Hole in cylinder wall
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Joined: May 2002
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From: Raleigh, NC
timing doesn't really do that.. That is from a very lean condition for a long time at high loads. Lots of pre-igniton.
Pre-ignition can be caused by detonation from too much timing, but if the tune was "conservative" then I would guess that there was not enough timing, which causes really high egt's which will then lead to pre-ignition and everything else melted.
There is no such thing as a "conservative" tune.. only right and wrong. You either had a really wrong tune or injector failure.
RC750's do not work above 55psi of fuel pressure.... They are absolute junk. If you notice they put a warning on the box.. thats because of me. We lost 3 motors before RC finally fessed up and told us that the injectors were partially locking up above 55psi and thats just how the injectors were and to keep the pressure below 55psi. Those are words directly from RC after we sent 3 sets of 750's back to be checked after 3 blown motors.
Keep in mind that all 4 wont lock up exactly the same. The wideband can still tell you a good afr, but one cylinder be very lean. It only takes one pull to do this kind of damage. Reading the spark plugs wont help you.
Pre-ignition can be caused by detonation from too much timing, but if the tune was "conservative" then I would guess that there was not enough timing, which causes really high egt's which will then lead to pre-ignition and everything else melted.
There is no such thing as a "conservative" tune.. only right and wrong. You either had a really wrong tune or injector failure.
RC750's do not work above 55psi of fuel pressure.... They are absolute junk. If you notice they put a warning on the box.. thats because of me. We lost 3 motors before RC finally fessed up and told us that the injectors were partially locking up above 55psi and thats just how the injectors were and to keep the pressure below 55psi. Those are words directly from RC after we sent 3 sets of 750's back to be checked after 3 blown motors.
Keep in mind that all 4 wont lock up exactly the same. The wideband can still tell you a good afr, but one cylinder be very lean. It only takes one pull to do this kind of damage. Reading the spark plugs wont help you.
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Joined: Oct 2011
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From: dfw
i would agree that piston saw alot of heat and to little timing will raise egt ive seen the same thing in diesel motors late timing means exhaust valves over heat causing preignition flame front starts to late so these guys are telling the truth no such thing as Conservative tune its right or wrong i run alot of timing 30 down low 28 at start of boost 24 at redline supercharged 7 psi and this is the stock ecu with water meth i did what you did in my old nova with a roots supercharger at 5psi this was before afr gauges i ran too little timing and eroded top ring land and in a diesel a bad injector causing to much egt and a bad injector pump it wasnt advancing its all the same no matter the fuel type fi demands respect and knowledge on the tuners part im sorry you experienced this good luck on the up coming build also are the rc injectors bad as im looking for some thing in the 440cc-550cc range that will handle 85 psi ill stop rambling 
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I agree this looks like heat rather then detonation. Detonation is combustion happing at the wrong time in the normal combustion cycle, this will typical show not the look of melting, but rather pitting marks and breakage to varying degrees, whether it be a broken ring land or the top of the piston looking like its seen 25 grit sand paper. The scuffing of the cylinder walls would just be the aftermath of the deformation of the piston traveling up and down. This is my take after observing the pic.
Too much timing retard will cause cylinder temps to rise and can be enough to melt pistons and exhaust valves. How do the valves look?
An injector failure in that cyinder is also very possible.
Too much timing retard will cause cylinder temps to rise and can be enough to melt pistons and exhaust valves. How do the valves look?
An injector failure in that cyinder is also very possible.
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Thank you all for your input. I spoke with Tim from Fuel Injector Clinic regarding the condition of the injectors. All of them are within 5% of each other, but the injector that was in the failed cylinder had one of the 3 outlet nozzles clogged. I'm not sure how it could maintain a similar flow rate given a 1/3 reduction in outlet surface area, though I can get my head around the injector not spraying homogeneously and causing a local hotspot in the piston crown.
As far as getting the fuel/timing maps, I tried powering the AEM while in the car but wasn't possible since the fuel feed line is open and the master relay just clicks repeatedly (I'm guessing there must be load on the fuel pump). Have you ever worked on the AEM without it being in the car? Otherwise I'll try to try to plug the banjo feed line with a screw and couple washers.
As far as getting the fuel/timing maps, I tried powering the AEM while in the car but wasn't possible since the fuel feed line is open and the master relay just clicks repeatedly (I'm guessing there must be load on the fuel pump). Have you ever worked on the AEM without it being in the car? Otherwise I'll try to try to plug the banjo feed line with a screw and couple washers.
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Yeah... didn't think about that
. So took the fuse out, but there's no communication from the AEM to the laptop. Says the AEM is offline. I thought it was a com/usb cable issue, but then I plugged in the serial gauge and couldn't even get a battery voltage reading. So apparently the AEM is not turning on.
