Maximizing Power Gains with the Mishimoto Catch Can on Your Turbocharged Setup

Turbocharged engines offer exhilarating performance, but they also introduce unique challenges. One of the most common issues is oil blow-by, where combustion chamber pressure forces oil vapor and other contaminants past the piston rings and into the crankcase. In a naturally aspirated engine, the Positive Crankcase Ventilation (PCV) system can handle these gases reasonably well, routing them back into the intake to be burned. However, under boost, the PCV system is overwhelmed. The intake manifold is pressurized, so the crankcase gases must find another path, often through the turbo inlet or charge pipes. This is where a high-quality catch can, like the one from Mishimoto, becomes an essential upgrade. By preventing oil and fuel-soaked vapors from entering the intake tract, a catch cans keeps the intercooler, throttle body, valves, and turbo vanes clean, directly translating to more consistent power and reduced maintenance.

Understanding Oil Blow-By in Forced Induction Systems

To appreciate why a catch can is critical, you must first understand what blow-by is. During the combustion cycle, a small amount of exhaust gas escapes past the piston rings into the crankcase. This gas is a noxious mixture of unburned fuel, water vapor, and, most importantly, oil mist. In a turbocharged engine, the added boost pressure increases the volume and velocity of these blow-by gases. The stock PCV system, designed for low pressure, cannot efficiently separate the oil from the gas. The result is that oil-laden air is recirculated into the intake tract, where it coats internal surfaces. Over time, this leads to carbon buildup on intake valves (especially problematic for direct injection engines), fouled spark plugs, reduced intercooler efficiency, and increased likelihood of detonation. A catch cans acts as a separator, condensing the oil vapor and capturing the liquid, while allowing the cleaned gases to return to the intake.

How a Catch Can Works: The Core Technology

A catch can is essentially a small chamber that uses physical separation methods to capture oil mist. Inside the Mishimoto catch can, you'll find a series of baffles, a mesh filter, or a combination of both. The incoming blow-by gases enter the can, expand, and lose velocity. This sudden change in flow causes the heavier oil droplets to fall out of suspension and condense on the baffle surfaces. The oil then drips down to the bottom of the can, where it accumulates. The cleaner gases exit through a separate port and are either returned to the intake (for closed loop systems) or vented to atmosphere (for catch cans that require a breather filter). Mishimoto's catch cans are fully sealed with O-rings and feature a sight glass or dipstick so you can easily monitor the collected oil level. This design prevents any leaks and ensures the can is maintenance-friendly.

Why Choose the Mishimoto Catch Can Over Competitors?

While there are many catch cans on the market, Mishimoto's units stand out for several reasons. First, they are engineered specifically for turbocharged applications. The internal baffling is optimized to handle the higher flow rates and pressure fluctuations common under boost. Second, Mishimoto uses high-quality billet aluminum construction, which resists corrosion and heat better than plastic or steel alternatives. Third, the packaging is compact enough to fit in tight engine bays, and the mounting hardware is included for a straightforward installation. Many OEM-specific kits are available for popular turbo cars like the Subaru WRX/STI, Ford Focus RS, and BMW N54/N55 engines. Finally, Mishimoto provides detailed instruction manuals and customer support, making the installation process much less intimidating for the home mechanic.

Comprehensive Installation Guide for the Mishimoto Catch Can

Installing a catch can is a weekend project that requires moderate mechanical skill. The process involves rerouting the PCV hoses to incorporate the can. Ensure you have an appropriate kit for your specific vehicle, as routing varies between engines. Below is a step-by-step guide that covers the general procedure.

Tools and Materials Needed

  • Socket set (metric and SAE, depending on your car)
  • Wrenches (combination and/or crowfoot)
  • Flathead and Phillips screwdrivers
  • Drill and appropriate drill bits (only if the catch can bracket needs new mounting holes)
  • Measuring tape or ruler
  • Metal file or deburring tool (if drilling through metal)
  • Zip ties (nylon cable ties for securing hoses)
  • Hose clamps (typically 5/8" to 7/8" range)
  • Safety glasses and gloves

Step 1: Choose the Mounting Location

First, find a mounting spot that is flat, accessible for draining, and away from exhaust manifolds or other heat sources. Common locations include the inner fender well, the firewall, or a bracket on the intake manifold. Ensure the location allows for easy hose routing and does not interfere with hood closure. Hold the catch can bracket in place and mark the holes with a marker. If you need to drill, use a center punch to prevent the bit from wandering. Drill through the sheet metal, then deburr the hole edges to protect the hoses.

Step 2: Secure the Bracket and Can

Attach the mounting bracket to the chosen location using the provided bolts or self-tapping screws. Tighten securely but do not over-torque. Then, mount the catch can onto the bracket. Most Mishimoto cans use a clamp or screw-type mount. Check that the can is oriented vertically (or slightly tilted) so that oil drains properly and the sight glass is visible.

Step 3: Identify PCV Hoses

Locate the PCV hose coming from the crankcase (typically a larger diameter hose near the oil cap) and the hose going to the intake manifold or turbo inlet. On many turbo cars, there are multiple ports: one from the PCV valve on the crankcase, and another from the valve cover (sometimes called the "stump line" or "clean side" separator). Consult your vehicle service manual or an online forum for exact routing. For most applications, you want to intercept the main PCV line and route it through the catch can. The clean side (often on the valve cover) should also be connected to the catch can's second inlet, if equipped.

Step 4: Cut and Route Hoses

Disconnect the PCV hose at the crankcase end. Measure and cut a new section of hose (usually included) to connect from the crankcase outlet to the catch can's "IN" port. Use a razor blade for a clean cut. Then, cut the original PCV hose in the middle and attach it from the catch can's "OUT" port to the intake manifold or turbo inlet. If your can has two ports, you may need an extra hose for the clean side connection. Route all hoses away from moving parts, sharp edges, and hot surfaces. Use zip ties to secure the hoses at intervals.

Step 5: Check All Connections

Once all hoses are attached, tighten each hose clamp with a screwdriver. Ensure no leaks by gently tugging on the hoses. Start the engine and let it idle. Listen for any hissing sounds that indicate a vacuum leak. With the engine running, you can also use a can of brake cleaner or soapy water to check for leaks at the hose ends. If everything is sealed, rev the engine a few times to verify the catch can holds the pressure. The can should remain sealed, and only gases should flow through.

Maintenance: Keeping Your Catch Can Effective

A catch can is only useful if it is regularly emptied and inspected. Mishimoto recommends checking the can every 1,000 to 3,000 miles, depending on driving conditions and engine health. Track cars and heavy stop-and-go traffic will fill the can faster. The accumulated oil will look dark and may smell of fuel. Dispose of this waste oil according to local regulations.

  • Emptying: Most Mishimoto cans have a drain plug at the bottom. Place a drain pan underneath, unscrew the plug, and let the oil drain. Clean the plug threads before reinstalling.
  • Cleaning the Baffles: Over time, the baffle material may become clogged with sludge. To clean, remove the catch can from the bracket, disassemble it (if possible), and wash the internals with carburetor cleaner or brake parts cleaner. Let it air dry completely before reassembly.
  • Inspecting Hoses: Check the hoses for cracks, kinks, or soft spots. High underhood temperatures can degrade rubber over time. Replace any suspect hoses immediately.

Performance Gains and Real-World Results

Many enthusiasts report significant improvements after installing a catch can. While a catch can won't directly add horsepower, it prevents the loss of power that occurs when intake components become oil-fouled. Mishimoto's own dyno testing on a turbocharged Subaru showed that after several hard laps, the catch can reduced intake system oil contamination by over 50%, leading to more consistent air-fuel ratios and reduced knock counts. Other owners on forums like IWSTI have documented lower intake valve carbon deposits after 10,000 miles with a catch can installed. In direct injection engines, the effect is even more pronounced because there is no fuel spray to clean the valves. A catch can can save you from a costly walnut shell blasting service every 30,000 miles.

Common Questions and Misconceptions About Catch Cans

Will a catch can affect my emissions?

In most states, a properly sealed catch can that returns gases to the intake (closed loop) does not affect emissions. However, some states require all PCV components to remain unmodified. Check your local laws. Vented catch cans are generally not legal on public roads.

Do I need a catch can on a naturally aspirated engine?

While beneficial, catch cans are less critical for NA engines because the PCV system can handle blow-by better under vacuum. Turbocharged engines see much more severe blow-by.

Can a catch can cause crankcase pressure issues?

If the catch can is the wrong size or becomes clogged, it can increase crankcase pressure, leading to oil leaks. That's why regular maintenance and proper sizing (Mishimoto offers different sizes) is key. For most street cars, the standard size (0.5L) is sufficient.

What's the difference between a catch can and an AOS (Air Oil Separator)?

An AOS is a more advanced unit that often includes a built-in heater to keep the separated oil flowing back to the engine. Catch cans simply collect the oil. For extreme cold weather, an AOS might be preferable. Mishimoto also offers an AOS for some applications, but the standard catch can is simpler and more cost-effective.

Conclusion: A Small Investment for Long-Term Reliability

Installing a Mishimoto catch can is one of the most effective bang-for-buck modifications you can make to a turbocharged car. It addresses a fundamental weakness in PCV systems under boost, keeping your engine cleaner and more consistent. The installation is straightforward with the right tools, and the ongoing maintenance is minimal – just occasional draining. As Mishimoto continues to refine their designs, the fitment and performance only get better. Whether you are building a high-horsepower race car or just want to protect your daily driver, a catch can is a proven way to maximize power gains and reduce maintenance costs. Add one to your turbo setup today, and enjoy the peace of mind that comes with a cleaner, healthier engine.