Ask ten people whether a catch can matters and you will get ten answers. Here is ours, based on what comes across the counter: on a stock naturally aspirated car it is close to jewellery, and on a boosted engine making real cylinder pressure it earns its keep every time you open the intercooler piping and find an oil film inside.
The short answer
- If the car is boosted and tuned, fit one. Oil in the intake charge lowers its resistance to knock, which costs you timing.
- Pick a vehicle specific PCV kit if you want the factory crankcase ventilation kept intact and a tidy install.
- Choose a vent to atmosphere can for a race car that already runs that way. It is the wrong answer for most street cars.
- Empty it. A can that has never been drained is doing nothing except storing a mess.
How blow by works and what a can is doing
Combustion pressure leaks past the rings into the crankcase. That is normal, and it gets worse as boost, bore wear and rpm climb. The crankcase has to breathe that pressure out somewhere, and on a factory engine it goes through the PCV system back into the intake to be burnt.
The problem is what rides along with it. Crankcase vapour carries oil mist, and once that mist is in the intake charge it behaves like a low octane fuel. The engine becomes more knock prone at exactly the load where you need it to behave. On a turbo car the same mist coats the intercooler and the piping, which slowly hurts heat transfer.
A catch can sits in that line and separates the oil from the vapour before it reaches the intake. Good ones use internal media and a design that holds the collected oil rather than letting it slosh back out under lateral load. Radium call theirs a fluid lock, and it is the reason their kits carry the FL suffix.
None of this fixes a tired engine. A can manages the symptom. Heavy blow by means the rings, bore or seal pressure need attention, and that is a rebuild conversation rather than a plumbing one.
Picking the right catch can for your build
Vehicle specific PCV kits
These are the easy ones, because the fitting work is already done. Our Radium catch can range includes a PCV kit for the Evo 4 to 6, a dual can kit for the R32 Skyline GTR, a dual kit for 02 to 21 Subaru EJ turbo, and kits for the Z33 and V35 VQ35DE, the Chaser, Mark II and Cresta family, the S2000 and the Civic Type R.
LS swaps
The LS crowd is well covered with a PCV kit for LS2, LS3 and LS7 and a general LS engine kit, both with the fluid lock design. Worth sorting early, because an LS in a light car with a big cam pushes plenty through the breathers.
Universal and competition
For a one off build or a heavily modified bay, the Competition Catch Can XL gives you volume for a long event, and the VTA Competition Catch Can covers a car already set up to vent to atmosphere. Add the universal mounting bracket rather than fabricating one.
| If you want | Go for | Why |
|---|---|---|
| A clean street install that keeps the PCV system | Radium vehicle specific PCV kit, FL | Brackets, fittings and hose lengths included |
| A dual can setup on an RB or EJ | Radium R32 GTR or Subaru EJ dual kit | Both breathers handled, not just one |
| Volume for long track sessions | Competition Catch Can XL | More capacity between drains |
| A race car that already vents to atmosphere | VTA Competition Catch Can | Built for the job, no PCV path |
| A tidy mount on a custom build | Universal mounting bracket | Saves a fabrication job |
What to buy with it
Think about hose and fittings before you order. Braided or push on lines look better and last longer than the hardware store hose that usually goes on first, and the Radium fittings range covers the o rings and adaptors that always come up mid install.
The turbo oil side deserves the same attention. Our Turbosmart oil management range covers oil pressure regulators and 44um turbo oil feed filters, which protect a bearing cartridge from the debris an older engine sends its way. If you are fitting a catch can because the engine breathes hard, a feed filter is a sensible thing to add at the same time.
Fresh oil and a good filter matter more than any of this. A stretched oil change interval on a boosted engine fills a catch can faster than anything else you can do to it, so keep the Motul range and a decent oil filter on the shopping list.
Where NZ Performance fits
We stock the Radium catch cans and kits in New Zealand, including the vehicle specific fluid lock kits that most of our customers end up wanting, and they sit alongside the rest of our engine components. Orders leave Palmerston North, so you are not waiting three weeks on a kit to finish a weekend job.
If the can is filling quickly, that is worth investigating rather than ignoring. Our RB rebuild kit guide covers what a worn bottom end looks like from the parts side, and the head studs, gaskets and pistons for big boost guide explains why cylinder pressure and seal quality are the same conversation. On the turbo side, our Turbosmart range guide covers the oil control gear that pairs with it.
FAQ
Does a catch can actually do anything on a street car?
On a healthy stock engine the gains are small. On a boosted engine with real cylinder pressure, the crankcase pushes oil mist into the intake, and that oil lowers the effective octane of the charge. If your intercooler piping has an oil film in it, the can has a job to do.
PCV kit or vent to atmosphere?
A PCV kit keeps the factory crankcase ventilation path and routes it through the can, which stays tidy and works well on a street car. A vent to atmosphere can removes that path and suits a race car that is already set up for it. If keeping the factory system intact matters to you, choose the PCV kit.
Do I need a drain back or can I just empty it?
Emptying it is fine as long as you actually do it. A can that overflows sends oil straight back where it came from, and the first sign is usually a puddle or a smoking exhaust. Check it at every oil change, and more often on a track car.
Will a catch can fix an engine that is blowing oil?
No. A can catches what the crankcase pushes out, but heavy blow by means the rings or bore are worn or the engine is seeing more pressure than it can seal. Fix the cause, then fit the can to manage what is left.
Are the vehicle specific kits worth it over a universal can?
Usually yes. The Radium vehicle specific kits come with the brackets, fittings and hose lengths for the car, so the install is a couple of hours rather than a weekend of adapting fittings. Universal cans make sense on a one off or heavily modified engine bay.
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