Sorry - just got back from work but I agree with Tianci.

Just eMetered my setup. Proves that I shouldn't max throttle excessively and explains why it was so damn quick when the ESC was behaving.

Flightpower EVO25 5S3700 lipo
4.7 x 4.7 APCe prop
Hyperion 80A OPTO ESC v3.1W
HET 2W23

16.54 Volts
79 Amps
1308 Watts
39000 RPM

Spec for motor from HighEndRC.COM...

For pylon /EDF jets up to 1600 grams
Suitable for HET EDF unit 6904 or WeMoTec 480 mini fan
-Diameter : 28 mm
-Length : 57 mm
-Shaft Dia. : 3.17 mm
-Weight : 100 grams
-No load current(lo) : 2.4
-Internal resistance: 0.015
-KV : 2850
-Max Current: 54 A
-Max efficiency: 87%
-Power Nominal: 850 Watts on 5 cells
-Recommended Props: APC E 4.7 X 4.7 )

Note: Don't run 2W-23 for over 30 seconds at full throttle. On 5s the RPM is close to 45000 in our 6904 fan unit. It is better to use throttle management. After flight cool the motor for 20-30 seconds at low RPM