So What is an oil catch can?
It is a container or sorts that collects oil from blowback gas vapours an engine produces. I don't think it is very effective and you'll see later.
An Oil/Air separator is better as it is design to extract the oil and soot as well act as a catch can.
With just some easy modifications to the catch can you will hopefully eliminate oil and soot from you intake.
Do I need one?
Dunno... you might, but it depends on how you car is doing Crank Case Venting (CCV) and recirculating the vapours for vehicle emissions.
These vapours are caused in ANY car by the combustion process. Some combustion exhaust gas escapes past the piston rings (blowback gases) and into the internal cavity of the engine where it gets mixed up with your oil.
This caused 2 issues...
1) These blowback gases contaminate your oil with noxious fumes and un-burnt fuel and soot... turning oil black.
2) The reverse also happens... the blowback gases contain oil and soot particles and then are released back into you engines intake via the CCV to be re-cycled as part of the combustion process and then pass out the exhaust through the catalytic convertor. Yes TDi's have special catalytic convertor!
It is problem 2) that creates havoc with my TDi car (and maybe normal petrol turbo engines as well)
Here is my scenario...
I have a Mk3 TDi 66kw engine.
Here is the engine:
![]()
The CCV is the disc looking thing ontop of the engine at the right with a hose going to the left and a hose going down the front of the engine.
The hose coming from the CCV to the left across the top of the engine goes straight into the Air Intake.
Hot CCV gases enter the intake's cold air, after the Airfilter and MAF but before the Turbo inlet.
When the Hot CCV Gasses meet the Cold Air condensation occurs and the oil and soot start coating the turbo inlet, the turbo inlet chamber, then all the piping to to the inter-cooler... the inter-cooler then condenses the rest of the Oil and soot from the vapours. The inter-cooler is a very efficient oil air Separator... BUT I don't want it to ba a Catch Can.
So over time Oil collects in your air-air inter-cooler and make it less efficient at what it is supposed to do... and this makes it an oil catch can of sorts and it is a PITA to clean.
What also happens is that the oil and soot that is coating the intake pipe before the turbo also dry out, and a hard sooty coating builds up and starts to block your intake reducing you air flow!
TDi's need air and lots of it to be efficient. So blockages to the turbo intake and oil in the inter-cooler makes for a less efficient engine, and robs you of power and money as you tend to use more fuel to go faster...
this is the catch 22...
as the engine is now less efficient at burning the fuel due to less air and not as good inter-cooler operation, the extra fuel used to go faster makes the problems worse as it is not effectively burnt and this produces more unburnt fuel and soot!!!.
So it makes sense to add one... it will save you problems later. Why car manufacturers don't add one someone will tell me!
Here is the catch can:
![]()
Fittings for Inlet and outlet, fluid level sight gauge, and on the bottom a screw plug for draining fluids.
Connecting ip up is pretty simple... You just disconnect the CCV hose to the air intake and add the kit.
The problem is with me and my anal approach to making things work better!
There are issues with nearly ALL Catch cans... the name says it loud and clear... it's a catch can!!!
They are empty containers. Vapours go in and vapours go out, nothing is inside to help stop the vapour problem. (It is best suited for oil spray catchment for those drifters and high G racers. It just catches the oil that comes out of the engine through the CCV.)
Some catch cans contain a baffle or wall to make the vapours take a longer path inside the container... this is better but still not that good.
The Quick and dirty modification to fix this is to just add Stainless Steel wool scouring pads (SS wool).
Yep a simple fix.
Stuff the container full of SS wool. This creates more surface area for the oil and soot to stick to as the vapours enter the container and then tries to leave. Much more effective - and now is an oil air separator!
Now if you look at the design of your catch can you start to wonder how effective is it really!
Well my catch can inlet and outlet pipes are only 2 inch apart... so how effective is it going to be anyway!
There are no baffles inside... so I made one! Baffles are good. If you don't want to spend $$$ on a can with baffles make the baffles!
So what I did was cut my can in 2, and braze a copper angle and pipe around one of the holes... this is now my inlet hole!!!
The design is to force the air to the bottom of the can where it will pass more SS Wool and be extracted.
How I welded Aluminium and Copper:
I bought some of those Aluminium welding rods from the Home Show years ago.
Back then I could not get the rods to work correctly with my primus torch back then... the job was melting before the rods!
![]()
So I searched on the net a found a site that had some videos of using a similar rod to weld and repair aluminium.
I came to the conclusion that I did not have a direct enough heat source.... so I went out and bought a portable MAPP torch.
I did a little net surfing on welding dissimilar metals as that is what I'm doing.
I could not find any site of FAQ or Forum that has a method for welding 2 different metals like Copper and Aluminium.
Most of the sites said you just don't do it as there is no need for it in plumbing or tank fabrication. The join would fail under stress from movement or pressure.
Brazing the parts together with plumbers brass rods will not work.
Lead Soldering was an option as the pipe was not under stress or under pressure.
Tig Welding... I don't think so!
Because these Aluminium welding rods can weld non ferrous metals... so I thought copper and Aluminium should be ok.
Here is proof!
![]()
Bit untidy... but it worked and it is so strong. the copper pipe was flexing when I tested to see how strong the weld was!
Some closeups...
![]()
![]()
![]()
The Center hole is for the fluid level sight gauge.
The copper pipe comes to about 2cm from the bottom of the can.
I was not going to attempt to Weld the can back together... so I sent it off to get TIG welded...
Because the can is Chromed Aluminium, the chroming process 1st involves plating the can in copper then chroming ontop of the copper.
You cannot TIG weld with copper or chrome layers around the weld so they had to grind back the layers to aluminium.
![]()
You would think that the guy who welded it together could have lined up the alignment marks better!!!
![]()
So now i wanted to reduce the weld so that it was flush with the can surface.
I especially cut the can here as this is where the mounting ring is positioned.
The Weld:
![]()
![]()
Filing down the weld... weld is easy... chrome is a biatch to get off!
![]()
Hit it with the orbital sander and plain 120 grit paper!
You can see the copper and chrome layers... I thought this was a cool effect and even though of leaving it.
![]()
Taking too long with orbital sander... back to filing the whole can surface back to aluminium. Filing was much faster:
![]()
Final process... hit it again with orbital sander and 120Grit:
![]()
Hit it with orbital sander and Wet and Dry 400 grit then up to 1200 grit:
![]()
![]()
Thought of polishing it up... can't be bothered.
The top and bottom are still chromed... that's enough blink in the engine bay!
I then filled it up with SS Wool.
It is ready now for mounting... when I pull my finger out and redo my alarm mounting point!
I am pretty happy with the outcome.
Edited: Fixed broken Pics
Modified by Gigitt at 12:44 AM 8-14-2008
It is a container or sorts that collects oil from blowback gas vapours an engine produces. I don't think it is very effective and you'll see later.
An Oil/Air separator is better as it is design to extract the oil and soot as well act as a catch can.
With just some easy modifications to the catch can you will hopefully eliminate oil and soot from you intake.
Do I need one?
Dunno... you might, but it depends on how you car is doing Crank Case Venting (CCV) and recirculating the vapours for vehicle emissions.
These vapours are caused in ANY car by the combustion process. Some combustion exhaust gas escapes past the piston rings (blowback gases) and into the internal cavity of the engine where it gets mixed up with your oil.
This caused 2 issues...
1) These blowback gases contaminate your oil with noxious fumes and un-burnt fuel and soot... turning oil black.
2) The reverse also happens... the blowback gases contain oil and soot particles and then are released back into you engines intake via the CCV to be re-cycled as part of the combustion process and then pass out the exhaust through the catalytic convertor. Yes TDi's have special catalytic convertor!
It is problem 2) that creates havoc with my TDi car (and maybe normal petrol turbo engines as well)
Here is my scenario...
I have a Mk3 TDi 66kw engine.
Here is the engine:
The CCV is the disc looking thing ontop of the engine at the right with a hose going to the left and a hose going down the front of the engine.
The hose coming from the CCV to the left across the top of the engine goes straight into the Air Intake.
Hot CCV gases enter the intake's cold air, after the Airfilter and MAF but before the Turbo inlet.
When the Hot CCV Gasses meet the Cold Air condensation occurs and the oil and soot start coating the turbo inlet, the turbo inlet chamber, then all the piping to to the inter-cooler... the inter-cooler then condenses the rest of the Oil and soot from the vapours. The inter-cooler is a very efficient oil air Separator... BUT I don't want it to ba a Catch Can.
So over time Oil collects in your air-air inter-cooler and make it less efficient at what it is supposed to do... and this makes it an oil catch can of sorts and it is a PITA to clean.
What also happens is that the oil and soot that is coating the intake pipe before the turbo also dry out, and a hard sooty coating builds up and starts to block your intake reducing you air flow!
TDi's need air and lots of it to be efficient. So blockages to the turbo intake and oil in the inter-cooler makes for a less efficient engine, and robs you of power and money as you tend to use more fuel to go faster...
this is the catch 22...
as the engine is now less efficient at burning the fuel due to less air and not as good inter-cooler operation, the extra fuel used to go faster makes the problems worse as it is not effectively burnt and this produces more unburnt fuel and soot!!!.
So it makes sense to add one... it will save you problems later. Why car manufacturers don't add one someone will tell me!
Here is the catch can:
Fittings for Inlet and outlet, fluid level sight gauge, and on the bottom a screw plug for draining fluids.
Connecting ip up is pretty simple... You just disconnect the CCV hose to the air intake and add the kit.
The problem is with me and my anal approach to making things work better!
There are issues with nearly ALL Catch cans... the name says it loud and clear... it's a catch can!!!
They are empty containers. Vapours go in and vapours go out, nothing is inside to help stop the vapour problem. (It is best suited for oil spray catchment for those drifters and high G racers. It just catches the oil that comes out of the engine through the CCV.)
Some catch cans contain a baffle or wall to make the vapours take a longer path inside the container... this is better but still not that good.
The Quick and dirty modification to fix this is to just add Stainless Steel wool scouring pads (SS wool).
Yep a simple fix.
Stuff the container full of SS wool. This creates more surface area for the oil and soot to stick to as the vapours enter the container and then tries to leave. Much more effective - and now is an oil air separator!
Now if you look at the design of your catch can you start to wonder how effective is it really!
Well my catch can inlet and outlet pipes are only 2 inch apart... so how effective is it going to be anyway!
There are no baffles inside... so I made one! Baffles are good. If you don't want to spend $$$ on a can with baffles make the baffles!
So what I did was cut my can in 2, and braze a copper angle and pipe around one of the holes... this is now my inlet hole!!!
The design is to force the air to the bottom of the can where it will pass more SS Wool and be extracted.
How I welded Aluminium and Copper:
I bought some of those Aluminium welding rods from the Home Show years ago.
Back then I could not get the rods to work correctly with my primus torch back then... the job was melting before the rods!
So I searched on the net a found a site that had some videos of using a similar rod to weld and repair aluminium.
I came to the conclusion that I did not have a direct enough heat source.... so I went out and bought a portable MAPP torch.
I did a little net surfing on welding dissimilar metals as that is what I'm doing.
I could not find any site of FAQ or Forum that has a method for welding 2 different metals like Copper and Aluminium.
Most of the sites said you just don't do it as there is no need for it in plumbing or tank fabrication. The join would fail under stress from movement or pressure.
Brazing the parts together with plumbers brass rods will not work.
Lead Soldering was an option as the pipe was not under stress or under pressure.
Tig Welding... I don't think so!
Because these Aluminium welding rods can weld non ferrous metals... so I thought copper and Aluminium should be ok.
Here is proof!
Bit untidy... but it worked and it is so strong. the copper pipe was flexing when I tested to see how strong the weld was!
Some closeups...
The Center hole is for the fluid level sight gauge.
The copper pipe comes to about 2cm from the bottom of the can.
I was not going to attempt to Weld the can back together... so I sent it off to get TIG welded...
Because the can is Chromed Aluminium, the chroming process 1st involves plating the can in copper then chroming ontop of the copper.
You cannot TIG weld with copper or chrome layers around the weld so they had to grind back the layers to aluminium.
You would think that the guy who welded it together could have lined up the alignment marks better!!!
So now i wanted to reduce the weld so that it was flush with the can surface.
I especially cut the can here as this is where the mounting ring is positioned.
The Weld:
Filing down the weld... weld is easy... chrome is a biatch to get off!
Hit it with the orbital sander and plain 120 grit paper!
You can see the copper and chrome layers... I thought this was a cool effect and even though of leaving it.
Taking too long with orbital sander... back to filing the whole can surface back to aluminium. Filing was much faster:
Final process... hit it again with orbital sander and 120Grit:
Hit it with orbital sander and Wet and Dry 400 grit then up to 1200 grit:
Thought of polishing it up... can't be bothered.
The top and bottom are still chromed... that's enough blink in the engine bay!
I then filled it up with SS Wool.
It is ready now for mounting... when I pull my finger out and redo my alarm mounting point!
I am pretty happy with the outcome.
Edited: Fixed broken Pics
Modified by Gigitt at 12:44 AM 8-14-2008
