View Full Version : Catch Can

Monday 23rd May 2005, 17:22
Hi All,
Does anyone use a catch can for the crankcase gasses?
Anyone have any comments on there use?

Monday 23rd May 2005, 17:31
It is beneficial to allow crankcase gasses (oil) to enter the engine as it provides lubrication.


Monday 23rd May 2005, 20:59
??? via the intake ??? , oil in the intake mix increases the likelyhood of detonation, you want clean air in there, not air and oil.

Theres plenty of oil in the engine anyway lol.

I use one on my car mate, but cant comment on their use on volvos.


Tuesday 24th May 2005, 17:40
Its been a common practice on 4 stroke engines for many years to draw crankcase vapours into the inlet to provide upper cylinder lubrication, honest!


Tuesday 24th May 2005, 18:55
True, most cars have the breather set up that way, however, when tuning and upping the power, you stick a catch can in as the chance of oil breathing becoming excessive increases due to too much crank case pressure. The level of boost pressure at which you should do it is widely disagreed upon lol.


Tuesday 24th May 2005, 21:04
On my 850 T5 the breather pipe connects to the inlet pipe just before it connects to the turbo inlet. There is a vacume operated valve there which partly closes the breather pipe during boost conditions to stop excessive amounts of oil being consumed as the crankcase pressure will be high.
I've heard from people who have disconnected the breather systems on cars that excessive amounts of condensation develop in the crankcase which when mixed with the oil produces a white sludge.
The combination of blow by gasses getting past the piston rings and sucking from the inlet creates a circulation of air through the crankcase to prevent condensation/sludge.


Tuesday 24th May 2005, 21:54
You can create a sucking effect without having it connected to the inlet if such problems arise. These catch tanks wouldn't be present on many many big power tuned cars if they didnt work. They remove contaminants, oil vapour, from the inlet, so that it is just air, and fuel.

If the sucking force is necessary you can use the exhaust to draw the gases out.


Tuesday 24th May 2005, 22:43
i run a different breather,that removes the vac feed to the inlet pipe,and means i don't feed hot oil through the compressor side of my turbo lol.The thing you describe as a valve in the inlet tract actually heats the crank case gases to stop the oil condensing,it gets surprisingly hot,my intake does'nt have one ;)

Tuesday 24th May 2005, 22:53
Catch tanks where originaly supposed to be used in competition cars, to stop oil being dropped on the track if the engine goes tits up during the race. Oil could be past into the inlet manifold through the breather and onto the track, hence the catch tank to 'Catch' any oil coming through the breather pipe.

I've not heard of any gains to be had from fitting them, only passing scrutineering before a race.

Wednesday 25th May 2005, 19:07
I had one on my rs turbo cos the throttle housing was getting a lot of oil coming through that affected the idle speed when it clogged up the hole, worked a treat on that. Don't know of any other reason to have one, unless they look shiny! :biggrin:

Wednesday 25th May 2005, 21:10
basically stops oil going into the intake again if the car breathes any, due to crank case pressure arising from increased boost.