Evo IX MR here with a newly built 2.0L engine that's been tuned. Running a hybrid 20G turbo at 1.7 bar (24.5 psi) producing 340WHP on 98 Ron (93 Oct). Car was tuned in Dec 19 with a safe tune and zero knock. Recently I've been experiencing random slight misfires and/or hesitation under boost and the knock sensor randomly flashes under boost with or without the misfires/hesitation. Idling is fine and around town driving is fine. Spark plugs were stock NGK LFR7AIX and about 6 months old.

I swapped out the spark plugs for Denso IKH24s and now it's gone away and drives perfect under boost with no misfires/hesitation or knock sensor flashing.

I would like to learn a little bit more about how the engine is running from the spark plugs, and based on my limited knowledge it looks like the AFRs are good but perhaps a little too hot for the stock spark plugs. Plugs 1&2 seem to have cracked with heat while 3&4 are fine. Was switching to IKH24s the right choice?

 

What is the afr reading ? Most target 11.-11.4 on pump gas and 11.5-11.8 on ethanol.

If the timing is too low it could also be an issue.

What timing does it have.

4@5000
5@5500
etc.

 

Unfortunately I don't have the logs for timing. Only the tuner has it. AFRs are good, holding at 11-11.2 until redline. I'll ask the tuner to check the timing just in case.