1.6 THP Engine

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Revision as of 08:57, 17 December 2016 by Xantia v6 (talk | contribs) (Crankcase ventilation systems)
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The 1.6 THP engine is found in several PSA models, and also some BMW models. It was developed as a joint project by BMW and PSA.

It is also known as the "Prince" engine.


There have been several variants of the THP engine

Technical features

The THP engine is a petrol engine.

Direct fuel injection

Variable valve timing


Crankcase ventilation systems

From 2007 until mid-2011

The turbocharged versions of the engine manufactured before mid 2011 had two more or less independent PCV systems:

  1. A path for crankcase fumes to flow from the crankcase through a pressure regulating valve directly into the inlet manifold near the runner for cylinder 4. This path contains a check valve which prevents the crankcase from being pressurised when the turbocharger causes the manifold to be at a higher pressure than the crankcase.
  2. A path from the crankcase to the turbocharger inlet. This path contains a check valve to prevent air from the turbocharger inlet being drawn into the crankcase and (potentially) out through the other PCV system.
From mid-2011

The crankcase ventilation system was modified to eliminated the first of the ventilation paths of the earlier design. The engine top cover and the other PCV valve were redesigned at the same time.

Known issues

Timing chain and sprockets wear

Inlet valve carbon fouling

There have been many reported instances of reduced engine performance and sometimes engine failure due to a build-up of carbon behind the inlet valves. The source of the carbon is usually attributed to oil vapour from the PCV (positive crankcase ventilation) system, although some sources blame leakage of the valve seals or even turbocharger bearing seals. These sources of oil contamination of the valves are present in many petrol engines, but with more conventional indirect injection or carburettor fuel delivery, the inlet valve is washed by petrol on every cylcle, so any oil vapour is moved into the combustion chamber before it can form a deposit on the back of the valve.

Engines with the earlier of the crankcase ventialtion systems seem to be much more susceptible to inlet valve fouling, leading to speculation that the redesign of the PCV system was an attempt to resolve the issue.