Tuners Rejoice! Free Tuning For M4.4!

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Software AC mod for M43 cars with a M44 brain implant:



The schematic on the right is with the HARDWARE MOD !!




I wasn't very happy with the AC hardware mod for a M44 in my M43 car.

It works but there are a few serious disadvantages.

The ECU has totally no control over the aircon aymore.

For instance normally the ECU checkes if the pressure in the aircon sytem isn't to low or to high and will disengage the aircon with abnormal pressures.

Normally the ECU disengages the aircon at WOT and prevents the compressor clutch being engaged at high RPM.

Also engages the ECU the aircon in relation to engine coollant temperatures.

Non of these functions are active anymore with the hardware mod.



It all comes down to B25 wich is the biggest difference between M43 and M44.

With M43 the ECU just checkes with it if the AC relay succesfully is engaged.

With M44 the ECU receives a request from the ECC unit through B25 to engage the aircon.


The reason why the aircon will not work with a M44 in a M43 ECU is that de ECU needs a positive signal on B25 to engage the aircon, but there will be no positive signal on B25 unless the aircon is engaged, so.....


In the M44 bin the B25 is used for two main things

1. to see if the ECC unit is requesting an engagement of the aircon

2.idle speed adjustment and the earlier described control functions


Since in the M43 the AC relay is not only controlled by the ECU on the negative supply side but also by the ECC on the positive supply side a request signal is unnecessary anyway, the ECC already has direct control over the realy.

That's why the request function of B25 can be deleted, but l its other functions has to be left intact.

That way the aircon wil be engaged if the ECC want's it to and if the ECU decides that it is safe to do so.


Looking at the aircon routine in the bin I saw that only two bytes needed to be changed to achieve this.

So I did. I changed these two bytes in the bin, flashed the bin in an unmodified M44 and put it in my M43 850R and the aircon now works like it should work again.


So my advise for my fellow M43 car drivers with a M44 brainimplant will be:

-Remove the hardware mod and restore the original situation

-Change both bytes at address $6AC8 and $6AC9 in the manual bin or address $6B42 and $6B43 in the automatic bin into #00


No hardware alterations are required with this, non in the M44 and also non in the M43 car itself.

M43 and M44 will stay interchangeable with this.

Edited by Piet
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Awesome Piet! Really nice work!

My M4.3 to M4.4 switch won't be needed then! :) What needs to be done HW wise to prevent fryed components if I happen to have the S/V/C70 bin in the ECU by mistake? At whitch stage do the ECC module get fryed w/o HW or bin mods? At key-on or when the ac is on? Anyone who got some more info?


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An unaltered bin in a M44 will NOT fry the ECC module of your M43 car.

The aircon just won't work with it, that's all.

On the other hand don't use a for a M4.3 car AC modded bin in a M44 car !!

(but why would you, anyway ?)

Edited by Piet
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I have been thinking about every day data logging, any trip, It would nice to have the facility to turn any daily drive into a data logging session.

What do you need: A PC small enough to fit in your hand shoe department, Can be an intel NUC or an Asus Transformer.

This PC will run Tuner Pro.

I have an Android double DIN device but any Android device like your phone can take over the screen of this tiny device running Windows and TunerPro. Just using RDP.

What will be the result:

In car real monitoring data everyday. As well as logging and saving te information concerning your ride.

To make this idea more visuable i'll illustrate this with an example:


This was a carputer I created a long time ago. You see the one touch interface around the central screen. The central screen can be anything. TunerPro too. Nicely resized.

With the use of frontends like CentraFuse, Stardock or Frodo and some help of NirCMD it is possible to put TunerPro into the main sceen.

How should this look? A raw scetch:


Edited by razorx
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Piet, I've just noticed that the original addresses $6AC8 and $6AC9 in a 608 bin don't contain the same bytes like in 611, 612 bins for instance.

Do you have any idea why?

Being these bytes related to the AC routine, shouldn't them be all the same across M4.4 ECU's regardless of being a T5, R, GLT, whatever?

Edited by S70-R
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No, all these bins certainly aren't the same.

Even though many routines will be the same, their addressing isn't.

The addresses I gave only apply to the 608 and 609 bins we use.

Edited by Piet
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No, all these bins certainly aren't the same.

Even though many routines will be the same, their addressing isn't.

The addresses I gave only apply to the 608 and 609 bins we use.

You meant 607 (auto) and 608 (manual); yes? ^_^

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