So it's basically a fuel cutoff. I got my Civic to about 115 and I stopped so I don't know the exact speed it can go. Sure, they can go 140+, but you also have to factor in aerodynamics, thats what kills the Civic.

Edit: You have an auto tranny, so would that play a role in the speed limiter? I've heard of guys getting to 125+ in their Civics.