Better known as the 13B-REW, the 1.3L 2 Rotor TT engine swap from the Mazda RX-7 debuted in the original Forza Horizon where it could be installed in the 1994 Mazda Miata MX-5, 2010 Mazda MX-5 Superlight and 1973 Mazda RX-3. After being absent in Horizon 2 and 3, it returned in Horizon 4 and 5. But there’s a catch, it wasn’t available in any Mazdas. Instead it was exclusively an option for the 2013 Caterham Superlight R500, likely in reference to Mazda rotaries being an engine offered by Caterham aftermarket tuners.
Going into Horizon 6 I’d like to see this engine swap carried over to all Mazdas which aren’t already powered by the 13B-REW, as well as the 1993 Autozam AZ-1.