Oh thanks for the replies, i was a litle bit discouraged as you said Hawkeye3

. And sorry for my late reply, i was in hollidays.
Hawkeye3 : many partameters can be set for each particle system, and one of them allows the one you''re talking about. It''s the "attraction" parameter, where you can set an attraction point and an attraction power for the particles. The same parameter is used to achieve the "blob" effect you can see at the top left, just with different settings.
In fact i have a ParticleSystem class that have a method for each parameter you can set (position, gravity, attraction, speed, angular speed etc ...), and you just code :
MyFireSystem.SetAttraction(AttractionPoint, AttractionPower);
Those this answer your question about "hard coded" thing ? I didn''t anderstand it, sorry.
WhiteCrow: i didn''t limit the FPS to 50, in this exemple i limited it to 100 FPS, so i don''t understand why the performances are so bad

(i can imagine some vertical sync problem since 50 is exactly the half of 100, but only 2000 particles in a scene should run much better no ?)