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Thread: provent/catch cans?

  1. #1
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    provent/catch cans?

    I was just reading a thread on these and decided to get some whys and wherefores.

    why do you need one?

    I was chatting to my indy about it because he gets asked to fit them for some of his clients.

    He does not recommend that I fit one.....my oil is always so clean.....my exhaust runs clean.....negligible oil loss between servicings.

    btw my indy has Ferrari and Rolls Royce certification .....he's no dummy.

    just interested in what some members may say as to their reason for fitting one.

  2. #2
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    Depends on if you have a diesel or petrol, turbo or not.

    The most common reason for mounting one is if you have a turbo diesel with Exhaust Gas Recirculation (EGR). ie. any modern-ish turbo diesel. The egr does exactly what the label says, it recirculates exhaust gasses back into the engine through the intake. Some people delete the EGR though the legality of that is of course questionable and even the use since it seems engines with egr need it to run at their best. In any case, I digress. The exhaust gasses are recirculated very close from the source so it has not passed any emissions devices yet and thus contains the most amount of soot. In a clean car this should not be a problem but over time soot will start to stick here and there. Now add to that the Positieve Crankcase Ventilation (or PCV) and things will start to get messy. The PCV is basically the over pressure valve of your engine. As you load the engine, exhaust gasses slip past the liners and create a higher pressure in the crankcase, This pressure buildup needs to go somewhere else your engine will start leaking past the seals. Normally the pressure will escape to the top of the engine where there is a (small) tube from the valve cover that is connected to the air intake. This is done because the oil is hot and there is vapour hanging around. By sucking this back into the engine we make sure it gets burned nice and clean in stead of just drip or drift around in the environment.

    What happens is that the oil vapour, or at least some of it, cools down in the metal air intake and turns back into a liquid and starts sticking to the intake, we've all seen it I guess? Add to that sooty air from the exhaust and it will clog up your air intake in "no time" since the oil/soot mixture will form a physical barrier.

    The same story goes for non turbo diesel although some argue the effects are less. I am not sure about that but I guess the turbo creates even more pressure in the cylinders and with that potentially more blow by.

    As for petrol engines, theoretically they do not need them since the exhaust gasses are so much cleaner it won't cause that kind of buildup (in practice they do but a lot less). The exception could be those modern direct injected engines. Since fuel is injected into the cylinder rather than the intake fuel no longer passes the intake valves and the egr starts blocking them up. A real menace these days...

    All in all, I mounted a provent (200) on my petrol rover V8 and although it works keeping my inlet clean, the problem that arises with a petrol like that and that bloody crap bio ethanol (which I no longer use) is that the fuel does contain quite a bit of water, even proper fuel does. What happened in my case is that water vapour got caught in the catch can and eventually the filter got clogged by a mix of oil and water. I guess it had run it's course with some 30K on it, it just never got black like a diesel engine would The end result was that oil started leaking past my seals, and since it is a land rover...

    In short, any diesel engine I would definitely recommend but it is not a cheap solution. The filters cost quite a bit and need regular replacing. A petrol engine can have benefits, but less so then a diesel and the costs vs benefit might not work out for you.

    Cheers!
    -P

  3. #3
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    I have a ford ranger 2.2 turbo , same as Defender.

    The egr has been blanked since new.

    I asked the local ford dealer workshop foreman about the blank before I fitted it , he wasn't concerned.

    I just ask it's purpose as it sends exhaust gas to be reburnt which was always obvious on gear changes....follow a Nissan ...it's really noticeable.

    Now that the egr is blanked what has happened to the exhaust gases that were being rerouted to the inlet manifold.

    When I started my engine without the blank there was always a cloud of soot. Where or why has the cloud gone now?

  4. #4
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    On the earlier Rangers/BT50 the EGR reduces combustion temperatures, ergo EGT. The PCV lubes the valve stems.
    If you don't like trucks, stop buying stuff.
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  5. #5
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    The oil in my 2.4 tdi Triton goes dark pretty quickly. I have had a Provent catch can on since new. Modern TD's benefit from the can. I empty mine every few months and it always drops out watery oil. This helps a lot with any modern diesel with EGR but I don't want the butterflies in the intake manifold to carbon up. Likewise I prefer it not going into the variable geometry turbo. I have a 7 year 150,000k warranty but want to see 300k before my first carbon clean up.

    Cheers

  6. #6
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    Good point about the valve stem lubrication, I did not know that. Would this argue against using an oil catch can?

    -P

  7. #7
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    The modern TDI runs a very light weight oil too. That would get up nicely in the head. I am trusting Mitsu to have made nice hard valves. I have seen a bad build up of carbon on valves and it isn't pretty. EEverything is a trade off I guess but like cooling system filters manufacturers leave off catch cans on cars because most of the market doesnt want to lift the bonnet or turn a tap under the front guard.

    Cheers

  8. #8
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    From what i have read and seen,i recon the EGR blank is the most important, illegal,but the chance of being caught is very remote.

    A bit of oil blow by,as all Diesels have had for years won't be an issue,its the exhaust fumes that cause the gunk.

    On another note,on the Jap forums,many of the guys that have very high mileage engines,have stock engines,nothing done to them.

    Sure they often need an inlet manifold clean at 150 to 200 000K's,depending on the vehicle,but thats it.
    paul

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  9. #9
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    Yep the 2.4 Mitsu motor for example seems very reliable and people are now readily getting to 300k klm untouched or at worst a carbon clean of the intake manifold which is cheap.

    Cheers

  10. #10
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    Quote Originally Posted by scarry View Post
    From what i have read and seen,i recon the EGR blank is the most important, illegal,but the chance of being caught is very remote.

    A bit of oil blow by,as all Diesels have had for years won't be an issue,its the exhaust fumes that cause the gunk.

    On another note,on the Jap forums,many of the guys that have very high mileage engines,have stock engines,nothing done to them.

    Sure they often need an inlet manifold clean at 150 to 200 000K's,depending on the vehicle,but thats it.
    Must be earlier pre egr engines then if they are stock and not needing egr delete or regular inlet manifold clean .. Son's zd30 engine failed at 130ks due to intake runners being blocked due to the egr system. Very common issue so I believe. And don't mention the dpf issues😞

    We fit catch cans to all our vehicles..rather that than expensive engine damage.

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