Playing Catch — Why Your Modern Engine Could Use An Oil Catch Can

When it comes to oil catch cans for engines, there are a lot of opinions out there. I’ve heard people say, “If my car needed an oil catch can, the brilliant engineers who designed the engine would have installed one from the factory.” That could be considered a very reasonable argument.

If people with engineering degrees chose not to install an oil catch can, why do I think that I — a dude with a simple set of Costco sockets and an Amazon-purchased oil catch can kit — can improve on the design of the engine while wrenching in my driveway? Because of the Internet, that’s why!

This baffled oil catch can system from Mishimoto, designed for the 2014-2019 Ford Fiesta ST 1.6-liter EcoBoost engine replaces one single hose on the stock engine.

Yes, the Internet. A place where everybody has an opinion, a YouTube channel, and an Instagram account. Besides cat videos, the Internet does allow people to share good-to-know information and explain the “how” and “why” of things. It was while surfing the web searching for some speedy parts for our FordMuscle project car that I realized (because the Internet said so) we needed an oil catch can for the direct-injected, turbocharged vehicle. There was this thing called “blow-by,” and apparently it was ruining the engine in our Fiesta.

According to John Petty, Product Manager at Mishimoto Automotive, an oil separator can keep the inside of an engine cleaner, ensuring horsepower doesn’t drop off over time.

What is blow-by?

Our internal combustion engines ignite these little explosions that push down our pistons, thus turning the crankshaft and allowing us to move on down the road (thankfully keeping me from having to walk places). However, the process isn’t perfect, and there is always just a little “blow-by,” where the piston rings don’t capture all of the pressure from the explosion. That pressure then finds its way into the crankcase.

The crankcase is just a place to store oil and keep things nice and lubricated as the connecting rods move up and down on the spinning crank. As blow-by gets past the piston rings into the crankcase, it pressurizes that space, which makes it harder for the pistons to move up and down, harming performance.

To solve this problem back in the day, engineers utilized something they called a “road draft tube.” It was simply a tube that allowed this pressure to escape the crankcase. It worked, but it stunk. The inside of the crankcase is an insane mix of oil and air mixed with other contaminants. As this air was released from the engine, it smelled like burnt oil (surprise, surprise, right?).

Besides the olfactory assault, the mixture isn’t exactly what we are looking to just spill out into the world’ it’s called pollution. It’s 2020, we know better. There is this thing called the environment, and even gearheads want to protect it these days.

An oil catch can system is not an overly complex device to add to an engine. A couple of hoses, fittings, and a can. The installation takes less than an hour.

As emission programs came along in the 1970s, engineers resolved this stinky pollution issue. They said, “Hey, I’ve got an idea. Let’s just take this blow-by, and pipe it back into the engine!” Essentially, they took the blow-by, known as pressure in the crankcase, and used Positive Crankcase Ventilation (PCV) valves to recirculate this pollution back into the intake so it can be burned in the combustion chamber. This reduces emissions, and all of the birds and bunnies are happy. But is your engine happy? That is the real, important question.

The red arrows point to the ends of the OEM hose from Ford, which recirculates positive crankcase ventilation back into the intake. A baffled oil catch can system disrupts this line with an oil separator.

The answer is no, the engine isn’t that happy about recirculating this pressure and it’s associated contaminates from the crankcase. And newer modern engines are extremely unhappy about it. When PCV was considered normal and all the rage for emissions, fuel-injection engines essentially mixed fresh air and fuel with the noxious junk coming from the PCV back into the engine.

Over time, people would start to see their throttle body was getting covered in oil and crud. That wasn’t coming from the air filter. It was coming from the PCV line (which enters the intake tract after the air filter). Simply spraying down the throttle body with some brake cleaner usually fixed it, but the real problem was deeper in the engine. Those deposits would land on the inside of the intake manifold and the intake valves (where we can’t see it or spray brake cleaner).

The issue of deposits wasn’t that big of a deal on the intake valves, because the fuel, being mixed from the fuel injectors, helped clean the valves. But now with direct injection engines, that cleaning action isn’t happening anymore. The fuel goes directly into the cylinder when the valve is closed, meaning nothing but air and PCV contaminants are hitting the top of the valve.

The installation of the Mishimoto baffled oil catch can system took less than an hour and only required a few basic tools.

The Direct Injection Issue

Because this ongoing mixture of fuel, air, and PCV junk hitting the intake valve on a fuel-injected engine has changed to just air and PCV junk hitting the intake valve on a direct injection engine, it means the intake valves are beginning to show signs of oil/junk/sludge deposits. These deposits begin to add weight to the valve, making the engine less efficient. The junk on the valve also inhibits the airflow into the cylinder, resulting in lower performance. That, folks, is something we cannot have!

The stock line on this Fiesta ST was replaced with the Mishimoto baffled oil catch can system where positive crankcase ventilation goes through an oil separator prior to the pressure going back into the intake of the engine.

Oil Catch Can Solution

The solution to keeping this PCV junk from getting into the intake of a vehicle, while not going back to the stone ages of just breathing that pollution into the environment, is a baffled oil catch can. This simple device is placed between the ventilation line from the crankcase and the line going back into the intake.

The oil catch can’s job is to separate the oil from the air, trap the oil, and just let air and its associated pressure go back into the engine’s intake. It sounds like a good idea to us, but the obvious next question is this: If this is such a simple remedy, why doesn’t my car come with it?”

The reason is that oil catch cans need to be drained, meaning continuous maintenance from the vehicle owner. I know this may come to a shock to some of you, but cars are designed for the lowest common denominator. To ask someone to remember to drain their oil catch can occasionally is an unreasonable request for the general driving public. So, the manufacturers don’t include an oil catch can.

For direct-injected turbocharged cars driven aggressively with their engines at high engine speeds for long periods, like the FordMuscle project Fiesta ST autocross car, the engines can benefit from an oil catch can to keep oil from being sucked back into the intake. (Photo: Anthony Topalian)

But this opinion is just the opinion of the Internet. It probably shouldn’t be trusted without verification. So, we’re going to chat with some people who know what they are talking about. First, we will ask John Petty, Product Manager at Mishimoto Automotive.

According to Petty, “Every engine is susceptible to blow-by from the piston rings. Blow-by flowing through the PCV or CCV (crankcase ventilation) system can coat the internal portion of your intake or intercooler system, cause excessive oil/carbon buildup on your intake valves, and burn in the combustion chamber. An oil separator will separate those particles, helping your engine stay clean.”

That sounds quite similar to what the Internet is saying. Maybe the Internet isn’t wrong, after all? Talking further with Petty, he stressed that direct-injection engines, even dual-injection ones like the [Gen-3] Ford Coyote, can really benefit from a simple oil catch can. He also talked about turbocharged engines having much larger volumes of intake systems to keep clean, including intercoolers. An oil catch can ensures that no crankcase junk lands in the intercooler.

Second Opinion

In the quest for understanding, we decided to also talk with Steve Bussius from UPR Products as well. UPR, which started as “Unlimited Performance and Racing,” makes high-quality oil catch cans for a number of vehicles. Steve’s official title at UPR is actually “Official Catch Can Man,” which means we were talking with the right dude.

UPR makes easy-to-install, plug-and-play kits that use OEM hose attachments, like this kit for the Ford Coyote engine.

Bussius agreed with the Internet, in that modern engines can really benefit from an oil catch can. “Especially for late-model V8s. like the 5-liter engines in Mustangs and F-150s,” said Bussius. “Those engines are having issues with oil consumption, and it is just oil being pulled through the PCV back into the engine. Ford tried to fix with a more restrictive PCV, but the best solution is an oil catch can.”

UPRs Ford F-150 kits uses dual check valves to ensure the engine doesn’t suck in the ugly stuff, especially at wide-open throttle (WOT).

Bussius said what really separates UPR from other manufacturers is the owner, Joe Manero, with his passion and dedication to make sure the products are the best they can be. UPR uses quality machining, quality brackets, aluminum or nickel-plated steel fittings. The catch cans feature billet-aluminum construction with multi-stage oil separation, not a simple sintered bronze or honeycomb filter which could allow oil to pull right through. Additionally, UPR uses Continental rubber hoses, which will not collapse under vacuum.

UPR manufactures easy-to-install kits for Ford, GM, and Mopar products as well as numerous universal kits.

When asked how often these tanks need to be drained, Bussius recommended emptying the catch can — which would probably be only 2 to 4 ounces, essentially the catch can half full — during each oil change. He did add the caveat that in colder weather, you may find condensation, so it is important to check the catch can more often when it’s chilly outside.

He recommended using soap and water to clean the can and the rubber oil ring. UPR kits are easy to drain and can be done in less than five minutes. He said, if the can is forgotten about and it fills with oil, then it will start to push oil into the engine. That is not what we are looking for. These catch cans need to be drained.

From The Street to the Race Track

The UPR universal kits also come with a breather for use in a race-style application where you don’t have any connection back to the intake tube or manifold. Open breather tanks are more of a race option for high-boost applications. These styles of oil catch systems are not emissions compliant. But if the customer is building a high-horsepower, big-boost beast (something more than 15 pounds), it may be best to go with a single- or even a dual-breather tank.

This baffled oil catch can from Endyn (upper left corner of photo), designed for the Honda B18A1 engine, differs from the Mishimoto or UPR catch can because it has a drain tube that redistributes oil back into the engine near the oil pan. This catch can does not need to be emptied; gravity does that. However, it does vent into the atmosphere, which isn’t optimal for the environment.

Not all oil catch cans need to be physically drained during routine maintenance. Endyn builds a catch can for the Honda B18 engine, which is recommended by engine builder Rich Olivier. Olivier owns TEM Machine Shop and sees the inside of engines all day long; he knows where deposits end up. Rich seconded the advice of Mishimoto and UPR that an oil catch can is a very good idea on direct-injection engines and turbocharged engines, saying, “You definitely need an oil catch can.”

TEM Machine Shop’s Rich Olivier, who builds the race engines for Double Nickel Nine Motorsports, requires oil catch cans be run on all of the team’s Honda Challenge racecars.

So, don’t take it from the Internet or your author — listen to the pros. Your car can benefit from an oil catch can, as long as you can remember to drain it occasionally. If you have a direct-injection or turbocharged engine (or both like many of today’s forced-induction engines) then your engine can undoubtedly benefit from using an oil catch can. At the very least, you are adding peace of mind with zero downside to your engine’s performance.

Article Sources

About the author

Rob Krider

Rob Krider will race absolutely anything. He is a multi-national champion racing driver and is also the author of the novel, Cadet Blues.
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