Maybe it would have been better to have small engines turbos, if they didn’t cater to the lowest common denominator. As they have to make a car they will survive any manor of mechanical mistreatment.
If they were able to make an engine that had a higher tolerances and better tuning it would likely be far better in terms of economy, however would be far more highly strung and therefore likely to break down if mistreated.
It’s this very reason that supercars tend to get far better economy figures for their relative engine size than small mass market engines. A supercar is far less tolerant of a bad driver but far more effective and efficient in the way it creates power.
So the twinair actually has the potential to be a good and very efficient engine, it is those who drive them who are the problem not saying anyone on here is the problem, but 90 year old Dorris who rides he clutch and drives everywhere in 2nd gear at 20mph and alike who have to expect a certain level of performance and robustness, that means fiat have to release a car to the mass market that isn’t as good as it could be. So as highlighted in the video, they have to put things in to work around problems caused by the turbo and small engine size (such as deliberate over fueling) where as with a high (more expensive) level of refinement the engine wouldn’t need these work arounds.
But then who would pay £30,000 for a 900cc two cylinder 100hp tiny hatch back ?
I suspect the reason for the Ferrari and Maserati as well as the biposto editions of the 500 with the 1.4 multiair with much higher levels of power, help fiat refine and research better tuning set ups on their usually detuned engines. They are more highly strung cars and only bought by certain types of people not the general public.