Stoffl

Just went through the logs from my dyno session on thursday and realised that the knock-in values are much higher than usual and knock retard even kicked in a couple times >6000rpm, going to up 10° retard at one time. From what I can see this wasn't in lean situations.
Setup from this thread https://www.miataturbo.net/megasquir...s-tune-107965/ here but to summarize 1.8 NA Naturally Aspirated, 85mm bore, forged 12:1 Wössner pistons, 1929ccm, ms3 basic from rev. Stock NB knock sensor.
Knock window and knock sensing settings are from revs ms3 basic basemap. No knock was noticed in the power curve / power runs by the tuner but also no detonation cans used.

Here's three logs from said dyno session and my current tune.

So am I actually experiencing knock here or do I just need to alter the knock settings with the new engine rebuild ?

Any input would be appreciated, literally driving to a track day now :welp:

Reverant

iTrader: (10)

Enable knock monitor per cylinder in the knock sensor settings. This will give you infinitely more useful data. The log I opened seems like there's little to no knock, but without per-cylinder data, this is just an average.

Stoffl

Right - this is with knock monitor per cylinder enabled on today's last turn.
https://www.dropbox.com/s/bfma0jerhc...turn3.msl?dl=0
*edit* I guess I wasn't imagining the worse performance on that last turn, pretty much always 10° spk:knock retard.


So it's just a matter of adapting the knock detection sensitivity to the new engine ?

Stoffl

Right - a more sensible approach.
Two full throttle pulls from 1st to 3rd gear - one with 2degrees timing pulled >5800rpm.
Two full throttle pulls from 4th to 5th gear - one with 2degrees timing pulled >5800rpm.
Each set same conditions and same stretch of road, all with knock sensing per cylinder enabled.

From what I can see with my noob eyes the timing doesn't really make much difference. Both logs top out around 100% knock in ?


*edit*
learned that I needed to alter cylinder gain levels to match up knock values. these are the new gain levels and logs for gear 1-3, will have to redo gear4-5 pulls later.

Reverant

iTrader: (10)

Integrator time constant should always be 100 for Mini and Basic MS3s. This is why loading basemaps from the internet is a bad idea.

Also, since these are SD card logs, you want to add knock cyl 1-2-3-4 to the logged variables in the SD card datalogging options.

Stoffl

Noted. Was from a friend who told me how to work out the gain levels.
Do I have to evaluate the gain levels again when this is set back to 100?

Right - another thing I forgot while wondering why my logs from the trackday weren't showing cylinder specific knock levels
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Reverant

iTrader: (10)

Yes. Reducing the time constant will increase the sensed knock levels.

curly

iTrader: (25)

Fix your TPS too, it's going to 105%.

Have you taken a log with no load (aka neutral)?

Also why is your AFR target 11.5, and you're only hitting 12.5. If you're not turbo, no need to go richer than 12.5, but if that's the case, set your targets correctly. It's an easy way to visually detect fueling issues in a log. If the AFR line doesn't closely overlay the AFR target line, look at why. Keep in mind because you "include AFR", you'll have to retune your fuel table after you fix your targets, but you shouldn't have been tuning your fuel table until target was set anyways.

Stoffl

Tps has been acting up - like no idle anymore because the previously set closed value is now suddenly 2,5%. Trying to compensate for that. Better >100% than not reaching 100%?Log what in neutral? The big log from the trackday has minutes of idling in neutral if that's what you're asking?

Yes I'm aware, it's what the dyno tuner told me to do. He's not familiar with megasquirt and I'll most likely have to redo the afr target and ve table.
Attached the afr target table i started with, just redo ve with that ?

curly

iTrader: (25)

Knock. Take a log slowly revving to redline while in neutral. You use this to set your knock threshold. Right now it appears to just be set at 50% across the board. It should increase significantly with higher revs, much like you’re currently seeing in your logs, you just want to make sure it’s not significantly higher than your low/no-load threshold.

Stoffl

Thank you, will do that!

Stoffl

Right - these are current knock settings.





Also compared a 5th gear pull and neutral sweep and the knock is pretty much on the same level. Thanks guys!

Reverant

iTrader: (10)

I see knock on cylinder 3 from 4800rpm to redline. Take note especially at 5847rpm. This is why knock monitor and control per cylinder is essential. You wouldn't be able to see this without monitor per cylinder. Cylinder 2 also shows some slight activity, but nowhere near where cylinder 3 is.

Stoffl

Thank you - exactly what I was looking for. Wasn't sure how much difference is just general noise and actual knock. Have also enabled knock control for all cylinders and will do another set of pulls with -2° timing.

New settings:

Stoffl

Here's another set or runs in 5th gear - one with -2° and one with -4° ignition timing down to 4000rpm.
Are those small spikes on cyl 2 & 3 still knock or am I just looking at general noise levels / variation now ?

Here as pictures.

26° topend / -2°





24° topend / -4°

Reverant

iTrader: (10)

-4 looks ok to me. Some knock in -2. Create a base noise profile by revving to redline in 1st or 2nd with very little load (minimizing the possibility that this is knock). Don't do it in overrun, you actually want some load AND to have active ignition events in your base profile.

Stoffl

Like downhill accelerating in 1st / 2nd gear with very little throttle up to redline ?

btw all of this has been with 100(+) Octane fuel. :/

Reverant

iTrader: (10)

Yes.

Stoffl

Here we go - 1st and 2nd gear run with ignition table from dyno day(28° table).
Ignition Table



1st gear run



2nd gear run







Now the same with -2° pulled from >5800rpm (26° table)
table


1st gear


2nd gear







And once again but with -4° pulled overall(24° table)
table


1st gear


2nd gear






So ok, maybe I should've also pulled timing in the midrange for my -2° table..but then again, why is the 2nd gear run with the -4° table also showing knock around 6000rpm ?
AFR related ?

Stoffl

Also possibly silly question to ask but could loose stainless cable ties and wire on the individual exhaust manifold pipes cause noise inside the combustion chamber / get picked up by the knock sensor ?
Found out during the engine swap that most of the heat wrap had disintegrated and simply haven't had time yet to remove it all and put on the new thermotec sleeves. It's audible at certain load and rpm ranges from driver position.


*update*
Just pulled the plugs - pictures in this thread https://www.miataturbo.net/megasquir...5/#post1635963 - and I guess they confirm detonation on cylinder 2 & 3.
Thank good knock control was running from the beginning.