Sqlite insert performance for smartphone

I'm trying to optimize the insertion speed for sqlite in android. I've tried numerous methods. Like setting the pragma settings, journal mode and etc.

Besides that, i've also tried individual inserts, prepared statement and bulk insert. Keep in mind that all of those has already been wrapped in a transaction.

The insertion speed in my smartphone(Samsung Galaxy SIII) is only up to about 250 rows per second for a 20 column table. According to Sqlite faq, sqlite can easily insert 50,000 inserts per second. Therefore, i'm really optimistic about the insert to have at least up to the thousands rather than hundreds. However, none of the above mentioned works. Or 250 rows of inserts is already optimized?

Please help me. Thanks.

Regards, Dexter