Quote:
Originally Posted by rueyme
what was the latest on this? did they ever get anywhere? looking for some project to squeeze any extra gains out above the euro headers so was considering this but haven't heard any follow up.
|
I suspect they won't work due to the way the ECU calculates fuel trims. Here's some background:
The MS43 ECU has a parameter that controls the number of O2 sensors the ECU uses for fuel trims. The logic exists to reduce that number all the way down to a single O2 sensor, which is perfect for 6:1 turbo manifolds or applications like this.
The MS45 ECU (2003-2005 6-cyl BMWs, including the non-M Z4) does not have the same logic built into the ECU. The only way to run a single O2 sensor is a change to the program code, which is significantly more complicated. If a single O2 sensor is used without such a change, one cyl bank will attempt to control all the fuel trims while the other will sit at 0%. So, if fueling was 10% rich, the ECU would compensate by removing 20% fuel from one bank while the other would have no trim.
Placing both O2 sensors into a single exhaust pipe next to each other has even worse results. Each bank's fuel trims will fight with each other and diverge. One bank will go full rich while the other will go full lean, even though overall AFR will look ok. This has to do with each sensor reading slightly differently and the ECU reading each sensor separately at a different time.
BMW N54 ECUs have the same challenge that must be overcome when installing a single turbo 6:1 manifold. As far as I know, the only solution for those cars involves 6:2:1 manifolds. The MSS54 ECU in the E46 M3 has the same challenge too. NickG was able to overcome it with a program code change.
I assume the MSS70 ECU in the Z4M has the same issue. It would be easy to test, since the parameter for O2 sensor configuration exists and can be modified. If the logic exists and the parameter can be calibrated so the ECU only uses a single primary O2 sensor, then one bank will show no fuel trims while the other will show trims with both sensors plugged in. This can even be tested with stock headers. However, considering that no other Siemens ECU after MS43 has the logic built in, it's doubtful MSS70 has it programmed in.