do it at all. It's personal preference but adding an attachment point is suggested.

[Kingtal0n]

If you put a restriction on the hose and fail to measure crankcase pressure while cruising and at idle you run the risk of pulling too much vacuum on the crankcase which will pull all the oil seals into the engine i.e. damage the front and rear main seals. which of course means rebuilding the engine.

So if you dont plan to measure the crankcase pressure properly using a gauge (it should measure approx 2-3" of Hg maximum at all times) then do not use a restrictor at all just leave the hose open.

this will ruin the effects of PCV pressure drop but it will remove any concerns over whether the oil seals will be damaged.

[DonVaughnS13]

That's a subjective question. Like S14 said, some do it as a precaution while others swear by it and then there is the crowd that doesn't do it at all. It's personal preference but adding an attachment point is suggested.

If you put a restriction on the hose and fail to measure crankcase pressure while cruising and at idle you run the risk of pulling too much vacuum on the crankcase which will pull all the oil seals into the engine i.e. damage the front and rear main seals. which of course means rebuilding the engine.

So if you dont plan to measure the crankcase pressure properly using a gauge (it should measure approx 2-3" of Hg maximum at all times) then do not use a restrictor at all just leave the hose open.

this will ruin the effects of PCV pressure drop but it will remove any concerns over whether the oil seals will be damaged.

Thanks all, it's really appreciated.

[TheRealSy90]

Wouldn't a restrictor on the hose lower the vacuum applied to that hose...

[d1zguy2]

The PCV side left side of the VC is the one that provides vacuum, not running the right side to intake pre maf will cause a lean condition and no vacuum in the crank case. the restrictor is there to prevent sucking up oil but running a closed catch can is and routing it to the intake pre maf is all you need, the restrictor on the stock hose is there to prevent sucking up actual oil. With a closed catch can you don't actually need it.

[Kingtal0n]

The PCV side left side of the VC is the one that provides vacuum, not running the right side to intake pre maf will cause a lean condition and no vacuum in the crank case. the restrictor is there to prevent sucking up oil but running a closed catch can is and routing it to the intake pre maf is all you need, the restrictor on the stock hose is there to prevent sucking up actual oil. With a closed catch can you don't actually need it.

wrong. the restrictor has nothing to do with 'sucking oil'. Look at where it is positioned.

please read
https://www.sr20-forum.com/information-library/!42637-crank-case-ventilation-fully-explained-turbocharged-edition.html?page=1

From Ben,
Without it, idle air is less controllable, and the crank case can't ever really hold a vacuum at all.

Repeat: the restrictor is there to assure the crankcase can hold a vacuum

[d1zguy2]

wrong. the restrictor has nothing to do with 'sucking oil'. Look at where it is positioned.

please read
https://www.sr20-forum.com/information-library/!42637-crank-case-ventilation-fully-explained-turbocharged-edition.html?page=1

From Ben,


Repeat: the restrictor is there to assure the crankcase can hold a vacuum


Well that makes sense. I?ll have to see where the restrictor is so I can replace it when I install a closed catch can. Is it on the stock rubber boot or the stock hose?

[Calver]

If you put a restriction on the hose and fail to measure crankcase pressure while cruising and at idle you run the risk of pulling too much vacuum on the crankcase which will pull all the oil seals into the engine i.e. damage the front and rear main seals. which of course means rebuilding the engine.

So if you dont plan to measure the crankcase pressure properly using a gauge (it should measure approx 2-3" of Hg maximum at all times) then do not use a restrictor at all just leave the hose open.

this will ruin the effects of PCV pressure drop but it will remove any concerns over whether the oil seals will be damaged.

That explains it. Learned something new today.

[Kingtal0n]

Well that makes sense. I?ll have to see where the restrictor is so I can replace it when I install a closed catch can. Is it on the stock rubber boot or the stock hose?

this is a picture of stock restrictor for sr20
https://zilvia.net/f/showpost.php?p=6022100&postcount=19


however the size of restrictor depends on the flow rate of the pcv system, suction from the intake manifold and size of orifice of pcv valve.

SO if you've modified the intake, the engine, the pcv valve, anything between the intake manifold vacuum signal, the intake port, the pcv system, then the size of the restrictor will need to be adjusted to return the crankcase resting pressure to the correct range of 1-3" Hg,

Anything over 3" Hg can damage the oil pump and ruin the engine seals (engine rebuild)
so err on the large side if in doubt

[d1zguy2]

this is a picture of stock restrictor for sr20
https://zilvia.net/f/showpost.php?p=6022100&postcount=19


however the size of restrictor depends on the flow rate of the pcv system, suction from the intake manifold and size of orifice of pcv valve.

SO if you've modified the intake, the engine, the pcv valve, anything between the intake manifold vacuum signal, the intake port, the pcv system, then the size of the restrictor will need to be adjusted to return the crankcase resting pressure to the correct range of 1-3" Hg,

Anything over 3" Hg can damage the oil pump and ruin the engine seals (engine rebuild)
so err on the large side if in doubt

Thank you for all the OG info and saved me lots of time and headaches! Replace the forward section, salvaged the restrictor from OEM hose heated up and inserted it into homedepot vynil water hose, fitted a close catchcan.

The restrict or was actually in the hose itself, the boot barb was just a fitting to allow it to take a hose into the stock rubber boot.

https://i.imgur.com/JN4tQkF.jpg