I'm using Angular 4.1.3 and came across this requirement and wanted to share my solution to it. Unfortunately the documentation on www.angular.io doesn't really list all the available props and methods on system components such as ngForm elements (or at least I couldn't find it).
My requirement was that I needed to have an <input> element that was part of a <form> that updated the value of its binding only after the blur event. Apparently this is only possible without using [ngModel] it seems:
<form #f="ngForm">
<input (change)="myVar = $event.target.value" [value]="myVar" />
<span *ngIf="f.dirty">Form is Dirty!</span>
</form>
But since this input isn't bound to an ngModel Angular doesn't know it's part of the form. So when the value is changed the form is not marked as dirty.