SFS4'04

New S4 owner with a dumb question:
Are the two items below related or seperate? meaning do you guys all put both on the car or is one better then the other? I need a S4 exhaust education here. thanks.


Milltek Audi S4 2004 Dual Stainless Steel Cat-back Exhaust (RESONATED, has center mufflers) [pictured above] $1095.
and
Milltek S4 Hiflow Cats and Downpipes for 2004-on 6-Speed $1995

oatzel

going to run them into the stock exhaust, but you can put the exhaust on without adding the dp's.

dp's change the cats and downpipe, which depending on your state may be smog legal or not (i don't think anyone has CARB certification) for dp's and highflow cats.

i think miltek is claiming around 20 hp for each, so a total of 40 hp or so.

JDBlueAudiS4

The downpipes are the part that connects the headers which exit the engine to the muffler assembly designed to dampen the sound of the exiting exhaust of the car. The downpipes house the catalytic converters and has the O2 sensors. you can just do the cat back, which will get you a small gain, and better sound or add the down pipes for more power and a slightly louder sound. Hope that helps a little

nirad

that's a good point about the 02 sensors. what stops a fault code from appearing?

JDBlueAudiS4

even thought the second O2 sensor in our cars is really a check for the 1st one, they still have a spot for it. I have been scanning the car every night, no faults yet so.....

nirad

sorry, but what do you mean by "spots?" i don't know much about this.

JDBlueAudiS4

The 2nd O2 sensor sits behind the secondary cat in our cars. Once you put the Miltek's on they sit in part of the straight pipe.

nirad

thank you for your prompt reply :-)

JDBlueAudiS4

trying to avoid doing my System Architecture Homework :-)