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Can somebody tell what could cause this kind of damage in engine? 3 of 4 spark plugs burned off electrodes. (NGK number6)
Engine: Subaru EJ20 2.0 turbo N group. old RA type
Looks like damage from heavy detonation
the valves also look burnt like when they get carbon caught in the seat or the valve clearance is too tight.
What kind of boost / power levels were you running? Grade 6 are quite a hot plug, I'd have thought if it was running the 300odd bhp of a rally car with high boost and a restrictor in place you should have been using grade 7or even 8or9's.
The spark plugs themselves car heat up causing them to burn and also cause self ignition like you'd see in a diesel because of the hot element, this can cause similar damage to detonation
Boost at max torque aprox. 1.45bar to 1.5bar (250kpa) - power arox. 285hp. Fuel e98 lambda 0.80
And ignition angles qiet small for this kind of engine 7deg at bax boost and 12deg in max rpm 6500...
It is very possible because of spark plug heating up and making self ignition..
but exhaust valves should not burn off... thats, because of bad seat or clearance.
Judging from pics - you are using spark plugs heat range 6 - too hot.
Also timing seems away too low for e98 - could lead to excess heat...
Toxin is right, running E98 should allow a lot more ignition advance, basically it will be like running retarded in this webinar:
I'll assume when you say Group N that you mean you're running a restrictor? If so, 12 degrees timing at 6500 is exceptionally low even if you were running on normal pump gas. I'd say a lot of your problem is due to excessive heat and the inability for the exhaust valves to get rid of that heat into the valve seats. On E98 you should be able to comfortably tune the engine to MBT timing, particularly at higher rpm. This will reduce your exhaust gas temps substantially as well as showing what I can only imagine will be a significant increase in torque.
In that installation I'd be running a minimum of a heat range 8 if you're using NGK spark plugs.
low ignition angles because of getting knock.. i needed to reduce timing about 4 degrees or more.
would it be possible that bad valve seat leads to this situation - knocking ?
Unless the seat was modified prior to tuning I wouldn't have thought so, it's more than likely been caused by your hot plugs
problem caused by:
together with hot spark plugs, there also was problem with waste gate actuator - on road it stuck in closed position - causing higher boost than boost aim in closed loop. Engine started to overboost
Over boost cut didnt worked, because it was set 25kPa above boost aim and I didnt checked calibration of MAP sensor - max sensor reading was 5kPa lover than over boost cut - that way boost was higher, fuel mixture leaner about 0.9lambda - more heat, knock and result.
i suggest always for turbo engines check map sensor and its calibration.
Thanks for the update Rolis. A properly configured boost cut is a very important step in any calibration for a turbocharged engine. Good luck with the project.