rusefi.com

A few people have run into issues with starting using the default NA6 tune. I ran into some issues with poor cold starting recently, so I made this topic to discuss improvements for the Miata and get a better starting point to work from. As far as general tuning of starting and idling, there are two topics about crank/start and idling with some great information in the forum.

I initially had made some changes to mine to improve my idle, but I started having issues with cold starts as the temperatures have been getting colder. My primary issue appeared to be when the car was transitioning from cranking to idling. The car would drop RPM then just die without any throttle input. If I find the correct log I will show an example (or maybe just recreate it).

Here is the default NA6 Tune (https://rusefi.com/online/view.php?msq=703).

BeerMoneyMotorsports had mentioned that his car didn’t have the same cold starting issues, so I took a look at his tune here(https://rusefi.com/online/index.php?vehicleName=Lemon&user_id=1408&sorts[uploadedMsq]=-1&sorts[uploadedLog]=-1). Using that I mostly copied/referenced from the ‘Cranking Settings’ and the ‘Idle Settings’. This in general improved my startups and idling. Some settings such as the Base fuel mass weren't copied. I have a 1.6 vs his 1.9 so I left that at 24.

Here is my adjusted tune https://www.rusefi.com/online/view.php?msq=659

I think the two most significant differences were that I increased the amount of ‘After cranking IAC taper duration’ which will take more cycles to transition from cranking to Idle (this will result in more slowly reducing the IAC and hold the initial revs a bit longer), and I mostly copied the ‘Closed Loop Idle’ settings which seemed to improve the controller response to the dropping revs after the IAC had finished tapering down.

Here is an example of my current cold start with vertical markers.
1. Start of log
2. Just before attempting to start
3. During cranking
4. Starting at the set ‘Cranking base IAC position’ then tapering down
5. Finished tapering the IAC down and transition to idle
6. Idle

You can see in the plot there is a dip during the transition to idle. I'm not sure if that is where others were having problems, but was the primary spot I was having issues.

Thank you for starting the important conversation!

At the moment the toolset for hard-coding default tunes is still pretty limited, so someone would have to be extremely specific about what fields need to be updated and than I am available to adjust those in the firmware - but I am ONLY available to follow the exact instructions, not available to do the research unfortunately.

Great news we have tune comparison tool! (open question if it works perfectly but that's separate)

https://www.rusefi.com/online/diff.php?msq1=703&msq2=659

So what's going on with injector flow? why is it different?



Idle page https://www.rusefi.com/online/diff.php?msq1=703&msq2=659&page=9

Idle page https://www.rusefi.com/online/diff.php?msq1=703&msq2=659&page=10



offtopic interesting differences

Keith wrote: ↑

Thu Nov 04, 2021 3:10 am

I increased the amount of ‘After cranking IAC taper duration’

I am super confused now.

Default says 200?
Jesse say 100?
You also say 100?

Ideally I would need exact instructions: "change default parameter XXX default value from YYY to ZZZ"

I've set defaults at least for three io pins https://github.com/rusefi/rusefi/commit/4f05d088ddd101be8aefd03823e91c234a258215

Sorry, some of the confusion is due to how I adjusted based on my prior settings, not from default. I should have mentioned clearly that I had a different starting point. The injector setting is based on info I saw online when I did the initial setup, it looks like that is incorrect. They were rewired for sequential so that change is correct.
I didn't give exact changes because im not sure that you will want to copy what I have now exactly. It does start up okay cold so I figured I'd at least get this topic started. It might be more useful to start from default and take better notes about the changes. I should have time this weekend to work on that.

TL,DR: at the moment we are missing the _process_ / _strategy_ and separation of responsibilities is unclear to me.

Personally I can only insert exact values into exact fields. Personally I have zero capacity to make decisions on values. Which begs the question of: who would be making what decisions and what is the process we are following here.

hey Keith. the dying when going from crank to idle will be related to your cold iac and fueling settings. the taper doesnt seem to matter too much if those are right. so your coolant multiplier for iac needs to be adjusted higher or your open loop setting is too low i think.

This is default while this is what you have now copied from mine. I am noticing that your min/max is 0 which means the closed loop idle cant really do anything. they need to be something like -15/15

Thanks for pointing all of that that out. I did see the offsets were wrong when looking at the differences Andrey linked. I definitely have some things that aren't correct so I do need to go back through the tune. I should have some time to more carefully go through it this weekend.

I still need to adjust some things, particularly with the idle settings, but I started from the default settings and made some changes. Here is where I am currently at https://rusefi.com/online/view.php?msq=719
Here is a compare https://rusefi.com/online/diff.php?msq1=719&msq2=703

I had to change some of the inputs such as AC and clutch, and adjust for some sensor inputs.

For cranking settings,they were okay when the ambient temperatures were warmer, but with lower temperatures it started to become more difficult to start the car. I copied most of Jesse's setting since they seemed to work, but I did use far fewer cycles for the fuel duration multiplier and adjusted setup the cranking IAC a bit differently.
Cold start log https://www.rusefi.com/online/view.php?log=410

For Idle I could still use some adjustments, but the one of biggest things I noticed was the Min / Max values under the offset. It caused some excessive oscillation in the idling RPM, probably bouncing between idling and coasting. The Warmup Idle multiplier also helped to keep running after cranking while cold.
Here is a start and idle log while a little warmer https://rusefi.com/online/view.php?log=411

Morning cold start https://youtu.be/qso1dYWL4hQ
Less cold morning cold start https://youtu.be/g7RJxg9wj4U
Afternoon cold start https://youtu.be/27-ZW8xx-NA

Great work!

And colder days are coming so this would have to be continued? Valuable data thank and it has to get into default settings one day!

The temperature has been fluctuating a bit but I had a few colder days again. I was able to crank and transition to idle okay with my current settings. I did end up making some additional changes by reducing Warmup Idle Multiplier in some places and increasing the target RPM for colder temperatures. It would end up exceeding the target + upper limit go into coasting, and not go fully into idle state until it warmed up.

I did notice that the IAC value seems to have some limits on where it works the best. For example when I start getting below 20 and closer to 10 it would start increasing RPM. So I will need to play with that some to determine where I should have that and use the idle screw to help. Also I do have the coolant controlled idle air valve still attached to the intake manifold. I'm thinking it is probably the unnecessary since we can control IAC and have modifiers based on CLT, but that will impact the air during warmup and I'm not sure when it switches.

Here is my most recent tune https://rusefi.com/online/view.php?msq=739
Compare to default https://rusefi.com/online/diff.php?msq1=739&msq2=703
Here is a video of the startup (around 0C) https://youtu.be/-IiYGa08DyU