The top shouldn't admit fumes from your own car. If the fumes are from your car, it has an exhaust leak somewhere in the exhaust system, and maybe even open holes in the firewall and body.
No defense against some diesel trucks, pickup trucks and diesel cars. Some of them just stink. And they are BAD smelling.
Drive it more and try to sort out what sort of smell it is-- gasoline, coolant, exhaust odor, diesel odor.