Hi folks,

I installed a set of AWE cat pipes last night on my '05 C2S. Stock headers, stock mufflers.

Volume levels were expected, but the raspy nature of this change was not. At first, I suspected a leak at either the header flange or muffler 'sleeve', but everything is airtight (checked hot and cold).

My research via search tells me that swapping out the headers for either AWE units or x51s would solve (or at least reduce) this issue. Am I on track? It appears that headers + sport cats with the stock cans is the way to go with this issue, versus stock headers + sport cats and aftermarket cans for instance. Please correct me if I'm mistaken here before I spend more $.

I'd love to splurge on the AWE headers, but can't justify the price difference over the Suncoast offering (x51 at half of the AWEs) at the moment.

Primarily I'm just interested in eliminating the part throttle rasp/nasal tone I'm hearing between 3K ~ 4K, not looking for more power or volume at this point.

FWIW, full stick WOT sounds fantastic. It's simply that 3K partial throttle tone that had me, sadly, short shifting all day to avoid that range as it sounds rather obnoxious IMO.

 

are the cats new or used? could be a loose or broken cat element.

 

The rasp is a byproduct of replacing the cats only. I've heard a few different cars that put on a 'straight-pipe' to replace the cats & the result seems to be the same...

You're on the right track by looking to replace other exhaust pieces to get your desired result, of better sound quality.

FWIW, my car sounds just fantastic w/ the entire AWE setup...

 

GTB is right..high flow race cats are a recipe for rasp with the stock cans. I get a little rasp at WOT near the top of the tach with my setup..I actually like it. Gives it that raw sound..

Dave

 

Thanks for the replies guys - sounds like I'm on the right track.

So if I was to purchase only one more component, would I be better off replacing the headers or the mufflers to reduce the rasp? Of course, both would be nice but if I was going to do just one.

 

I see headers in your near future!!! Do you have a sound clip for us?

 

Here is a sound clip with FULL AWE Exhaust and there prototype "Loud" mufflers.

http://www.youtube.com/watch?v=t8uA6kCTowg

 

Rennsport-1 - I posted in your for sale posting re: your headers - can you PM your email address if you still have them available? Thanks, and thanks for the clip!

Stuart, I should take a clip and see if it shows up. I'm uncertain if it will be audible without load in neutral but it's worth a shot. At idle, it sounds no different than stock from what I've noticed. PS - I need to come see you soon...I managed to run over what I can only refer to as Gandalfs staff the other night after that great storm we had here in DFW last week. Said staff managed to ding in the drivers side rocker panel a bit (grrrr).

 

A bit more info...

The cats are used, sold to me by Gundo. Someone above posted that it could be failing cats, but I doubt very much they are. I inspected them in and out before install and there was nothing loose or moving around inside. Beyond that, I have no idea how I'd know if they were bad. Checks via Durametrics diags shows nothing and no cels in 50 miles.

After a proper warm up, say 15 minutes, the annoying nasal/tonal quality is reduced. Not GONE, but less irksome.

Windows down, frankly, the car sounds like most cheap imports I've heard over the years with ridiculous fart cans as I pass 2,600rpm and through 3K. Below that, it's fine. But in that range, something isn't resonating in a happy fashion. By rasp, this is what I mean. If you've ever watch Conan O'Brien when he does his nerdy-guy impression...this is the first thing that pops to mind when describing it. haha...

Windows up, not nearly as bad, but not melodious.

I'm on the fence between just going back to stock or replacing the headers and cans. Maybe headers and the gundo hack? Volume isn't an issue with me as I come from rather loud American iron for the most part, but tone is SUPER important to me. I also have an '07 Boxster S with the Remus race system and the sound is just pure sex. No way in hell am I shelling out the cheddar for the 997 Remus system however, so I'm going to have to do the best I can with the budget I've set for the car.

I'm sorta bummed...so many people have posted being absolutely thrilled with how their cars sound after replacing just the cat pipes. But I can't see for the life of me how anyone would find this tone pleasing in the slightest.

 

I recently installed X51 headers and "pre-owned" AWE 200 cel cats to compliment my previously installed "pre-owned" Remus mufflers ('06 C2S) . I think it sounds pretty good. I can see where you could get the "raspy" sound from the stock cans. I was actually thinking of going back to my stock cans. But after reading your post, I think I'll stick with the Remus mufflers for now The tone is totally non-offensive when cruising part throttle at the RPMs you mentioned.

Good luck with your search. I would recommend going full tilt with headers and aftermarket cans.

 

Pm sent. I hope I can help

 

Thanks Renn - checking now...

 

Forgot to mention, the serial # is
H14W04W

As I understand it, the new (good) cats were put into service in 2007 by AWE and begin with "G"

If so, I'm guessing that I have the newer 200 count cats but I'm unsure. Can anyone confirm that my serial # is a 200 or 300 cell cat set?

 

Ugggh- just went around the block to test some more and it's flat out AWFUL.

This can't be right. I'm guessing that one or both of the cats have internals that have come loose in some way. There are no leaks, I'm 100% certain and incredibly **** about using proper torque specs and procedures. Even used brand new gaskets for the header to cat pipe connection.

I paid good money for these pipes, too - if they are buggered, there's no warranty for them.

I just don't think this is how it's supposed to sound. I had my wife do a few drive bys so I could listen outside, and it does, in fact, sound "broken" as she stated flatly.

I've asked the fine gents at AWE if I can send them in (my shipping costs) to have them diagnosed. Either way, they're coming off the car and it'd be a shame to just toss them in the closet.

 

Thinking out loud here...

When I installed the cat pipes, I did not loosen or remove the mufflers. The AWE cat pipes lined up nicely in the cat-to-muffler sleeves without issue so it never occurred to me to mess with the mufflers. The sleeves didn't slide loosely, but in my experience with these sleeves, they bind a bit with wear and corrosion anyhow so I didn't think much of it.

Is it possible that even though they lined up nicely during the install, they are at a slight angle with the mufflers that is allowing a leak there at the sleeve at 3K and upwards, but not at idle? At idle, there is zero leak, but I have not tested for leaks under the car with someone holding revs at 2,500 for instance. Cold is the best time to test, letting the car sit overnight. This way you can wrap your hands around the seams before they are too hot to touch and have someone else start the car. Typically, even the smallest leak with be immediately noticeable so no leaks at idle should mean no leaks whilst driving...

I'm grasping here, but I'm eager for it to be something small that I can fix. I imagine the solution would be to loosen everything, including the mufflers this time, and tighten down the chain (from header to tip) to allow for better alignment. There are no gaps at that sleeve that I can see, but who knows...if the sleeve is off by a few degrees, perhaps it's allowing exhaust to blow past once it reaches a certain volume (3K rpm). This may also explain why it's sounding a little less crazy with some heat after 10~15 minutes due to expansion there.

Anyone else been through this? I may just be off my rocker...but I figure it's easy enough to try. It also makes me wonder if this is why rasp and odd sounds seem to vanish when folks install mufflers after just doing cats. It's not necessarily that the new cans have fixed it, rather the proper re-alignment of joints that takes place when you put the new mufflers on.