Catch Can

A catch can is a small sealed container installed in a race car's engine system to collect oil vapor, moisture, and other contaminants before they can enter the engine's intake and cause performance problems.

In simple terms, think of a catch can as a filter jar that traps dirty fluids your engine produces during operation. When an engine runs, especially under the high-stress conditions of racing, it creates pressure inside the crankcase (the lower part of the engine where the crankshaft spins). This pressure needs to escape, and modern engines use something called a PCV system (positive crankcase ventilation) to let these gases out safely.

The problem is that these escaping gases aren't just air—they carry oil droplets, fuel residue, and moisture along with them. Without a catch can, all these contaminants get routed directly back into your engine's intake system, where they eventually enter the combustion chamber. Over time, this creates a sticky carbon buildup on intake valves, pistons, and other internal components, which reduces engine performance and efficiency.

A catch can solves this problem by sitting between the engine's crankcase ventilation outlet and the intake manifold. As the contaminated gases flow through the catch can, internal baffles or filters separate the oil and moisture from the clean air. The clean air continues to the intake system, while the oil and contaminants collect at the bottom of the can where they stay trapped.

The design is fairly straightforward. Most catch cans are cylindrical containers made from aluminum or steel, with inlet and outlet ports for hoses. Inside, there's usually a series of baffles (metal plates or mesh screens) that force the air to change direction multiple times. This causes the heavier oil droplets to separate from the air and drip down into the collection chamber.

In motorsport applications, catch cans are especially important because race engines operate at higher RPMs and under more extreme conditions than street cars. This means they produce significantly more crankcase pressure and oil vapor. A properly installed oil catch can keeps the intake system cleaner, maintains consistent engine performance throughout a race, and can even help prevent oil from being expelled onto hot exhaust components where it could smoke or create a fire hazard.

The collected fluids need to be drained regularly—how often depends on the engine and how hard it's being driven. Some racers check and empty their catch cans after every race or practice session. The amount of fluid collected can actually tell you something about your engine's health; excessive oil accumulation might indicate worn piston rings or other internal issues.

While catch cans originated in professional motorsport, they've become popular modifications for street performance cars too, particularly those with direct injection engines. These engines are more prone to carbon buildup because fuel isn't washing over the intake valves like it does in traditional port-injection engines. Installing an oil separator catch can helps keep these engines running cleaner for longer.