The air filter in the classification can be divided into 4 types, respectively, with pre filter function of the T type desert air filter and oil bath air filter, and single stage air filter has no pre filter function and double stage vane air filter.

1.  Analysis of original inlet resistance of air cleaner assembly

In the air filter, air filter and single stage although does not have the pre filter function, but this kind of air filter for air intake of the original resistance is the smallest, and double stage air filter with blade ring resistance slightly larger, followed with the oil bath air filter pre filter function. This filter for the original air resistance has been considerable.

The biggest is the desert air filter of the swirl tube, this filter is the largest for the original air intake resistance. Different air filter due to its internal structure is different, the original air resistance is not the same. 

2.   Assembly initial efficiency analysis of air filter

Air filter with different structure, the assembly between the original filtering efficiency difference is very big. But the general use for car air filter for more emphasis on the filtration efficiency of the assembly.

For the analysis of the air filter assembly initial efficiency, usually using gravimetric method were analyzed. But this approach has limitations in use, if the two vehicles with the same filter the filtration efficiency of the same, it is 99%, then by weight method to further on the two the filter performance is analyzed. So in this case using the gravimetric method obviously has no meaning. Usually this situation by counting method, analyzed the filtration performance of air filter, the filter was counted by specific number of each filtering stage, the performance of the air filter is very good to distinguish.