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Thread: Blow by Valve into Exhaust pipe?

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    Question Blow by Valve into Exhaust pipe?

    Details: 4d56 diesel 2.5 pajero engine
    Reason: Too much blow by causing Air Filter chocking & Turbo leaking

    Can PCV / Blow by valve be fitted into exhaust so that it can burn the blow thru exhaust pipe outside rather than throwing it back into the engine causing turbo leakage & air filter blockage?

    Vehicle History: Pajero 1 & 2 (4d55 Non-Turbo - 4d56 Turbo & 4M40 I-C Turbo) / Land Cruiser BJ60(13B-T Turbo) / Nissan Patrol GQ(Td422 Non-Turbo)

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    Theoretically, Yes. Technically, No.
    Almost every turbo diesel sucks in oil from the sump or the blowby pushes the oil into the intake. Pajero's are famous for doing that.
    The turbo most of the time sucks a huge amount of air from the intake at a negative pressure. Crankcase is usually positive pressure, once it start to suck enough air to change the pressure in the crankcase to negative oil is sucked into the intake. Thats why there is a PCV valve equipped. Its job is to keep the pressure from switching to negative. Bad PCV valve is also a solid reason for oil to be in the intake.

    Other case is that you have enough blowby that is vaporizing oil and carrying it into the intake. Which is pretty common with 2nd Grade oils especially in Pakistan. Due to the amount of insane temperatures turbo diesels run, regular oil breaks down quickly and is vaporized. Use a thicker oil recommended for turbo diesels and high temperatures.

    If you just want a simple fix to the problem. Buy a catch can and install it to the blowby hose.
    Its job is simple, has a bit foamy stuff in it and when oil laced gas is pushed or sucked into it the foamy filter catches the oil and sinks it to the bottom and the gas is pushed or sucked out of it nice, clean and hot.

    If you try to hook up the blowby to the exhaust, you will have to get two things. A one way valve which can operate in temperatures in excess of 800 Celsius and be able to handle an insane amount of pressure difference. Exhaust temperature and pressure is insanely high high compared to the crank case venting gas. Finding a valve like that is impossible. The job is to push gas at 80 C at a pressure of 2psi into a gas at 800 C with a pressure of 20 psi (only an example) without letting the hot gas into the cooler gas. You will most likely end up pumping the exhaust (hot) gas into the sump at a violent rate. The concept defeats the Law of Thermodynamics and the Ideal Gas Law.

    Second you would need a oil separator, because once blowby is directed to the exhaust oil will stick the metals walls and in no time you will have your whole exhaust choked up with motor oil. Back pressure in the exhaust will get very high due to choking and their goes another jerooo head.

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    Default

    Oil catch cans be DIY as well. Many tutorials out there...
    Here is the basic principle:

    Blow by Valve into Exhaust pipe? -1486347

    DIY - Cheapo Oil catch Can - Team-BHP

    The other option is to disconnect the pipe and install a breather on the crank case like the one below:

    Blow by Valve into Exhaust pipe? -1486348
    Death is not the greatest loss in life. The greatest loss is what dies inside us while we live.

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