In order to give better emissions test readings, Yamaha put a "hole" in the power curve around 4-6000 rpm and unfortunately it's built into the ECU fuelling map.
If you look at the graphs below, you can see the flat spot on the top one and the hole in the second one around that rev range.
fz6_power_curve_before_power_commander.jpg (Size: 18.93 KB / Downloads: 5)
fz6_torque_curve_before_power_commander.jpg (Size: 18.44 KB / Downloads: 5)
Personally I bought a Power Commander III which let me change the map to smooth out the delivery, but there are cheaper versions available too.
Also it can help reduce the "jerk" you get when rolling the throttle on again after a bend, because the ECU cuts the fuel flow when you roll off and there's a momentary "lag" before the power comes back in again.
Another good modification is to get the 4 degree ignition advancer which improves starting and low to mid revs response.
If you look at the graphs below, you can see the flat spot on the top one and the hole in the second one around that rev range.
fz6_power_curve_before_power_commander.jpg (Size: 18.93 KB / Downloads: 5)
fz6_torque_curve_before_power_commander.jpg (Size: 18.44 KB / Downloads: 5)
Personally I bought a Power Commander III which let me change the map to smooth out the delivery, but there are cheaper versions available too.
Also it can help reduce the "jerk" you get when rolling the throttle on again after a bend, because the ECU cuts the fuel flow when you roll off and there's a momentary "lag" before the power comes back in again.
Another good modification is to get the 4 degree ignition advancer which improves starting and low to mid revs response.