[Aetae]

Cache, объект и сортировка несовместимы. Ты не властен над порядком ключей объекта. Так или иначе тебе придётся пердолить объект обратно в массив, сортировать массив, и пердолить результат обратно в объект:

obj={
	31061:{"id":31061,"v1":21,"v2":3,"v3":25,"v4":337,"v5":70,"v6":0,"v7":0,"v8":0,"v9":8,"v10":17,"v11":70,"v12":0,"v13":0,"v14":0,"v15":0,"v16":0},
	4659:{"id":4659,"v1":14,"v2":2,"v3":397,"v4":473,"v5":58,"v6":0,"v7":0,"v8":0,"v9":0,"v10":0,"v11":0,"v12":58,"v13":0,"v14":0,"v15":0,"v16":0},
	34501:{"id":34501,"v1":12,"v2":2,"v3":122,"v4":401,"v5":54,"v6":0,"v7":0,"v8":0,"v9":0,"v10":0,"v11":30,"v12":24,"v13":0,"v14":0,"v15":0,"v16":0},
	33700:{"id":33700,"v1":23,"v2":3,"v3":31,"v4":332,"v5":52,"v6":0,"v7":0,"v8":0,"v9":0,"v10":45,"v11":27,"v12":24,"v13":10,"v14":0,"v15":0,"v16":0},
	33465:{"id":33465,"v1":11,"v2":2,"v3":340,"v4":416,"v5":47,"v6":0,"v7":0,"v8":0,"v9":0,"v10":0,"v11":47,"v12":0,"v13":0,"v14":0,"v15":0,"v16":0},
	35485:{"id":35485,"v1":10,"v2":2,"v3":97,"v4":516,"v5":47,"v6":0,"v7":0,"v8":0,"v9":0,"v10":0,"v11":37,"v12":10,"v13":0,"v14":0,"v15":0,"v16":0},
	4420:{"id":4420,"v1":22,"v2":3,"v3":25,"v4":319,"v5":45,"v6":3.75,"v7":18,"v8":0,"v9":10,"v10":0,"v11":45,"v12":0,"v13":0,"v14":15,"v15":0,"v16":0},
	2624:{"id":2624,"v1":20,"v2":3,"v3":25,"v4":304,"v5":44,"v6":0,"v7":0,"v8":0,"v9":0,"v10":6,"v11":21,"v12":23,"v13":0,"v14":0,"v15":0,"v16":0},
	3888:{"id":3888,"v1":10,"v2":2,"v3":370,"v4":446,"v5":41,"v6":0,"v7":0,"v8":0,"v9":0,"v10":0,"v11":41,"v12":0,"v13":0,"v14":0,"v15":0,"v16":0},
	31505:{"id":31505,"v1":8,"v2":2,"v3":103,"v4":516,"v5":41,"v6":0,"v7":0,"v8":0,"v9":0,"v10":0,"v11":16,"v12":25,"v13":0,"v14":0,"v15":0,"v16":0},
	9148:{"id":9148,"v1":27,"v2":3,"v3":99,"v4":286,"v5":39.3,"v6":3.75,"v7":0,"v8":0,"v9":0,"v10":0,"v11":15,"v12":18,"v13":63,"v14":15,"v15":0,"v16":0},
	8814:{"id":8814,"v1":13,"v2":2,"v3":77,"v4":461,"v5":38.2,"v6":0,"v7":0,"v8":0,"v9":0,"v10":0,"v11":0,"v12":36,"v13":22,"v14":0,"v15":0,"v16":0},
	9863:{"id":9863,"v1":7,"v2":2,"v3":111,"v4":461,"v5":36,"v6":0,"v7":0,"v8":0,"v9":0,"v10":0,"v11":31,"v12":5,"v13":0,"v14":0,"v15":0,"v16":0},
	11403:{"id":11403,"v1":8,"v2":2,"v3":39,"v4":374,"v5":36,"v6":0,"v7":0,"v8":0,"v9":0,"v10":0,"v11":0,"v12":36,"v13":0,"v14":0,"v15":0,"v16":0}
};

var result = Object.values(obj) //получаем массив значений из объекта
.sort(function(a, b){
   return b.v2 - a.v2
}) //сортируем по убыванию v2 
.slice(0, 20) //отрезаем верхние 20
.reduce(function(a, b) {
   return a[b.id] = b, a;
}, {}); //набиваем новый объект, где ключами - id

alert(JSON.stringify(result,0,'\t'));