John Magee’s scientific contributions

... By targeting a specific GHSV value, exhaust constituents are allowed enough residence time at catalytic sites to react and be converted to non-harmful compounds. In the automotive field a GHSV value of 60,000 ℎ −1 has been widely accepted whereas in performance applications, where substrate area is sized based on maximum flow conditions, a value of 120,000 ℎ −1 is generally accepted [2]. It has also become apparent that when working with performance two stroke applications an even higher GHSV constant of 200,000 ℎ −1 is typically used because exhaust emissions concentrations are much higher. ...

Reference:

DESIGN AND IMPLEMENTATION OF AN OXIDATION CATALYST FOR A SPARK IGNITED TWO STROKE SNOWMOBILE ENGINE