problem with a steyr

[orizaba]

the steyr is a 166 turbo.normally run at around 1400 rpm,the turbo kicks in at around 1800 +. all electronic controls ecu etc
occasionally the revs rise too 1600 rpm for a few seconds then drops to 1400 then up then down etc. by holding revs at 2000rpm for a short while the engine goes back to running normally.the engine is new ,less than 600hrs ,the fuel system/tanks are all clean, fuel is double filtered into a day tank then filtered again.
the ecu was replaced after 6 months by steyr as they could not find the fault but put it down to the ecu.
the engine sits at less than 10 degrees on its bed but not by much.the sump breather is at the rear of the engine,and goes by a short pipe into a filter then another short pipe into the air inlet casing in front of the turbo,the turbo is situated at the rear of the engine.
the owner said he had an oil leak on his turbo ,however the oil is coming from the breather and it would appear that with the engine running ,in certain sea states, the oil covers the breather and the sump pressure pushs a small amount of oil up which over a time pools in front of the turbo,
my assumption over the revs rise is that when the boat rolls heels to starboard the oil ,flows past the turbo is sucked in so alters the air mix and the revs rise,by running the engine at 2000+rpm the turbo kicks in sucks all the oil out and clears it until the next time it builds up.
does it sound feasible that this oil air mix would cause the revs rise and if so do you think that if the pipe was taken from the turbo inlet and put in a suitable receptical to catch the oil that would be ok or is there a danger of the sump overpressurising due to not having the suction from the air inlet.
i guess some of the mobos must have this problem or have had

 

[Bilgediver]

If the oil is going into the turbo in large enough quantities then yes it might effect the revs instantaneously but the governor should then restore the revs to the correct setting...Not sure how ecu works but believe the revs are electronically controlled so suspect there is a problem here.

 

[orizaba]

the governor does reset the revs but it may do it a couple of times ,the revs are electronically controlled but the computer does not diagnose a problem re fuel flow,apparently it can be fine for days weeks,months then all of a sudden does it the owner does seem to think that it was in certain sea states that it tended to happen,
it has 2 computers to run it all one backs up the other and takes over if there is a problem,
it would not appear to be a large quantity but its hard to tell how much is pooled in the turbo/inlet manifold,
as he said things were alot easier with his old basic engine,
the electronic throttle is a possibility and i guess if it sits in one position on the pot then it could cause a problem ending in a bad contact then,by revving it up you move it,maybe cleans the contact area til the next time,

 

[oldharry]

A leaking oil seal in the turbo can pressurise the sump sufficiently to force oil up the breather into the air inlet. When there is sufficient oil in the manifold the engine will run away on it. The injector governor and ECU will make no difference as the 'fuel' source is not being controlled by them.

There should be little or no actual pressure in the sump, other than pressure fluctuations caused by the movement of the pistons. If there is it suggests piston/ring problem allowing blow by, or the leaking seal in the turbo is causing sump pressurisation.

Also an engine running away on its own lube will produce a very large amount of blue/white smoke which leaves you in no doubt there is a problem!

Sounds more like a fuel problem of some sort to me.

 

[orizaba]

when this happens the turbo is not running as it has to rev at a higher rate to kick in,the piston/ring scenario is a possibility ,
but its a new engine which i know means nothing as such,
my thought on it was that if the engine was all ok producing just the normal pressure you would expect and the vent in the sump was covered in oil,would that pressure be enough to force it up to the manifold aided by the suck of the intake,

 

[VicS]

[ QUOTE ]
The injector governor and ECU will make no difference as the 'fuel' source is not being controlled by them.

[/ QUOTE ] But wouldn't you expect them to still control the revs by cutting back on the fuel flow they do control? Unless of course the amount of oil being drawn in is so great that it is out of their range, but then smoke would "give the game away"

 

[orizaba]

the rise in revs only lasts for a short while,seconds but may happen a few times,when it does do it, a blast at 2000rpm solves the problem and all settles down,
it would seem that the ecu is cutting the revs back but due to the oil there it does it again until the turbo is put into action and so clears the manifold etc,
or should i say does this sound a feasible scenario ,the quantity of oil is not great but would it take much?
as for the smoke,the exaust is underwater and the controls etc are all inside and some way from the stern so its not somrthing thats been noticed.