I was tuning my truck today and was bringing it up to full throttle for the first time. It is a dead stock 5.3 with 100,000 miles, twin turbos, 44lb inj., hptuners 2 bar speed density, air/water intercooler. I stopped to do a reflash and noticed a slight tick/knock loudest at 1500 rpm. Went back to the shop and pulled the plugs - all were the same except the #7 electrode was bent closed. Did a compression test and all were 135-150 psi except #7 which was 118. I'll attach the log (i noticed it after the logs ending at the 550 mark). The wideband was at 10.5:1 - 11.0:1 at wide open. Any ideas of what i did wrong?

 

sounds like the piston kissed the plug. might wanna pull the head and have a look before you mess more up. did you do a full rewrite for the 2bar? you log only shows 1 bar (105kpa). can you hook up your wide band to your hpt box? its easier to go back and look at the run with afr when its logged. what were you doing in that log? at the 550 mark it looks like your were in and out of the throttle alot. were you doing that or is you TM taking over? and you were running 30* of iming at wot. with a turbo i don't think that would be too good.

 

I did do a full rewrite. I have the cheaper hpt so i don't think i can hook in the wideband. I had it in 2nd gear and was going in and out of the throttle myself just watching the wideband. I haven't modified the knock sensor settings and I wasn't getting any KR. How can the piston kiss the plug? They are NGK TR65IX Iridium plugs.

 

30 degrees of timing at WOT. I think that should be closer to 17. IMO

 

My initial thought is broken piston... I agree with 4.8T about pulling the head. When you said a slight tick/knock and the plug electrode is bent over it screams broken piston. I am unable to look at your log but if you were running 30 degrees of timing well you will see the end result when you pull the head. Hope things are better than they sounds.

 

If it detonated then shouldn't i have seen some KR or heard it ping?

 

Not allways, I have never had my knock sensors work right so I don't even use them. Alot of times they get full of water and currode. How much boost were you running with 30*? There is no way the piston could hit the spark plug. It was most likley a pice of piston that broke off. My guess is that you detinated it, the rings butted, and ripped of part of the piston head. That piece hit the plug.

 

I saw 150kpa at 4900 rpms and 29* of timing on some of those blasts in the scan. I would say the problem is 29* of timing at 7-8psi is way to much timing. Have you scaled back the KR tables? If so thats why KR would not register.

 

All the KR tables are stock. I was seeing some KR at lower RPM's so they are working.

 

i started my timing at 9* and worked it up.. but im only running 5psi... ~135kpa..

Why the TR65IX Iridium plugs and not just TR6s?