If you own a modern turbo diesel without a catch can, you’ll probably look back in the future and wish you’d fitted one. You can get a variety of different brands and models of catch cans , and they play a hugely important role for your motor.
What does a catch can do?
By nature some oil, fuel and even water escapes from the motor and ends up in the crankcase. In standard form, this film of oil is sucked back through the positive crankcase ventilation line (PCV) and ends up in your air intake, where it goes back into the motor to be burnt in the combustion process.
A catch can sits in between your crankcase and the PCV, and it is designed to separate the fluid and mist from the air that makes its way through and catch it in the bottom of the unit.
Some catch can’s have filters in them, and others use mesh, steel wool or a variety of combinations. If its just a can with an inlet and an outlet, you have bought one that won’t work very well!
Why is it so important?
I can already hear you saying ‘So what; why does that matter?’, and I’ll cover that now. The biggest reason you want a quality catch can on a modern diesel motor is to stop the massive problem it causes when it mixes with your exhaust gas re circulation system.
Turbo diesel motors have had exhaust gas recirculation systems now for some time, where a portion of the exhaust gas is recycled back through the motor. This isn’t a massive issue, except that by nature your exhaust gasses have carbon in them, and when this black soot mixes with an oil mist, it sticks to anything that it can.
Without a catch can, your engine cakes up with sticky black muck and soon becomes badly restricted. You only have to jump on Google Images and look up EGR intake clean to get an idea of how bad this actually is. Left without being cleaned, you will suffer losses in power and fuel economy. There are a variety of ways of cleaning motors, which can be time consuming and expensive. Avoid the build up in the first place and you’ll be in a great position.
The second reason catch cans are very important is because oil reduces the efficiency of your intercooler when it covers the pipe work. The colder the air going into the motor the better it performs, and if your intercooler doesn’t function as it should you are missing out on its potential.
How much oil does it catch?
This question is very generic, but the amount of oil, water and fuel that is caught is actually fairly reasonable. In 10,000km you should easily get 50 – 300 ml of fluid. What ever you don’t catch goes straight into your engine. Not good.
Catch can legalities
Catch can’s are 100% legal, and on some well designed diesels they actually come as standard. Sadly, this isn’t the case for your average 4WD motor.
In the past, people would just run a pipe to the inside of their chassis, and let the oil film run into the chassis, for ‘rust prevention’! This is not legal.
Article from 4wding Australia.
