I start of with a list of mods that are on my 2000 miata
Stock Motor
Sr20 turbo/intercooler 12psi
Log manifold
SGDP w/ 3" exhaust
Synapse BOV
DIYPNP
RX8 yellow injectors
stock ignition

Now a little history
I just recently installed the megasquirt and intercooler. Before I had been running an AEM FIC only pushing 7psi of boost. Car ran well for over two years, but since I wanted to up the boost I wanted to get rid of the band-aids and have a proper setup.

Well I got everything installed and after much learning and time I was able to get it running. It wasn't perfect but it was enough to run smooth and no stalling.

So last night while driving to work the car ran great. Then in the morning it ran like ****. At first at idle every 15 seconds or so the rpms jumped up a little then settled back to normal. Started driving and it started bucking like crazy. Started dying when returning to idle. Wouldn't idle at all. Had to give it some throttle to keep it alive. Idle became stupid crazy rich. I was able to get it home. As long as I gave it enough throttle it would run ok. Light throttle and the bucking started.

I need someone to point me in the right direction. I'm thinking it's not so much a problem with the tune but more a component failure. Maybe no spark on one cylinder. Or, which I think more likely, an injector is feeding way to much fuel.

Attached current tune. Couldn't get a datalog on account of the car barely runs as it sits.

Disclaimer: I am very much a noob when it come to megasquirt so please be gentle with the criticism.

 

First thing that popped out at me is you have your accel enrich TPSdot % set to 25% - depending on how much noise your TPS signal sees, that may be too sensitive. I haven't looked at my tune in a while but IIRC mine was closer to 50-60%/s.

Another thing: While your ignition and VE maps are flattened in idle cells (which is good), your AFR table is not. This could cause some issues/oscillation as EGO takes over. @ 45 KPA, moving from the 800 rpm to 1000 rpm cell jumps half a point AFR - that's pretty large. IMO make <55 && <1200 all like 13.5 AFR.

 

I looked at that also. But this what i had it at when going to work and it worked great. But i raise it to 40 and had no change. I'll raise it more see if i get any change.

I had it originally set it to 100 at i had it running lean at throttle tip-in. setting it to 25 helped this.

 

I would try that. You may also want to switch from closed loop idle to warmup-mode to rule out a issue with closed loop not being tuned well enough.

Further than that though, I think we'll need logs.

 

I would suggest that you disable time based enrichment until you get your base tune in order. Set TPSdot and MAPdot to 1000.

 

So I raised the TPSdot to 45. Drove around for a bit. No bucking. Thanks for the help.

I just gotta do more tuning.

 

So i'm back asking for some more help. (hand holding)

For the entire time i've had the megasquirt installed I have had an issue with stalling when the rpms try to return to idle.

Accel enrichment disabled, using warmup idle, ego control off.

 

So I see several things going on here. First of all, you aren't configured for closed loop idle control. This is under "algorithm" in the idle control section.

I am attaching a tune that you can use as a reference for closed loop settings that work on an SC motor with a 7lb fly, which is a ***** to idle. You also don't appear to be bracketing your idle in your timing map, or allowing for decel loads in any of your maps. You will notice that my VEs are funky at low load, this is due to the friggen lousy injector linearity at low duty cycle.

My motor prefers to idle a little rich. I don't know if this is common or not. Pay attention to my idle advance curve. Idle advance is the shizznit. You also may want to add an advance wall below your target idle RPM.

Man I wish I was running IDs.

 

Oh, and your accel enrich is not disabled

 

I thought I would be able to drive the car using open loop idle until i get a decent tune. I've tried to use closed loop before and still had the same issue. Maybe its time to try again.

I just checked my tune again and it says accel enrich is off. And what do you mean with the idle timing bracketing. The decel loads should be at low kpa right? If so something is up because you can see it the datalog the kpa hang high even as the rpms drop.

 

I am on my phone so I can't confirm the accel, but it looked like you turned EAE and the TPS uses WOT off, but still had TPSdot is a place where it will come into play. Your enrich PWs were off the chart.

Bracketing the idle is where you put the target idle point in the middle (corners) of 4 cells in a table. This allows you to have more control over the operating conditions in the 4 quadrants around your idle, it allows you to have a static AFR target, ... Google "idle bracket megasquirt". Something has to show up.

Once again, I can't view the log, but decel loads (throttle closed) should be lower than idle. Turn the fuel cut on decel off to tune these areas.

 

One other thing is that when releasing the throttle when at a high map pressure 80 kpa-ish the map pressure hangs at this level. You can see this on the datalog. As the car dies the kpa stays around 80 kpa. Is this normal because the engine is dying and not pulling as much vacuum or should the map pressure sensor react faster and I should see a valley where i'm at idle rpm and 0 tps? Maybe this is why my car dies on decel?

 

there is def something funky going on in that log. The min MAP load is almost 60kpa, that is way too high. It should drop down to the 25-35 range at idle.

I would check for leaks in your vac system, especially the line running to the megasquirt. Get the car to idle and unplug the IAC, note if the engine dies, changes RPMs, if the map changes ...

You are also throwing CAM sync errors. I haven't ever setup a NB, so I do not know what the ignition configuration should be, but it would surprise me if these sync errors are to be expected.

It also looks to me like your TPS isn't calibrated.

 

so i little update. The dying when returning to idle is pretty much gone. Happened once yesterday when going to work then not at all returning home. Maybe a little more tweaking is needed. But what i did was added a more fuel in the very low kpa and 600 rpm areas. Not perfect but definitely driveable.

 

Well got some bad news. The stalling is back. And it is back with a vengeance. Every time the car tries to return to idle rpms it dies. Even now I turn the car on and it immediately dies. It won't even idle now. I have not changed anything since a few days ago when it ran pretty good.

 

Have you tried anything that has been suggested? If so what were the results?

Don't change more than one thing at once. Note the results.

We cannot help you if you don't follow the suggestions.

Did the weather change significantly over the past frw days?

 

Noobs helping noobs.

The min kpa is high because it doesnt make any power at idle because its out of tune.

Tune it.

Dann

 

Well i went for a drive today and after about 20 minutes the car started to die again. So I got back home and disconnected to iac while it was idling and nothing happened. Maybe its stuck? Maybe this is also causing my inconsistent AFR at idle.

 

Any chance you can throw the stock ECU back in there to see if you have issues not related to the engine management?

 

Not really feasible. The different sensors would prevent this. Kinda at a point of no return.