Just wondering what the very skilled mechanics amongst us think about this, I’ve watched this oil catch can video a few times now but no one who seems to know FL2s inside out is commenting n his video, it’s seems miraculous from the video he’s done 3000 miles and the catch can is full of dirty oil and he exclaims that would of been fired back down the air intake and burnt in the engine, is this a real life problem and something we should all be fitting it’s just I’ve never seen anyone mention it on here, what’s the general consensus thanks

Hi.
I did similar system with a water filter holder container glass with narrow cooling sleeves and filled with steel filaments. Let the air pass but the oil remains in the glass. There is no danger of the filament coming out.
It worked perfectly for me. It collects a lot of oil from the crankcase ventilation that would have ended up in the intake, fouling the intake system. I think it is beneficial that no oil reaches the intake.

He is not wrong – it’s a mod I do on race engines and have it on my Mini – may be a bit more crude but same idea – the engine needs to breath to get rid of back pressure which is not clean air so it will reduce the oxygen going in and therefore the performance. Suppose it’s a bit of work for what some would see as little gain, and in these modern engines with all the emissions controls as he pointed out an MOT fail. Modifying your car for an mot fail is probably the reason why it is not widespread.

Edit – not to mention the damage it does to sensors downstream depending on the set up MAF etc

The oil vapours in the intake system from the breather are beneficial, as it lubricates the lower stem of the intake valve.

I personally can't see the point in a catch can, unless the engine is suffering excessive blow-by, which would be obvious as the air space in block will be pressurised.

It's not something I'd fit to my FL2, as I don't believe it's a benefit, and just something else to remember to maintain. Not to mention that it'll use more oil, as an amount will accumulate in the catch can, which will need replacing with fresh oil.

As I understand it the idea of feeding the breather into the inlet manifold is to reduce pressure inside the crankcase therefore reducing any engine oil leaks. By just venting the breather to atmosphere via a catch tank, you are effectively creating a slight positive pressure in the crankcase therefore increasing oil leaks. Also there should be an oil separator behind the engine underneath the hose he’s replaced that takes out the oil that he is catching and returns it to the engine.
Presumably that is not working properly on his car and therefore oil is getting past it and being caught in his catch tank.

If his catch tank has removed all the oil why not send it back into the inlet duct so it will pass a mot and create a negative crank case pressure. Or just fix his built in separator?

The thing to watch is how much oil your car uses. Mine goes between services without being topped up.

I think now looking in to it a bit more I’m edging more in the side of nodge and Stv123, I was lead to believe the oil separator does that job so minimum or no oil gets slung up the air intake, In his previous video he shows us the below pipes section of air intake and it is indeed covered in a lot of oil, so much so it’s seeping from the joints, I’ve had mine off and it’s clean, plus I couldn’t get my head around losing that much oil each time, you’d be topping back up with at least a litre every 2-3 months, my 80k Td4 just doesn’t seem to lose oil over the year between services or at least very minimal

sharmanator43 said:

I think now looking in to it a bit more I’m edging more in the side of nodge and Stv123, I was lead to believe the oil separator does that job so minimum or no oil gets slung up the air intake, In his previous video he shows us the below pipes section of air intake and it is indeed covered in a lot of oil, so much so it’s seeping from the joints, I’ve had mine off and it’s clean, plus I couldn’t get my head around losing that much oil each time, you’d be topping back up with at least a litre every 2-3 months, my 80k Td4 just doesn’t seem to lose oil over the year between services or at least very minimal

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I meant Bellows pipe lol

Stv123 said:

As I understand it the idea of feeding the breather into the inlet manifold is to reduce pressure inside the crankcase therefore reducing any engine oil leaks.

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That's mainly true for petrol engine vehicles, where the crankcase vent is under constant manifold vacuum. This gives the crankcase a Negative Crankcase Pressure, or NCP vent system.

A diesel being wide open throttle, has no or minimum manifold vacuum, so has a mild positive pressure in the crankcase, hence the name Positive Crankcase Ventation or PCV.

Stv123 said:

By just venting the breather to atmosphere via a catch tank, you are effectively creating a slight positive pressure in the crankcase therefore increasing oil leaks.

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True, but a diesel is designed to run with a slight positive pressure, so it shouldn't increase the leaks, to any great degree.

Stv123 said:

Presumably that is not working properly on his car and therefore oil is getting past it and being caught in his catch tank.

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The FL2 TD4 doesn't have a true separator, just a couple of plates over the vent pipes, which forces the vapours to take a torturous route, to reduce the oil in the system.

The PCV pipes are also designed to feed oil back to the sump, while bleeding the gases to the intake trunking to be burnt in the normal way.