Pressure build up?

[AlanS]

My sons TZi has used oil from the day he got it at which stage it had 90K klms on it.
The usual suspects have been eliminated by doing the usual tests for rings and valve stem seals and the engine performs so well and the car is so reliable overall, that I really don't want to start ripping it apart unnecessarily particularly if at the end of the day, I still have the problem; a likely scenario, so I am again throwing ideas around.
Does anyone know if the piston rings on these TZi engines are the same as used on any other models? If so, that to a point eliminates one theory.
My recent thoughts have been (based on a problem a Pug owner had out here) do these engines have some kind of PCV in their breathing systems?
The guy with the Pug reckons he gets a higher crankcase pressure at the upper part of the engine than at the lower, and put this down to a blocked valve not allowing the pressures to equalise.
This to me sounds a logical explanation for this engine as we can't get smoke at cold, hot, power on, power off or at idle or high revs, so obviously it all happens at a certain ime when it's being driven and based on this theory, when the pressure builds to a certain thing it is then forced into the engine taking oil vapour with it.
If there's a valve of some description that could be jammed, faulty of clogged up, then this might be an explanation, but I'm unaware of such a thing, however I did find a honeycomb filter on the breather of the Trs that caused some strange issues, so I wondered if anyone can shed some light on where I might find such a thing?


Alan S

[AndersDK]

alanS -

What's the engine code of that TZI ? (I could find the exact schematic on PR.net)
You should not have any pressure difference from top to bottom, as the oil sprayed out on the camlobes and tappets simply seep down by its own weight - down the oil gallery to the sump.

The gauze filter seen at the block to head oilway is only present in the oil feed to the top - not causing any pressure difference.

The external honeycomb filter in tthe breather on the TRS is an oil trap meant to condensate the oil and make it flow back to the sump.

[AlanS]

This one does just not answer to reason which is why I'm looking for a weird cause that might match the equally weird symptoms.
Any suggestions regardless of how strange they might be are accepted.
Here are a couple of responses I've had elsewhere. An opinion on these would also be good.

Exactly how much oil does it use?

I assume that the TZi engine is the same as a 205/405 XU9J2 / XU9JA(Z) 8 valve motor, which the book specifies will use (from new) 500ml per 1000kms. The 16 valve does not suffer this problem.

This means that between 5000km services, the engine will use 2.5 litres of oil, and that's normal!! Sounds to me like a good excuse to check your oil more often.

and this I hadn't heard of before although this car was made in 1992 so that rules that one out I would imagine.

Didn't the XU9J2 engines of approx. '88-89 get recalled due to an oil ring control problem?

Alan S