Spark Knock at 10PSI? 92/93 Fuel
 

I noticed this last night while driving. I believe I'm hearing spark knock / detonation / bacon frying at full boost. I'm only running wastegate pressure which is about 10-11 PSI depending on the day. I don't feel any loss of power, just hear a crackling sound as boost increases.
This seems odd because my spark map is fairly conservative as far as I can tell. It's from DIYautotune's Turbo basemap.

Relevant info:
Stock Coils/Wires
NGK BKR8 EIX
8.6:1 Wiseco
BP4W head
92/93 octane (92 currently)
11:5 AFR in boost
Attachment 229707

I don't have a log currently but can grab one over lunch.

My exhaust is pretty loud so I guess I'm just looking for some opinions / ways to troubleshoot. Any way to verify this is knock? build a set of DET cans?
I'm going to take about 5 degrees out of the boost areas and see if that makes a difference. I may also try to loosen the wastegate and see if I can run more like 7-8 PSI to verify.

Did you confirm base timing when ms was installed?

This

Definitely. I'll do it again tonight, though.

Should be OK, that's a little less than I run and I'm on 91 octane. What's the knock sensor say?

Crazy, looking at the logs it almost looks like the RPM flattens for a moment. Log is attached.

With -5 timing I definitely heard the cracking less. My log didn't capture those pulls (shitty usb cable). I'll try to get another.

Heh - knock sensor? Not running one. This is a MSPNP2, which IIRC has shitty knock sensing anyway. I do have a knock sensor from a 2011 ford fusion - I wonder if I can make that work.

If this is truly knock I bet it's also why I'm seeing increased metals in my oil.

You should run some unleaded race fuel through it with the timing back where it was and see what happens then. With some like 100 octane in there you should get no knock, if you still head that noise perhaps its something else that you are hearing.

This is kind of what I was doing with backing the timing off 5 degrees. I still heard something, but much less of it. I can look around and see if I can get race fuel locally. I'm gonna do some digging on the knock sensor situation too.

Right, dropping the timing should achieve a similar result, but race fuel is so incredibly knock resistant that I think that may be a more definitive test for you. You could always go old school and run it hard then shut her off and check the plugs for salt and pepper.

If you have the stock crank pulley consider it may have turned and might not be accurate. It happens.

Supermiata Damper, hopefully it hasn't shifted.

Check grounds and make sure your coil is bolted down correctly. I had that issue i confused for det and retarding the timing lessened they symptoms, but still existed. Nothing on detcans I turned boost down and it vanished. I noticed one of my coil bolts backed off and plug wires was questionable. Fixed those 2 things and it ran fine.

Some feller on here made electrical det cans and i still use em. Try some detcans. They will tell you for sure.

Too much dwell can have coils fire early.

Cleaned the coil grounds. It's currently grounding to the back of the bottom half of the intake, I wasn't sure if that was correct so I added another ground going to the head itself. The plug wires are old but there's no cracking, I may just replace them.

Checked the timing, snapped a pic of it. I believe this is correct, yes?
I also snapped a lazy pic of my ignition settings (no internet in the garage).

Does everything look kosher?

Whew the mobile upload kills the resolution. Here's imgur links.
https://imgur.com/WTtrfKx
https://imgur.com/EB5camH

That appears to be advanced 10º from where it should be. Looks looks 20º BTDC

...holy shit

https://www.miataturbo.net/general-m...ry-here-89510/

I even posted in that thread. This is blowing my mind. What the hell was I thinking?? That means I've put almost 4,000 miles on this engine with it timed 10 degrees too far. Maybe 3000 of those boosted.
How can I tell if I've done any serious damage? I've had increased lead in my blackstone reports. Bearing damage? I may be able to scope my pistons to see if they show any signs of pitting.

comp/leakdown and just send it.

but man, that's a whole lotta detonation you've subjected it to. poor engine

Ugh. Makes my stomach turn thinking about it. I'm gonna buy a leak down kit today, already have a comp tester. I'll borrow a scope to look for pitting/sandblasting on the pistons. Change the oil. Cross my fingers.

https://imgur.com/a/oKKdP
Left->right 1234

#4 threads are covered in oil, probably just the valve cover gasket but worth noting I guess.

About to get a leak down now

Compression seems fine. I couldn't run a leakdown cause the harbor freight tool uses industrial style fittings and all my shit is "aro" style.

Cold Compression:
Attachment 229705

Warm Compression:
Attachment 229706

I re-timed the engine. I'm gonna get the right adapter for the leakdown and see what it says.

Scope pics. #4 looks really wet. I wasn't using flood protect so it might be fuel. But #4 plug was wet too.
1:
Attachment 229701
2:
Attachment 229702
3:
Attachment 229703
4:
Attachment 229704

Those compression numbers are VERY low. You should be around 160-190 in that range. What CR are your pistons?

8.6:1 pistons, 00 head on 96 block.

Well that may explain a lot since your CR is lower than the stock. It is even across the board which is good though.

Yeah I think the compression is reasonable for my CR. And it's very even. Gives me a bit of hope.

Do any of the scope pics look like there's pitting? It's so hard to tell if it's pitting or just carbon build up. I guess my options are really just run it, or rebuild it. I still need to get the leakdown done today (gonna try to find the correct fittings at the homeless despot).

Numbers don't matter much, consistency does, his look consistent.
And besides that's an HF tester which is known to read notoriously low.
Just send it (run it)

Realistically that's what I'm gonna do. I'm gonna do a few oil changes and just crank the boost up.

Correct, in a follow up post I did say his numbers are even across the board which is good, just lower numbers than I would have expected initially.

OP :

I wouldnt worry about rebuilding the engine just run it. The pistons just look like its a lot of carbon buildup. Hard to tell if there is pitting in the pictures.

The only thing that saved you was 8.6:1 can't imagine how quick it would have scattered at 9.0:1

Leakdown was 20% cyl1 40% 2-4, cold. All blowby. Machine shop set the ring gap loose, maybe that's some of it. Still gonna send it.

Since the leak down is so high you have to run at least 20 psi to make up for it. Send it bro!!