TheIglu

Once warm, the car runs good. I've been tuning, but ran into this issue that I can't seem to figure out.

Startup when cold, she has a hard time starting. Will fire but run and stumble at 2-300rpm on a couple (or less) cylinders before finally catching and reving up high (3k rpm+). Sometimes I have to try two or three times before she'll do anything but pop and stumble at very low rpms (under 500). Then she will oscillate until she evens out at a reasonable high-idle.

I captured just my cold start in both logs. My tune is included.

Until she's all the way warm, she tends to idle very high (1500-2000rpm) when in neutral or with the clutch in after driving.

Chowcow

I found that the best way to fix the startup issue was to start with less gas than needed when tuning the table. So I'd start with the cell that corresponds with the ambient temperature and lower it by half. When you crank the car, it'll just crank and nothing will happen. I'll then add 20 units everytime and crank it. As soon as the car begins to catch, you know you just need a bit more fuel.

I started doing it this way because with what you're experiencing right now, you could either be very rich or very lean. So starting from one way helps you narrow down your problems.

TheIglu

Which table specifically? I'm already fairly low in my normal VE Table. Should I be changing the idle VE table?

Chowcow

I was under the impression that you had trouble starting the car. If the car is running but stumbling, check your AFR and tune appropriately.

TheIglu

Yes, trouble starting. Once it's running, it rarely stalls. Though it does oscillate a bunch in neutral. From what I've been reading, it's likely a timing adjustment.

TheIglu

When adjusting timing initially, is there any difference in function from using the trigger offset wizard vs the fixed timing offset entry?

Morello

I've got a rev-built MS3 as well.. Same issue on cold (under 40F) starts. Cranks and cranks, sputtering a bit, until it finally catches and started. Above about 40F ambient it starts just fine.
I didn't get it quite to OE spec but cranking pulse width is where you want to start. Adding more fuel actually helped mine get started. But your idle VE table isn't where you want to be, so I don't know what chowchow is on about.

Braineack

iTrader: (62)

use adaptive timing. Your MS3 should be using timing control to control the idle, over opening/closing the idle valve.

you could also be idling lean, which makes it harder to smoothly idle.

Braineack

iTrader: (62)

Adjust your cranking table, and initial idle duties table. Need to get a good air to fuel ratio in that temp range. Probably not enough fuel if anything.

TheIglu

Is 14.7 happy with our cars for idle or do they prefer richer, like in the 13.5 range?

Braineack

iTrader: (62)

15 is fine, but you want it to be fatter during warmup. I liked 13.5 below 140°F CLT.

TheIglu

So I enabled the adaptive timing with the settings that were pre-populated. No change in behavior, or not enough of a change to notice. Still revs up and oscillates until it's hot. I'm talking 10-15 minutes of driving before it calms the idle. After that, it runs fine.

Braineack

iTrader: (62)

I'd determine my real min/max pwm% value, and turn my PID settings all back to 100 and back to basic and start from there.

TheIglu

I'm starting over. I don't think I got the right flow values for my injectors put in before I started tuning. This whole time I've been using 3 bar values (43.5psi) where my fuel system apparently runs at 4 bar (58psi). So instead of 644cc/min injectors, I really have 743cc/min injectors.

I am going back to the tune I had nearly new out of the box with the MS3. That means starting over, but it also means a clean slate without any of my learning mistakes.

I put in my dead times for my injectors (flow force 640's). I used this table (https://www.miataturbo.net/diy-turbo...5/#post1314428) to put in the following values:

Dead time: 1.261

10v = 168.1%
11v = 138.5%
12v = 119.5%
13.2v = 100%
14v = 89.8%
15v = 79.3%

Going to set my min value for VE Analyze to 1500rpm. What should I put for my min fuel load to keep it from adjusting cells as I go past them? I'm going to turn "include AFR target" on for tuning.

In my original tune, the CLT sensor was not mapped to the "Mazda" sensor. Should I change this to reflect the Mazda sensor in Tunerstudio? I'd say yes, but I've been wrong before.

TheIglu

So after a couple weeks, it runs well. I'm auto tuning only after driving for at least 15 minutes now instead of letting it auto tune as soon as the min CLT was met. I think the heat soak issue with the IAT sensor is the reason for the car always being a little off when tuning the first drive of the day (cool engine bay) vs on my way home from work (hot from sitting out in the direct summer sun all day).


I still have the problem of hesitating to start. When I crank it over, it'll sputter at 400-500 rpm, then sometimes die. Always fires right up normally after that though. It's like the injectors aren't tossing in any fuel right away on first run.

Any thoughts?

Braineack

iTrader: (62)

have you experimented with increasing or decreasing your cranking pulse and/or ASE/WUE?

TheIglu

No, but thanks to this breadcrumb, now I will.


I'll likely start with cranking pulse as this seems to be the most likely culprit. Once running, even cold, it idles fine.

Braineack

iTrader: (62)

start low. drag the pw very low and work up until it catches -- it only needs to inject so much fuel for it to catch -- too much and it'll flood and it's actually harder to get started. but too little and it'll never start (so remember to keep your laptop handy if you make a change). Once the RPM surpasses the cranking RPM and the MS determines the car is running, not cranking, it goes back to the fuel map and enrichments. Also keep in mind that your cranking fueling is always based off your 90-100kPa cells in the fuel map, so if they are outrageously out of whack so will you startup settings be to compensate.

TheIglu

That is the most helpful post I've ever been offered here. Thank you. This gets me started in a direction.

I haven't driven my car without my laptop at least in the car with the MS yet. Typically it's plugged in and running on the passenger seat. That's how I noticed that autotuning twice a day meant it was a never ending cycle of always changing my VE table just a bit depending on a heat soaked engine vs cold.


I know you experienced guys probably get sick of answering these questions, but it seems though everyone has a little bit different of an issue and the learning curve is steep to troubleshooting this stuff. Even after reading the entire Tunerstudio manual and MS manual, taking the real world issue you are experiencing and trying to determine which of the hundreds of parameters in TS to change is a daunting and rather scary task for the uninitiated.


In my long winded way, thanks for helping vs the "well you need to tune" response


I asked Rev about my issues, sent him my tune and logs, but never heard back from him. So this place is all I have for support until I can get it professionally tuned.

TheIglu

Increasing the priming pulse and bumping up my ASE did the trick. Typically it does a crank-sputter-sputter-sputter-die or crank-sputter-sputter-revtothemoon for 5 seconds then settle.


This morning was the first time in months that it fired up normally when cold. I'm happy and will continue to tune.


I wish there was a "A-Z, installing your MS2/3 and getting it to run alright" thread somewhere. The magic "most of our cars need 200-300% ASE" statement I read yesterday on a random thread here was the tidbit I needed to fix my nagging issue.