Hi Fabianoh, think I was doing 1:38's with it, but I'm not the best driver around that's for sure, so I think low 38's and high 37's would be possible by others. I created the set based on race though and not pure speed (it has 55L of fuel), so if that's what you are asking then you might be better off using Bram's set? Also I think the sets that come with GSC are the best default sets I've ever seen come with a sim, so they are a really good base to start with, that's what I did with this set.
What are you wanting to achieve though?