Catch Cans: Beware of cheap crappy ones

[Berto]

There is a reason why these "Greddy type" catch cans are cheap ...

Reason being: As they come they are basically useless crap.



1) They lack any internal baffles/meshes/wools to separate oil from air, so they will "catch" little if any oil:

2) Even worse, they are a significant vacuum leak. The fittings for the transparent level tube are pathetically cheap and leak like a sieve, as this guy demonstrates (go to 25:35):

So unless you're handy and willing to spend DIY time and effort rectifying their faults, stay away from these cheap catch cans.

 

[JonRobinson82]

Is there any reason these couldn't be used simply between the breather outlet on the cam cover and the air intake? I'm not gonna need to worry about vacuum leaks or anything then surely?

 

[Berto]

^ On a healthy Z22SE with unmodified OEM crankcase ventilation system, most of the time (anything but WOT) the engine is sucking air thru the pre-throttle breather into the cam cover and crankcase. Any air sucked in thru a non airtight catch can will be unfiltered air.

 

[JonRobinson82]

But if it's just a small leak and I make sure the can is filled with some wire mesh or something as a baffle it should be OK right? The air filter will filter air being sucked through from the intake pipe won't it?

 

[Berto]

If a tiny hole would appear on an OEM pre-throttle breather hose (which is downstream from the air filter inside the airbox), unfiltered air would be sucked in into cam cover & crankcase at anything but WOT.

Same effect with a non airtight catch can there.

Baffles & meshes are to separate oil from air, they will not filter the air.

 

[JonRobinson82]

K so I'd have to DIY it to make sure it's airtight then. I see this video on YouTube where some guy made a catch tank with some drainpipe and stuff lol he used a few of those stainless wire puff things you use for washing up. Now I don't want to make a catch tank but would the stainless puff thing be OK as some kind of baffle material?

 

[JonRobinson82]

I'm just trying to save a bit of money on sumat that can be quite expensive. The missus is getting fed up with "unnecessary" purchases lol

 

[Berto]

Not trying to break your party Jon, do as you like. But if you ask me: leaky catch can < OEM < airtight catch can.

In fact if we're talking about a street car, not a race car, I wouldn't even bother tinkering with a catch can on the pre-throttle breather. That line only pulls blow-by/oily air at WOT, and street cars spend very little real time at WOT.

The post-throttle PCV line, that pulls from the crankcase ALL of the time, would benefit much more from a catch can (the can would catch much more oil there). But in the Z22SE it is just a metered orifice buried inside the inlet manifold, no option to insert a catch can (barring creative modifications).


I'd use copper scrubbers better than stainless steel ones inside a catch can, copper is a catalyst to hydrocarbon breakdown (specially if there is water vapour around, like in crankcase gasses).

 

[JonRobinson82]

I do like a bit of WOT lol. Still if there's no point then sod it lol jus gonna have to clean the TB out every few months or sumat. Thanks mate

 

[JonRobinson82]

Is there much difference at WOT if the breather had a catch can?

 

[Berto]

... if there's no point then sod it lol jus gonna have to clean the TB out every few months ...

^ Exactly, IMHO inserting a cheap crappy leaky catch can in the pre-throttle breather line ain't worth the trouble. Just clean up the breather hose, airbox => TB pipe and the throttle body once a year, call it a day, and keep the missus happy .

 

[JonRobinson82]

Roger Roger