Dual Catch Can - Why you want to do it

[Cruizinmax]

thanks heaps for your reply

that radium one would be perfect but I’m in Australia so shipping will take ages and I want this sorted ASAP. I wonder if there is a similar option with AN fittings on either end.

can you tell me I’m guessing all PCV valves are different in the amount of pressure they open etc?? So not all are suited for the N54? Or are all pcv the same?

so all I need to do is replace my check valve that is on the out of my catch can on the line returning to my intake manifold and this will sort all of my issues?

is it possible that my cheap turbosmart kompact type looking BOVs are the issue? I think I’ll try and replace them with my stock BPVs today and see if that makes any difference. I’ve noticed when I’m driving and come off the throttle the BOVs go off a second or so apart from each other so I here the sound Twice. I also notice that when on freeway doing 110-120km/hr that they just keep going off like I’m on and off the throttle but I’m not.
Would that be because of the boost leak?

can you explain to me what actually causes the boost leak by not having a pcv and just a check valve? Are you sure it’s just the one issue or do I have more than one problem?

thanks heaps

The pcv valve limits the volume of air being drawn back in to the intake manifold during vacuum conditions. Drawing a huge amount of air through the crankcase isn't necessary during vacuum conditions. By allowing this huge amount of air to bypass the throttle body it is having to close more than programmed to keep your idle down therefore causing the code. This is probably causing your strange driveability problems as well.

The second function of the pcv valve (for a turbo car) is to act as a check valve during boost conditions. So essentially all you need would be any pcv valve from a factory turbo car. I have also used the pcv valve from a Evo 8 as well in some setups. It has a 1/4" npt thread on one side and 8mm (I think) hose on the side going to the intake manifold. Perhaps you could make something like that work more easily.

 

[Snertz]

@Trowy88

AN6 line may help but he is also using the RB External PCV adapter which has the Toyota PCV built into it. A -6 line alone will not be enough restriction, I had this on my car and it ends up pulling too much vacuum (it'll make a howling noise, that's air being drawn in past the seals). Returning to the manifold isn't the issue since it's essentially how the OEM setup does it albeit through the ports in the head. It doesn't matter where the return is located so long as it's somewhere after the throttle blade.

If you return to the front inlet, it's essentially doing the same as the highside line going to the rear inlet. It'll work but you'd be giving up the benefit of pulling crankcase vacuum during off boost driving.

I believe the Toyota PCV small end is -6, don't recall what the bigger end is but it might be -8. Easiest way to join while retaining your existing line would be to use some barbed reducer fitting to the appropriate size hose to the PCV, like the fittings here: https://www.mcmaster.com/tube-fitti...or-air-and-water/shape~straight/type~reducer/

If you want it to match the stainless AN lines then you could use an AN reducer fitting plus the appropriate couplers and AN hose barbs to connect to the PCV.

Something like this:

Fragola Aluminum AN Fitting - Swivel Expander (Female to Male)

Fragola Aluminum AN Expander, Swivel Expander for AN connections (Female to Male). Available from -3 AN up to -20 AN in black or blue.

www.verociousmotorsports.com

Fragola Aluminum AN Fitting - Swivel Reducer (Female to Male)

Fragola Aluminum AN Reducer, Swivel Reducer for AN connections (Female to Male). Available from -3 AN up to -20 AN in black or blue.

www.verociousmotorsports.com

Fragola Aluminum AN Fitting - Reducer (Male to Male)

Fragola Straight AN Reducer (Male x Male) AN Fitting in aluminum for adapting AN Hose. These Straight Reducer Fittings are available from -3 up to -20 AN sizes. Available in black or blue.

www.verociousmotorsports.com

It's a vacuum leak not a boost leak, this is why the car drives fine at WOT or anytime there's positive boost; The check valve closes in those situations thus no leak. Your BOV isn't causing the issue, the fluttering is from the DME trying to compensate for the leak with the throttle. Likewise for the vac canisters, deleting them will not cause the behavior you're seeing.

It would run fine with a check valve too as long as a restrictor is introduced, all you basically need to do is reduce the volume returned to the intake manifold. I think Cruizinmax is spot on, any PCV from a turbo application should do. I suggested the Toyota one because it's cheap, readily available, and proven to work on our platform.