RomRaider

Any got this working? I've done it with 32 bit ECUs, but I've hit two issues on the 16 bit ones (A4SD900B) specifically:

- boost target can't be set higher than 24.75 PSI.

- MAP sensor calibration offset can't be set > 0.

Are these limitations of the ECU?


Thanks,
Mike

Its a limitation of the ECU.

I assumed when this thread was posted it was for 16 bit ECUs; dunno if you saw it or if it'd help:
topic2924.html

Is there a DIY writeup for us 32 bit folk?

there's one around here- what sensor are you using?

To clarify, the ECU has no effective limit when it comes to target boost even with the 16-bit ECU. However, the target boost tables (16-bit ECU) are setup with an 8-bit boost value, but it is further manipulated and stored as a 16-bit target boost value. This limits the max target boost to something around 39.xx psia. It would be possible to modify the ROM to work with a 16-bit target boost table, but the problem would be finding enough unused space for that size table (you would have cannabilize other tables - maybe the AT target boost map if applicable). I would imagine the traditional method to this limitation would be similar to the 300 g/s limitation - modify MAP sensor scaling (half the actual boost, for example). I'm not sure if anyone has tried that before, but boost control should still work. Not sure if there would be other side effects related to undefined parameters.

As far as map scaling, the offset is cannot be greater than zero because:
x = multiplier
y = offset
MAP = (MAPv*x) - (y)

I represented the offset as a negative value in the defs only to avoid confusion. Y is an unsigned 16-bit value, so it cannot be negative and therefore the offset cannot be positive (as displayed in Enginuity).

Thanks for the clarification. Maybe I'll just rail it (24.75) which should effectively turn of closed loop boost control. That's what I did before- I was just trying to be crafty this time.

If you get bored (unlikely) and want to try taking over the AT table to give more range for boost targets, I'll be happy to test it out.

Thanks!
Mike

Stock sensor. I was more curious than anything, sorry for the thread jack.

No worries. It's actually quite simple to do on the 32-bit ecus.

Did you find the thread?