Had a high opinion before the test drive. Review on Hyundai i20

Since i20 was very much in the list of the cars under consideration, I requested the dealer to send the vehicle (i20 petrol base version) at my residence. They sent  a white magna version of petrol model.

First look at the car , got appreciation from all the members of my family. Inside the space was good. In the rear three personscan sit in a reasonable comfort.the inside which looked very impressive in the showroom, was appearing a shade less may be due to the fact each and every detals of the material used was visible  in bright sunlight.I must say that it is comparable to that of Ritz. Also the seat upholstery used was of greyish color giving a dull look and not going with the biege and brown scheme .

The pick up of the vehicle was satisfactory.I had seen reviews that it is sluggish due to underpowered engine but  it is almost as good as Ritz  .I drove the car at 110 kmph on the same patch of road where I had tested Ritz ( also achieved a speed of 110 ).

At speeds over 80, I noticed  a loud "Dag Dag" sound in the cabin as if whole of the cabin was vibrating or resonating.The sound was so loud that my family panicked and the dealer rep. also asked me to stop the vehicle immidiately. He thoroughly cheched but could  find nothing except overheating/burning smell  from the car.The explanation he gave to me was that since it is a new car , there was overheating smell. I donot really  buy that exlanation.

Just to recheck the problem I once again ran the car over 80 and again there was the same sound .The sound disappeared once I rolled up the rear window glass.

due to the problems, i cut short the test drive as overheating smell continuously coming from under the vehicle.

The next day , a senior manager of the dealer called me to assure that nothing is wrong with the product and may be there can be a minor defect in the test car.Also he said that if one of the window glass is down at high speeds , such sound due to aerodynamic design of the vehicle is bound to come.Since I am engineer by profession I do not agree to that explanation.I am keen to know if  somebody has also experienced the same.