The RPM here is important as that is the max performance rpm
and the engine power or torque starts reducing after that value,
so cultus toruqe will start dropping after 3000 whereas you can push the chevy upto 4900 rpm without acceleration loss,
Remember engine performace is curve not linear and these values are the maximum what the engine can deliver on the entire range of rpms.
It is eveident that the curve of chevy drops at 4600 and cultus drops at 3000
on this subject excellent articles are also available at the net.
So if you use gear shift at optimal points chevy can beat cultus even on petrol esp uphill or on a gradient.
And on CNG it is definate that chevy is lower running cost and greater performance.
This is what 796cc engine on EFI by M-Tech UK can give you. What else u want out of a small engine?