2007-2011 THP PCV delete

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To reduce the rate of carbon build-up on the inlet valves it is possible to make modifications to the PCV system.

On my 2011 Peugeot 308 CC I made 2 modifications to the PCV system.

  1. Delete the PCV route direct to the the inlet manifold
  2. Add a vapour separator and catch tank to the PCV route to the turbo intake

Deletion of PCV to inlet manifold

As this engine originally has two independent PCV systems, it is possible t delete one of them without losing the essential PCV function. As the engine manufacturer decided that the direct PCV to the manifold could be dispensed with from mid 2011, it seems obvious that this is the first thing to do.

Elimination of this PCV path should be a very simple path, as there is just one pipe to remove, which has clip fittings at either end. The end of the pipe that attaches to the manifold is unfortunately rather difficult to access. On the 308 it is necessary to remove the air filter housing, which in turn requires other items to be removed, and even then it is very difficult to see or grip the clip fitting on the end of the pipe.

Once the pipe has been removed, it is a simple matter to block the holes at each end with clip-on plugs which are available under a PSA part number.

Fitting a vapour separator and catch tank

With the PCV path to the manifold blocked off, all crankcase fumes will be directed through the remaining PCV system to the inlet of the turbocharger. This may be perfectly acceptable, but I had a suspicion that there might be excessive oil vapour present in this flow, so I decided to fit a vapour separator and catch tank.

The vapour separator that I used is a Mann ProVent 100. This is a compact vapour separator which has a coalescing element to strip the vapour from the gas stream. I would not recommend using a separator or catch can which does not have a coalescing element.

To plumb in the vapour separator, I cut the PCV hose near to the connection to the engine top cover. I extended the two cut ends of this hose to route the PCV gases through the vapour separator. Note that the hose and fittings must be compatible with hot oil fumes. I used 19mm fuel oil hose, but power steering reservoir hose would probably be cheaper and more elegant (as it has thinner walls).