Peugeot/Citroen 1.6 THP – Mini N14 – PCV delete modification (Prince engine)

PCV delete – why do it?

One of the most discussed and debated modifications on THP/N14 engines is deleting the rear PCV system. THP200 has this by default, but all smaller THP variants use the PCV system in the plastic cylinder head cover.

How the PCV system works

All engines with pistons always have a small quantity of exhaust gas that goes through the piston rings and reaches the crankshaft case. We call that blow-by gas. When the engine is being driven at low load, with no pressure, the vacuum in the intake manifold forces blow-by gas and oil fumes into it. This way they are burnt and not released into the atmosphere. Going through the intake manifold means that they stick onto the intake valves. And that is a major problem for all direct injection engines, as it leads to carbon build-up on the valves themselves, reducing the engine’s performance. You can see in the article linked just how badly the engine performs when the valves become clogged with carbon.

  • Advantages: The bonus of this modification is that exhaust gas blowby and oil fumes are eliminated from the intake system. They will never reach the intake manifold again. 
  • Disadvantages: Some engines do not like it very much and as a result, oil consumption increases. A lot of people claim that the modification increases crankcase pressure which is the reason why that happens. On built engines no increase in oil consumption is usually noticed. Stock engines – mixed results.

Parts you will need

  • Peugeot – Citroen: 0361.S4 (cap)

 

Following the photos below you can see exactly how this mod is done. The PCV pipe that connects the intake manifold to the plastic cylinder head cover is removed. Two special caps are installed in its place, on either side.

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3 Comments

  • Henk Westra Posted October 26, 2018 3:40 pm

    Hi
    Images link on the page do not work.
    Thanks

  • Mike Posted December 19, 2018 3:46 am

    It should be mentioned that in (approximately) April 2011 the engine top cover and PCV system was updated on all THP engines, and the later part does not have the PCV hose direct to the manifold, so the delete is not necessary. The later top cover also had (supposedly) better oil vapour separation so less oil vapour goes out the PCV into the turbo, and different PCV valves so that the crankcase does not pressurise. The new top covers are however not cheap to retrofit.

    On my EP6CDT (with the early engine top cover) I deleted the rear PCV hose, and routed the the top PVC through a coalescing vapour separator (https://oe-products.mann-hummel.com/fileadmin/user_upload/kataloge/kataloge-wartungsanleitungen-mann%2Bhummel/kurbelgehauseentlueftung/MANN_HUMMEL_Crankcase_Ventilation_EN.pdf), I also (accidentally) destroyed the PCV valve in the engine cover, so there is no more crankcase pressurisation.

    After 15,000km with this configuration, the engine is not using any significant amount of oil, and if you wipe your finger in the turbo inlet, there is no oil film at all, so much less oil is getting to the inlet valves. there is a small amount being caught in the vapour separator catch tank,

    • aHMAD Posted February 20, 2019 10:14 am

      HELLO MIke,
      Thank you FOR YOUR INFORMATION. DO YOU HAVE ANY FILE ABOUT HOW THIS ENGINE WORKS? THE MECHANISM AND PERFORMANCE OF THE ENGINE? I APPRECIATE IF YOU HELP.
      tHNAKS

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