Quote:
Originally Posted by Brabus 3.6-24
poor fuel is not the isue I think, here in my contry we general have very good fuels.
Im always running octane 95 as I should.
And the spark plugs are acording to BRABUS to be the Bosch F7DC
But you might got something right becasue the spark plugs looked very poor and I just changed them resently.
my car runs with catalyst and the lamda sonde o2 sensor.
So it would be nice to check if this work as it should.
But I donīt think that preignition is the cause because it runs with knock sensor as well and all the electronic works, I have never had any problems with faulty engine electronics or bad running engine conditions.
Until now I can see that all the pistons has some black "stuff"/oil on the tops and I only have taken 2 of the pistons out to check.
but all my valves was covered in black smokey "stuff" so it has been from all the pistons that the oil has been burned.
so my guess is that it is all the pistons that has problems.
therefore my guess was on wrong use of oil?
but I have the opputunity to run on 98 or 99 octane, it is just very pricy compared to the 95 and the brabus instruktions tell that 95 is ok but a minimum to run on, sp generaly it should be ok.
maybe the compression is to high? or simply the pistons rings where just worn out? I really donīt know, but im realy nevous if I put it all together with new rings and the reason is still there  and then it will only last few Kilometers
But the fuel mixture should be checked and the O2 sensor deffently checked if it works as it should.
Any ideas else? |
How long have you owned the car for?,were the spark plugs you removed the same as you reinstalled?
oil will make a mess of everything in the chamber,it will be heavily carboned,iv been told oil in the chamber increases the chance of detonation too.
I find it hard to imagine oil or general engine wear as being the cause of broken rings,that is assuming the rings are a reasonable quality!...but im no mechanic so ill leave that one for yours
What is the wear like on the piston skirts and around the top thrust side? is the ring to ringland clearance excessive at all?
Fuel quality is an interesting thing,i mean...who really knows what your getting and if the car is not used for a few weeks the grade can drop significantly...if your like mine and doesnt get used for 3-6 months i tend to play it safe and dump off-smelling bial green/yellow looking "98 octane" from the tank each time to avoid problems.
Knock sensor ignition retard is an interesting thing too...have thought about getting the knock sensor add-on motec does for its ECU range(utilises the OE sensor)...but its so damn expensive!...anyways,the thing that gets me about this system and this is just a personal opinion...is that for it to work preignition must happen...now generally it happens mildly and this will be picked up and timing retared to a suitable level...however,what stops this suddenly happening at high RPM when that spark plug or piece of carbon gets hot enough to cause ignition at the wrong time,sure the ecu will pick up the problem,but the ring/headgasket damaging pressures have already occured!.
I remember the day i brought my car...the owners said that i should run 96 as they put 91 in it and it made all sorts of funny noises under power...back then i didnt realise the significants of that comment,but it has some merit in the fact that very poor(audible inside the cabin) combustion can still happen with Knock control in place.
Could you get us some pics of the pistons? =)
Cheers,
Paul