ECU fuel calulations for boost change

[banaro]

Have for many years run a centrifugal supercharger (SC) and when boost at an rpm is altered the ecu accurately recalculates the fuel requirement without intervention.

I have now added a Turbo (T) feeding the same setup with the SC spinning slower, and i have starting testing with simular engine boost numbers to the SC in the past.

Using the previously established base fuel map under load the engine is way lean and is requiring 25% increases to the table, at part throttle burnout time the map needs large decreases to the table presumably because the engine is drawing less air through the now very long length of intake pipe work?

Previously with the SC only, when I asked the mixture table to adjust cells on the fuel map it was always close, but when I ask it to adjust the fuel table now, it goes no where near far enough, seems to go about half as far as required each time.

ECU fuel mode is traditional and load is map

I am missing something here, another influence, can anyone help me understand what's happening?

Thanks

[Adamw]

Its hard to guess without seeing logs but the different fueling requirement will probably mostly come from the large restriction that you have just added on to the exhaust side of the engine.  

As for the mixture table adjustment, assuming the main fuel table is tuned adequately so that the mixture is close to the aim then I would usually expect any change to that aim table to give a relative change to the mixture.  

[banaro]

Thanks Adam, I searched the logs and have test logs that show the afr's were intially uneffected by the turbo integration, but then i realised not so after the converter is tightened, so the answer to my question is that the engine is under greater load through the rpm range due to a way tighter converter, hence the need for more fuel at the corresponding rpms. I assume I was too far way for the mixture table to get close with a single suggested map update?

Thanks