especially engine and average on petrol

As far as differences in specifications:
The Wagon R Duo LXi seats 4 persons, & Wagon R LXi seats 5 persons.
Both have the same fuel tank capacity of 35 litres., & both have equivalent dimensions .

Both r equivalent with the engine specifications for Petrol, except that the Wagon R Duo Lxi has the LPG Mode, & the Wagon R Lxi does not.
The engine specs r as follows:
Swept Volume 1061 cc
Engine Type 4 cylinder in line, FC Engine
4 Valves per cylinder, MPF l
Engine Control 32-Bit Electronic Control Module (ECM)
Max. Power, bhp 646200 rpm ( Petrol Mode)
57.56000 rpm ( LPG Mode)
Max. Torque, Nm 843500 rpm ( Petrol Mode)
774500 rpm ( LPG Mode)

The Kerb Weight in KG. of the Wagon R Duo LX l is 885, & of the Wagon R LXi is 825.

The differences in equipment:
The Wagon R Duo LXi has a provision for Fog Lamps (Front) & the Wagon R LXi does not.
The Wagon R Duo LXi has a provision for Parcel Shelf & the Wagon R LXi does not.

Specifications & equipment may vary for the LX, VXi, & AX models.