Destroyed spark plug input

[MomentFD]

Hey guys,

I was at the track yesterday in northern California. It was hot.

Motor is an S14A SR20, all bolt ons, 550cc and Z32 MAF. Car was running excellent, albeit hot (210-220*F (104*C)) until my third session, I had took some pace laps because coolant temps were just getting to hot. When I went to get back on it, the car would build boost (12psi, I run ~13psi) and was just very choppy. I do not recall an 'event' under load where things went to shit, it just happened after my cooldown laps. I'm hoping I didn't detonate big time. Here are the spark plugs I pulled out.



Here were the maps I was running. I know timing is probably aggressive, it's in between a map I received from PL and the stock SR map. I figured plenty of idiots up the boost on stock ECUs with those timing numbers, so I'll be okay. Maybe I've joined the ranks of idiots.





I replaced the plugs with BRK 7 iridiums, kudos to this awesome chick who gave me 4 the day before. I don't usually pack them, but now I will. I added some fuel, pulled 2* of timing in load area, and took it back out on track. It ran like a champ and doesn't seem any different now. I'll be boroscoping that cylinder along with leakdown/compression test this week. I'll check out the turbine wheel of my stock T28.

Just looking for your guys input. Do you think this plug slowly eroded or it was a single event? Does this look like detonation? Speculation on damage caused or recommendations going forward? Should I be weary of this cylinder? I'll check out the plugs after a few 100 miles.

Keep on boostin..

[Matt]

Plug has green on it which looks like a little corrosion but I dare say detonation could be a factor.

What were your AFRs when you measured with the wideband. The fuel map you posted is in estimated AFR mode (which does not mean those are the AFRs you are going to achieve... just about to pull this 'view' out of the maps to avoid confusion here). We normally look at the raw numbers and compare against factory maps to see how it was tuned

Perhaps post a bin and your dyno sheet here showing the AFRs

[MomentFD]

AFRs from street and track observation were 11.5-12.2 all day. I think I'll aim for 11.5ish from now on. I don't have a dyno sheet, have primarily been street tuning.

I'll get the raw table view, it's drastically lower than my stock map which ran the car in the 9s for AFRs.

[unex]

http://www.contactmagazine.com/Issue54/ ... asics.html

differences between detonation and pre-ignition.

[raddy]

Hi there, my opinion is that destroyed plug is result of detonation, that was caused by over advanced timing. Broken insulator is good sign. When you look at the electrode of the undamaged plug, you will see that border of color change is quite close to the thread, what should point to the too high temperature casued by over advance of the timing. Ideally, you want this border line at the middle of the electrode. I would say that you are still running 2-3 deg more of the timing that you should regarding fuel and conditions. Without good knock detector you have no chance to dial timing correctly...

[s200rat]

How old are the injectors? Might be worth getting them cleaned and flow checked to make sure cylinder 2's one is working correctly. Your timing map doesn't look aggressive, if anything it's pretty tame for a t28 at 13psi.

[bachig24u]

That cylinder ran lean.

It melted metal, whether it be standard copper coats, platinum, iridium, or any plug for that matter,
The cylinders temps went off the scale for the metal in the firing line. Not surprised the piston spray didn't drop in the sump with it.
The piston & head will be pitted which eventually will cause a bigger pre-ignition event.
The exhaust valves and seats will almost always show signs of smashing molten metal along with the turbo wheel.

The timing map had nothing to do with this, nor fuel, nor corrosion, nor mystery.

mark the injectors with a scribe, then send the injectors away for test and or service.
Check the fuel rail is clear, and don't run so lean 11.5's - 12's is not a circuit track AFR, its a death sentence for a circuit engine.