My own inability earlier this week to get a link to the beta of Android 4.2.2 for the Onda V818 hasn’t stopped others from finding it.
Here are two posts:
English at Arctablet: Onda V818 mini (V1 hardware) Android 4.2.2 Jelly Bean root custom firmware V3.0 (2013-05-15) — which requires registration to see links (I wish forums would stop that practice)
Spanish at Forotablets: [TUTORIAL] Actualizar ROM v3.0 en Onda v818 mini. (Android 4.2.2)
Maybe combining the two can do it without registering at Arctablet.
I don’t own an Onda V818 so can neither test this nor vouch for it. Those of a less adventurous nature might want to wait for the final non-beta firmware via OTA notification.
If you do this, run a new AnTuTu test and Comment with the score and other observations.
The Onda V818 runs on an AllWinner A31s CPU. Do not try this firmware with either the HKC Q79 (Quest) or the Chuwi V88!