Oil Catch Tank

[MrBen2k7]

What use is an oil catch tank/upgraded oil catch tank?

I see them being put in in higher performance LCR's and TDi's etc, and cant figure out their use..

Is it just to keep the egnine bay clean? or what does it actually do?

Cheers...

Ben

 

[robepton]

When your engine uses high compression ratios some of the gases force there way pass the piston rings and into the crankcase. So the crankcase has to be able breath. This is usually through a port to the top of the engine. The hot gases usually pick up some oil along the way.

Due to emission regulations manufacturers recirculate the hot gases back into the air intake. Which results in all ya boost pipes getting covered in oil.

If ya use an oil catch tank you can catch the oil before it recirculates keeping ya boost pipes and intercooler clean.

Or you can let the oil catch tank breath to atmosphere.

 

[MrBen2k7]

Good answer.... many thanks...

 

[robepton]

It's difficult to see the benefits but it should reduce detonation and it's a quick easy mod.

 

[MrBen2k7]

oh really? rough costs?

Any install guides around?

 

[robepton]

I think you can get an oil catch tank from fleabay for 20 or 30 quid. You might have to buy some tubing. If ya get a brand name one you can spend between 40 and 90 quid.

I think there's some guides on briskoda.

I'm sure somebody with a leon will give ya some advice.

 

[Muttley]

robepton wrote

It's difficult to see the benefits but it should reduce detonation and it's a quick easy mod.

You're going to have to explain that detonation remark to me, because I can't begin to understand it

My understanding is: All engines have positive crankcase pressure, every engine suffers some blowby past the piston rings, the seal is never perfect. This pressure needs to be ventilated or it will build up and impede the pistons. It used to be acceptable to ventilate directly to the atmosphere via some chickenwire mesh in the oil filler cap on top of the cam cover. California decided this was no good, and forced the rest of the world to design engines to rebreathe their effluent, so now crankcase breathers are connected to the inlet tract.

Crankcase gas is oily - the crankcase is full of hot oil and splashes from the crank and cylinder lubrication systems. The blowby gas is hot and full of partly-burned fuel. All of this gets fed back into the inlet air, which up to then is nice and clean.

This is why almost all inlet systems, intercoolers and turbo inlet side systems are oily.

When this oily gas gets to the EGR valve, it meets exhaust gas: burning-hot, and sooty. The oil gets caramelised and combines with the soot to produce a sticky sludge that builds up on the inlet manifold. Worst on diesels.

Replacing the breather connection to the inlet by an oil catch can removes the oil from the inlet system, a good thing.

 

[Andrewcupra TDI]

would this be why i have like oily sludge by my egr valve then ??

 

[Muttley]

Downstream of the EGR? Yes. If I were you I'd get VAG-com and reduce the EGR to its minimum setting. On your car you will get a warning light if you just disconnect the EGR.

 

[robepton]

When the fuel air mixture ignites ideally it should be almost like a flame. Controlled explosion.

Detonation is when areas inside the fuel air mixture pre ignites because of the heat, pressure and the fuel being more concentrated in that area eg droplets.

So if ya have oil mist adding to the fuel air mixture then your more likely to get detonation because it's not been vapourised as much as the fuel.

Diesel are more prone to detonation. This is why they have to be stronger and they make a lot more noise.

If ya increase the boost this will also lead to more detonation.

If ya use a fuel with a higher octane or cetane value it means the fuel is less prone to pre ignition.

Detonation leads to wear in your engine.


I did some reading on wikipedia before i got one!!!!!!

 

[MrBen2k7]

When the fuel air mixture ignites ideally it should be almost like a flame. Controlled explosion.

Detonation is when areas inside the fuel air mixture pre ignites because of the heat, pressure and the fuel being more concentrated in that area eg droplets.

So if ya have oil mist adding to the fuel air mixture then your more likely to get detonation because it's not been vapourised as much as the fuel.

Diesel are more prone to detonation. This is why they have to be stronger and they make a lot more noise.

If ya increase the boost this will also lead to more detonation.

If ya use a fuel with a higher octane or cetane value it means the fuel is less prone to pre ignition.

Detonation leads to wear in your engine.


I did some reading on wikipedia before i got one!!!!!!

Was yours hard to fit? Is it worth doing? How much did it cost?

 

[Muttley]

There is not sufficient oil in the crankcase vapour to affect the engine's fuel/air ratio. Most of it drops onto the charge pipe walls in any case, where it would be no trouble if it wasn't for the EGR.

In addition to that, your petrol engine will have one or two anti-knock sensors on it which will control any incipient detonation. They are there so that you can use any petrol you can find without damaging the engine, although power will be reduced.

The only place I've seen crankcase vapour mentioned as cause of knock is in advertising copy for oil catch cans and aftermarket PCV valves. I'd regard that as biased

 

[carew]

What about this on ebay

http://cgi.ebay.co.uk/Polished-Oil-...14&_trkparms=72:1683|66:2|65:12|39:1|240:1318