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Hey y'all, I have been running MegaSquirt N/A for a couple of months & I would appreciate a review of my tune. Eventual goal once I am confident in the tune is to install my kraken turbo kit. I have been tuning over time following tutorials and things but I am very much a beginner to MS. Please don't hesitate to share feedback
Everything had been pretty good until I was messing with my tune today & I had a weird knock event. Seems the car exited overrun but the fuel cut continued for another 5~ seconds. Any ideas what I can do to resolve this?
Knock for each cylinder generally hovers around 3.5~ going up to 5/6 at certain times. I've been trying to pull some timing to keep it in the 3-4 range. Am I being overly cautious or am I risking my engine by consistently going so high?
My understanding of this might be limited but where are you getting those knock sensor settings from ? Doesn't look like anything I'd expect on a Miata.
What sensor is this ?
Why is your knock scaling linear for all 4 cylinders ?
Why is your knock input threshold NOT linear ?
Your knock sensor inputs should look like a noisy analog signal, it's basically a microphone. Your log looks like a digital delta voltage signal on an oscilloscope.
I’m going to be honest maybe I missed something during setup but I really did not see much about the knock. It is using whatever knock sensor comes with a 2000 NB & the values from the base tune.
The full log looks like what you are describing. It’s specifically this chunk where there is knock reported & it is rather strange.
Yep stock engine and compression ratio, & I’m running 93 pump gas. I have really only seen the knock like that this time. It looks like the fuel did not start when overrun ended.
- The knock settings are incorrect, mainly the bandpass frequency. Try the settings in this post: https://www.miataturbo.net/megasquir...1/#post1651838
- AFR targets are too lean in my book. Contentious point, I know. But you shouldn't be leaner than 12.7 at NA WOT and I wouldn't target more than 15.2 at cruise. Personally, I run 14.7 at cruise. I see spikes in your AFRs around 15.6 which usually indicates slight misfires.
- Turn off EAE until your engine is fully tuned and you have lots of time to play with it. EAE will change your fueling based on what it is attempting to model. The spot in your log you're asking about was caused by EAE as it was at 0 (pulling all fuel, look at the correlation between EAE1 and PW too). EAE is active all the time, even in overrun. Here is a good writeup on the forum: https://www.miataturbo.net/megasquir...eae-ms3-83753/
- The knock settings are incorrect, mainly the bandpass frequency. Try the settings in this post: https://www.miataturbo.net/megasquir...1/#post1651838
- AFR targets are too lean in my book. Contentious point, I know. But you shouldn't be leaner than 12.7 at NA WOT and I wouldn't target more than 15.2 at cruise. Personally, I run 14.7 at cruise. I see spikes in your AFRs around 15.6 which usually indicates slight misfires.
- Turn off EAE until your engine is fully tuned and you have lots of time to play with it. EAE will change your fueling based on what it is attempting to model. The spot in your log you're asking about was caused by EAE as it was at 0 (pulling all fuel, look at the correlation between EAE1 and PW too). EAE is active all the time, even in overrun. Here is a good writeup on the forum: https://www.miataturbo.net/megasquir...eae-ms3-83753/
Thanks, tweaked my knock sensor settings to match what you provided & lowered the max AFR to 15.4 & will continue to tweak that.
I also turned off EAE but the knock still happened under the same conditions. Overrun ends but it seems the fuel cut remains.
The stock NB knock sensor usually won't output enough voltage to matter. I've never seen a knock code on an NB, even with it unplugged. I'm half convinced it's just to throw a CEL if you forget to install rod bearings.
Install a Bosch donut type, it'll give you a decent 0-5v signal, I usually see 0.05v max from an NB unit, most of which have their potting mixture melting out.
I'm no expert with knock sensors on MS (I've got MS2 and never attempted to even mess with it beyond using the headphone jack to listen), but if it is happening during decel I personally wouldn't worry about it but simultaneously it would **** me off not being able to fix. Its weird that the worst of it is only showing up on a single cylinder... let alone that everything else looks great except for the one section in your data log where it appears to get really bad.
The stock NB knock sensor usually won't output enough voltage to matter. I've never seen a knock code on an NB, even with it unplugged. I'm half convinced it's just to throw a CEL if you forget to install rod bearings.
Install a Bosch donut type, it'll give you a decent 0-5v signal, I usually see 0.05v max from an NB unit, most of which have their potting mixture melting out.
@LilPlum One thing to note about the Bosch sensor is that it's too small for the stock bolt. I believe the Bosch is sized for an m8 bolt, while the Miata uses an M10. So if you do go that route you'll either have to drill out the sensor, get a custom m10->m8 conversion stud or figure out something else. Not a very hard issue to remedy, but something to note.
Still have no clue how you manage to get your knock signal looking like THAT.
My knock sensor settings with NB oem knock sensor (different bandpass frequency because 85mm bore/cylinder)
And a log from the knock sensor looks like this:
I think your knock sensor is either broken, wired up wrong or the settings are still fubar.
Knock sensor is supposed to be connected through a shielded cable and connected to signal ground of your ms3.
I didn’t make any changes to it, maybe it’s just past its prime. I’ll see what the donut reports.
Originally Posted by SimBa
@LilPlum One thing to note about the Bosch sensor is that it's too small for the stock bolt. I believe the Bosch is sized for an m8 bolt, while the Miata uses an M10. So if you do go that route you'll either have to drill out the sensor, get a custom m10->m8 conversion stud or figure out something else. Not a very hard issue to remedy, but something to note.
Thanks for the advice. I’ve read a threadsert can handle it as well. Will I need to splice into the wiring harness to change sensors?
@LilPlum One thing to note about the Bosch sensor is that it's too small for the stock bolt. I believe the Bosch is sized for an m8 bolt, while the Miata uses an M10. So if you do go that route you'll either have to drill out the sensor, get a custom m10->m8 conversion stud or figure out something else. Not a very hard issue to remedy, but something to note.
Click on the link in my previous post.
Originally Posted by LilPlum
Thanks for the advice. I’ve read a threadsert can handle it as well. Will I need to splice into the wiring harness to change sensors?
Yes, cut the stock knock sensor plug off, crimp on a DT connector like this:
This is the first link I found, might be able to find a 2 or 3 pack for even a bit cheaper. Then make a small jumper from the stock plug to the knock sensor. The plug is directly off the donut, and it's hard to reach with the intake manifold installed. If you do it this method, you can still easily unplug the harness to flop it out of the way for injectors, valve cover gasket, etc.
This is the first link I found, might be able to find a 2 or 3 pack for even a bit cheaper. Then make a small jumper from the stock plug to the knock sensor. The plug is directly off the donut, and it's hard to reach with the intake manifold installed. If you do it this method, you can still easily unplug the harness to flop it out of the way for injectors, valve cover gasket, etc.
Perfect, thank you for the help, I really appreciate it.
Ah, apologies I thought it was the correct size. There were some members here making adapter studs in the correct size though. I thought I had clicked on Miata specific stuff from ballenger
I called that out because I'm pretty sure I found that same thing on Ballenger and almost ordered it.
Like I mentioned before I used a step bit to widen up the hole and continued drilling it out with a regular bit. I know others who have done this as well, it's just not as plug & play as that custom stud would be.
Knock and Tune Review
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