The Fiat 500 X 1.6 E-torq has a 4-cylinder, 16-valve, single-shaft, chain-driven engine and is built in Brazil, also designed to work "completely" on ethanol; the designation is Flexi Fuel.
I know that this engine is installed on 500 X and 500 L sold in the U.S.A. just because it is suitable for the fuels that are there.
For that in Italy, even if ethanol is not yet used, those who buy it transform it to burn LPG or CNG (my 500 X E-torq is LPG).
No problem with catalyst and other mechanical parts, over 68,000 km traveled with an average consumption of 10 km per liter at EUR 0.58 per liter of LPG.
The arrow indicates the gas filter, the small cylinders (4) mounted on the intake manifolds are the gas injectors mounted subsequently.
The gas passes through the radiator to be preheated and is controlled by a pressure regulator which is in turn controlled by a separate ECU which controls the entire LPG injection system; it is sequentially phased and injects the liquid gas in a gaseous way, homogenizing combustion.
In this particular system, when you want a peak of power, the ecu provides to inject even a small part of gasoline, assisting the lower power (about 7% max) of LPG alone.
When the gas runs out, the system automatically switches to petrol and marks it with LEDs and acoustic warning.
Of course, if you wish, at the push of a button, you can also walk only on gasoline.