I went to the field and did one engine run-up and range check.

Atmospheric conditions:
OAT 37°c
Pressure 997 mb
Humidity 65%

Bare in mind that these conditions are about as far from ISA as it could be.

In these conditions we have had flameouts on all our engines: P-120SE, P160SE, G-booster 160.

Here is the video of the test:

http://www.geohei.lu/olin/videos/Mod...ion%20test.wmv

First part: acceleration from idle to full. Second part: acceleration from idle to half, then from half to full.
The acceleration from idle to full thrust takes about 6 seconds. The acceleration is not smooth. It sounds like the engine is stalling passing 50% N1.
The 1210SE and 160SE exhibit exactly the same behaviour in these atmospheric conditions and are slightly slower. The G-booster is slightly smoother but has flamed out 3 times on the last flight session...
The acceleration from idle to half takes about 4 seconds and from half to full about 1 second.

On standard atmospheric conditions, I believe that the acceleration from idle to full would take around 5 seconds.

The G-booster seems a bit smoother and faster from these first test. I have no thrust bench, so I cannot compare this characteristic.