Modifying Motronic 2.3.2 ECU hardware and software.

[Acki]

That's why you should ask bosch for your sensors.... ;-)

[-ice-]

Hi,

I'm not sure, but I think ABH and AAN Maf are totally different. is there a curve for 034133471K MAF?

Bye

[Acki]

For my V8 I got an MAF sensor curve from Bosch.
Maybe you can also get this for both MAF sensors and you can better image what happens?!

[-ice-]

Ok, good to know that it's even non linear. But therefore we have the linearisation curves, which are consequently different between aan and adu.
In the pulsewidth calculation, when the linearisation factor is get from the curve, there are some constants used. One is added and the other one used as a multiplier. Do they have a name in the real world? Or is it just meant as gain and offset?

Regards

[prj]

I have all that data (voltage to frequency curve) etc, from when I made the ECU work to accommodate the HFM5.

Suffice to say, it takes voltage and outputs frequency and the frequency output is non-linear.

If you want to know more, then you will have to scope the output on the bench… although it is not really interesting...

[-ice-]

I searched a long time to find a datasheet of the 91535v2 VFC chip from Harris cooperation. But i couldn't find anything. Would be interessting, because it's adjusted by many external resistors. So i'm satisfied with the determination of the voltage to frequency factor at the moment.

Bye

[prj]

It's connected through S201 (op-amp) to S200 (VFC).

[-ice-]

correct, i'm still mixing ADU/AAN resistor

Makes sense to use the whole input voltage range of the vco to get the best resolution and of course it must not max out.


Bye

[prj]

It's the other way around, RS2 software + AAN resistor = too much fuel, as signal is higher than it should be.
Until the point where you max out the VFC that is (which is why this resistor modification was done on ADU in the first place).

[-ice-]

Yes, i think so too... i didn't measure R201 by myself, read it somewhere...


R202 doesn't play a role, because its connected to an operational amplifier or something like that (very high impedance input). There only flows very little current and so there won't be a remarkable voltage over R202.
I think R202 is used in an RC configuration and acts as a lowpass-filter.

So if you run RS2 components and Software with AAN Resistor the ecu will "see" less airflow than it actually is and inject to little fuel. Dangerous under WOT i think.

Bye

[prj]

R1 = R200 = 4.86k
R2 = R201 = 5k6 or 6k2

For AAN you get 6.2/(4.86+6.2) = 0.561x
For ADU you get 5.6/(4.86+5.6) = 0.536x


To me everything checks out. I think you had resistor values between ADU and AAN mixed up.

[prj]

Scratch that, divider is indeed R200 and R201, but R202 is also in play.

I had it worked out somewhere… Let me look it up.

[prj]

It's 6k2 for AAN and 5k6 for ADU, and the divider is 202/201. 200 has nothing to do with it.

[-ice-]

Maybe i've made a mistake measuring...

R200 is on top of the devider, R201 is on bottom connected to ground. R200 is 4,86 kOhm, R201 for AAN 5k6, for Adu 6k2


Uvco = Uinput* R201/(R201+R200)

The devider ratio is 0,5353 for AAN and 0,5605 for ADU


..or a mistake calculating.


But thanks for your answer

[prj]

Your calculation is wrong, that's all there is to it.
Maybe Ohm's law needs a little revisiting?