mrelia100

So a little about my car, I have a 2001 NB2 base model 5spd https://imgur.com/Bi4y88q, no A/C. I'm working on a turbo build but before I do that I wanted to have a reliable ECU to work up from. I went with a DIY MS3 + MS3X + DIYBOB122Pin. https://i.imgur.com/g8l49mp.png

I followed mainly trubokitty.com's build guide with a bit of extra knowledge from Frank's Westfield MX5 guide I found and general internet searching.

So the car starts, I did all the checks from the MS3 manual prior to check for crank signal etc and it looks good. Also did a continuity check of the circuitboard and output pins before hot gluing everything in place to ensure no short circuits. I have a AEM X-Series wideband wired in, but haven't put in the wideband O2 sensor yet. They thought it was an O.K. idea to not have a narrowband output on their new wideband UEGO for some reason?? So it is still a narrowband for now as I can switch from megasquirt to the stock ecu easily with the 3 nippon connectors to drive around in the meantime. I also do not currently have the GM IAT sensor yet (I'll be getting it soon), so I'm running off the stock IAT + snorkel intake + MAP sensor vacuum line off the intake manifold.

My problem is with starting and tapping the throttle. (I haven't started driving with it yet) When I start the car it immediately jumps to to 2.5k, slowly creeps to 3.2k over a period of 5 seconds, drops to idle speed, then dips below idle speed, and then jump and repeat the process from 2.5-3.2k rpm's again. I had driven the car recently when I tested so the coolant was at 70C / 158F. This happens 4 times or so and then it will settle. Touching the throttle in the slightest after that will cause it to do a repeat of before one time. I don't have the wideband in so the AFR is pretty vague for me to see what's happening.

The tune is identical to the one found on trubokitty.com except for changing wideband->narrowband and GM IAT->Stock IAT and turning off A/C idle up.
Clip of problem:
If there are any related resources or tips I would be very thankful!

Braineack

iTrader: (62)

wha tbasemap did you use? sounds like you should actually put the WBo2 in and see whats going on with your fueling...

Artifex

Could it maybe be that Closed loop idle is enabled?
kind of a random suggestion but a friend's car that I helped with the initial setup and tune had a wonky, oscillating idle out of the box. CL idle was enabled on the basemap he used for some reason. We flipped it to open loop and it idled much better.

I 2nd brain's notion of plugging in the WBo2. More info is always helpful.

Braineack

iTrader: (62)

ugh I'm so sick of people saying to use open loop....

mrelia100

Artifex

I don't mean use open loop indefinitely. I understand closed loop is better in every way.
From my understanding and research, I thought the best practice was to run open loop at first until you get your VE table somewhat dialed in. Then start setting up closed loop. I'm all ears though if I'm wrong in my thinking.

mrelia100

Braineack

iTrader: (62)

i have a feeling your biggest problem right now is fueling.

mrelia100

Alright I got everything installed, wideband (after a couple of hours wrestling with o2 sensor), and the stock ECU is now gone. So the issue still is the same, and I should mention I haven't checked my timing yet, is that something necessary for NB2's? It appears it is leaning out causing it to oscillate.


I have the AEM 30-0300 X-Series, and the 2 AFR calibration points were off in the selected menu so I made a custom wideband AFR calibration: https://imgur.com/dIpaKF0 https://imgur.com/RMB1YyC
Any reason the 'gauges' in tuner studio are off? The voltage input is correct based on the AFR table in the manual.

Another video of tapping the gas:

mrelia100

Here's a screencap of tuner studio I did today. When it first starts it idles pretty well, then it starts to fluctuate when it warms up. I turned on idle advance for this but it didn't help much.

Artifex

Have you tried lowering the Closed Loop initial value table?

When tuning my car for CLI, lowering the initial values fixed the slight rev hang I had on throttle lift. Off-throttle after free revving (or clutch in when coming to a stop) the idle would hang at ~1500 and slowly settle to the target RPM of 950. This could be an apples to oranges comparison as my car is a '91, but my initial values wound up to be much less than yours. 25-40.

This is clearly much less than what you're experiencing, but it seems similar. I hope this helps!

mrelia100

Awesome thanks Artifex, I halved the values in the table to around 35, turned off Idle advance and it idles great now! Hovers around 14.7. Revving acts like it should too. I also fixed the AFR wideband settings, had to change it from narrowband to wideband in the project properties. Starts are a little rough, but it returns to idle pretty quickly now.

Now my next problem: On acceleration, it sounds a bit like diesel engine from what I assume is preignition? Its somewhat difficult to hear in this video, but I'm not sure what to change up.

Skamba

In that clip we don't see AFRs going higher than 8. You sure everything is set up right?

mrelia100

Yeah that is weird, AFR gauge looked OK while driving but tunerstudio had it way off. Anyway I set up a fresh tune file as I messed with too many settings. Idles slightly rich after coming off the throttle a couple seconds.

Artifex

It seems like you just need to sort out the gauge and TS AFR readings then go for an auto tune drive. Then go from there.

mrelia100

AEM and tunerstudio are now in sync, Idle's and revving only need some fine tuning to prevent overshoot but overall I'm happy with it. I bought tuner studio MS and did a tune analyze live for about 30 minutes regularly applying and saving to ECU. On throttle it still sounds like a diesel, if I floor it it is around 30% less power than stock, and will have a soft rev limit of 4.5K for some reason. Actual set rev limit is 7200 with no launch/2step. I followed these steps on setting timing https://www.miataturbo.net/megasquir...ruggles-85037/ and everything was fine and didn't need to be adjusted.

Skamba

Could you post your latest tune and a log where you hit the soft rev limit?

You might also have to calibrate your TPS as it doesn't seem to get over 40%. Probably not the reason for your issues though, but will help to analyze the logs.

mrelia100

Sure I made a video synched up with audio/megalogviewer. Floored it twice, it started to bounce a bit around 4600rpm.
I also attached the tune and logs. "SecondLog" is the one seen in the video. TPS is good, just didn't want to floor it in a residential neighbourhood!

Skamba

Taken a quick look, doesn't look bad at first glance. My guess is that you're not running on all cylinders - the sound does kind of remind me of a two-cylinder.

Artifex

I agree, it doesn't look bad (the video) but it does sort of sound like you're not running on all 4 cylinders. You also mentioned that it feels down on power too right?

If you have any feeling that it could be detonation/ping, pull 2-3° of timing in that range and see if anything changes.