modify idle rpm by mapping?

[maicol76]

Hi guys~

Is it possible to modify idle rpm by ecu mapping?

ex: 650 -> 780

[jcolley]

Yes, it's a temperature dependent map.

[SYT_Shadow]

Yes. I have 900-odd rpm on the E90 as it has solid rubber engine mounts

[maicol76]

Originally Posted by jcolley

Yes, it's a temperature dependent map.

Temperature means intake air temp? or water temp?

[amrazM]

Originally Posted by maicol76

Temperature means intake air temp? or water temp?

Engine coolant temperature.

I’m sure there’s a way to adjust the actual idle at operating temp tho from remapping.

[E92_TYLER]

Ah good to know !
Thanks!

[maicol76]

Thanks~!
good info~!

[jcolley]

Originally Posted by amrazM

Engine coolant temperature.

I’m sure there’s a way to adjust the actual idle at operating temp tho from remapping.

There are several curves which control the ultimate idle speed with various precedence checks and the end result is the highest of all the calculated variables is the idle speed.

LLR is leerlauf regulator (idle actuator), n is engine RPM, soll is sollwert (setpoint), tmot is coolant temp, toel is oil temp, kh is katheizen (cat heating). llr_flags are the status bits passed via LL-CAN (idle actuator CA bus).

[maicol76]

Originally Posted by jcolley

There are several curves which control the ultimate idle speed with various precedence checks and the end result is the highest of all the calculated variables is the idle speed.

LLR is leerlauf regulator (idle actuator), n is engine RPM, soll is sollwert (setpoint), tmot is coolant temp, toel is oil temp, kh is katheizen (cat heating). llr_flags are the status bits passed via LL-CAN (idle actuator CA bus).

Attachment 1965715

OMG~ U R genius

Is there a software to change the data, called mapping tool or reflash software?

[BPMSport]

Originally Posted by maicol76

OMG~ U R genius

Is there a software to change the data, called mapping tool or reflash software?

Why do you want to change it?

We've had a few customers request it to reduce vibrations from certain mounts, but other than that, it's best to leave it as is.

I don't think there is DIY software for this. There are a number of idle speed and idle speed offset maps.

[maicol76]

Originally Posted by BPMSport

Why do you want to change it?

We've had a few customers request it to reduce vibrations from certain mounts, but other than that, it's best to leave it as is.

I don't think there is DIY software for this. There are a number of idle speed and idle speed offset maps.

Thanks~!
Maintaining alternator charging voltage(>14V) is the reason why.
I'm using Lithium battery. As you know, lithium's nominal voltage is 13.1V, and charging voltage is almost 14.6V. But, the Voltage at 650rpm is 13.5~14.0V(My alternator is brand new, not RMFD).

I think ECU controls voltage regulator to reduce charging voltage, because battery's nominal voltage is higher than AGM & Lead/acid. lithium's nominal voltage 13.1~13.3V is higher than fully charged AGM.

In this situation, when cooling fan runs at 650rpm, the voltage drops to 12.5~12.8V. As I know, if the voltage drops below 12.8V, it is not good for the lithium battery. But, 12.5V is the best condition of AGM and Lead/acid. haha.

[BPMSport]

Originally Posted by maicol76

Thanks~!
Maintaining alternator charging voltage(>14V) is the reason why.
I'm using Lithium battery. As you know, lithium's nominal voltage is 13.1V, and charging voltage is almost 14.6V. But, the Voltage at 650rpm is 13.5~14.0V(My alternator is brand new, not RMFD).

I think ECU controls voltage regulator to reduce charging voltage, because battery's nominal voltage is higher than AGM & Lead/acid. lithium's nominal voltage 13.1~13.3V is higher than fully charged AGM.

In this situation, when cooling fan runs at 650rpm, the voltage drops to 12.5~12.8V. As I know, if the voltage drops below 12.8V, it is not good for the lithium battery. But, 12.5V is the best condition of AGM and Lead/acid. haha.

Voltage regulation is not controlled in this manner. It's controlled by the IBS and other modules, not a direct function of engine speed.

[M3 Number 86]

Quick question. So what's normal idle for you guys? I bet we're all different lol

[BPMSport]

Originally Posted by M3 Number 86

Quick question. So what's normal idle for you guys? I bet we're all different lol

There is no "normal idle". It will fluctuate depending on a number of circumstances within the range of roughly 600-800 if I recall correctly (when warm).

[maicol76]

Originally Posted by BPMSport

Voltage regulation is not controlled in this manner. It's controlled by the IBS and other modules, not a direct function of engine speed.

yes, I know that BMW has 'super ultra scientific electrical logic' on battery charging system. why?
So, I've been monitoring and testing voltage, ampere, battery registration and etc for months. My conclusion is that raising the idle rpm to 700~800 is the only and 'easy' way to increase voltage at idle.

I think voltage regulator acts like oil pressure relief valve.

low idle rpm(<680) : low voltage(13.5~14v, avg 13.5V) + high amp
high idle rpm(>750) : high voltage(14~15V, avg 14.5V) + low amp

raising rpm(normal driving) : 14v~15V + high amp
during track driving : 13.6~13.9V + very high amp

These are just data from my car installed lithium battery.

IMO, higher than 650 is a way to prolong lithium battery's life span and use it reliably. JUST IMO

Anyway, I think 730~780rpm is suitable for my mod.

[jcolley]

IBS was developed as a means to:

- maximize engine efficiency by not charging the battery when unnecessary (less charge current = less countertorque from the alternator)
- maximize battery life by monitoring battery state of charge (SOC) and state of health (SOH).
- Ensure starting capacity reserve is maintained but providing data to the DME of SOC and SOH so the DME can signal for shutdown of "hotel" loads by the CAS module when needed.

In your case with a non AGM or lead acid battery, I wouldn't allow the IBS to work at all. It can be disabled in the DME calibration file or most likely by simply disconnecting the IBS lead. Also, disconnect the one-wire BSD cable from your alternator and I believe the alternator will out max voltage at all times.

[M3 Number 86]

Originally Posted by BPMSport

There is no "normal idle". It will fluctuate depending on a number of circumstances within the range of roughly 600-800 if I recall correctly (when warm).

Just mentioning because some ppl think 500 is normal others think 750 is normal.

[maicol76]

Originally Posted by jcolley

IBS was developed as a means to:

- maximize engine efficiency by not charging the battery when unnecessary (less charge current = less countertorque from the alternator)
- maximize battery life by monitoring battery state of charge (SOC) and state of health (SOH).
- Ensure starting capacity reserve is maintained but providing data to the DME of SOC and SOH so the DME can signal for shutdown of "hotel" loads by the CAS module when needed.

In your case with a non AGM or lead acid battery, I wouldn't allow the IBS to work at all. It can be disabled in the DME calibration file or most likely by simply disconnecting the IBS lead. Also, disconnect the one-wire BSD cable from your alternator and I believe the alternator will out max voltage at all times.

Thank you so much~!!!

"the one-wire BSD cable from your alternator"
Is this 3 in pic? As I know, 3 is IBS connector, may be.

Could you check the cable in this wiring diagram?

[IanMan]

Originally Posted by SYT_Shadow

Yes. I have 900-odd rpm on the E90 as it has solid rubber engine mounts

I'd like to hear your take on having a 900+ idle. Gas mileage significantly lower? Any other things that you've observed?

Thanks,
Ian

[jcolley]

Originally Posted by maicol76

Thank you so much~!!!

"the one-wire BSD cable from your alternator"
Is this 3 in pic? As I know, 3 is IBS connector, may be.

Could you check the cable in this wiring diagram?

No, will be a small plug on the back of the alternator.

[maicol76]

Originally Posted by jcolley

No, will be a small plug on the back of the alternator.

I know that connector. I got it.
'disconnect one-wire BSD' cable means 'unplug the connector'. right?

Thanks bro~!!

[jcolley]

Originally Posted by maicol76

I know that connector. I got it.
'disconnect one-wire BSD' cable means 'unplug the connector'. right?

Thanks bro~!!

Yep, should do it. You will get a DME fault for BSD generator communication, but without DME control of alternator voltage reg over the BSD bus, the VR will put out it's max voltage as an old conventional VR would.