Hello everyone. I acquired a boosted 2000 Miata this evening, my first Miata. It is tuned and has a MS ECU. I don't know much about these cars but after acquiring it, I drove it home 50 miles with zero issue. It seemed to run fine. Seems to max at 8lbs of boost, the kid I got it from couldn't tell me much about it. I really don't know what's all done to the car other than it having a clutch that chatters like crazy when taking off, hoping it's quality. Build seems pretty solid.

My concern is with the AFR, gauge is saying it's running pretty rich. 13.xx cruising and at idle, WOT seems good in the 11's. My only tuning experience is NA k series Hondas but looking at TunerStudio it seems very similar. I am wondering if maybe I have an o2 sensor issue, or if maybe someone could take a look at the tune I pulled from the ECU and maybe give me some advice.

TIA

 

14.7 is stoichiometric but mine preferred idling in the 13s. Cruise can be around 15 if you have a lot of timing advance. More numerically than that would yield a lean misfire occasionally.

11.x in boost is safe and may be a little rich to allow more spark advance in the boosted cells.

Overall, I'd say it sounds normal for these cars. Our cylinder heads aren't as efficient as Hondas and some others so they need to be a little richer.

 

Thank you for the reply. I won't worry about it to much right now.

 

After taking all the kids and the wife for rides in it today, I notice oil has been being spit out the muffler on "cold" starts. Not a crazy amount, but it's noticeable. Do I need to assume the worst and have the engine rebuilt, or should I try a catch can first? I'm new to this platform and just trying to figure things out.

Where could I start a thread on this car and post progress on what I'm doing, maybe get some help along the way? I looked around briefly and couldn't decide where that would be.

TIA

 

You'd want to post a build thread in the builds threads section.

https://www.miataturbo.net/build-threads-57/

That tune is pretty rough, my main concern is the fuel injectors say "440", are they yellow injectors? Those are typically "rx8" injectors, and no one around here has any respect for them. They flow terribly, and most of the time they're knock offs, making them even worse. Get some quality ID injectors or similar, then have a competent tuner retune it on a dyno.

Add your location to your profile to get some tips on who/where that competent tuner might be.

 

I will start a thread there, and update my profile. Thank you. Unfortunately I don't know anything about the car other than it has a turbo. The kid I got it from played dumb. Or sincerely didn't know.

 

Let me try this again. Here is the same tune, with a log. I was hoping to catch it stall during the log, but it waited til I stopped the log to do it. to do it. Car runs good, AFR seems rich during idle and cruising, idle surges once warmed up and dies when pushing the clutch in coming to a stop about 30% of the time.
I attached a shorter log idling to see if anyone could see anything in the tune that would cause the poor idle when warm. I checked at about a 15% for vacuum leaks or hoses that need replaced, nothing really stood out.

 

I'm wondering if the car is tuned on e85? The kid I got it from didn't know, but with it running rich basically everywhere it does make me wonder.

 

I don't think this was tuned on E85, I just don't think it was tuned very much at idle or cruise. I say that based on the fact that AFR's are fairly appropriate at WOT. Timing looks likes its in the ballpark for 93 Octane.

I'm guessing the fluctuating idle is due to the PID settings. You might try changing the closed loop idle to simple and setting the gain to be fairly central. I can see in that first log that the idle looks reasonably stable in open loop, but once it switches to closed loop it oscillates. The Idle valve duty cycle seems super high for closed loop as well. It sits around 39 in open loop and closed loop opens it up to about 45.

Like Curly said, this tune looks pretty rough.

I attempted to make some of the changes I mentioned above. If you want you can load the attached tune and see if it idles any better. I'm not a pro, so try it at your own risk.

 

I will definitely try it, thank you for taking the time. you hit the nail on the head with open vs closed loop idling. That's why I started the log when it was cold, to catch that transition. Wot definitely seems right, but outside of that it's rich with some occasional 14.xx while cruising. Not often. It really does run pretty well outside of dying occasionally when letting off the throttle and pushing the clutch. I just let the clutch back out and it starts right back up, still annoying though.

 

SimBa was close, but I made some more tweaks. Your idle valve was set to inverted, so closed was 100%, which should be 0%. I'd love to test what the min/max duty cycles it likes, and also what it runs at with the idle valve off/closed. You may need some more mechanical bypass if you're actually idling at ~45%.

 

Here is a log with your tune SimBa, she did NOT like it lol. I just started the car and let it idle, didn't drive. I started poking around in tuner studio and found the auto tune function. I used this on flashpro to fine tune my fuel tables on my honda and it worked well so I figured I'd give it a shot. Seems to have gotten afr more in line at idle and cruising, but the car still dies when pushing in the clutch to stop. I got it in the log this time, it'll be towards the end.

 

Thank you sir, I will check this out right now.

 

Alright curly, car liked that one a little better. afr was better, when I first started it idle was a little rough. After driving and coming home it was better. still surging.

 

I just drove the car again, no laptop in the passenger seat. Just drove. Curly, it could be placebo but the car seemed a lot different. Seemed to pop and bang a lot less on decel which I'm ok with. Seemed to get into boost sooner and smoother. Again, I don't know if you changed anything that would effect those things but it definitely seemed different. I like a few burbles on decel but the tune that came on the car was pretty obnoxious lol.

 

I enabled Decel fuel cut, which cuts fuel when you're off throttle. That's why you're not getting pops and bangs. IIRC the delay is 1 second, so you'll probably get a pop or bang and then it'll cut fuel.

Curly made a good catch with the inverted idle control solenoid. I'm not surprised the car wasn't happy with the tune I posted.

I didn't make any changes to the ignition map, not sure if curly did either, but that or fueling changes would be the only reason I think it would be driving/spooling happier.

 

Oh ok, same way we add pops and bangs on Honda's. I just don't know my way around tuner studio to find that stuff. I haven't really had a chance to sit down and go through it. I definitely like the way the car drives better with the tune curly posted for the reasons I mentioned. It's much more refined and less street racer speeder kid. I really need to figure out why it dies though. Someone on here mentioned the vacuum lines going to the ms. I was looking under the dash trying to adjust clutch engagement and realized there are a few lines behind the pedals. Tomorrow I'll double check those in the daylight.

 

The log you posted looks like it was with a different tune that Curly posted. The idle ignition is not kicking in like it should. It's static at -2 degrees and it should be pretty dynamic.

IMO the lazy way to fix the car dying when going to idle is to go to the Startup/Idle menu and change the minimum closed loop idle duty cycle to ~44. It won't give the ECU the proper control it needs to control idle, but it should prevent it from stalling out.

Raising the dashpot offset would help as well, but I think both of those are workarounds more than fixes.

 

I'm 99% sure the log is from curly's tune, unless I posted the wrong log which is possible. I don't think I did though. I don't really want to put a bandaid on the dying issue, I'd rather fix it. I do see this is a pretty common issue with these cars and there has been so many different thing's that cause it might take me a while to figure it out.

 

SimBa, you were correct. That log wasn't from Curly's tune. I'm still trying to figure out tuner studio. When I did for sure flash Curly's tune the car wouldn't even start. I am confused though, the car was back to popping and banging this morning, not getting into boost as early or as smooth.