Link E36G4X Idle Questions

[Adamw]

Mostly dashpot I would say, it looks like you have zero.  You will likely need to set base position back to the correct value, add some dashpot offset and experiment with dashpot hold and decay.  You can do this by giving it small throttle blips while watching how RPM approaches idle target in a time plot.  Adjust 1 dashpot setting at a time and watch what the approach looks like after each adjustment.  Increase offset or hold until it doesnt undershoot.   

[essb00]

Pls attach your latest tune file used to record that log.

[Ryno]

Here is the complete tune. 

 

[Adamw]

That doesnt appear to be the map that was in it when that last log was produced.  Many of the settings in it dont match what is recorded in the log.  

Its pretty hard to advice adjustments when we dont know what settings gave us the data we are using to determine those adjustments.  

[Ryno]

I did update the cranking enrichment and WU enrichment settings this morning to correct lean stumble on start up and long crank@ lower temps. Dash pot I also adjusted as stated above. The idle seems to under shoot less but cannot confirm fix as I have not road tested yet. Ill post a new log if the engine stalls again... 

[Ryno]

Spent about two hours adjusting my settings and I am still have issues with undershoot. After a road test of normal driving the engine did stall again. Adjusting the dashpot settings individually I can see where they change the idle entry. My main issues now is no matter what settings I test I always end up with under shoot.  A slight blip to the throttle will rev up and enter idle smoothly but if I rev up to maybe 4500 or closer to redline the idle entry will always under shoot (deeper undershoot) even if the same settings don't under shoot on lower engine speed revs. 

1. I feel I am not fully understanding the procedure to tune this feature correctly.  Do I tune min clap first then move onto dash pot and decay? Is the min clamp even set correctly as is...? Not sure if the order matters.

2. No matter what settings for dashpot or idle settings I set the engine always under shoots to a small degree. Should a properly tuned idle entry not under shoot at all? Is it ok to have a bit of under shoot as long as the car doesnt stall? Ive ran dashpot up to 20% or so and I can clearly tell it's too high of a setting (revs bounce off idle base position then settle depending on my hold and decay time. What is a normal dash pot setting for this engine?

Attached is my current tune, a log example and a screen shot showing the idle entry and undershoot (pink line). 

Alot going on in this post. Just wanted to get it all out there as this is the main feature I cannot figure out and it seems to be very inconsistent when adjustments are made. 

 

Any help appreciated. Thanks to those who have contributed so far. 

 

* Note some settings related to idle adjustment may be different in the tune and in the log as I have been changing dash pot and idle base to try and find a happy place where the engine operates correct.

 

 

 

 

 

[essb00]

Try to load this one and try to do the same tests and logging.

E34 Tune.pclx

[Adamw]

Change your RPM lockout above target to 500RPM.  With it at 1200 your dash pot is kicking in and will be all finished before it is anywhere near idle.  

[Ryno]

On 8/31/2023 at 6:12 AM, Adamw said:

Change your RPM lockout above target to 500RPM.  With it at 1200 your dash pot is kicking in and will be all finished before it is anywhere near idle.  

Changed to 500 and it made the undershoot worse. 

On 8/31/2023 at 2:53 AM, essb00 said:

Try to load this one and try to do the same tests and logging.

E34 Tune.pclx 474.8 kB · 3 downloads

The undershoot did not change with these settings

 

 

 

Here is  a new log 

 

 

Thinking I could have an issue mechanically with the car causing this but the engine ran perfect on stock DME.. 

[essb00]

On the last log, I can see that your lambda dips on closing throttle and takes too much time before recovering. You at least have to tune your fuel table to the idle regions before fine tuning the idle.
Plus, I recommend put maybe 10-20% for Wall Wetting Compensation.

Closed loop lambda low rpm lockout change to 500rpm.
AFR Target table at least put 14.7 for idle regions as well. Are you using pure gasoline (no ethanol)?

[Adamw]

If you look at where I have placed the yellow cursor in the pic below, your rpm is already below target when you start to decay.  Obviously if you close the idle valve when the RPM is already below target then it is going to undershoot more.  The hold should end with the RPM above target, then the decay brings the RPM gently for the last bit.  So you need more offset or a longer hold (I think probably a bit more of both).  They both have a similar effect, but often a larger offset with shorter hold works better than a smaller offset and longer hold.    This seems to vary a lot from engine to engine, so I cant offer a good one-size-fits-all suggestion, you have to experiment.  

You will also notice just before 0:22 the idle status jumps up and causes an overshoot, this is because your MAP went above the MAP lockout, so you need to increase the MAP lockout.  

[Ryno]

^ Thank you for the explanation and the screenshot. I will make adjustments. As for MAP Lockout I assume this setting here needs to be increased.

[Ryno]

Made some more adjustments and this is what Ive got. Undershoots and stalls... 

 

Any help appreciated.

 

 

E34 Tune smoothed maps AFR MAP LOCKOUT 80kpa.pclx

[Adamw]

On 9/2/2023 at 12:16 AM, Adamw said:

The hold should end with the RPM above target, then the decay brings the RPM gently for the last bit.  So you need more offset or a longer hold (I think probably a bit more of both).

Same still applies.  

[Stranger24]

@Rynohope it is ok to revive an old thread, I have the same exact issue and car is e36 with g4x. spent hours with dashpot and still having same issues. Did you fix this at the end ?

[Adamw]

Attach a copy of your tune and a log showing the issue.  

[Stranger24]

Thanks Adam appreciate it, before I waste your time, i re read all thread and can confirm my accel and overrun is off. Could accel impact this? It is off as I am still doing base table

 

it only happens when i rev the car high say past 4k and when it drops my dashpot can’t hold it and it goes down to say 300 rpm and shut off

 

i also noticed in some areas of my log, idle valve didn’t kick in as my mgp was above 60kpa I had set probably because car was going to shutdown and mgp raise to 100kpa/ 14.7

 

would you disable lockout using mgp, maybe that is the cause or accel enrichment

 

[Vaughan]

18 hours ago, Adamw said:

Attach a copy of your tune and a log showing the issue.  

Probably best to do this at it will show what is happening on your specific vehicle.

[Stranger24]

sure, here is link to my log file, map v1 and map v2 which was modified based on log file using mixture map 

 

https://we.tl/t-TwwcEQmiXW

[Adamw]

Your idle gets very lean as IAT increases, I cant really see an obvious reason for that so you need to investigate that and improve that.  The IAT trim is only pulling 1.5% out at 60°C which is less than typically required so if anything it should go rich.  The Injector PW's look similar comparing areas where it is lean Vs on target.  Your injector deadtime table is using fuel pressure instead of differential fuel pressure but that doesnt look like it is contributing in this case.   

Some of the stalling is caused by this change in mixture, you can see at the end of the log when hot it needed 46.5% idle valve to idle on target whereas it only needed 40% earlier in the log when lambda was on target with all the fans working etc. 

What injectors does it have?  What is the fuel?  Some of the bosch CNG injectors give terrible variation with fuel temp.  Is the IAT of 60°C towards the end of the log realistic?  ECT and IAT match at the beginning of the log when cold so that suggests it is accurate.   

As for idle control settings, we need a repeatable base position before we can really evaluate those, but the main ones that I would change initially are in green below.  

   

 

[Stranger24]

thanks Adam injectors is bosch 900cc, I am still getting fuel map sorted on road

 

re idle gets lean as iat increase, any thought on what could cause it ? finally re map lockout of 80kpa, what would happen if you set this to high say 100kpa / 14.5 psi as I see in log in areas as car is about to stall mgp is around 100kpa and map lock out kicks in. appreciate the advice

 

re fuel pressure table, I have fuel pressure regulator which is 1:1 . would you expect to see ecu referencing diffrential fuel pressure so it changes injection timing depending on raised pressure? I say the answer is yes, just tryng in my mind to distinguish between role of regulator and how that relates to the ecu calculation of injection pw

[Adamw]

2 hours ago, Stranger24 said:

re idle gets lean as iat increase, any thought on what could cause it ? finally re map lockout of 80kpa, what would happen if you set this to high say 100kpa / 14.5 psi as I see in log in areas as car is about to stall mgp is around 100kpa and map lock out kicks in. appreciate the advice

MAP lockout higher than necessary is generally not an issue.  It is just a lockout to prevent idle control kicking in when you dont want it to.  The mixture leaning with IAT I dont have a theory for, this is why I asked what fuel, what injectors and if the IAT is accurate.  Injector part number would be more useful than a size. 

 

2 hours ago, Stranger24 said:

re fuel pressure table, I have fuel pressure regulator which is 1:1 . would you expect to see ecu referencing diffrential fuel pressure so it changes injection timing depending on raised pressure? I say the answer is yes, just tryng in my mind to distinguish between role of regulator and how that relates to the ecu calculation of injection pw

 I was talking about the deadtime table.  Differential fuel pressure is what affects injector deadtime (difference between pressure on top of the injector compared to under the injector).  At idle for example if you are idling with 300kPa fuel pressure in the rail and -70kPa in the manifold, then differential pressure is 370kpa, you should be applying the deadtime that is quoted for 370Kpa pressure, if you had fuel pressure on your deadtime table then you will be applying the deadtime for 300Kpa pressure instead of 370kPa.  

[Stranger24]

Sure injector number is ev14-xt-900 as sold but bosch number is 0280158040

 

my iat is bmw e36 standard one inside of the manifold so maybe heat soak when sitting idle as most cars have iat just before throttle body I think. Could that be a cause ?