Knock at very conservative ignition timing

Hello once again, sorry for the long question. I really appreciate you guys helping me out.

iv been having issues with my car(built 2003 Mazdaspeed protege) pinging on very low ignition map. I blew a hole in 2 Pistons about 6 months ago. And before it happened I heard the same noise I'm hearing now. And even then the ignition timing was pretty conservative at about 12 degrees of ignition timing at around 15 psi. But I thought the problem was caused by another issues. so I rebuilt it, set the ignition timing even lower than it was, to play it safe because i dont have a knock monitor or sensor. I have been driving it hard for a while & I haven't noticed any pinging. but I had a hood exit exhaust and just changed it back to a full exhaust. So maybe I didn't hear it? but.. i doubt it because I'm sure it would have blew up again the way I have been driving it.

Anyway..Currently the ignition timing is extremely low at about 9-10° of timing at WOT At 17 psi. And I'm hearing a slight pinging again. Sounds like 4or 5 small ballbearings in a can being shaken around at higher rpm. Almost positive its knocking. But doesn't make sense to me. My afrs are very safe and timing is very low I also run LSPI Protection oil. What else could cause the pinging? Could it have anything to do with changing it from a 3" hoodexit back to a 2.5" full exhaust with a catalytic converter. Not sure why that would mater but that's the only thing I can think of that is different from before when I was not hearing the pinging. I plan to buy the tuner nerd knock monitor soon. But still won't help me solve my issues if my ignition timing is extremely conservative. Thank allot for the advice and help!!

Okay I've come to the conclusion that maybe the pinging I'm getting is coming from carbon build up on my pistons causing pre ignition from the carbon getting hot. I'm going to try some carbon cleaner to help clear some of the carbon out.

Hi Travis, first of all I'd strongly advise you to invest in some audio knock detection equipment if you want to get into tuning. It is invaluable and could literally save you thousands of dollars. The sound you're hearing may or may not be knock and using audio knock gear will let you distinguish from other mechanical noises. You'd almost certainly not hear knock with a hood exit exhaust and even with a stock exhaust that's quiet, you'll find knock begins well before you can audibly hear it.

You may find that your timing numbers aren't as conservative as you think they are, particularly if you're . running the quoted timing through peak torque where you'd typically need to remove timing. You'll also find that adding back pressure to the exhaust system will make the engine more prone to knock. As an aside, knock and LSPI are different types of abnormal combustion. LSPI normally will destroy a piston in a matter of a handful of engine cycles (dependent on specific power level) while knock can often be sustained for some time before damage occurs.

Thanks Andre yes I am going to buy some knock equipment as soon as I have the funds. I haven't been driving in boost much until I figure out what's going on. But I've set my ignition timing pretty safe in comparison to other guys with almost the same set up as my car (same engine& ecu) just until I get some equipment. I'm going to put a much larger high flow catalytic converter and bigger exhaust on also. But I think another contributing factor or maybe the main cause could be carbon build up heating up causing the pre ignition possibly? From running pretty rich for a month or so because my wideband wasn't reading correct. I took a look inside the combustion chamber and seen quite a bit of carbon but i have already got most of it out threw a few different methods. But still not 100% sure this is the only reason it's pinging. Thanks for the help

First thing that comes to mind is if you have confirmed the crank timing marker's indicated TDC position is actually the mechanical TDC, second thing is that you have confirmed that the ECU's reported TDC position, that is is working from, is the actual TDC of the engine.

What I suspect is that you haven't got the ECU set properly and there is an offset that is adding timing that you're not aware of.

You haven't given any information on the actual engine - static compression, charge cooling, boost, camshafts, fuel used, etc. It's possible your particular combination needs a better octane fuel than you're currently using.

It may be something quite off the wall, such as using stock heat range sparkplugs that are causing pre-ignition - tried a couple of heat ranges colder?

Oh, could be late timing causing the exhaust valves to run hot enough to increase the chance of detonation/pre-ignition?

Anyway, as Andre said, a set of cans will allow you to better identify the problem.