The Blown Motor Mystery - What Caused Our Engine Failure?

**UPDATE** In reviewing footage from ALL WEEKEND the engine was running AFRs in the high 13s and low 14s WOT. This is difficult to see in the footage, but this was likely the cause of the piston issues. That said, I don't know why it was running so lean. New injectors, ECU, and fueling setup is on its way!
Let me know what you think caused our engine failure:
Detonation?
Moneyshift?
Oil Issue?
Lean Condition?
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[@stevec5280]

Best guess with information and evidence provided...... intermittent lean condition caused by fuel slosh. Cylinders run lean, get hot, butt the top ring, and pop the lands.

[@ruggedbadgerracing]

Thanks for the input!

[@malcolmaustin2197]

I’d be surprised if you encountered enough detonation to destroy pistons without it being obvious on the rod bearings. Maybe pull the connecting rods and have a look, the bearings usually start to pinch inwards and wipe the oil from the journal. Even if they aren’t spun you should be able to tell by the bearing fit/crush into the connecting Rod.

[@ruggedbadgerracing]

I am going to pull them Friday I think. I will reply then.

[@davidcoyle7125]

Only a guess but extra clearances are needed on both ring gap, piston to bore and even crankshaft bearings when running higher than stock power.

[@a914freak]

Detonation. Who did the tuning, and was it done on a Dyno?

[@jeffwasilko]

Hmm KZbin ate my other comment.....1) were you able to check timing before you pulled it apart? 2) Any chance mechanical timing moved due to the keyway issue or was wrong when you put it back together Sunday?

[@ruggedbadgerracing]

Everything looked good keyway wise

[@ReneES-em1ye]

I am going with a combination of the exhaust leak giving the oxygen sensor bad feedback and the damaged pulley triggering the knock sensor to pull back the timing. The combination of pulled back timing and a lean mixture could have made everything run hot internally including the oil.

[@SSR2696]

Data point. I've ran mine quite lean to make 2hr stints and never seen any signs of detonation on the plugs. Ecotec ECU flash with lowered fuel pressure, ~100hrs at 13:1 afr on pump 91

[@ruggedbadgerracing]

I am going to see if I have AFRs captured by the AiM and review that data.

[@jeffwasilko]

Do you data log your wideband values? Do you data log Fuel Pressure?

[@ruggedbadgerracing]

I can check the AiM, I do have fuel pressure.

[@mcgregor711]

Rings butting up together will pull the head off of the pistons ot break the ring land in between the 2 compression rings.

[@ruggedbadgerracing]

Would you be looking for something on the piston or rings to indicate that?

[@RB-zn2xu]

Got hot and rings butted? Try to avoid stock ring gaps if it possible engine may get hot in racing like losing cooling. Look for intermittent vertical ring gouges in cylinder walls once you get pistons out.

[@Trevor6264-sp1wr]

Agreed

[@wht420aeclipse]

I know there's a big community for ecotec buggys, have you reached out to them to see if they have similar issues (I know they run their stuff hard). I wonder because they run the stock ecotec oilpan...just a thought

[@ruggedbadgerracing]

That's a good call. I will try to find that group to ask.

[@AverageJoesracingteam]

Hoe was your oil level throughout? Was it consuming oil thru the pcv lowering the octane creating detonation . Maybe try venting the pcv and valve cover to a catch can then road draft it

[@ruggedbadgerracing]

It was really hard to tell. Sunday our front crank seal became dislodged because it wasn't installed properly, but we still had like 5-6qts when I drained the pan.

[@malcolmaustin2197]

I will guess pre-ignition ( not detonation ) caused this. Just a guess. As to why, that remains to be seen....

[@scottkastelic2787]

Timing dude!

[@ruggedbadgerracing]

I think I am going to get a new flashed ECU to eliminate this or the octane issue. Its my understanding the timing is fixed and adjusted in the ECU. Is that your understanding?

[@Trevor6264-sp1wr]

This looks like you need some ring gap.what Octane did you use

[@ruggedbadgerracing]

We used 93, but we found our AFRs were in the high 13s and low 14s that we believe caused the failures. Not sure why, but we are investigating now.