Hacking the Motronic ECU (Audi RS2)

[Jonas_R]

I could buy an emulator, but it would be overkill since all I want is a bit more fuel at the top end.

The car has a map made by a tuner but seems to be just a bit lean 0.84 at the top end and I wanted to add just a little more fuel. So reading your above post I assumed it was a matter of changing the fuel map values.

[prj]

I use TunerPro, but adjusting the fuel map will not bring you much if you do not understand load and how motronic works, as you won't know which cells to adjust.

Plus, it's just not feasible to tune the car that way. Get an emulator if you are remotely serious about this.

[Jonas_R]

Quick question:

If I wanted to adjust the fuel offline at 4800-7000 rpm what would I need?

I got the eeprom eraser and burner, but wondering what software could be used to edit offline?

[prj]

Most if not all the links are contained in this thread. But you will not learn enough from links.

[bimmerboy]

Prj seems you have made great progress on this. I'd love to start getting setup for this, can you share some helpful links you used to read up on this? I'm sure with a little more reading and actually trying it with a trace it will make a lot more sense.

[prj]

Let's post some more info regarding Motronic in general.
This time on the topic of load, the MAF and fueling in Motronic.

So what is load?
Load inside the Motronic ECU is the injector time open to reach lambda 1.
It is calculated from the following:
1) Engine RPM
2) Mass airflow (kg/h)
3) The injector constant programmed into the ECU.

The formula is:
LOAD = Mass Airflow / (Engine RPM * Injector constant).
Of course, this is a bit simplified, but that is what it boils down to.

Fueling
The main fueling map in motronic is an enrichment map. It is a basic multiplier map, that either increases or decreases LOAD (injector time open) based on RPM and LOAD itself.
Let's take a look at the stock AAN fuel map:

Now, if we have set our injector constant correctly, then 1.00 will be more or less close to stoichometric.
If we know how much our injectors flow, we can easily turn this map into a target AFR map using basic math.

The MAF
So, why do our cars use a MAF? It is because the MAF allows us to set an AFR target without running closed-loop with a wideband. This is not really an issue now, but it was back then.
Basically it makes fueling in motronic very easy to tune, as you can just punch in target AFR and the MAF will get you there. Of course it is not 100% perfect, but it is a lot easier than using a speed-density system.
An additional wideband O2 sensor is always useful though, as it can be used as insurance.

[prj]

The reason I am asking for this, is because I want to create a launch control function.
I can create it now using load and tps, but with the VSS in the equation, the algorithm could be much better.

http://www.youtube.com/watch?v=aaiCZKp0w6Y&fmt=22

[prj]

Talking about VSS, from the ECU pinout, it looks like there is VSS also going into the ECU.
Does anyone know whether the main (80C535) chip has access to it?

[S2central.net]

There is a project in there for someone with a lot of time on their hands... reverse engineering the RDS interface to the trip computer and using that to communicate something like boost pressure.

Fuel usage signal is just an analogue voltage output from ECU iirc - the scaling of that is used along with VSS from the speedo to work out MPG.

[andy10v]

Bram there was this for urs4's, the TDS-1

http://www.boost-instruments.com/TDS-1.html

There are a few of old threads about getting the display to do other things and one newer one IIRC.

[prj]

To be honest, I don't really remember how the trip computer gets it's data.
I remember there being a good writeup about it somewhere, and reading it, but since I have not really had any interest in it, I've forgot.

There is definitely /some/ communication between the ECU and the Computer, since AFAIK for a long time the computer did not work for VEMS users, but it does now. Perhaps that'd be a place to start digging?

I think it is possible to make corrections the MPG display using VAG-COM though.

[Bram]

Nice work. Could you also send different data to the onboard computer in your dash, like boost, etc. or is that display totally disconnected from the ECU?

[prj]

I would like to encourage people to learn the workings of Motronic.

I got my AAN engined Audi at the end of April, now it is start of July and I know enough about it to be able to remap the car as needed.
This makes two months of tackling it as a hobby project, using 1-2 hours per day on average.
Thanks go to everyone who have helped/hinted me in one way or the other .

All you need to learn is a wideband lambda+controller (which you need for tuning anyway), an emulator, such as the Ostrich II, and your head on the right way.
There is a wealth of information available online regarding to how these ECU-s work, in fact, it is possible to find a lot of stuff without making any investments. The investments only help you verify what you have found.

So basically, what I wanted to say, is that you don't need 1 million euros and 2 years to learn this. 400-500 euros and a month or two are enough, given sufficient motivation.

Good luck.

[prj]

Made a small addon to the Motronic software, which allows me to monitor various inputs and outputs in the ECU.
Here is a sample, monitoring RPM's:

http://www.youtube.com/watch?v=M7AGSsvIm2k&fmt=22

I probably should write some custom software, which would also log the data and display it nicely in a digital form, instead of a 16x16 table in TunerPro...

[vertigone]

ok sorry that's why I asked if it was ok
you can delete my post I'll ask my question in an other one