Dex Fulton gives us the low down on catch cans, including why you need one, what it does, who needs one and what to look for. Keep reading to learn more…
Let’s have a quick refresher on engine basics, shall we? A piston moves up and down in the cylinder – sucking a fuel-air mixture in through the intake valves on its initial down-stroke; it pressurises the mixture to a flammable point on its second up-stroke; combustion occurs near the top of its travel, the rapid expansion of gasses sending the piston back down for its third power stroke; then pushing the left-over gasses out through the now open exhaust valves on its fourth and final trip upwards. Then the process repeats a few thousand times per minute.
Petrol and diesel engines both essentially function on this same four-stroke principle. The piston is sealed in its cylinder by the piston rings, which hold it in place against the cylinder walls and create an effectively airtight gap so that the fuel mixture and exhaust gasses cannot escape during the combustion cycle (except via the valves).
Unfortunately, piston rings wear over time, and larger gaps between the cylinder wall and piston are allowed to form, which in turn allows gasses to escape from the combustion chamber into the crankcase – a process known as blow-by. It’s nothing to worry about at normal levels. Almost every engine does it, but it can lead to issues down the line.
Bear with me, I’m nearly done explaining…
Blow-by tends to pressurise the crankcase, pressure which needs to be released before it gets to the point where it starts blowing out gaskets and sending oil all through your engine bay. This is the job of the positive crankcase ventilation (PCV) valve, which vents these gasses from the top of your engine. Back in the old days, the PCV would vent to the atmosphere – usually in the form of a hose running down into the chassis rail. However, with ever more stringent environmental concerns playing a larger role in modern engine design, an eco-friendlier solution had to be found.
Now, concurrent to this, the never-ending benchmark for minimising emissions was also being aimed squarely at engine designers, who came up with the execrable invention of the exhaust gas recirculation (EGR) valve, which, as the name suggests, reroutes a portion of the spent exhaust gasses out of the exhaust system and back into the intake manifold to be mixed with the fresh air and fuel and be re-burned in the combustion chamber.
The problem is though, the PCV hose that used to run into the chassis has now (again, for ‘environmental’ reasons) also been plumbed back into the intake, and the fine oil mist is allowed to mix with the exhaust gasses from the EGR. The result? A thick, black, oily sludge of carbon deposits that will eventually clog your intake and cause havoc with your engine internals. That’s bad, mmmkay.
What’s a catch can do anyway?
Luckily, companies like Ryco have come to the rescue with the invention of aftermarket catch cans. While not a new thing (they’ve been around on agricultural machinery forever), they’re a viable answer for modern diesel and petrol engines that have been saddled with EGR systems (which are illegal to remove or disable, because environment).
They essentially take the blow-by gasses expelled by the PCV and ‘catch’ the oily residue in a ‘can’ which can be drained, before allowing the now-filtered and non-oily gasses to pass back into the intake, preventing the carbon build-up that happens when the oil mixes with the EGR gasses from occurring.
They’re an elegant solution to a messy problem with any newer vehicle, especially those with a few kays on them or that live a life of heavy loads (like, y’know, a tow-rig).
Who needs one?
Really, the only engines that don’t NEED a catch can are petrol engines with throttle body injection that mix the fuel and air in the intake before it makes its way to the cylinder. The fuel acts as a solvent and washes any built-up carbon into the combustion chamber. Even so, these engines still have PCV valves, so fitting one up definitely won’t hurt the environment.
But basically, any engine that has a fuel injector that squirts fuel directly into the combustion chamber (pretty much every diesel and almost all petrols built after the mid-90s) will benefit from having a catch can fitted.
Diesels are prime candidates as their exhaust is a lot sootier than a petrol engine, so carbon build-up can occur much quicker. Older, mechanically injected, pre-common-rail diesels did vent their PCVs into the air, but again, if you’re an environmentally conscious sort or just don’t like oil covering your chassis rail, then a catch can will help.
How to fit one to your engine
A catch can will have three main ports: an inlet, an outlet, and a drain. The inlet, usually around midway up the side of the can, should be connected to the PCV outlet via a hose. The outlet, usually the uppermost port, should be connected via a hose back to the intake. The drain should be opened and emptied regularly as part of your servicing routine.
Installation and upkeep will all depend on the engine you have, the kilometres it has on the clock, the amount of blow-by it has, the brand of catch can you’re fitting and several other variables. The Ryco RCC360 catch can, for example, can be fitted to almost any vehicle, but may require a little customisation to make it all work properly and be fitted out of the way.
If you’re not 100% confident with what you’re doing, it may be worth letting the pros handle it. But if you’re mechanically proficient and have a lazy Sunday spare, it’s a fairly straightforward and worthwhile mod to any vehicle.
What to look for in a catch can
You may have noticed us referencing the Ryco RCC360 catch can a couple times already in this article. That’s because it’s one of the better ones on the market, is reasonably priced and comes highly recommended by diesel specialists.
Ryco’s design features include a handy service indicator on the top of the can that takes the guesswork out of when the internal filter, available anywhere that sells Ryco Products, needs to be replaced; a 1-micron filter; a 12mm drain hose for easier emptying; a quick connect lower fitting; no relief valve – so it won’t leak when full; and a healthy 290mL sump for longer intervals between drains.
It’s also worth pointing out that Ryco have been making catch cans for a long time now, and they know what works and what doesn’t. They’ve done the R&D to ensure their products will work with both positively and negatively pressurised crankcase ventilation systems and how to avoid the pitfalls of catch can ownership (hence the service indicator).
More information
Ryco have a long-established name for top quality filters and associated products and have developed their latest RCC360 catch can after extensive R&D testing in Aussie conditions and feedback from their customers. They know a catch can is not a set-and-forget addition to your vehicle, so have made it as user-friendly as possible.
The RCC360 is available from wherever Ryco products are sold all over the country.
For more info, jump on over to www.rycofilters.com.au/rcc360-catch-can
