How different are Indycar and Formula 1 racing cars?
How are the technical differences are between F1 and Indycar?
They are very different. The fundamental difference is unlike contemporary F1 racing cars, Indycars don't have Hybridtechnology (e.g ERS and KERS). In addition Indy is is different that the cars are built by manufacturers.
Car constructors manufactore aerodynamic packages which can be bought by teams.This is a very different approach to Formula 1 where each team builds their own aerodynamic package. This is why it is a lot cheaper to run an Indycar racing team than a Formula 1 team.