传递0或NaN的ajax文本变量

I'm trying to pass the variable var_nome to a php file using the code bellow. The value of this var is coming from a text field in a html form. If the value of the field is a number, it works perfectly and I get the data on teh php page BUT if the value of var_nome is a text, I got 'NaN' as a result?

function AlteraNomePortfolioAjax(portfolios_id, var_nome, SuccessDiv) {
  $.ajax({
    type: 'POST',
    dataType: 'text',
    url: 'PRT_ope_ajax.php',
    data: {
      'portfolios_id': +portfolios_id,
      'var_nome': +var_nome
    },
    cache: false,
    success: function(data) {
      $(SuccessDiv).html(data);
    }
  });
}

</div>

Remove that + sign, it is attempting to convert the variables to an integer:

data: {'portfolios_id' : portfolios_id , 'var_nome' : var_nome  },