thanks for the formula sir 
i got my car weighted it was 815 Kg without driver and adding the 95kg of driver
it becomes 915kg fuel tank was at half..
=0.915 ton
assuming engine is providing 90hp to wheels
90/0.915= 98.36 hp/ton 
okay now if civic i-vtec's engine is rated at 138bhp
and we assume civic's weigh is 1300kg
so a cvic's power is 106.12hp/ton ?