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High cell density (HCD) (≥ 600 cpsi) and /or ultra thin wall (UTW) (≤ 4 mil) extruded ceramic monolith substrates are being used in many new automotive catalyst applications because they offer (1) increased geometric surface area, (2) lower thermal mass, (3) increased open frontal area and (4) higher heat and mass transfer rates. Delphi has shown in previous papers how to use the effectiveness, NTU theory, to optimize the various benefits of these HCD / UTW catalysts. A primary disadvantage of these low solid fraction substrates is their reduced structural strength, as measured by a 3-D hydrostatic (isostatic) test. The weakest of these new substrates is only 10 to 20% as strong as standard 400 × 6.5 substrates. Improved converter assembly methods with lower, more uniform forces will likely be required to successfully assemble converters with such weak substrates in production.

Thinwall substrates used in modern catalytic converters are more sensitive to assembly and operating forces. Various converter assembly processes are characterized using real time force transducer technology. The force distribution data from these assembly methods are presented. The analysis of this data leads to recommendations for packaging of converters depending on catalyst strength.