kiesan

Well, my mechanic is up to his ears on my '91 S4 automatic.

I decided to renew or replace, well, everything. I'm taking off the air pump and associated plumbing in anticipation of a cat-less X-pipe that takes 2-plus months to get.

How loud is the car with only that mod? One of the local Seattle 928 specialty shops thought I might not like the resonating that you get with the X-pipe. How bad can it be?

How loud is it with the X-pipe and the rear muffler bypass? Does just unbolting the rear muffler and running the engine more or less replicate how it would be?

danglerb

Two kinds of how loud, inside the car and behind the car.

X pipes do sound different, removing the factory cats is louder, if you are asking the louder question, chances are good you will want some kind of rear muffler.

Given the performance of modern cats I don't think its ethical to run without them for no reason.

Charley B

Glerb - Would that ethical issue of cats in Seattle fall in the same catagory as you exceeding the posted speed limit in California?

AO

Man this topc seems to come up ever other week. Use the search button next time please!

But to satisfy your need for an answer, in general here is the concensus.

X-pipe + no cat + stock rear muffler = Just right!

X-pipe + high flow cat + stock rear muffler = a bit quiet but nice

X-pipe + no cat + RMB = Way loud!

X-pipe + High flow cat + RMB = Loud, but bearable

Stock Cat + RMB = Just right!

kiesan

Well, I suppose the inside the car loudness is my main concern. I guess I'll just try it first with just the X-pipe and see how it is.

The cat removal thing, I've noticed, is quite the divisionary topic on many boards. There is a guy on Ferrarichat that will essentially threaten to call the EPA if you even hint that is what you are thinking of doing.

I agree that running without them for no reason would be unethical. My reason or reasons would be I'm looking for cooler running temps, better performance and maybe some less weight with lower cost thrown in to the mix. 928 Specialists sells the part either with or without cats, the cat-less version being less $$$ and (according to them) worth another 5 horsies.

kiesan

Thanks man, thats just the answer I was looking for. I tried searching, it kept saying "timed out".

MGW-Fla

What Andrew said!

Mrmerlin

Hi i have the X with no cats plus the GT resonators and the GT rear muff, I like it , it is just loud enough to hear it when I step on the loud pedal but with the windows up and cruising it is not a nusance and a normal tone can be carried while talking. i did try the same setup with the RMB and it was waay too loud for me, sounded like a nascar stocker. one thing is for sure it is awesome to bolt on the pipe and notice the extra power, you will feel it, Stan

Charley B

Andrew - How about X pipe + stock cats + RMB?

the flyin' scotsman

Charley.........the X replaces the stock cats.

Charley B

Yeah, I thought about that after I posted. So if I want the HP benefit of an x-pipe I may have to put the muffler (RMB now) back on in order to live with the sound?

AO

Yep... can't be done.

the flyin' scotsman

My set up also......experimemted with the OEM rear muffler and the RMB but this, to my ear, SOTPD and others tolerability works.

X w/no cats + GT resonators + GT rear muffler.

Cliff Ruckstuhl

I think it all depends on your driving habits. If you drive the car every day to work and go say 30-50 miles and throw in some highway driving the drone might be more then you can take. But if you drive the car for fun on weekends and so on the X pipe no cats and RMB might be the most perfect WOW that is really cool sound. It really all depends on what you want. My wife loves the sound with the just the RMB and I will find out what she thinks this weekend after I am done. I am in the middle with my install. I have the X pipe installed with no cats and the RMB and am waiting on a new O2 sensor. If it is too loud I can always put the muffler back on and sell the RMB but I am thinking it is going to be just perfect for me. Ther is a sound bite of the X pipe no cats and the RMB here on the boards from the last few weeks. I played it for my wife and she then checked to see if I was sporting some wood over it. She knows what I like.

Cliff 87 S 4

the flyin' scotsman

Cliff...........don't get me wrong I loved the free wheeling LOUD sound; X w/no cats, GT res, RMB but its too loud for any kind off distance, sets off staionary car alrams and attracts unwanted attenion.

Don't sell your rear muffler, you find out for yourself.