[manuelga]

We've driven about 600km in the X-Trail so far.
About 4 or 5 times we could smell a sulphur smell.
Other than that, the engine seems to run okay.

Does anyone know if this smell is normal or is it an
indication of some improper combustion?

The cathalytic converter (not shure about the spelling) is braking-in, it's not so normal at Nissan cars, some VW's I had smell terrible during the first month, later they smell "normal".