Aftermarket dump pipe cat location queries.

by **cruisn** » Wed Jun 22, 2011 8:00 pm

In all aftermarket dumps ive seen for the Gen4's they do away with the lower cat and maintain the top one.

Is it a requirement for it to be done this to keep the o2 sensor readings happy? Is it possible to do away with the top one and keep the bottom as long as its still between the two sensors?

Cheers

by **smythie** » Wed Jun 22, 2011 11:58 pm

Catalytic converters work best when hot. The hotter, the better. I'd say this is high on the list of reasons why people put them so close to the turbine outlet (the turbine sucks a bunch of heat out of the gas as it is)

by **Gambit** » Thu Jun 23, 2011 8:12 am

Not too sure on the technicalities but one cat in the mid pipe is usually effective in producing more power. This is how mine is setup and it does sit between the two oxygen sensors. I also still get good fuel economy and closed loop fueling is a non issue.

by **Ben** » Thu Jun 23, 2011 8:35 am

Don't quote me, but I'm fairly sure pre-facelift and post facelift OEM are different. The 2.0T has one cat and 2.5T has two.

by **stew07gt** » Thu Jun 23, 2011 9:17 am

Mine an 05 gt has 2 .... Also, I think the second sensor sits before the second cat? which I think is why you can have just the one cat?

by **hypeboy** » Wed Feb 29, 2012 3:58 pm

Not too sure on the technicalities but one cat in the mid pipe is usually effective in producing more power. This is how mine is setup and it does sit between the two oxygen sensors. I also still get good fuel economy and closed loop fueling is a non issue.

that's a great set up. the set up of yours is really efficient. I thought that the fuel consumption would rise.