L337TurboZ

iTrader: (1)

Lately I have been having an issue as temps outside warm up where I have the car running 0.5-1.0 leaner than desired AFR after extended driving or running errands.

For example today I drove from my work to another part of town about 15 miles away. Car ran fine, AFRs good. Parked the car for about a half hour or so while I talked with a friend then got into the car to leave. Driving back I sat at a light for a few minutes (2-3 max) then noticed my AFRs we're starting to get lean. Desired at idle was 14.7, actual was 15-15.5. Then I continued driving and about 2 miles later during cruising the AFRs we're leaner at 16.5-17. As I kept going trying to get home by the time I got to my neighborhood it was basically full lean on the wideband at 17+ and the car wasn't happy. Keep in mind I didn't enter boost, and kept very light throttle to keep the engine load down.

MAT on TS displayed about 93F and my coolant temps were between 190-200. If I let the car sit and fully cool off then it goes back to normal with AFRs being good.

Car is a 90, 1.8 BPW swap, MS3Pro, FF 640cc injectors, FM fuel rail, stock 90 FPR and 320lph AEM pump. The fuel pump is wired with it's own relay triggered by the Main relay since a long time ago the main relay burned up from the current draw of the AEM. Recently tuned by Speedbyy

Not sure if this is due to a MAT correction issue or if the pump and or wiring is getting hot and a resistance issue is at fault. I know the ground for the fuel pump wiring is good as it's connected directly to battery negative. Voltage is also good from the alternator as TS usually displays 14.4-14.7

I can upload data logs tomorrow as my laptop is at work. If anyone has suggestions or ideas of common faults that can cause this in the mean time it is greatly appreciated. Thanks for any help.

Bryan Z.

Post your data log and tune. Without those we can do little more than guess.

However, there was a thread on a similar sounding issue a few months back, WB reads full lean after highway driving.

I would begin by looking over MAT Air Density Table. Your intake may be getting heat soaked. It might not be the problem, but is a good start. Also disclaimer: I am not an expert when it comes to MS.

Good luck and hopefully this helps.

L337TurboZ

iTrader: (1)

I'll definitely do that in the morning. I had read that thread you linked previously. Without my laptop I can't compare my ADT. I will say that once I had the tune done the car was driving better. However it was about 2 months ago when temps were cooler and I wonder if that's a factor. I have a feeling it is more a mechanical or electrical concern than tune related.

Ted75zcar

iTrader: (2)

Pretty easy to see if the ECU is pulling fuel, or if you have an external issue by comparing the total correction field and the pw field between a "good AFR" log and a "bad AFR" log at similar operating points.

Also your EGO isn't setup correctly.

L337TurboZ

iTrader: (1)

I drove the car again today and it did not run lean. I assume it is a heat soak issue and possibly MAT factor. Here is a copy of the tune and some logs. I tried to isolate an area with the lean issue. I also attached a log that should be running normal before the issue and one while the issue occurred. The tune I posted has Auth table turn ON but before when these logs were taken it was off. I made that change but had not driven it with that setting yet.

L337TurboZ

iTrader: (1)

I could definitely use some help with this. I sent an email to my tuner but it's been days and haven't heard back from him. I'm getting to the point where I'm about to just sell this car and change platforms if I can't get this thing figured out. Been dealing with issues on this car for over a year.

Stoffl

Assuming you get your EGO settings sorted the MAT Air Density Table is where you'd finetune for increased IAT
https://www.miataturbo.net/megasquir...e-89026/page2/

LeoNA

Raise your idle to 900rpm and change the ego authority idle cells from 0 to15%. Change the EGO delay after start to 1. Change all of the 14.7 cells in your AFR table to something better. The lower rpm's can be much lower and for the idle cells 14-14.4. I also recommend learning how to change the X-Y axis values to something that better matches your application. Once you figure that out change the ASE taper to 1000+ to help with hot starts. I also recommend a dedicated timing cell for your idle with the neighboring cells that have the same value. The MAT air density table has been little to no value to me. I run 100% up to 120deg. Also your spark latency is set at 50 which seems high.

L337TurboZ

iTrader: (1)

Alright I'll make those changes and report back. All of the tables and settings were setup or changed by my tuner. What should spark latency be at?

LeoNA

If you use the curser to hover over the "?" it explains how to do it. Strobe is old school for a timing light. I noticed that my timing was falling a little behind and it only required 1. I have no idea what 50 is doing and with 19psi of boost on gas you should be very careful. What is in your ignition table might not be what your actually running. I personally would not run more then 15psi on gas without a good egt setup and substantial amount log time.