[n54fanatic]

i get that if you go with just catless downpipes on an otherwise stock exhaust its not gonna sound a lot louder just gain 20 rwhp. but will the catless downpipes make the car smell... i just bought a pair of ar design catless downpipes this post got me thinking if itll still smell like sulfur after the exhaust goes through the secondary cats?? anyone have any experiences running just a catless downpipes on an otherwise stock exhaust.

[Black Sheep]

I just ordered some AR pipes cant wait to get them in

[ETS Michael]

Anyone have a link with 2.5" downpipes vs 3.0" downpipes. I'm curious to see the difference between the two. It seems that 2.5" downpipes should be more then enough for the stock turbochargers.

I would be interested to see some dyno results.

Michael

[OpenFlash]

Originally Posted by ETS Michael

Anyone have a link with 2.5" downpipes vs 3.0" downpipes. I'm curious to see the difference between the two. It seems that 2.5" downpipes should be more then enough for the stock turbochargers.

I would be interested to see some dyno results.

Michael

+1

[BrianMN]

Originally Posted by ETS Michael

Anyone have a link with 2.5" downpipes vs 3.0" downpipes. I'm curious to see the difference between the two. It seems that 2.5" downpipes should be more then enough for the stock turbochargers.

I would be interested to see some dyno results.

Michael

http://www.e90post.com/forums/showthread.php?t=316974

It does seem the 2.5" downpipes would be adequate for 500+hp,but does that mean that larger won't yield more power?

I have a set of AR dps to replace my 2.5", and will have another dyno comparison.

[momstmg78]

I just ordered ar catted dps. What kind of difference would be expected between catted and catless? Thx in advance. I've also ordered a hpf fmic also.no tune as of yet. Leaning towards procede.

[ETS Michael]

It seems funny to run 3.0" downpipes then reduce the pipe down to 2.5" at the flange for the 2.5" exhaust system. Removing the cats from the system should be the most bang for your buck mod on the exhaust system even with 3.0" piping I doubt you will see a huge if any differences since they reduce down to 2.5"

Michael

[BrianMN]

Originally Posted by ETS Michael

It seems funny to run 3.0" downpipes then reduce the pipe down to 2.5" at the flange for the 2.5" exhaust system. Removing the cats from the system should be the most bang for your buck mod on the exhaust system even with 3.0" piping I doubt you will see a huge if any differences since they reduce down to 2.5"

Michael

Well you're still getting a bit more room for the ~16 inches after the turbos...which is an important area. But I agree the cat's are without a doubt the biggest impact.

[ETS Michael]

Dual 2.5 inch

Pi x 1.25 x 1.25 = 4.9 x (2) pipes = 9.8
equivalent flow to a single 3.5" inch exhaust

Shouldn't have any problem with back pressure

[tibra1]

Originally Posted by ETS Michael

It seems funny to run 3.0" downpipes then reduce the pipe down to 2.5" at the flange for the 2.5" exhaust system. Removing the cats from the system should be the most bang for your buck mod on the exhaust system even with 3.0" piping I doubt you will see a huge if any differences since they reduce down to 2.5"

Michael

I gotta think that having a 3 inch downpipe that tapers down to a 2.5 inch exhaust is better for exhaust gas velocity then a 2.5 dp to a 2.5 exhaust? Considering ur using catless dps ofcourse.

It seems like simple physics, but then again nothing is simple w exhaust science :/

[Drakos]

Here is a simple vid with just AR DP's and the golf tee mod. It def sounds better than stock. Will prob get an AE exhaust setup in the spring.