Sorry i made a mistake.The ratio is not 14:1 but it is 14.7:1.
There are 3 types of mixtures.
1-rich mixture which is less than 14.7:1.
2-Ideal mixture which is 14.7:1
3-Lean mixture which is more than 14.7:1
In the 1st and 3rd case both result in excess pollution
In the second case,less pollution is caused,hence the second case is the best for us.
But in 2nd case a lot of heat is produced on greater loading,i.e when lot of power is developed,where as its not the same in 1st and 3rd case.So most light weight automobiles use the mixture as in 2nd case.Where as heavy vehicles use the mixture as in 1st ans 3rd case as the combustion process takes place at a cooler level.
I hope your doubt is clear.If anything else...ask!!!
