If you've been modding your car or driving it hard, there's a hidden problem inside your engine that you might not see until it's too late.
It's called blow-by, and it could be affecting your performance. Your car's performance, that is. Let's get into what's going on and how a catch can help you avoid a lot of hassle.
What's Blow-By?
Every time your engine fires, some combustion gas slips past the piston rings and into the crankcase. This is totally normal. But, it brings some stuff with it:
- Oil vapour
- Unburnt fuel
- Carbon deposits
Your PCV (positive crankcase ventilation) system is supposed to vent this gas back into the intake to be re-burnt. It's an environmentally friendly thing to do.
But that means all those oily vapours and carbon particles get sucked back through your intake manifold. Over time, they coat your intake valves in sticky black sludge.
Why It's a Problem
Modern engines, especially direct injection (DI), are more vulnerable. Fuel doesn't pass over the valves in a DI engine to wash off buildup. So the junk just sticks.
The result?
- Clogged intake runners
- Poor airflow
- Reduced performance
- Rough idle
- Expensive valve cleaning
Enter The Catch Can
A catch can is a simple device that catches oil vapour and sludge before it reaches your intake.
It tees into your crankcase breather or PCV hose, and filters out the bad stuff, letting only clean air through.
Clean Air = Better Running Motor
Benefits of a Catch Can:
- Keeps intake valves clean
- Reduces carbon buildup
- Improves engine longevity
- Lowers oil consumption
- Easy to drain and check
How to Install a Catch Can
Most catch cans are universal and easy to fit:
- Tap into your PCV or breather line
- Mount the can on the firewall, strut tower, or similar
- Use quality hose and clamps
- Check if the can has internal baffling or a filter — that's what separates the oil from the air
If you're boosted or building for performance, go with a baffled catch can for the best results.
When Do You Really Need One?
You should definitely run a catch can if:
- You've added a turbo or supercharger
- You've tuned or built your engine
- You track your car or drive it hard
- You want your engine to last
- You live in a humid climate (more condensation = more blow-by), Auckland probably counts.
Ready to Add One?
Scarles stocks a range of universal and baffled catch cans — available in black, silver, and polished finishes.
We ship fast NZ-wide, and we're open 7 days if you want to come in and grab one.
Browse Catch Cans NowScarles Tech Tip:
Check your catch can every few thousand km. If it's doing its job, you'll see gunk at the bottom, and that's a good thing.
