Filter data using params in ember

I'm developing search feature in my app. What I'm trying to do is to filter a car by brand. I have the following in my route:

import Ember from 'ember';

export default Ember.Route.extend({
    actions: {
        filterCars(car){
            this.transitionTo('cars',{ queryParams: {brand: car}});
        }
    },
  queryParams: {
    brand: {
      refreshModel: true
    }
  },
    model(params) {
        if(params['marca'] != null){
            this.get('store').query('car', { filter: { brand: params['marca'] } }).then(function(cars) {
              return cars;
            });
        } else {
            return this.get('store').findAll('car');
        }
    }
});

When I get the brand from params, I filter only the cars with that given brand. I thought it would work, but it's not working. Any idea of what I'm doing wrong ?