These films were utter BS from the start, ...sorry I've said it F&F fans.
Take one of the first races in the film for instance: the racers were all accelerating in their cars for approximately 1 minute 15 seconds before you see Paul Walkers speedometer which reads 120mph, which then goes up to 140mph+ as the NOS is applied, ...so a tuned Mitsubishi Eclipse running NOS takes over a minute to get to 120mph on a flat straight road?
Of course not.
It's a film so it's bound to be unrealistic at times if not the entire way through and although there may be a few glimpses of realism with regards to modifications that's it.
Don't get me wrong I've enjoyed watching the F&F series of films but I've never once pretended that they are realistic in any shape or form.