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I deal with a ton of subarus on a day to day basis and see a bunch of stock engine failures. Car in question is a 2014 wrx running 91oct with bolt ons. Car was tuned by a very well known and successful subaru tuner in the states. Car recently suffered bearing failure. Knowing the engines flaws from the factory in the clearancing department, I'm more curious as to figure if it could've been tuning related. If oil pressure and proper oil weight was maintained, which I know it was, could high EGTs from the extended high speed/high load pull cause detonation? At 91oct, we all know it's knock limited. Afr's were suitable for the fuel and ignition advance was conservative. Knock detection is still turned on and no knock was recorded. Im curious if the heat produced from this long pull could've cause some det even tho fuel and timing was good. Do you add extra fuel up top when doing high speed runs?
Any sustained high load driving will result in higher combustion chamber temperatures and this can make the engine more prone to detonation. Detonation is a big problem with the Subaru engines due to the narrow big end bearing, hence it doesn't take much to cause bearing problems.
If I'm worried about a particular customer going out and doing repeated high speed runs, I'll often trim a little extra fuel in and remove a little timing at high speed or in top gear for protection.
If no knock was recorded this would suggest however that the failure was either no related to detonation or the knock detection system isn't tuned correctly.
Ok I see, so if knock was never recorded, then either detonation never occurred or the knock system isn't right. Due to the big end issues, I increase the rod clearance to right at .002. on my EJ engine and is a common practice in building bottom ends. Do you do any engine building, Andre?
Yes I do. On a journal with the size of the Subaru big end I'd also normally aim for about 2 thou clearance. They are a fussy motor to keep reliable.
Has only one bearing failed or is there damage to more than one?
I found out the hard way that they can suffer from oil starvation in the high RPM range with the standard WRX sump.
The pump is more efficient than the oil return galleries in the heads.
Heaps of information on the subject on the net.