ragpicker said:infrasilver said:
I think it was happening due to a seized wastegate causing it to run very lean. It was in the lower revs that it happened though, say 3krpm. I've since freed the wastegate and its not happened since. I saw 1.5bar at the time (normally runs 1.1). The mods so far are in my sig.
Its not got bigger injectors at the moment although it will have in the next month. I've discussed my car recently with Ken (not about this particular issue) and he's been very helpful as usual.
Again, I'm more interested in how catastrophic det can be, and whether a single episode could be enough to ruin an engine, or whether (as demonstrated above by Mike) it is a gradual thing like water eroding the walls of a building. Also, how common is it? I personally have never experienced it in any of my cars before and they have always been modified.
Maybe its always been happening but I've not been listening....
Rags, it is cumulative detonation that caused the damage in the photographs. The aluminium gets crystallised by the heat and local, uncontrolled combustion.
Your car pulled 'load' when the wastegate stuck, as demonstrated in your graphs. So, in short, it already knew it was detonating (hence the load pull) but ran out of range. At this point it became audible but the DME still has tricks up it's sleeve to protect the motor.....
Nicholas has done a TON of background digging in these ecus, I'm reasonably confident of the number of degrees of retard available under knock conditions, but Nick would be able to furnish you with the remaining pieces of the safety regime puzzle. Best to ask him on the specifics. And boy does he know his subject!
Bear in mind though..... A turbo engine by definition has more charge in the cylinders at the time of knock, therefore the potential for damage happens a lot quicker than it would in a normally aspirated engine like the Big Healey in the thread. So whilst the ecu did it's best to protect the engine, the loads placed on piston, cylinders, head gaskets, big ends and head studs etc, is huge during the knock event. Modern engines have great ecus on them, protecting from so-called Super-knock, a kind of run away knock which can only be stopped by resting the engine for a few cycles, in order to break the chain of events. This may have been instigated in yours, leading to the fact that you noticed rough running and turned it off.
Glad you found the culprit. Better still you logged the conditions under which it took place, excellent effort that man :grin:
