Uh Oh, that's not good. Any Ideas?

[GangsterMD]

Problems at the track yesterday After fighting with some knock problems again...I over-reved the car by accident on a run. Turbolink showed 6250 I finished the run and it seemed to be running totally fine. On the next pass just as I crossed the line it felt like it shut down. Turbolink showed 21# boost to 7 inches of vac on the frame. It was still running, and I drove it back to the pits. It was idling a bit rough. I checked the oil for coolant and oil was clean. I checked and the coolant was down, but no bubbles in the rad, and no leaks. I don't know if the low coolant is relevant or not. I did change the rad recently... To start I had to hold the pedal down, and it would run rough - but it would run and idle. No smoking under hood or out the pipes. I loaded it on the trailer and had a look at it today. As you can see by the attachments, #6 plug was destroyed, and the cylinder is down on compression. I didn't do a leakdown test on it. I did pull the valve cover and the pushrods and rockers appear ok. What would cause the damage to the plug? Could the pieces of the plug damage a valve? Or a ring or piston? Any ideas? Either way I think a teardown is in my future... Sounds like a good winter project.

 

[ct67_72]

looks to me like you had some serious heat going, or very bad detonation. the plug is melted. and I would bet that the cylinder is scored or the piston has damage, I would do a leak down to see if there could be a problem in any other cylinder you may have missed in a compression test

 

[GangsterMD]

Hmm.. Ok is detonation the opposite of pre-ignition? In other words the opposite of knock? And if so could that be caused by retarding the timing too much? I had taken timing out of 3/4 to get rid of KR - I started at 23* and dropped twice to get to about 19*.

 

[ct67_72]

nope they are all the same, just in other words

 

[87we410877]

Hmm.. Ok is detonation the opposite of pre-ignition? In other words the opposite of knock? And if so could that be caused by retarding the timing too much? I had taken timing out of 3/4 to get rid of KR - I started at 23* and dropped twice to get to about 19*.

I think your backwards. Advancing will give you knock.

I would bet my 2 cents that #6 piston has a peice missing from the top to the first comprssion rigng along the outside of the piston. Pull the heads and check it out.

 

[GNXwannabe]

Just a guess...cracked piston or broken/damaged ring. NO smoke?

 

[Cme2fly]

nope they are all the same, just in other words

Pre-ignition and detonation are completely different..Detonation is the spontaneous combustion of the end-gas (remaining fuel/air mixture) in the chamber. Pre-ignition is defined as the ignition of the mixture prior to the spark plug firing. HTH

 

[SloGN]

i think i would have those injectors flowed. I'm thinking that that cylinder went lean and melted stuff. if you were running race fuel that would explain why no knock was recorded. high octane gas don't knock when the run lean only pump 93 or unleaded fuels.

 

[GangsterMD]

That's for the responses. My detonation vs knock question is because of the following. I've been to a 1/4 mile track twice now, and both times the first pass of the day the car runs clean - little or no kr. Default tt chip is 24*/23*. Ran 12.82 @ 106 on Saturday spining on the start line as I didn't do a burnout. Run was clean @ 19# with alky. I shortened the wastegate 1 turn and made another pass. No kr in 1st & 2nd, then 30* kr in 3rd. I backed up timing in 3/4 to 21* and again no kr in 1/2 and 7* in 3rd. I took 3/4 timing back to 20* on final run - no kr reported. It was a cool day - 55*F, and boost was up around 21 lbs ish, then dropped to 7 inches of vac on the last frame when power was lost. So I have many questions... Why so much kr in 3rd? Is 23* timing to much at 20# of boost? Alky was set to 4.5 - 5. Could I be getting false knock readings? 160,000 kms and only the valve covers have been off. Yup as far as I know stock timing chain & gears. Could that be causing valve timing issues? Or the chain slapping around (not that I cna hear it) causing false knock? The car used to start, idle, run super smooth - better than new. Why did it run so good on 1st runs then develop knock? The one run I stayed in it to see if I could hear it pinging - so could I have damaged something that didn't show up till the last run? I know I need to take it apart now which I'm not that upset about - like I said the timing chain & gears and head gaskets likely should be changed anyway. However I don't want it to happen again. It's been frustrating figuring out why all of the kr in 3rd... Please give me your thoughts.
Thanks

 

[MikeL.]

....pull your downpipe off and check the turbine wheel to see if the broken electrode took out the wheel. It had to go somewhere.....sorry to see that happen.

 

[Syclone0044]

Run was clean @ 19# with alky. I shortened the wastegate 1 turn and made another pass. No kr in 1st & 2nd, then 30* kr in 3rd.

Is that a typo? 30 degrees of Knock in 3rd?

 

[SloGN]

you always tune the motor for the highest load and the highest load is in 3rd and 4th gears so that means it needs more fuel in 3rd and 4th. you killed that motor by it being lean and on top of that it was lean on pump gas/alky. it may have survived a little better on race gas.

 

[GangsterMD]

So my O2's at the end of the run were 781mv, which shouldn't have been too lean? Or was it? It was running richer before, but I figured as I upped the boost the O2's would come down into the upper 700's. However like SloGN said perhaps one injector failed? Cyclone 0044, 30* kr is not I repeat not a typo? I'm wondering now if I got some bad premoum fuel in the car? At the price of premium it might not be getting used very fast... Like I said I'm kind of looking forward to freshening up the engine, but I don't want to have it happen again.

 

[1985GN]

cracked piston is what im going with as well....

 

[SS_Sean]

cracked piston is what im going with as well....

+1. Sounds like a lean cylinder. Check the injector flow first for #6, imho...

 

[mygn276]

You ran the car on the lean side and # 6 hole got it. You need the pull the head and i bet your exhaust valve is stretched because of the heat in the cylinder, that would be the cause of the lack of compresion and miss. The piston is most likely torched as well. Ok you know what that means:frown:

 

[GangsterMD]

Yup I know what that means... Where can a guy get a good set of heads, a new turbo, and pistons while I'm at it I was hoping it was a head gasket

 

[mygn276]

You dont need a new set of heads. Just get the ones freshened up. Need to first double check after the heads are pulled as to what is damaged before buying anything.

 

[GangsterMD]

Update - Piston scorched - What now.

Hey guys, last night and this morning I started pulling apart my engine. Pulled the head and it was hard to see if anything was wrong. There was some flaky crap on #6 valves - not much but like ash. The #6 piston is fried, it is burned at the edge. The cylinder looks ok, the other pistons look good. The turbo appears fine. So now it's decision time. I was hoping it was a valve and I could buy some new heads, turbo, ic etc. and not necessarily have to pull the motor. Is it possible to drop the oilpan, crank and pull the piston out the bottom? Or is that just plain stupid considering the engine has 100,000 miles on it. My plan is still to do head work or replace, upgrade turbo and ic, and replace timing chain & gears. Maybe I'm answering my own questions, if I plan to change the turbo, does that mean changing the converter anyway? Is there a ball bearing turbo that would work well with the stock converter?

 

[GangsterMD]

One more thing, with the look of that one piston which is scorched compared to the others. Does that support the suggestion of one injector problem? The other plugs by the way were quite black - which wouldn't that indicate that they were rich or not lean at least?