So, here is my code, don’t know how you want to make use for it, but here it is in case it helps someone!
First of all, I just set a couple of values in the admin, 0-100 – it makes no difference since I am unsetting the initial options anyway:
function change_car_engine_size($input_object, $sfid) {
if($input_object['name']=='_sfm_car_engine_size') {
unset($input_object['options']);
$input_object['options']=array();
$arr = ['0','100','200','300','400', '500', '600', '700', '800', '900', '1000','2500','3000','3500','4000'];
foreach ($arr as $value) {
$new_option = new StdClass();
$new_option->value = $value;
$new_option->label = number_format($value, 0, ',', '.');
array_push($input_object['options'], $new_option);
}
}
return $input_object;
}
add_filter('sf_input_object_pre', 'change_car_engine_size', 10, 2);