Originally Posted by mx594

Also if you can hear audible detonation, you probably already have done damage to the engine. Not to mention if the stock ecu hears detonation (well before you can) it will switch to the low timing map to prevent it.

Originally Posted by Blu_Blur

Might also have to dowith load. Depending on the fuel/timing maps andother related mods,sometimes detonation might only happen under certain load/rpm.

My Sentra had its timing advancedmany years ago. Lately I've noticed at a certain RPM, I am hearing pining but onceit goes higher, it stops.

I also asked if the sound was more accurately described as 'BBs in a can' instead of marbles. He said it sounds like BBs. It could be anything I guess but my guess is pinging.

Originally Posted by mx594

Because this: "Ill change my assumption to BB's sound happens only in low RPM's when i gas it real quick. Its just for two seconds but clears up as soon as the rpms climb above 3K." is a dead accurate description of what my G sounded like with a lightweight flywheel. Have you ever driven a G or a Z with a lightweight fly? Perhaps his stock dual mass unit is getting tired and is not doing such a great job dampening anymore. I know mine doesn't dampen out the gear rattle as much as it used to, so sometimes I hear the "marbles in a can" very faintly when I lug the engine at ~1500-2000 rpm.