I think i chipped a seal in my engine tonight, but when i did it the O2 meter was reading 10:1 (lowest my o2 sensor goes). The car was tuned to run at about 10:5 to 11:1 in the upper rpm range, but around ~7200 the VE drops off significantly and it was running really rich from there on up (10:1 or lower). Hitting this range caused ignition breakup, which is what i wanted to tune out. However, on one test run it apparently caused detonation? Is this possible? Logs say there were no lean spikes of any kind.

Car is running single turbo gt40, vmount, 1600cc secondaries, all supporting mods.

 

Slap me if I'm wrong but I believe you have a timing issue... depending on the amount of boost, you are making,your timing should be retarded 1 degree for every LB of boost pressure over stock

 

Actually, looking deeper into the logs i think i figured out what happened. In short, I hit 100% duty cycle. Probably caused an instantanious lean condition that was inperceptable in the O2's readout. FML.

 

it can cause pre ignition with excessively rich mixtures and can cause high egts also both can cause apex seal damage

 

it looks like there was a small boost spike that maxed out the injector duty cycle, causing it to run lean. Taking into account O2 sensor lag, i can now see where the o2 breifly spiked to 12.6:1 or so before i let off the gas. Originally i thought this was just me lifting off the gas, but i didnt take into account enough lag i think.

 

I'd love some more info on setup? You maxed out 1600's on pump fuel or E85? What boost and port?

 

are you running AI? your secondaries are 1600.. what are your primaries? which GT40? what was peak boost?

 

what did the timing look like?

I've seen many motors survive a short lean condition

 

Running very high AFRs causes a lot of carbon fluff to be deposited on the rotor faces.
The carbon can start burning like a wick and cause pre-ignition and detonation.
Running WI will remove it.

Some tuners think that most of our detonation is caused by the carbon buildup associated with rich AFRs.

 

what boost? timing? ecu?