Here is a section of a thread on the subject seems most of the problems stem from a badly conceived PCV system. The last paragraph/post says it all!
This thread is dealing with "knocking problems". Does this mean the standard "engine knocking" (abnormal combustion)? Or also the "Super knocking" (it is called like that in the error memory by Peugeot, I think that means "pre-ignition"), this is especially a problem of direct injection engines? While the standard knocking is already bad for the engine, the super knocking/pre-ignition is even worse...since the it appears whilst the compression, when the piston is going up. The standard knocking appears after ignition, and hence closer to the time when the piston goes down, such that the pressure can be released earlier.
While standard knocking can for sure be caused by timing problems, is this also the case for super knocking?
As far as I know, in case of the THP engine there are two main reasons that can cause super knocking: carbon deposits (especially at the back side of the intake valve) caused by the crankcase ventilation system. Since it is a direct injection engine, the back side of the intake valve doesn't get cleaned by fuel. Another possibility can be a insufficient injection. The injection is done whilst the compression phase (the THP engine works only in homogeneous, never in stratified-charge operation). Hence, in order to get a homogeneous distribution of fuel, one needs a high pressure and good working injectors. If the high pressure fuel pump doesn't produce a high enough fuel pressure in the common rail, or if a injector is not working correctly, the fuel-air-mixture isn't homogenous. I think, that the cooling property of the fuel will not work then?! What exactly happens I don't know. But this not optimal injection/air fuel mixture can suffer from a pre-ignition. A defect high pressure fuel pump was the reason for super knocking at my car last year.
Can anyone confirm all these ideas? Do I make something wrong? Can there be other reasons for super knocking?
Furthermore, in this context: In case of the 200 THP engine, Peugeot removed the PCV (crankcase ventilation) that goes directly to the intake manifold. See http://www.etuners.gr/en/index.php?s=12&t=299. This can also be applied to the 150/156 THP engines by simply removing this hose as explained in the link. But, in http://www.northamericanmotoring.com/forums/drivetrain-cooper-s/200835-occ-needed-on-2011-mcs-8.html there is a discussion about the N18 mini cooper S engine, that is compatible with the 200 THP Peugeot engine. In Posting 175 AZblackOUT wrote:
"The valve cover has 3 individual runners going down the backside and into 4 port holes for each intake port. The gasket secures these areas separate as we saw in the diagram. The Valve cover is not only equipped with a check valve to stop flow up, but it also is equipped with a vacuum restrictor to prevent overflow down."
Some of the writer say that the outer hose going from the valve cover to the intake manifold is removed. But there is now a internal connection between valve cover PCV and the region of the intake valves. This would mean, that the 200 THP engine still has both PCV connections. Is this true? If it is true, one should really think if it is a good idea to remove one hose in case of the 150/156 THP engines?! Nevertheless, if the PCV only goes over the turbo (when the hose to the intake manifold is removed) and the charge air cooler: in that case, the dirt/crankcase gas/oil mixture will only go through the charge air cooler, and it would work like a oil catch can, but it cannot be emptied. If think in future there will be problems due to this?! Furthermore, the turbo is very hot. Maybe carbon buildup can develop inside the turbo?!
Many ideas, many questions...but all conncected to knocking, especially super knocking... and possible explanation and solution attempts.
Joined: Wed Sep 28, 2011 10:35 am
Re: Peugeot 207 1.6 Turbo - Knocking problems
by Pepsimax » Wed Sep 28, 2011 3:22 pm
Detonation on the THP engines is caused by the oil ingestion in the rear PCV lowering the effective octane rating of the fuel by approx 40 ron points.
I had this on a new DS3 THP156 which got so bad it destroyed a piston land, and the new engine started detonating almost instantly, so no carbon build up there. Deleted the rear PCV and all detonation stopped, oil consumption greatly impreoved also.