Why a Catch Can Matters in a High-Performance Forced Induction Build

When you’re chasing serious horsepower with a turbocharged or supercharged engine, every component in the air and fuel path must work flawlessly. One often overlooked but critical part is the crankcase ventilation system. In a high-output “Nashville” turbo or supercharged setup — whether it’s a built LS, a modular Ford, or a boosted import — blow-by gases containing oil vapor and fuel mist inevitably escape past the piston rings. Without proper management, these contaminants get recirculated into the intake, coating intercooler cores, throttle bodies, and intake valves with oily sludge. Over time, this leads to carbon deposits, reduced airflow, detonation, and a drop in performance. A catch can intercepts those vapors, cooling them and allowing the oil to condense and collect in a reservoir while clean air continues back to the intake. Installing one is a straightforward upgrade that pays dividends in engine longevity, consistent power, and peace of mind.

Understanding Blow-By and Crankcase Ventilation

Every internal combustion engine experiences some level of blow-by — combustion gases that leak past the piston rings into the crankcase. This is caused by the high pressure inside the cylinder during the power stroke. The blow-by consists of unburned fuel, water vapor, and acidic combustion byproducts mixed with atomized engine oil. If left unchecked, these contaminants pressurize the crankcase and force oil seals to leak. The PCV (Positive Crankcase Ventilation) system routes these gases back to the intake manifold to be reburned, reducing emissions under normal driving conditions. However, under heavy boost or high RPM, the volume of blow-by increases dramatically. The factory PCV system can become overwhelmed, allowing oil-laden air to enter the intake charge. A catch can acts as an inline separator — it slows the flow, causes condensation, and traps the liquid oil before it reaches the intake. On forced induction setups, where intake pressures are much higher and the air is denser, clean airflow is especially critical. A catch can ensures that only clean, dry air returns to the intake tract, protecting both the engine and the forced induction components.

Types of Catch Cans

Not all catch cans are created equal, and choosing the right design is key to effectiveness in a boosted application.

Vented vs. Non-Vented

Vented catch cans have a filtered vent to atmosphere, which releases pressure and vapors directly to the environment. While legal for off-road use only, they effectively relieve crankcase pressure without any vacuum signal. For street-driven cars subject to emissions regulations, non-vented (closed-loop) catch cans recirculate the cleaned air back into the intake manifold, preserving the vacuum signal that helps seal piston rings and reduce oil consumption. Most high-performance builds go with a non-vented, sealed system to maintain emissions compliance and optimize ring seal under boost.

Baffled vs. Non-Baffled

A baffled catch can contains internal plates, mesh, or a labyrinth that forces the vapors to change direction sharply, causing heavier oil droplets to fall out of the airstream before they can exit. Non-baffled designs rely solely on a volume chamber — they work but are far less efficient, especially during sustained high-RPM pulls. For a boosted engine, a high-quality baffled can is strongly recommended.

Single vs. Dual Port

Most catch cans come with two ports: an inlet (from the crankcase) and an outlet (to the intake). Some high-horsepower setups use a dual outlet can (or two separate cans) to handle both valve cover vents. A boosted engine often sees increased blow-by, so a dual-port or dual-can arrangement can ensure adequate vapor capacity without restriction.

Selecting the Right Catch Can for Your Setup

When choosing a catch can for a turbo or supercharged Nashville build, consider these factors:

  • Oil Capacity: A can that holds 300–500 ml of liquid is typical. Larger cans (1+ liter) are available for high-blow-by engines but can be harder to mount.
  • Fitting Size: Most factory PCV hoses are 3/8″ or 1/2″ ID. Ensure the can uses compatible barb or AN fittings. -10 AN or -12 AN are common for large boosted builds.
  • Mounting Location: Choose a spot in the engine bay that is away from extreme heat, moving belts, and where the can can be drained easily. Often mounted on the strut tower, inner fender, or firewall.
  • Drain Valve: A petcock or threaded plug at the bottom makes periodic emptying simple.
  • Material: Billet aluminum is lightweight, resists corrosion, and dissipates heat well, aiding condensation.

Installation Steps for a Turbo or Supercharged “Nashville” Setup

Whether you’re working on a boosted LS engine, a Coyote with a Vortech supercharger, or a turbocharged 2JZ, the basic installation remains the same. Always reference your specific vehicle’s service manual for exact factory vent locations. The following steps assume a typical PCV system with a single valve cover vent and a clean side air intake connection.

Step 1: Gather Tools and Parts

  • Catch can kit (with mounting bracket, hoses, clamps)
  • Additional lengths of fuel/oil rated hose (silicone hose resists oil vapors better than rubber)
  • Hose clamps (preferably worm gear or constant tension) in appropriate sizes
  • Socket set, wrenches, screwdrivers
  • Drill with bits if you need to mount the bracket using sheet metal screws or rivnuts
  • Marker and tape for labeling lines

Step 2: Locate the Crankcase Ventilation Outlet

On most engines, there is a hose running from the valve cover or the valve cover breather port to the intake tubing. In boosted setups, the fresh air intake side (before the turbo/ supercharger) often has a “clean side” connection that provides filtered air to the crankcase under vacuum. The dirty side PCV valve (typically on the opposite valve cover) routes gases into the intake manifold. Identify both circuits — you may want to catch can the dirty side only, or both sides depending on your system’s design.

Step 3: Disconnect and Route Hoses

Carefully remove the factory hose from the valve cover outlet to the intake tube. Note the orientation. For a boosted application, you typically install the catch can inline between the valve cover outlet and the intake manifold or air intake tube. Some builders prefer to run a dedicated line from each valve cover to a dual catch can. Use your new hose, cut to length, and attach to the catch can’s inlet port. The outlet port connects back to the intake manifold or air intake hose where the original hose ended.

Step 4: Mount the Catch Can

Position the catch can in a location that allows the hoses to have smooth arcs with no sharp bends. Use the provided bracket or fabricate a simple L‑bracket from aluminum. If using self-tapping screws, ensure they won’t penetrate any wiring or fuel lines behind the panel. For a secure mount on painted strut towers, use M6 or M8 rivnuts. Orienting the can vertically (inlet at top, drain at bottom) ensures proper drainage.

Step 5: Connect Hoses and Secure Clamps

Push each hose over the barb fittings — a small amount of oil on the barb helps them slide on. Install a clamp over each connection and tighten until snug but not biting into the hose. Double-check that the hoses are routed away from exhaust manifolds, turbo hot sides, and moving accessories like belts and pulleys. Use zip ties or loom to secure the hoses to existing harnesses if necessary.

Step 6: Test for Leaks

Start the engine and let it idle. Listen for hissing around the catch can and all connections. Rev the engine gently — if you hear whistling or air escaping, recheck clamps and hose routing. Also inspect under any mounting bolt or hole you drilled — ensure no oil or coolant leaks. After a short drive, shut down and check for any accumulated liquid in the catch can. It’s normal to see a small amount of oil and condensation after a few miles.

Routing Considerations for Forced Induction

Turbocharged and supercharged engines have different intake tract pressures, affecting where you connect the catch can outlet.

Turbocharged Engines

Under boost, the intake manifold is pressurized — connecting a catch can outlet directly to the intake manifold would push boost pressure back into the crankcase, defeating the purpose. Therefore, in a turbo setup, the catch can’s outlet should be routed to the air intake tube before the turbo compressor (i.e., the clean side of the air filter). That location is under vacuum at idle and cruising (since it’s before the compressor), but at full boost it experiences slight positive pressure. Many aftermarket kits include a one-way check valve inline to prevent backflow during high boost. If your factory PCV system uses a PCV valve that closes under boost, you may need to remove it and use an inline check valve oriented correctly. Always consult a turbo specialist or the catch can manufacturer’s instructions

Supercharged Engines

With a supercharger (especially positive displacement like a Kenne Bell or centrifugal such as a ProCharger), the intake manifold sees boost throughout the powerband. The same issue applies: you cannot route catch can outlet directly to a boosted manifold. Instead, the outlet should connect to the intake tube before the supercharger inlet, where the air filter is. If the supercharger has a blow-through design (throttle body before supercharger), the intake tube before the blower is under slight vacuum most of the time. Use an integrated PCV valve or inline check valve to prevent boost from pressurizing the crankcase. Some supercharger kits include a dedicated port for catch can connection — use it.

Maintenance and Drain Intervals

A catch can is only effective if kept empty. Overfilled cans can allow liquid oil to be sucked directly into the intake, causing smoke and possible hydro-lock scenarios. Check your catch can every 1,000–3,000 miles, depending on driving style and engine condition. Aggressive track use or a built engine with high ring clearance may fill it faster. Drain the can into an approved oil disposal container — the liquid is a mix of oil, water, and fuel. If you have a drain valve at the bottom, you can simply open it and let the contents drain into a cup. For cans with a threaded plug, remove the plug carefully. After draining, inspect the inside of the can — if it has internal baffles, a quick spray with brake parts cleaner can remove built-up gunk. Replace the hoses if they become hard or cracked from heat exposure, typically every 2–3 years or after major engine work.

Performance Benefits of a Properly Installed Catch Can

  • Cleaner Intake Valves and Ports: On direct injection engines especially, oil vapor accelerates carbon buildup on intake valves. A catch can drastically reduces that, preserving airflow and fuel economy.
  • Enhanced Knock Resistance: Oil in the combustion chamber lowers the effective octane of the fuel-air mixture, promoting detonation. Removing oil vapor raises the knock threshold, allowing more aggressive tuning.
  • Protects Intercoolers and Charge Pipes: Oily residue inside the intercooler cores reduces heat transfer efficiency. A catch ensures only clean air reaches the intercooler, keeping charge temperatures lower.
  • Stable Idle and Throttle Response: When oil film coats the mass airflow sensor or throttle body, it throws off air/fuel ratios. A catch can prevents that contamination, resulting in smoother idle and sharper tip-in.
  • Reduces Oil Consumption: By trapping oil vapor before it’s burned, you may see less oil lost through the PCV system, though this is secondary to the engine’s internal consumption.
  • Extends Turbo/Supercharger Seal Life: Oil mist can damage compressor wheel seals and cause premature bearing wear in turbochargers. A catch can protects those expensive components.

Common Mistakes to Avoid

  • Using the wrong size hose: Too small restricts flow and can pressurize the crankcase; too large may cause leaks or poor sealing. Stick to hose sizes that match the OEM PCV hose diameter or the catch can ports.
  • Mounting the catch can with outlets level or below the inlet: This prevents proper drainage — the can should be mounted vertically with the inlet at the top and drain at the bottom.
  • Forgetting a check valve on boosted systems: Without a check valve, boost pressure will flow back into the crankcase, causing oil leaks and poor ring seal. Always verify the valve orientation.
  • Blocking the clean side intake (fresh air) passage: The crankcase needs makeup air to equalize pressure. If you remove the hose from the air intake to the valve cover, you must install a filtered breather cap. Otherwise, the engine can pull a strong vacuum and suck oil past the seals.
  • Neglecting to empty the can: A full catch can becomes a liability. Set a reminder on your phone every oil change to inspect and drain.

Conclusion

Adding a catch can to your turbo or supercharged build is one of the highest-value reliability upgrades you can make. By keeping oil and combustion byproducts out of the intake system, you preserve peak performance, extend the life of critical components, and make your forced induction setup more consistent on the street or the strip. Whether you’re building a dedicated track car or a weekend cruiser destined for a Nashville dyno tune, investing a few hours in a proper catch can installation will pay off every time you hit the boost. For more detailed guidance, consult resources like the Summit Racing technical library or the EngineLabs PCV system explainer. Remember that every engine is unique — tailor your routing and hardware choices to your specific combination, and you’ll enjoy a cleaner, more reliable power plant for years to come.