Parameter(s)/Table(s) to set the desired idle speed in low range? GPEC2/Wrangler/3.6

[HaasExp]

Hi all,

Just wondering if anyone has come across the correct parameter(s)/table(s) to set the desired idle speed when in lowrange with D/R selected?

In high range (2wd or 4wd) the desired idle speed in D/R is 680rpm (or 650rpm in low idle mode). This can be easily set via the various tables and parameters that are currently accessible through HP tuners.
However, once low range is selected the desired/commanded idle speed gets bumped up to 784rpm in D/R. Furthermore, the desired/commanded idle speed gets bumped up even more to 900rpm when the vehicle is slowly rolling (4-5kph). The rolling/moving table idle speed table [ECM] 34305 does not set the idle speed when in lowrange, only high range.

This all becomes quite an issue with extremely low gearing (transfer/diffs) as the bump in idle speed causes the vehicle to try and drive over the brakes. Not particularly what you want when you are about to descend a rather large ledge.

Anyone else experience this or have any ideas?

[dhoagland]

Post up your tune

[Dozer]

Easy try might be raising the [ECM] 44216 Stopped VSS found under Engine, Idle, General. Maybe try 5mph. It should keep the idle at PN idle rpm under 5mph. Only reason I say easy try is I have only found 1 table in the Jeep tune listing 4lo. Its in the trans settings for maximum allowable torque for the trans in 4lo.

[HaasExp]

Easy try might be raising the [ECM] 44216 Stopped VSS found under Engine, Idle, General. Maybe try 5mph. It should keep the idle at PN idle rpm under 5mph. Only reason I say easy try is I have only found 1 table in the Jeep tune listing 4lo. Its in the trans settings for maximum allowable torque for the trans in 4lo.

Cheers for the suggestion. Ill see if increasing the stopped VSS will stop it creeping to 900rpm desired once it starts rolling. I guess there's currently not much I can do about the idle speed bumping upto 784rpm when in lowrange D/R which is a bummer. This is the biggest issue.
Shame I dont have access to the .bin file so I can hunt for these unmapped parameters myself.....

Tune file attached

2013_JKUR_StockTune.hpt

[Dozer]

From what I understand the idle is torque based (airflow and timming) to control idle rpm.. You could lower airflow and timming in the idle tables to create less torque at the same idle rpm. Being in 4low due to the huge gear reduction you are feeling the same torque used in 2hi being transfered to the wheels. The nag1 trans tcm dose not have and provisions in the tune for 4low. The tipm intercepts the trans calculated output speed signal and feeds in your 4low tranfercase gear ratio to make the ecm and everything else happy. I could be wrong but thats the way I understand it. Might not be any bin files hidding due to the nag1 trans.. The 6 speed and 8 speeds have tuning for 4low in the tcm.

[Dozer]

Your same problem I took in consideration when doing a 5.7 hemi into my 13 Jeep jku rubicon with the 4.1 low range t case. I went with a higher then stock stall torque converter. I do not have this issue in 4low with the 5.7 in my jeep.

[HaasExp]

Might not be any bin files hidding due to the nag1 trans

I'm very sure there is a desired idle speed table somewhere in the ECU for 4low regardless of the trans as even the manual vehicles bump up the idle speed when in 4low. I guess they implement this to help with throttle control and stalling with the manual. With the auto it is definitely not needed.
I might be able to play with the closed loop idle parameters to try and limit the throttle opening/spark advance but I guess that would have repercussions elsewhere eg start up and cold desired idle speed.

When the behavior is datalogged its the actual desired/commanded idle speed that get bumped up to 784rpm. Some parameter/table must be setting this.

Whats the stall you got on the 5.7? Does the idle get bumped up on that too in 4low?

[dhoagland]

Have you tried to send your Tune and logs (with the logs showing the elevated request) to support as a help ticket?
I agree with you, I was surprised to see almost nothing referenced to 4L

Mine was much easier.
There was one table missing in my Camaro Transmission (that was present in other OS of the same ECM) and they added the table to my OS.
Until that I wasn't aware you could do that with a Help ticket.

Do you know anyone that works for Dodge?
Assuming they must have some kind of adjustment for this, you could include that info in support ticket.

[HaasExp]

Have you tried to send your Tune and logs (with the logs showing the elevated request) to support as a help ticket?
I agree with you, I was surprised to see almost nothing referenced to 4L

Mine was much easier.
There was one table missing in my Camaro Transmission (that was present in other OS of the same ECM) and they added the table to my OS.
Until that I wasn't aware you could do that with a Help ticket.

Do you know anyone that works for Dodge?
Assuming they must have some kind of adjustment for this, you could include that info in support ticket.

I've already submitted a support ticket accompanied with tunes/logs of the issue and also asked if they could search the .bin for the particular RPM "numbers" that are being set to see if they could find any relevant variables/data structures that may match.

However, they said they could only add something if I knew the particular address of the variable/parameter table or if it was present in other Dodge OS's.
Just like you I've had them previously add missing tables to my OS (which I found in other OS's of the same ECM) without issues, but I don't know the process of finding/searching for missing parameters that have not been mapped yet on any other similar OS.

So I guess this is why I'm on here asking around to see if anyone else had any info.

[Dozer]

Tested desired/commanded rpm on the scanner and it stays at 800rpm 2wd 4wd and 4wd lo. I am running a cam in my 5.7 it dosent like anything much under 800 for idle. The 2800 stall converter alleviates any push through the brakes feeling in 4low even at 800rpm Drive idle speed. I am also running a challanger pcm and os. The 4low desired rpm table your looking for might only be in the JK os.