Removed from my 1992 turbo’d 1.6 (standard internals, TD04 turbo, Revent manifold and DP, EV14 injectors, MS Labs Mini MS3 ECU, tuned by Basset Down Balancing, 14psi from ECU controlled EBC)

Ive since swapped in a replacement engine, but kept the EBC unplugged to limit the boost. I want to figure out why this happened, but don’t really know what to look for. I took the old engine apart and the conrod is shattered into fragments as expected, but the piston is completely FUBAR.

This happened at highway speed, around 4k rpm as I hit the accelerator to go for an overtake. Initial observation was a lack of power, oil pressure gauge took a dive and shortly afterward the mechanical noise of the conrod shattering.

How can I know what caused this?

 

14psi on a TD04 is more likely what killed it, the rod snapped and the piston hit everything on the head.

 

Why would 14psi on a TD04 kill it though? Why would this make the rod snap? Seemed to run fine for a year or so….?

 

How much torque do you think it was making at 14psi?

 

31 year old engine with somehwat weak rods from the factory. I guess you should leave it at 11-12psi or put some rods in it and give it everything that TD04 has to offer

 

How do the other pistons and rods look? Can't really tell due to damage to this piston, but I don't see any signs of detonation which would point towards overly aggressive timing. Odds are if you bent one rod bad enough to grenade the motor, you probably bent the others which would point towards too much boost/rpms. If running ebc, you could ask for a boost taper from 10-12 psi at peak torque then ramp it up after. That or just reduce boost overall with the new engine.

 

The other rods are straight and the pistons also look fine - all the damage was on #4. What signs of detonation would I be able to see if I was looking?

The car may have run low on oil, I did have a valve stem seal leak issue which I hadn't got around to fixing, and was coming towards the end of a 2 hour journey. Although I think Reverant is probably right - in fact it was likely more than 14 psi that killed it; I had my overboost protection set a bit higher than this (220kpa) so it was probably a boost spike resulting from opening the throttle up at circa 4k rpm.

 

how does the rod big end look? and the crank? possible bearing seized, broke the rod and sent the piston into the head.
I would bet on the overboost but curious.