i was out doing some street re-tuning last night with a friend, and the AFRs are quite nice now, running in the low 11's. the low boost 6000+ area needs leaned out slightly, but everything else is very smooth, and this is apparently what the car wants:






the car hits full boost at about 3000rpms (very response EFR 8374 turbo) so i am clueless as to how the engine requires such a spike in fuel at 4000rpms and such a dip between 4500 and 5000rpms.


what does this mean?

 

post staging bar point .. before this.. only 2 injectors are operational

 

hi bumpstart. i'm aware of how staged injection works.

i was asking about the 4000 rpm 6/8/10psi area where the blue lines are...

 

several complex interaction are occurring .. first thing to grasp is this map in no way reflects a consistent AFR target result


at around 3500 to 4500 rpm is pk TQ.. the plot reflects both the volumetric efficiency curve

( after 5000 rpm airflow begins to drop off through the port as its size and port timing window becomes restrictive )

and at same time reflects the nuances of port injection angle timing..
at around there,, it appears the injection angle value becomes ideal and all of the injected fuel reaches the port while it is still open in a timely manner
and less of it wasted an left to wet wall for the next engine cycle

all whilst an underlying strategy of overfueling to provide boundary layer cooling to prevent detonation is happening.. high values past 5000 rpm may be reflecting a tuners desire to send the afr rich in detonation prone areas

needless to say ,, dips like this in plots are typically,, normal.. and in some ecus may also be a result of the tuner using selected RPM and load bins to tune back excess fuel at a specific cruise rpm and load ..

 

peak torque is at about 5800rpms, not 3500-4500.

 

Some cars are just weird like that. If that's what the engine like and runs good don't worry about the number.