For a group G and an automorphism φ: G → G, the algebraic mapping torus of (G, φ) is the HNN extension Mφ = ⟨ G, t | t−1gt = φ(g), ∀g ∊ G ⟩. I will describe how the Dehn function for mapping tori of small-generator RAAGs can be read off from properties of φ.