question about cat and EGT

[dmaxcattle]

I am curious as to how much the cat restrics exhaust flow. My EGT's seem a tad higher then some of those others are posting. I have a 4 inch exhast but choose to retain the cat as it is a california truck. WOuld replacing the cat with a 4 in down pipe help lower temps significantly or not.

[More Power]

The construction of a diesel cat is somewhat different than that used with a gas engine (more free flowing). In addition, the LLY's got an even more free flowing cat than was used on the LB7.

Generally, a clean cat doesn't affect performance all that much. But, a few years of light-duty driving in cooler climates can plug one.

You can drill a 1/8" hole in the exhaust pipes ahead of and behind the cat to measure pressure differential. A small fitting can be screwed into the holes. If the pressure difference is less than 3 psi or thereabouts during a hard run (someone may have some other suggestions for pressure differential tolerance), just weld the holes shut - cat's OK.

Jim