Why do we need oil catch cans?
Piston rings do not seal 100%. As a result, pressurized gasses from the combustion process leak into the crankcase. This is known as "blow-by" and is a byproduct of the modern internal combustion engine. Pressurizing the crankcase can lead to damaged crank seals, oil leaks, poor engine performance, etc. These crankcase gasses are vented through the PCV system which recycles the gasses back into the intake air stream to be burned. When the recycled PCV air (loaded with oil and water vapor) combine with the fuel mixture, it will lower the effective octane rating of the mixture, resulting in reduced performance. Simply put, dirty air results in less horsepower.

As shown below, the vented/recycled PCV gasses contain oil vapor, water vapor and unburnt fuel.

Over time, this nasty mix can create an oily sludge buildup on the inside of the intake manifold and on the intake valves. These contaminants can clog sensors, restrict air flow, cause poor idle and create other issues. The photo below shows an intake manifold with a large amount of "sludge" buildup.

This issue is further intensified with turbocharging and supercharging, where these PCV contaminants can collect inside intercoolers and reduce their efficiency. 
To prevent the sludge from reaching the intake system, a catch can is used as an in-line filter.  When dirty crankcase gasses pass through the catch can, oil and other condensed material collects in the bottom. This oil would otherwise be sent through the engine's combustion process.
Our friends at Donut Media made a good video explaining PCV function and catch cans:

What makes one catch can better than another?

If PCV gasses are routed to a non-sealed reservoir in the engine bay (like a soda can), an unsightly film of oil will form in the area around the can. There is also nothing preventing the back flow of oil, water, sludge, or dirty air back into the engine. Furthermore, an open container of oil in the engine bay is a potential fire hazard.

A good catch can will collect contaminants in a sealed cavity, will use hoses and fittings designed for hydrocarbon compatibility, will be easily serviceable, and will contain a means for promoting the condensation of oil and water vapor. Easy installation and servicing are other factors to consider. Since 2010 Radium Engineering has been designing and producing oil catch cans that meet all of these requirements, and offer innovative features. During this time, Radium has been busy continuously improving the catch design.

Radium Engineering Catch Cans are CNC machined from solid aluminum bar, then they are anodized, and laser engraved.

Radium Engineering's Family of Catch Cans
Radium Engineering has spent significant time in 2022 revamping the Standard Catch Can and releasing a new Competition Catch Can. 
These changes have expanded Radium Engineering's family of catch cans to the five models shown below.

The 8 fluid ounce Standard Catch Can has been completely redesigned internally for 2022 and now features Raduim's patented Fluid Lock® mechanism.
The "vent to engine" competition catch cans are the same as they has always been. The "vent to atmosphere" competition catch cans are a new design from the inside out and are the newest members to the family.
Each will be discussed in more detail below.

All Radium Engineering catch cans feature material in some form another to assist the air/oil separation. This material (also called media) is stainless steel and it can be easily removed for cleaning or replacement. It provides ample surface area for the oil, water and other fluids to condense and drop out of suspension.

All Radium Engineering Catch Cans Feature:
-CNC Machined aluminum construction
-10AN ORB main ports
-4AN ORB bottom drain port
-Integrated air/oil separator
-Stainless steel cleanable and reuseable filter media
-Unscrewing body for easy draining
-O-ring sealed two or three-piece design 
-Anodized & laser engraved finish
-Included mounting bracket
-O-ring sealed dipstick

Benefits of an oil catch can:
-Lowers hydrocarbon emissions
-Excessive oil collection can be an early indicator of a damaged engine
-Prevents oil buildup in the intake or intercooler system walls, throttle body, and intake manifold
-Increased engine performance through cleaner inlet air and a cleaner air/fuel mixture

Standard FLUID LOCK® Catch Can

In 2022, Radium Engineering implemented a revolutionary design change to the 8 fl-oz Standard Catch Can. An inherent problem always existed with typical catch cans when not serviced regularly. The fluid contaminants will eventually leave the reservoir pouring into the air intake system causing poor engine performance.
To resolve this issue, Radium created the Fluid Lock® Catch Can. This contains a patented mechanism that prevents the reservoir from overfilling and traps the collected fluids until it is emptied.

Once the reservoir of the catch can is full of the contaminants, an internal mechanism prevents any additional fluid from entering the container. The air passage is not blocked at any time, so the engine can still breathe as normal. These components keep the trapped fluids from leaving the catch can. This prevents the catch can from overfilling and impedes fluid from emptying into the induction system. The Fluid Lock® catch can still needs to be emptied when it is full, but there are no detrimental effects if it is not.
The 8oz Standard Fluid Lock® Catch Can is the one found in all Radium vehicle-specific kits but is also available to purchase for universal installations.

Vent To Engine Competition Catch Cans
Originall called just "competition catch can short and tall", these oversized VTE catch cans were specifically designed for competition vehicles that experience a high amount of blow-by. The large capacities hold an ample amount of fluid that may be expelled through the PCV system when a race vehicle is operating at the limits.
These catch cans feature a single 10AN ORB inlet port and a single 10AN ORB outlet port and is designed to be re-routed back to the engine induction system, creating a closed loop system. The extra large (or tall) version has a 1qt (0.9L) capacity which meets the requirements of many racing sanctioning bodies. Check with your sanctioning body for catch tank requirements.
For more details on these catch cans, refer to the product page CLICK HERE.

Vent to Atmosphere Competition Catch Cans
New for 2022, these vent-to-atmosphere (VTA) catch cans were redesigned from the ground up based on real-world competition feedback. They are specifically designed to vent to atmosphere with minimal restriction. They feature two 10AN ORB inlet ports and vent to the atmosphere out of the top of the catch can through a series of baffles and oil separation media. These are a great choice for vehicles that need the least restrictive catch can solution, but still want effective air/oil separation. Because these vent to atmosphere, they are legal for off-highway racing vehicles only.
Like the VTE catch cans above, these are available in two capacities. Check with your racing sanctioning organization for catch tank requirements.
For more information on the VTA Competition Catch Cans CLICK HERE.


What about the Radium Air/Oil Separator (AOS)?

An air/oil separator works much like a catch can. The main difference being that the AOS-R "returns" oil back to the engine. In order to allow the oil to drain back, the bottom port on the AOS-R must be connected to a compatible port on the crankcase or oil pan, in a way that gravity will allow the oil to flow into the engine. 
A key component of the Radium Engineering AOS-R is the heated bottom plate. Engine coolant is plumbed to the AOS-R bottom plate in order to keep the AOS-R heated. This is critical in keeping water vapor from collecting, as the goal is to only collect and return oil to the crankcase. An AOS-R system eliminates the PCV valve and associated connection to the intake manifold.
The main benefit of the AOS-R system is the low maintenance. Because any oil collected is returned to the engine, it does not have to be emptied on a regular basis. To learn more about the Radium Air/Oil Separator, CLICK HERE


Shown below is a common crank ventilation system. The vacuum from the intake manifold draws air through the system pulling the crankcase gasses out and burning them in the combustion process. The PCV line is shown in blue and the crank vent line is shown in orange.


A key component of the system shown above is the PCV valve. It opens and closes depending on the amount of vacuum (or pressure, if boosted) from the intake manifold. If the hose going to the PCV valve is not connected to the intake manifold, the PCV will not function properly. The PCV valve allows air to be drawn through the engine's crankcase, using the vacuum of the intake manifold to do so. The air enters through the crankcase vent side and then is sucked into the intake manifold. This helps draw out moisture from the crankcase.

Radium Engineering catch cans can be installed on either the PCV line, the crankcase vent line, or both.

Shown below are catch cans installed on both the PCV line and crankcase vent line (dual catch can kit). This is considered a "closed" system because all hoses route as they did in the OEM system (above). Nothing is venting to the atmosphere. This system replicates the function of the OEM system with the added benefit of oil separation accumulation in the catch cans. A closed system is great because no matter the intake manifold pressure, the PCV system is always promoting negative pressure in the crankcase via vacuum created by the intake manifold or the intake pipe. Furthermore, this setup remains emissions legal.
The Radium catch cans do not have a specific inlet or outlet port. Either the top or side port can be used for the inlet or outlet.


For high performance vehicles that experience excessive blow-by, the primary goal is to let the crankcase "breathe" as much as possible when under high load/RPM. Generally, these applications include loosely built race engines that spend a lot of time at full throttle/full boost.

Shown below is an open system using a catch can on each line. For this system to work properly, some customization must be done. First, the port on the intake pipe that was connecting to the crankcase vent line must be capped. The same goes for the port on the intake manifold for the PCV line.  Furthermore, the PCV valve MUST be removed and replaced with a large diameter straight-through fitting. This may require some modification or creation of a special fitting depending on the vehicle. NOTE: Eliminating the PCV valve and the corresponding connection to the intake manifold will remove the ability of the PCV system draw out moisture from the crankcase.
This system essentially creates two large, high-flowing ventilation points through which the crankcase can breathe. Radium Engineering offers optional breather filters that install on the outlet port of the catch can. They can be found HERE. Note: VTA catch cans will have an oil vapor scent. This undesireable smell can make their way into the fresh air intake of the HVAC system and be noticeable inside the cabin.


Do I need to install a check valve to keep boost out of the catch can?

No. Radium Engineering catch cans are designed to withstand boost pressure and thus can be plumbed directly to the intake manifold without the need for a check valve.

Should I drain the oil that accumulates in the catch cans back into the engine?

The Radium Engineering catch cans are equipped with a female 4AN ORB threaded port on the bottom which could be used to allow draining of contents back into the engine. However, keep in mind, that the catch cans do not ONLY collect oil, they also collect condensed water and unburnt fuel. When these mix together in high temperatures, they form a nasty, foul-smelling "sludge" that you do not want back in the engine. The Radium Engineering catch cans can be easily drained using a few different methods.

Here is a sample of what you can typically expect to find in a catch can:

However, if a proper heated Air Oil Separator is used, the oil can be returned back to the engine.

 If I only want to use one catch can, which line (PCV or Crankcase Vent) should I install it on?

This question is asked quite often and the answer can be different for every application. The best way to solve this is to do a simple inspection of the engine. Look inside the intake pipe in the region of the crankcase vent line barb and throttle body (region A in the diagram below). If oil accumulation is found, it is most likely coming from the crankcase vent line and a catch can should be installed on that line.
While slightly more difficult to do, it is worthwhile to inspect the inside walls of the intake manifold (region B) in the area of the PCV inlet port. Once again, if heavy oil coating is present, it could be coming from the PCV line and a catch can should be installed. Note: Since this region is downstream of the crankcase vent line, oil could also be coming from the crankcase vent and collecting in the bottom of the manifold. Keep this in mind when inspecting.

Radium always recommends both catch cans are used for maximum effectiveness. You may find one catch can collects at a faster rate than the other and will be emptied more often.

Radium Engineering offers universal catch cans as well as application-specific kits for certain vehicles that offer an easy bolt-in installation.  Note that all application-specific kits use the Radium 8 fl-oz Standard Fluid Lock® catch can. Fittings and hoses are also available for custom installations.