Oil Catch Cans – What You Should Know – How They Work

All-CC-ColorsPreviously, I mentioned the situation I am currently facing with my car that is making me look into oil catch cans. (You can read here https://torquepost.wordpress.com/2013/05/05/oil-catch-cans-what-you-should-know-the-backstory/). That got me to do some searching, and researching, and researching on my researching so I could do better searching, and I searched.

The reason it took so much looking is because I found out that not all oil catch cans are created equal. As a matter of fact, unfortunately, the oil catch can is one of those products where you run the risk of buying cheap junk that is just a copy of another brands copy of a legitimate brand. Even worse, the oil catch can is supposed to have other parts inside of it, and you run the risk of simply being charged for an empty can without the bits inside that are required for the can to actually do its job of catching oil. Sometimes, this isn’t bad if you just want a can to modify and you intend on opening it up. But if you need to buy one ready, read on.

0502ht_08z+1995_Honda_Prelude+Oil_Catch_CanCatch_Can-3588First off, lets explain how catch cans work. The purpose of a catch can is to take what is being sent out through the positive crankcase ventilation (PCV) valve, and separate the actual oil that may come out, collect it, and send just air and vapors back to the intake manifold, as opposed to the PCV system sending both air, vapors, and oil back in the intake manifold. The goal is to avoid getting oil into the intake manifold. Oil is meant to lubricate, and unless you drive a diesel, you should not be burning it in any way.

For turbocharged cars, the purpose of an oil catch can is incredibly important. The can should work to prevent blow by of oil, which could lead to dangerous situations of coating couplers, causing them to slide off under boost, coating the fins inside an intercooler which drastically decreases its efficiency, and ultimately end up cooking inside your turbo, contributing to a nasty condition of what is called “oil coking” where the oil turns to a charcoal like substance in the turbo over time. In addition, you don’t want any blow by on your pistons either.

catch-can1-bTo do this, a catch can works by having one line of high quality hose that can withstand heat and enormous pressure created by the engine, running from the PCV valve into one inlet on the catch can. From there, it goes into a tube of some sort, and past a filter. The oil should collect at the bottom. Catch cans come in different sizes to hold more or less oil. The filter is to prevent any oil from then escaping back out of the catch can through the other outlet and hose that will run back to the intake manifold. Different companies will make their own filter medium and inlet designs, and some serious performance applications may have baffles inside to absolutely prevent any oil in the can from sloshing around and returning through the outlet.

Now how do you choose one and avoid getting ripped off? Read on in part three of this series.


21 thoughts on “Oil Catch Cans – What You Should Know – How They Work

  1. Hi …
    There is a problem if the oil can came full after one run in 1/4 mile ??
    The car : mk4 supra
    Engine : 2jzgte … fully built
    Boost : 42 – 45 psi
    Note : the A/F ratio is good … The tuneing is good also

    1. It depends on the size of the catch can. Sounds like you may be running one of the smaller less expensive cans. You are also running a lot of boost and running in race conditions you are creating a ton of blow-by vapor. You should look into a high capacity catch can like the RX Monster Can or The UPR Mega can. Personally I only run the RX products, they have the best baffling system on the market and the support is second to none. Here are links to both:
      RX Speed Works: http://www.rxspeedworks.com/product/catch-can-kits/
      UPR Products: http://www.uprproducts.com/ford-f150-billet-oil-catch-can-mega-css-ecoboost-11.html

  2. what happens to the oil that the catch can catches ? Does it return to the oil pan ? Would i just dump it out but if i do that, isn’t that wasting oil ?

  3. Hi, i got a hi performance 351 that runs a oil catcher can, in 15 minutes the can is full and oil is all over the motor i put new rocker covers on that they are baffle still made no different…anybody got any suggestions

    1. u got a problem ..could be a cracked piston that charges the sump and creates excessive blowby..if not then I would increase the catch can size and run a return line back into the sump with a one way valve ..that should work

  4. Have had fitted to my 2003 GU Patrol 3 Ltr turbo an aluminium oil catch can ($85).Have had recent repairs for turbo exhaust leak and following this repair the catch can now emits substantial oil/smoke through the filter on top. Is this normal as my mates 2014 Patrol has the same can with little to no vapor emitted via filter?.Any advice appreciated. NOT mechanically gifted!!!

    1. Hi there! Your exhaust leak should not normally affect to such a substantial degree on pressure in the crank case that it would be related to oil and vapour leaking out of your catch can. Try draining, emptying and cleaning the can first. Then replace the filter on top of the catch can (unless it is the type that can. E washed and reused). Thanks!

  5. My question is, Why, all of a sudden, is there such a thing as a “catch can”? I mean, I wasn’t
    the best hotrodder shade tree mechanic in the world, but I did the ‘soup up’ cars seene back
    in the day and I have never heard of a catch can until last year when I bought my new Challenger.
    Just curious,

    1. They’ve been around in the drag racing world forever to deal with the blow-by byproduct and oil ingestion. The goal is always to just burn clean fuel for maximum performance while avoiding the mess of relieving crank case pressure on the track.

      The reason they are so popular and relevant now is because of the advent of Direct Injection. The fuel no longer washes the valves and the blow-by byproduct is re-ingested. This results in excessive valve coking and loss of performance and fuel economy.

      Manufacturers won’t put them on new vehicles because of the extra maintenance that they know people won’t follow through with. Besides the increased visits to the dealership make them money.

      In 2008 the EPA made it mandatory that all auto manufacturers go to GDI by 2015.

      I’m in the catch can business now for about 3 years. I know PCV systems and their relationship to OCC’s, if anyone ever needs install advice or has general questions, reach out anytime.

      Tommy Thomsen
      RX Speed Works

      1. Hey tommy,

        I’m wondering why you would hook up the outlet of the catch van to the inlet side of the turbo and not just to the intake manifold of the engine. Or why you, if you’re scrubbing high boost numbers, wouldn’t just leave out the ventililation to the intake and just send it into the big wide world 🤔

        Cheers Wouter

  6. I have a 2008 rodeo with a 3 litre turbo diesel that I’ve just had rebuilt and was wondering if an oil catch can would be a good idea

  7. Fitting catch can to a BMW e46 320i UK will I have trouble getting it though the m o t on the emissions as a modded pcv catch can although done right it run cleaner

  8. I have a oil van catcher installed on my Mazda Bravo 2000BT 2500 diesel turbo and noticed it needs cleaning. I have drained the bit of oil out of it and there looks to be gunky inside the can. How and what do I clean the inside of the can?b

  9. Can I simply say what a comfort to discover somebody who genuinely understands what they’re talking about over the internet. You actually know how to bring an issue to light and make it important. More and more people need to check this out and understand this side of the story. I was surprised that you aren’t more popular given that you definitely possess the gift.

  10. While the general gist of what is said here is true there are a number of incorrect statements and references made. The OP does not really know what they are talking about

    1. Ryan. You are a dipshit. If you know everything why don’t you post a correction rather than vague hints condemning unspecified statements and references in the post as untrue?

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