Why did my piston melt?

[Audivotee]

Hi, can anybody shed any light?

Earlier this year my ADU engine went bang. When we stripped it down we found that number one piston had a hole in it and had melted, also did damage to a valve, the bore and rings.
Obviously after a period of deep depression I managed to look on the bright side and replaced the valve stem oil seals and added the Mark H mod. (thanks forum)

I’m close to the end of the rebuild and would like to know what could have caused the piston to melt in the first place.

If anyone could help or direct me to a post that would be great.

Cheers Dave

[Rusty]

Sounds like it was running too lean. Might be worth checking the injector over in case it's defective and not delivering enough fuel Good luck.

[Audivotee]

Thanks for that, It makes since, after the event it was only firing on four, in fact it was still only firing on four when after the rebuild, It was the next day when we started it up again that it seemed to clear itself.

Do these things clear themselves or should I take it apart and see if there are any blockages etc (if that’s even possible)?

Cheers for any help

Dave

[Flat on my back]

.

Might be worth getting the injectors checked over...fuel lines flushed and a new filter stuck in.

[20vQC]

I agree with AndyCasey... too lean mix!

[a4kquattro]

hole in piston usually means pre-ignition actually.. going lean usually causes pinging which eats away at the ring lands and the edges of the piston. Not that it cant cause a hole in a piston, but more commonly its pre-ignition that does that.

[terrybullwon]

Did the valve leave the head?

[Rusty]

hole in piston usually means pre-ignition actually.. going lean usually causes pinging which eats away at the ring lands and the edges of the piston. Not that it cant cause a hole in a piston, but more commonly its pre-ignition that does that.

Faulty coil pack, coil pack wiring, poor mapping then.... has the car been remapped?

[Audivotee]

No the valve stayed put, just a little dig out of it.

I didn't here any pinging by the way.

I got the impression that it all happened very quickly. The car was running great and at the time of failure I was in the processes of going past a rather irritating Ford focus who had insisted in crawling past a lorry, making me about 45 seconds late. I was trying to make up time!

[a4kquattro]

No the valve stayed put, just a little dig out of it.

I didn't here any pinging by the way.

I got the impression that it all happened very quickly. The car was running great and at the time of failure I was in the processes of going past a rather irritating Ford focus who had insisted in crawling past a lorry, making me about 45 seconds late. I was trying to make up time!

Almost DEFINITELY pre-ignition then. Going lean / detonation is a relatively slow killer while pre-ignition causes immediate and devastating damage.

Potential causes of pre-ignition:

large carbon deposits in the cylinder causing hot spots, specifically the 'embers' will glow and cause the mixture to explode before the spark event.

ignition component failure, EG the infamous 'spark hop' on a 3B engine when the wrong distributor rotor tip is used. Or in the cause of an AAN or ADU motor a misfiring coil (although typically a misfiring coil will *fail* to spark which wont cause pre-ignition.. it needs to spark at the *wrong* time for this to occur).

Hope that helps. Sorry to hear about your motor

[Audivotee]

Fairly new coil packs and wiring. The car was remapped in late November by a respected company in Banbury

[a4kquattro]

Fairly new coil packs and wiring. The car was remapped in late November by a respected company in Banbury

Oh, I almost forgot, pre-ignition can of course be caused by your ECU telling the plugs to fire for example very early in the compression stroke. It'd have to be *very* bad mapping for that to be the case though, either that or the ecu received an implausible signal that would cause that to occur (trigger errors)

[Audivotee]

Thanks for the pre-ignition thoughts

How do I fix this?

[Rusty]

De-coke everything (part of the rebuild anyway?)
Get it back to Banbury and get it checked over map wise.

[EspenW]

Hi, can anybody shed any light?

Earlier this year my ADU engine went bang. When we stripped it down we found that number one piston had a hole in it and had melted, also did damage to a valve, the bore and rings.
Obviously after a period of deep depression I managed to look on the bright side and replaced the valve stem oil seals and added the Mark H mod. (thanks forum)

I’m close to the end of the rebuild and would like to know what could have caused the piston to melt in the first place.

Cheers Dave

Easy: Too much torque delivered by the RS2 turboed ADU, get forged pistons

As others have said, probably pre ignition. Remember, though, that detonation can cause pre ignition due to the heat buildup. Overheated spark plug tip, burnt exhaust valve, but most commonly, carbon buildup causing hot spots are the typical causes.
what grade of fuel were you running? How much boost?
Would not surprise me if this was yet another engine blown due to N75 failure.
Check injectors and install A/F gauge and KnockLite.