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I would leave it in..... it’s a DCV ie a Depression Control Valve, it’s there to regulate the crankcase pressure. It’s normal state is open - unless the engine is breathing really hard, whereby it progressively closes as engine speed increases, thereby limiting depression in the crankcase. Its operation is the reverse of Positive Crankcase Ventilation. Nothing is gained by it’s removal.Quote:
Originally Posted by twr7cx
Any disadvantage to its removal? [bigwhistle] Just curious!Quote:
Originally Posted by onebob
Any disadvantage to its removal? .... yes, but how much depends on how hard the engine works. The CDV actually controls pressure/vacuum in crankcase to prevent oil consumption through the intake system via the turbo air inlet. For example when the Td5 takes a sudden deep breath, like what happens when the auto trans kicks down and the revs slam up to 3000+ plus in a nano second, the CDV valve will in that circumstance be pulled and held closed until the revs diminish.Quote:
Originally Posted by Bohica
I bolted mine to the Aux battery shelf’s heat shield...Quote:
Originally Posted by Kaaaiju
https://uploads.tapatalk-cdn.com/201...43ed93220d.jpghttps://uploads.tapatalk-cdn.com/201...89ee62da11.jpg
I’ve had my PROVENT installed 1 week now and I’ve changed my thinking - yes the CDV in a factory configuration is there to prevent the engine consuming (sucking) oil under high inlet vacuum / high engine speed situations, however a PROVENT will perform that function also when installed. I imagine also that a PROVENT would be most efficient operating with a constant air flow, especially under high speed engine conditions / high inlet vacuum situations when blow-by gasses would be at their greatest, however a CDV under these conditions would be pulled closed, and shut off crank case breathing altogether for the duration....Quote:
Originally Posted by onebob
I have replaced my CDV with a brass elbow.
Welcome to the club! You’ve reached the same conclusion a group of us had in discussions sometime ago.Quote:
Originally Posted by onebob
Thank-you [emoji4] .... at first it occurred to me that with the CDR and now a PROVENT inserted into the breather circuit it would slow down the air velocity and volume and perhaps work to pressurise the crankcase instead of maintaining the normal de-pressurised situation. Although the normal state of the CDV is ‘open’ a peek inside of it revealed it’s design created some restriction and that a 3/4” or 19mm elbow would allow more more air / gas to pass. All things considered i thought it best to have ‘full time’ crankcase ventillation. CheersQuote:
Originally Posted by twr7cx
I must admit I haven't looked closely but my impression is that the diaphragm in a Provent and others is a pressure relief valve that opens when the filter is blocked.
Regards PhilipA
The valve in discussion (CDV ie crankcase depression valve) is the disc shaped valve at the end of the factory breather pipe that connects onto the rubber bellows pre turbo.Quote:
Originally Posted by PhilipA
I am aware of that and how the CDV works. I have also pulled one apart. It works by inlet depression pulling it shut and is usually open.Quote:
The valve in discussion (CDV ie crankcase depression valve) is the disc shaped valve at the end of the factory breather pipe that connects onto the rubber bellows pre turbo
The point I was tentatively making is that Many think that the valve in a Provent can replace the valve.
First I have never seen specs on the manifold depression required to shut the valve or even if the valve is a CDV.
After having a look at my fake one a week ago, I wondered if it was actually a relief/bypass valve for when the filter became blocked. In other words the opposite of a CDV. Can anyone confirm the function of the valve? I cannot recall it's function in the specs as listed on the Mann Hummel site.
In the meantime I have left my CDV alone.
Regards PhilipA