Sounds like it was running lean to me if you managed to melt the piston, they don't melt when they are running rich. Someone screwed something up on that tune or their equipment was borked

 

I know and I don't get it. A brand new wideband o2 sensor was used and the afr's never spiked during the last pull. I can't think of what would cause this. Bad gas possibly? I filled it with 93 right before I left.

 

Detonation alone would not melt the piston like that? Wouldnt the plug melt well before the piston if detonation was the case? I would think you had to go lean if you melted that badly. IMO. Serious case of detonation and running lean. Wierd your gauge was telling you other wise though.

 

Not only the piston but like I said, it took a decent sized crater out of the cylinder wall.

 

this was pre ignition from the sound of it, not detonation... and yes there is a difference. I don't know if it's even possible on an F series but did you check the cam timing when you took it apart? If you skipped a couple teeth (the noise you heard) and some air/fuel got in there while burning exhaust gas was still in the cylinder you'd have about what you've got there.

 

There was a tech problem on some early engines. Number four cylinder developed piston rattle which is probably what you heard. Honda warrantied a lot of them. Mine developed the same problem- I have a 2002 and had 9k miles on it at the time. Was properly tuned and running 12lbs. boost. Engine was running okay powerwise but developed that clatter. At first we thought the noise was timing chain tensioner. But it turned out that number 4 cylinder was scored and piston warped. I went with a new short block. One of the tuners that works with my tuner (Synapse motorsport) used to be at a large Honda dealership and told me about the problems with some F20's which Honda covered (stock engines) not boosted. You may have been lucky like me and caught one of those. On my new engine I went water-meth , low temp thermostat and fan switches to keep the charge as cool as possible. Hope this helps and gives a heads up to everyone that it may not be your fault.

 

I didn't check the base timing. I asked miller if it was possible that the base timing was off and I'm pretty sure he said if it was it would show in the aem. But to me that sounds like it was deff a possibility that the base timing was advanced, so even with 14-16 deg timing in it the total timing could have been too much. No way to tell now that I pulled it apart. Stupid on my part because I really want to know what caused the failure.
And it's a possibility that the noise we were hearing was detonation.......

 

what did the piston rattle sound like? almost like rod knock?

my engine had a weird sound, it's being replaced now, was still running fine, but the noise it was making sounded terrible. it will be torn apart to see if what the problem was/is

 

you have to set the base timing in the EMS although I have never seen a car differ from what is set in the base map that does not mean its not possible. (excluding cars with CAS, or distributors)

 

He didnt set timing before he tuned it? Melting pistons wow interesting to see what the tuner says about this?