Catch Cans - Why They Are A Must For Direct Injection Engines
In almost every dedicated race car, track day toy, and even modified daily driver, you are likely to spot a funny little cylinder with an inlet line and outlet line nestled somewhere in the bay. You probably already know that is a catch can, but haven’t given it much thought if you aren’t running one yourself. Even many people who do install catch cans in their BMW don’t rightly know their exact purpose, as is evident in online discussions. As BMW and other manufacturers have moved to exclusively Direct Injection for fuel systems, catch cans have become imperative to both protect your engine and allow for higher horsepower ceilings so you can enjoy your Ultimate Driving Machine for a long time without too much worry. Today, we’re going to explain why a catch can is an absolute must for your direct injection BMW engine and show you why the Turner Motorsport catch can systems are just what you need. | 
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It’s important that you first understand how a catch can works and what its purpose is. A catch can is designed to intercept the pressure released from the crankcase and catch the particles, contaminants, and oil that is blown from the crankcase. Ordinarily, there is a simple solution to relieve that pressure in the form of a PCV or Pressure Crankcase Ventilation valve that allows the buildup of pressure to be released through that valve back into the intake. This is an effective way to release the built pressure and return it to the intake but does not allow filtration of that pressure buildup. The byproduct is that oil and contaminants that are blown through the PCV system into the intake make their way through the throttle body and onto the valves inside the head. This causes eventual buildup from that oil which can be detrimental to performance.
This is why a catch can is important in almost every engine application, as it separates the particulate matter from the air before that air is returned to the intake from the crankcase. However, with Direct Injection engines, it is even more critical. You may have some awareness of the natural buildup in early direct injection systems, like the N54, which requires regular walnut shell blasting to clean the intake ports and valves to prevent power loss and possible engine damage. |
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So why does carbon buildup on your valves and intake ports happen more dramatically with direct injection engines? With direct injection, fuel is directly supplied to the combustion chamber rather than through the ports and onto the valves like traditional port injection. Because fuel has detergents, it acts as a sort of cleaner as it is sprayed into the combustion chamber, which eliminates some buildup that has accumulated due to the reintroduction of ventilated air from the crankcase. With direct injection, the fuel that would ordinarily provide cleaning to the ports and valves never passes through that part of the engine, so buildup is never removed. This means that the longer you drive your car, the more buildup you accumulate, and the more your performance will suffer as a result until you have the intake ports and valves blasted.
With this being the case, a catch can that intercepts the contaminants and oil particles before they reach your intake ports and valves is critical. Since they aren’t cleaned by fuel, you need to preemptively address the root cause of the buildup itself by installing a catch can system that prevents the buildup of carbon deposits before they happen. |
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Now that you understand what a catch can does and why it is important, especially for direct injection engine applications, we can tell you a bit more about what makes the Turner Motorsport catch can design your best choice to keep your BMW happy and healthy under daily driving or track conditions.
The Turner Motorsport Catch Can design features a four-chamber baffle system that is engineered to offer the maximum air and oil separation possible. This means the air recirculating through the intake from the PCV system will be as clean as it can be to dramatically reduce oil vapor and carbon buildup on your ports and valves. Additionally, it has multiple changes in the direction of airflow to prevent droplets of oil vapor in suspension from making their way through the catch can and into the intake for the best air and oil separation you can achieve. Naturally, all this buildup has to go somewhere. The catch can itself harbors all those particles of vapor and eventually fills up. While it is an added step in your routine oil service, it is much easier to maintain than the process of walnut shell blasting that would otherwise be a requirement in regular intervals. Our catch can includes a dipstick to check the fill level of the can and uses a universal drain system to easily empty the can when it reaches capacity. You just have to remember to drain it periodically. | 
| The last fact answers the final question you probably have: why doesn’t BMW install catch cans from the factory if they know direct injection allows for carbon buildup that could be prevented with a catch can? Put simply, the best answer we could find is that it is an added step in routine service and more expensive to engineer and manufacture en-masse than a simple PCV system that is required by emissions regulations to clean up that pressure released from the crankcase before it is ultimately expelled through the exhaust. As near as we could tell, the biggest reason is that BMW doesn’t want their customer to have to add a step in maintenance that could potentially turn them away from purchasing the car. Regardless, with the Turner Motorsport Catch Can system for your BMW, you can effectively remedy that oversight and prevent unwanted carbon buildup, thus saving yourself the future headache of incredibly regular walnut shell blasting.
Now, we want to stress that adding a catch can does not completely eliminate the need for regular maintenance. While it will clean the air before it enters through the intake ports, there is always going to be some buildup. The catch can drastically reduces that buildup and exponentially increases the interval between walnut blasting, but at some point, you may find that you do need to perform that essential maintenance. You can, of course, find everything you need to walnut blast your intake side here at Turner Motorsport, but you definitely won’t need to use it remotely close to the regularity you would need without a catch can. | 
| | So, in summary, if you have a BMW, you should probably have a catch can. If you have a direct injection engine in your BMW, you absolutely need one. With a cleaner intake air, your valves stay cleaner for longer, your ports stay open and clean for longer, and you won’t need to regularly blast everything to eliminate the buildup from oil vapor that is never cleaned by fuel. With the Turner Catch Can, you can expect the absolute best in operation and design, and with our effective walnut shell blasting equipment, you can take care of the otherwise costly maintenance associated with direct injection engines for a fraction of the cost right at home. Don’t forget: you won’t have to do it nearly as often if you go ahead and make the forward-thinking decision to install a catch can. Now go out there and protect your BMW before you start to wonder where all your power went! | | | | | | | | | | | | | | | | | | | | |
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