http://plnkr.co/edit/cFeD3tLOYWcPVwMAFQG3?p=preview
How to replace all occurrences of a string in JavaScript?
You can use interpolate service of angularjs. Interpolate service works with angular js expressions,  which should consist {{ }}  instead of {} for replacement.
app.controller('MainCtrl', function($scope,$interpolate) {
  $scope.name = 'World';
  function escapeRegExp(string) {
    return string.replace(/([.*+?^=!:${}()|\[\]\/\\])/g, "\\$1");
}
  function replaceAll(string, find, replace) {
    return string.replace(new RegExp(escapeRegExp(find), 'g'), replace);
  }
  $scope.interpolate = function ( ) {
    var context = { cars :"myCars", color:"red"};
    var url = "/json/feed?car=${cars}&colour=${color}&model=VW";
    var t1 = replaceAll(url,"{","{{");
    var url2 = replaceAll(t1,"}","}}");
    var exp = $interpolate(url2);
    console.log(exp(context)); 
  }
  $scope.interpolate();
});
Output : /json/feed?car=$myCars&colour=$red&model=VW