power is directly proportial to torque x rpm
torque is diectly proportional to engine displacement
Speed is directly proportional to power (function of rpm)
Diesel cars run at very low rpms, and is thus are very much power and speed restricted.
In order for diesel cars to develop the same power (thus speed) as petrol cars, a higher engine displacement and less restriction are required.
Thus to make a diesel and petrol car indentical in terms of performance, the diesel car needs an higher engine displacement. The disadvantage is that the power to mass ratio gets reduced. The petrol cars have a distinct advantage as they are lighter.
Saying that the diesel car has an unfair advantage is not true, as these cars in your example are identical in terms of power.
I not think anyone will consider that a giant earth remover with an engine displacement of 20 liters will have an unfair advantage at Le Mans...
We can argue maybe about what is the sense in using diesel cars for racing, seeing that much more engineering and money need to go into these cars to make them more competitive. Well, less pollution, better efficiency, better torque - making for better cornering characteristics and less speed drop on inclines. The worse mass obviously require stiffer suspensions, cancelling out some of the better handling characteristics.
Evententually - diesels, love them or hate them. But diesel cars are the future, more so than hybrids.
