Liana and CNG ... infact any car having a waste spark ignition wud give issues on CNG.
Liana jst has some extra issues.
The Suzuki swift having a different head on the same engine is quite enuff for me to say why Liana is not the best car on CNG. And Liana with the same engine even Jimny with the same m13a is being offered with CNG but Swift isnt.