oem cats vs. free flow cats - BMW Forum

bimmerguy82 · 10-15-2007, 10:15 AM

Does anyone know how much of a difference in performance there is between oem cat converter vs. high flow cat converter? I'm thinking about replacing mine sometime soon cause there's some rattling happening down there.

dannyb · 10-15-2007, 10:43 AM

Depends on the price difference, seems the oem cat is not that restrictive.

Teh Prof · 10-15-2007, 03:24 PM

For FI applications, it can make a real difference. My ATL mechanic changed out his E38 cats on a motor already producing 725 bhp and that mod with Dinan M5 exhausts added almost 75 bhp.

trev0006 · 10-16-2007, 06:53 PM

I don't think there will be any HP gain from the freeflow cats.

dannyb · 10-17-2007, 07:06 AM

In case someone else cant read!

Quote:

Originally Posted by M3UOND

For FI applications, it can make a real difference. My ATL mechanic changed out his E38 cats on a motor already producing 725 bhp and that mod with Dinan M5 exhausts added almost 75 bhp.

Furious · 10-24-2007, 06:36 PM

there are so many levels of high flow cats. it depends on the cell count in them. however price wise they are far cheaper than OEM cats and some perform nearly as good given the proper matching.