jBox2D Android become very slow on mobil phone after 80-90 dynamic bodies

I have a simple game with 20-30开发者_运维问答 bodies (static, and dynamic)

If I add some more Dynamic bodies and joints (over 80-90 item), then the Box2D will be very laggy, and a little slow..

Am I doing something wrong, or this is the limit of JBox2D? If I change to Box2D JNI via java native calls, is will be faster?

As I heard the fastest implementation of Box2D for Android is there: http://code.google.com/p/libgdx/ AndEngine is using that implementation instead of jBox2D and they're happy they switched to that version :)