High Flow Catalytic Converters - What does C.P.I mean ?

CPI OR CPSI is the acronymn for cells per square inch in relation to the catalytic converter substrate (often referred to as the honeycomb). CPSI is the description used worldwide despite the metric system.

So therefore 400CPSI, 300CPSI, 200CPSI, 100CPSI and 0.00 CPSI equate to sqeezing 400 small squares into a 1.0" sqaure all the way down to only 100 square cells per 1.00" square. 0.00 would be a straight pipe or catbypass pipe. Therefore as one goes down the scale from 400 cells per inch >>>to>>> 100 CPSI you will be less backpressure and restriction per unit area given the same design criteria and washcoat.

The age old question " What is better" depends on who is asking what is better?

The EPA & Federal Government would say 400 cells is best as it scrubs exhaust the very best and allows the least pollutants and makes the car the most quiet. For the general consumer this also means less of a raw fuel smell coming out the tailpipe

For most car enthusiats ........going to 200 or 100 cells is the popular way to go or at  least head in that direction if maximum power and more sportscar sound and performance is desired. For those who like to live more dangerously and performance is number 1 priority or 50 cells or  NO CAT (if that is allowed or permitted please see your local states rules and regualtions)