I have a tuning issue I'm hoping someone will help with. It's been warming up here in Oklahoma reaching the mid 80's which is just the beginning. In a month we will be over 100 for probably 60 days straight. I struggled with iat's on my civic now I guess I'm going to have the same issue with the Miata. I noticed when iat's get to about 135 and higher she starts to idle lean. Fueling seems ok otherwise. I see there's a table for mat correction but my pee brain is telling me that will effect fueling across the board and not just at idle. What am I looking for to fix idling lean at higher iat's? The fix on my Honda was a true CAI that dropped down in front of the driver's side tire which worked wonders.

What's your MAT table look like? And does it run lean in other scenarios as well when IAT's get over 135*? That's the first thing I'd be looking at.

My FF640s seemed to be very sensitive to injector heat soak as well at idle.

This is my mat table. It only seems to get lean at idle as soon as I start driving it seems normal. Or it could be the temp going back down lol.

https://cimg5.ibsrv.net/gimg/www.mia...937659d60b.jpg

I'll await input from the more experienced folks on here but that MAT curve seems much too flat to me. There's a big difference in air density between 32*F and 140*f. I'd send you my MAT table from my last car but that data is long gone haha. I'd probably check out a couple other MAT tables on here while waiting for more input.

Yea no worries man. It's not a huge deal, yet. It's supposed to be 92 tomorrow and hit 100 by next week so I see this issue getting worse before it gets better unless I get it figured out. I figured it's the mat table but because it's only running lean when sitting idling at a stop light or whatever I'm hesitant to change it because it'll effect the overall fueling not just at idle.

Went over 600 miles today, here are some observations:

I mentioned having to add coolant a couple times the first few days. It seemed to have stabilized and not been "losing" coolant but this morning I had to top off the overflow. Yesterday it was full. So no coolant lost for several days and a couple hundred miles to suddenly being at the low line. I don't think I'm looking at a bad head gasket, nothing comes out of the exhaust. There are no leaks that I've noticed. I would think all the air would have worked itself out by now. The car doesn't overheat and even after driving it 70+ miles straight the temp never goes over 190. So this has me scratching my head.

I still don't like all the valve train noise. When the engine is running that's all I can hear. Even driving. The car runs great, doesn't misfire or act strangely but I do think the lifters are louder than they should be. Googling it and searching here this seems to be pretty common after having a head machined so I just ignore it. For now.

My clutch engagement has moved pretty high. I think I had the pedal adjusted as low as it would go with the other clutch so I don't think there's any adjustment to be made. I don't like the high engagement so I will have to mess with it again and see if I can move it closer to the floor.

Still hate all the drive train slop. I mostly notice it when shifting gears. I put new motor mounts right before I blew the old engine and those went in with the new engine. I feel like the slop is probably in the rear end so I'm going to lift it up when I get a chance and check everything out.

Overall she's running good. I haven't hit more than 2-3 psi yet but I think she's ready. I switched to synthetic oil tonight so break in is over. Just waiting for the new orings for the injectors to get here so I can swap that one out. I'm not sure it's even leaking but I smell fuel when I get into boost so at least I'll have peace of mind.

I can watch the afr go leaner and leaner as ait's go up. When I start the car in the morning it idles at 13.5 at or close to ambient and goes up from there. It seems to hang around 14.5 until temps go over 135ish then it starts creeping past 15. Sunday when me and my wife were driving around town with lots of stop and go it was idling between 15.5 and 16. Only at idle. My mat sensor is in the pipe coming from the intercooler just before the TB. Seems like good placement to me so I don't think it's reading wrong. I guess idling lean isn't the end of the world but throttle response gets a little dull when it's idling lean.

A more realistic MAT correction table would be adding 110% at -40F, 104% at 32F and taper to 100% at 86-100F. Beyond that I normally leave it pretty close to 100%, and use it as a heatsoak abatement table for cars that have very bad heatsoak issues. Of course, those MAT values will depend a bit on what temperature you initially tuned the VE table as well, so adjust accordingly and don't be afraid to adjust further if it doesn't fit your car. There are a lot of variables at play here, even your WUE and injectors will have an effect.

I recommend you give the MAT table more realistic values, tune your idle when the engine has been up to temperature for at least 15 minutes, but not heatsoaked too badly (i.e don't leave it idling for 30 minutes), and let EGO correction remove fuel during warmup/cooler temps. Also move your IAT sensor from the throttle body to the outlet of the intercooler. That has been found to help a fair amount with this issue.

Hope this helps.

Do you not have EGO enabled at idle? Should have around 10% of enrichment. I'd get it nice at hot, around 100-110mat, tune your idle, and make sure -10% can keep you idling around 14.5 when cold, and +10% is enough to keep it at 14.5 when relatively hot.

I don't have ego enabled at all currently. I was trying to get everything figured out first. I'm pretty happy with my fueling overall but still struggling with idle. It idles good but blipping the throttle it hangs pretty bad. Coming to a stop sometimes it'll hang sometimes it won't. Takes several seconds for it to get back down where it's supposed to be. I'm still trying to learn the ins and outs.

At this point I'd be willing to pay someone to help me get the tune dialed. I'm hesitant to take it somewhere because of my last experience with a well known Honda tuner. My car barely made it home after dyno tuning but hey, it made 255hp lol. Tuner said it was an issue with my car, it wasn't. They saw dollar signs when I came through the door.

Yeah you’ll want EGO enabled and more than likely you’re idle ignition control isn’t aggressive enough. As long as you’re meeting idle requirements with TPS and RPM, it’ll pull the RPM down or up until your idle valve closes or opens to the appropriate amount.

Thank you curly. I will mess with it when I get a chance. The only other issue I have is long crank starts when it's cold. Cold being not started for a few hours or more. When it's warm or up to temp it fires right up.

I'm going to suggest that you get the car to where it runs perfectly on the tune and then you can turn on ego just for that last one or two percent of fluctuation. I don't like to run ego because if the sensor goes out it screws you up. I don't always have my laptop with me to be able to turn off ego control.

I spent a few minutes messing with CL idle settings as well as EGO. You can see in the log when I initially turned EGO on it was oscillating pretty bad. Got it to stop messing with the PID then went for a drive and while it wasn't perfect, it wasn't worse than it was. Towards the end of the log you will see when I blip the throttle, the RPM hang I talked about. Not sure how to fix that. Idle afr is much better now, if I can get rid of the throttle hang I'd be pretty happy. Blipping the throttle is pretty sloppy as well, it stumbles then the rpm's go up. It did that on the old motor as well. I didn't think it was doing it initially with this motor but it is.

I just let EGO take care of differences in idle AFR due to temp changes. Also, nice writeup so far, sound like the guy who built your car did some shady stuff so good thing its in your hands to get straightened out and taken care of lol.

Here's my most recent tune if you want to compare EGO settings, I have mine working quite well. I also have an NB1 with a bp4w so they should be similar although for PID values for EGO that shouldn't even really matter.

I enabled ego last night and it seemed to idle well but today it's oscillating a little, between 4 and 5. It's warmer today than it was last night so that might be the issue. Thanks for sharing your tune I will definitely take a look at it.

@boosted_na_2025 You're running about 8 degrees too much advance on boost for pump gas. I suggest you make that 150kPa row 12-14*. I would even lower it if you were running e85. You should also rescale that table to have a bit more resolution on boost.

A few things based on issues you mentioned before on top of the recommendations already shared:
1. seems like you need to tune the idle closed loop initial values.
2. Not enough idle ignition control.
3. Cranking pulse is too low at operating temperature. Raise it at least 20%.
4. The dip in ignition timing at 1k RPM is likely not helping your idle. Make that and the cells around 15-16*.
5. Normally, EGO control uses a smaller P and larger I, with very little or no D. If it's oscillating, reduce P and/or increase D.
6. When using VE analyze/auto-tune lock the idle and deep vacuum cells, otherwise you end up with very low numbers during overrun conditions. I suggest you blend those areas of the table. 20-30VE at 4-6k RPM is not right.

I could help remotely if you send me an request here: https://www.ccmoto.net/services/engine-calibrations

Man, your tune is so much different than mine.

At the advice of running less timing in boost I did steal your ignition table. Had to adjust fueling but the car seems happier. I'm not sure why my ignition table is so aggressive, that's the one that came with the car and since I'm running e85 now I just assumed it would be ok.

I reached out to a remote tuner last night. He responded to my email and said he would look at my tune and get back to me later today. I haven't heard from him. I'll give him the benefit of the doubt and give him some time to reply.

I am done fiddling with the tune. The car runs good enough to drive but I've looked at a hundred different tunes I've come across here and other places and they're all so different for these cars. Seems to be a lot of variables and while I understand the end goal of tuning, getting these cars there is work for someone like me. I'm just ready for her to run good after all the time I've invested. And I'm itching to push her a little bit, afraid to really go without a solid tune.