Supercharged 350Z - Stall and idle issues

[Timboj]

Hi guys,

I've been tweaking a bunch of settings and surprise, I've made it worse (in some ways at least).

Of note, the engine stalled twice in fairly quick succession:

Is there anything obvious in the settings that might cause this?

 

Also, is it normal for the Ign angle BTDC to be so erratic at idle??

 

Map and log:

https://drive.google.com/file/d/169K1cr5QSIsqzOrQbv-rvS72a9txJcCn/view?usp=sharing, https://drive.google.com/file/d/1SdmPKQygUTOdKYkmg2NZOjEJlgnqqmwP/view?usp=sharing

[Adamw]

It is closing the throttle trying to bring the RPM down when you are in overrun.  

Reduce the speed lockout to 10kmh, and reduce the RPM lockout to 500RPM will likely solve most of it.  

 

5 hours ago, Timboj said:

Also, is it normal for the Ign angle BTDC to be so erratic at idle??

Yeah pretty much, yours is possibly a little more than usual.  1.0 for the idle ign proportional gain and 0.0 for the derivative would be what I normally start with so try dropping those.  

[Timboj]

I'm extremely limited by file size here so I can only post a very small png image to illustrate the issue, but while the stall is definitely solved, I've got kind of the opposite problem now where the revs are hanging too high for too long.

I've chosen a section where it's obviously terrible (from about 10:20), but anywhere in the log you'll see the issue show up. Clutching in at low speed off throttle naturally spikes the revs as the load is removed.

What's not pictured (because the file size would be too big) is potentially a too high idle position and switching on and off of idle hold - speed?

https://drive.google.com/file/d/1U-icI53g6G8qHGOZXREGckitq54XGDBc/view?usp=sharing,

https://drive.google.com/file/d/1sm6o9iyjMupmA4P5Q1-m5sCN8Vjw1n2d/view?usp=sharing

[koracing]

Usually it means your base idle position or dashpot is too high.  It needs to fall within the idle target+RPM offset to enable idle control.  Looks like in the pic above idle was on target at 3.5% throttle, but in this one it looks like it may be hanging up a bit higher.  

[Timboj]

Yep. I switched to open loop and lowered base idle (it was too high), and I'm forever tweaking the dashpot... I hadn't realised until just now that under closed loop conditions, the RPM lockout was above target, so that definitely helps to know.

It's much better now, thanks. Still needs some tweaking but it's plenty drivable.

There's no more capacity in this thread for screenshots ( @Adamw any chance this can be increased??) so I can't show what I'm seeing, but I've got a period where I'm idling (open loop idle, idle IGN control ON, closed loop fuel corrections off, no change in APS) but periodically it's switching between the base idle and the slightly higher idle position (2.6% vs 3.1) holding in one position for anywhere between 40s - 2 mins...
 

What setting would cause it to switch between base idle and a higher idle like that?

 

[koracing]

You have a fixed amount of data you can post to this forum.  Beyond that you either have to delete old data from previous posts or you can upload to a cloud storage system like dropbox, google drive, one drive, etc. and then post links to the content.

[Timboj]

Hey guys, leaps and bounds in terms of dialing things in but I'm still still on this issue with the idle sitting too high under certain conditions.

You can see here when slowing down and coming to a stop, the base position is fine but the idle wants to sit 0.5% higher which is adding ~400rpm above target. Do I need to drop the RPM lockout even lower??

For this log I zeroed my dashpot settings (which in general seemed okay).

Map and log:

https://drive.google.com/file/d/1GduvJUcJPgqyCQB9UeDmHKMPCJdza362/view?usp=sharing, https://drive.google.com/file/d/1NC_Evgbw8G404zomMR6yWfnCXGAymn4_/view?usp=sharing

[essb00]

You rather need to raise your RPM Lockout to maybe 500 rpm, then Speed Lockout to just 10 kph

[Timboj]

I'd made a few changes between the last post and now (including what you suggested), which corrected the high idle hang, but I'm finding my revs repeatedly approach stall (450-500rpm) when coming off throttle and slowing down (like approaching a stop).

You can see here idle control doesn't have a chance to catch it because it's still locked out (I've got dashpot set to 0% here but it's a moot point because it had already dropped too low). 

However I've got examples where the speed lockout is set to 25kph but that's still too low to catch the dip before it happens (off throttle but slowing at a faster rate).

 

That same log finished with the car actually stalling out of the blue:

 

[Adamw]

Attach the log and tune.  

11 hours ago, Timboj said:

I've got dashpot set to 0% here but it's a moot point because it had already dropped too low)

What do you mean?  That's exactly what dashpot is for.   If you had say 1% dash pot offset then the throttle would have been held 1% further open until idle conditions are met.  

[Timboj]

Best example is here:

 

I added 0.5% to the dashpot and 0.5s to both timers.

https://drive.google.com/file/d/1OWGOSjehFMc0CP4hUw4Msw0-9m8GMOi8/view?usp=sharing,

https://drive.google.com/file/d/1dqDS512M9Tz3FNThfO7-ioCiRvhoh7KQ/view?usp=sharing

 

I've been working on the understanding that dashpot doesn't kick in until the lockout conditions are no longer met. But are you saying the dashpot offset is on during lockout conditions, but once they're not longer met the dashpot timers are activated and then return it to the base idle position/target RPM?

 

I also have another issue with my cold tune if you wouldn't mind looking. At the beginning of the same log, you'll see it's leaning out as I go to accelerate. Appreciate I'm in cold climate with E85 but these values were already starting to seem a bit high to me? Do I just keep adding and see?

Thanks

[Timboj]

So the penny finally dropped around how the dashpot works. I guess the remaining question there is why the hard limit at 25kph? I'd like to see a little higher as an upper limit as it's not unusual for me to be in neutral just above this speed when approaching a stop, but the dashpot is keeping the RPM above idle until I slow down enough. Or am I misunderstanding another setting that would override this?

Still interested in your response on the cold correction when you get a moment, thanks.

[Timboj]

Keen for your input on the above, @Adamw

[castillaricardo]

The dashpot is meant to hold the RPM above your idle target during open loop, so during the lockout conditions. The idle valve or throttle in your case will be held at throttle target+base position+dashpot+idle up corrections (Fan, AC, etc.) during the lockouts. It seems you already understand that, just wanted to clarify it. I personally use the "In Gear" lockout instead of speed so it goes into closed-loop idle if the car is coasting in neutral. This really only happens when someone else drives the car, I'm always in a gear while coasting. It works well for me, but requires a neutral and clutch switch to work.

Based on some of Adamw's advice to others, I'm using a correction of 8 at full cold for acceleration enrichment on top of the wall wetting settings. Note that my engine has injectors further from the valves than most but I think the wall-wetting settings compensate for that. You might need more Accel Cold Correction in the colder side of the curve.

[Timboj]

Thanks man. Yeah it finally sunk in, but appreciate you taking the time to respond.

What you've described would be great but I'd need to wire in the clutch switch (maybe in future) but I do have a neutral switch so maybe I'll look at that.

If I wanted to coast in-gear down to a stop (clutch in late as possible) I've got a lot more fine-tuning to do as the car bucks if left to its own devices at low speed.

RE cold correction, I figure the answer was 'more' but good to know I'm not unusually high. My scan of a few threads in here were lower than mine so I wanted to be sure. Thanks.

[Adamw]

On 7/4/2023 at 11:51 AM, Timboj said:

I guess the remaining question there is why the hard limit at 25kph? I'd like to see a little higher as an upper limit as it's not unusual for me to be in neutral just above this speed when approaching a stop, but the dashpot is keeping the RPM above idle until I slow down enough.

Generally you dont want the ecu to control idle while the car is moving.  The problem with having the idle control activating at a higher speed is when you are coasting in overrun (in gear etc), the wheels are driving the engine, the ecu can not control the engine speed by closing the throttle.   So what happens is the ecu sees the RPM is above target so it closes the throttle more and more and retards the ignition trying to bring it down to target, but this has little effect since the car is driving the engine.  As soon as you push in the clutch the wheels are no longer holding the RPM up, and because the throttle is now way too closed the engine instantly stalls.  

It is not too common to shift to neutral during overrun so it is not something I have had to consider much.  I dont really see it being an issue if the idle was a little high when coasting in neutral?  

Its hard to tell much from your log without knowing what the driver was doing etc, but the common theme I see in it is you get a big undershoot when approaching idle then it bounces quite a bit higher than target.  I think the undershoot is probably coming from over-run fuel cut and retard.  Try turning that off or setting its deactivation say 500RPM higher so that is not interfering while you experiment with dashpot and idle approach.  

Note the 350Z does have the clutch and brake switch wired in series to DI6 (used for cruise cancel) so you may be able to use that to add some further logic.  Your neutral switch doesnt show any change of state in your log so im not sure it maybe it is only auto's that have that or if it isn't setup correctly.  

For the accel fuel I think it may need higher sensitivity in the cells 2000RPM and below, and probably a bit more cold correction in the 40-60°C area. 

[Timboj]

Thanks Adam. Good pickup on the neutral switch. I hadn't spent any time looking at it yet, other than seeing that there was a DI assigned. I can confirm it's working now that I've switched the pull-up resistor to "on" (it was set to 'off' since I started with the base map).

I can see the brake/clutch switches working (as well as neutral now) so I'll probably look to implement something like what castilla suggested.

I'll bump up those areas you mentioned and test.