AWE cat pipes installed...but....rasp?

[Ian_UK1]

Originally Posted by Nexus-6 Ian, I think this is precisely what's happening. I'm sure with new, matching AWE headers and cans, it would sound fantastic. I spent most of the early morning reinstalling everything by the book - taking a great deal of time to torque everything back to front precisely, new gaskets again, new sleeves and clamps this time as well - all joints cleaned and smooth. Alignment was much better with everything loose this time around and I hoped for a change. No change though - same results. As the my C2S is my daily driver, I wanted to hold off on any exhaust work as I commute quite a bit. All the weekend toys are loud, but I've managed to and wanted to keep this car quiet. The cat pipe swap was done simply because it was easy to do, and somewhat cost effective for the gains (especially when buying used). But with the stock headers and stock mufflers, it does not sound good. Frankly, it sounds horrible. Ian's description of what I'm hearing is exactly what it's like. I stgruggled early on to describe the sound, but he's nailed it. No offense to anyone who has this setup, but it's not pleasing in the slightest to me. I decided to go for it as there are many folks who have posted that this combo is fantaestic. Do remember that it's stock headers and stock mufflers...some of you have said that you have no issues with this setup, but then go on to mention X51 headers and/or PSE...here, 100% OEM headers + 100% OEM (base) mufflers + AWE cat pipes does not make for a pleasant tone. The good news of course is that there isn't a problem with these cats. AWE designed them to work as part of greater whole in their full system, and while they do work with stock bits, it's not a song I find pleasant. Given the two options I have in front of me - going for the full meal deal or back to stock, I think I'll have to suck it up and go back to stock. I hate to, as the gains are nice, but the car does not sound the way it should. I've "cheated" on my personal budgets before in regards to exhaust on other cars...way too many times in fact...and this time I think I just hang my head and chalk it up as an experiment. On the bright side, the exhaust is now thoroughly cleaned, checked and tightened with brand new clamps and gaskets! Before I take them off, I'll take a video of it and host it. I can replicate it in neutral I've discovered so I can capture what I'm talking about to some degree (under load, it's louder and more nasaly but the "essence" of the sound I'm hearing comes through loud and clear whilst revving in neutral). Perhaps this will give folks who are coming into this same decision gate a bit more data to help them decide if it's right for them. I'll have the cats off in the coming days and available if anyone wants them. Thanks again to the AWE guys and for all of the great insight provided here by other members - much appreciated. Another thing you might try in order to keep your cats and the gains they make is to look for used AWE mufflers on Ebay or similar. Maybe someone on here might even have some for sale - it's not unheard of.

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[Nexus-6]

I've been thinking about that this evening, Ian - some used AWE cans or perhaps set of used PSE or hacked mufflers. It'd be nice to just leave them on there and swap out the mufflers, that's for sure.

[dndodd]

Originally Posted by Andre5

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.

Same reuslts. Awe Headers and cats with A remus exhaust to me worked the best. Stock cans with the Awe headers and cats sounded raspy etc basically terrible.

Awe cans were too loud for me Remus worked the best and the car runs extremely well.

[jimlwest]

for your 06 C2S for flat spot. maybe someone knows a tuner in Orlando area?

Originally Posted by GTB/ZR-1

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...

[steve k]

If you do take off the cats Nexus- I'd be happy to take them off your hands. LMK

[GTSilver997]

FWIW - it appears that both Nexus and Ian_UK1 have 05's with the same symptoms. 2005 911's have an exhaust recall associated with the wields or its location. http://auto-recalls.justia.com/conte...RA-S-2005.html

Knowing that harmonic resonance is a tricky thing...just wondering if this has anything to do with the issue at hand?

[Nexus-6]

Intriguing - thanks for the link!

I have a few new bits on the way that will probably cure what ails me. I will of course post my results here. Thanks again to Todd and his crew - they have been extremely helpful which is all the more touching considering I'm a second hand, indirect customer.

FWIW, I tried a little experiment the other day. As many of you know, the tuning flap in the rear most crossover pipe closes at aprox 3100rpm, and opens again north of 5K. The more I paid attention to how and when the exhaust note changed at 3K (the rattle/rasp/awfulness I've been referring to), the more I noticed that it was a very sudden change - as in, almost instant...not a ramp up.

For kicks, I unplugged the changover solenoid that controls the tuning flap and eureka - the sound dissapeared. It's still not pleasant, but it's a linear tonal quality now with no sudden, dissapointing note change. This isn't a fix, merely information that to me anyhow demonstrates just how much Porsche tunes their exhausts to sound a certain way over the entire spectrum. With the OEM mufflers, the tuning flap changeover produces very little to no audible change in the exhaust note - the flow rate being what it is, Porsche have evidently tuned things to prevent this transition from sounding, well, un-Porsche like.

With the less restriction via the new cats, the changeover is no longer masked or tuned out as much and you get a most displeasing tone.

Anyhow, plugged it back in for the time being as the DME is obviously not keen to it being unplugged (no CEL, but a soft code observed via Durametrics). I imagine that Porsche tweak fuel and timing at this changeover and with the flap deactivated, the car ran fine but surely not ideally. At least it's an easy tweak if the sound drives me bonkers in the next little bit, but my new exhaust bits should be here in the coming days and this will all be an interesting experiment with something new learned.

[justatoy]

I know this may not be too relevant to the post but I just installed my AWE high flow cats...I already had Fabspeed mufllers and headers and too me and is only my opinion but it totally woke up my exhaust notes !
It is definately louder but it is such a sweet sound(intoxicating)!

And like one of the previous posts..Todd,Ralph and the AWE crew are amazing to talk/deal with..

Anyway I hope you sort this out for yourself,this is a definate must do mod....one of many that are my favorites,LOL...GL!

Stacy

[RonCT]

Just found this thread... I had two different setups on my 07 C2S. First was AWE headers, cants, and mufflers. Great stuff, better performance and sound for the track, but too loud for a street car around conservative CT. Second try was X51 headers, AWE cats, and stock mufflers. Sound was perfect.

In all cases, the rasp was there from day 1 with the OEM setup. In each modification combination, the rasp was reduced or eliminated. Meaning the "ball bearing in a blender" sound was most pronounced with all stock, and was eliminated with both of the mod systems.

[Bara]

Originally Posted by RonCT

Just found this thread... I had two different setups on my 07 C2S. First was AWE headers, cants, and mufflers. Great stuff, better performance and sound for the track, but too loud for a street car around conservative CT. Second try was X51 headers, AWE cats, and stock mufflers. Sound was perfect.

In all cases, the rasp was there from day 1 with the OEM setup. In each modification combination, the rasp was reduced or eliminated. Meaning the "ball bearing in a blender" sound was most pronounced with all stock, and was eliminated with both of the mod systems.

Ron, im glad you finally saw this thread. a couple of months ago, i started a thread about "modification regrets". in that thread, you said the cats and headers give the car an 'intoxicating sound'. based on this info, i purchased a set of awe cats.

i have not installed them yet and this thread made me reconsider the cats and i put them up for sale a few days ago. all i wanted to swap were the cats. some have said in this thread that the header is not going to fix the sound either.

since posting up the sale thread, i have had others tell me that the header/cat combo or even just the cats will give the car a nice bump in power and sound.

your post above again gives me hope and i think i will stop being a wimp and install these dang things and call off the sale.

[RonCT]

I'm no engineer, so I don't know if this even makes sense. But bone stock the car had a terrible rasp, tinny, high-pitched sound. With the X51 headers and AWE cats, the sound was fantastic. No rasp, deep tone, gurgle on release, etc. Must have something to do with the reduced restriction up-stream from the mufflers.

[deputydog95]

High flow cats are just noisy. Cat bypasses are obnoxious. Even headers add to the rasp. My car never sounded better than when it just had aftermarket mufflers and everything else was just stock. I just took off the muffler bypasses recently because I got tired of not being able to use my cell phone.

I would leave the headers, and especially the cats, alone.... People take it for granted but the cats do a lot of sound deadening. These engines don't sound good raw.

[Ian_UK1]

Another thing to bear in mind is that there are 3 different versions of the stock Porsche (non-PSE) 997S muffler. As the results people are getting with just a cat swap seem to vary from horrible (Nexus, me) to perfectly acceptable, I'm wondering now if it depends on the version of the standard muffler fitted to the car.....?

[Ian_UK1]

Originally Posted by deputydog95

These engines don't sound good raw.

Couldn't agree more.

Whereas some engines sound amazing with almost no silencing (Ferrari flat-plane V8s are a perfect example especially in the 355/360) the Porsche 3.8 in the 997S.1 is extremely agricultural sounding by comparison. I'm not sure if it's down to the cam timing, the fact that it's in effect 2 x 3-cylinder engines or other factors The fact is that as Deputydog says, this engine will never sing to you if you open it up too much - it just sounds loud, flat and unrefined.

The best sounding exhausts for this car do seem to keep the standard cats. I just love the Tubis with the rest of the exhaust stock - amazing. It's just a shame it's the cats that are the key to performance as it seems much harder to get a really tuneful sound once the cats are replaced.

[justatoy]

Originally Posted by deputydog95

High flow cats are just noisy. Cat bypasses are obnoxious. Even headers add to the rasp. My car never sounded better than when it just had aftermarket mufflers and everything else was just stock. I just took off the muffler bypasses recently because I got tired of not being able to use my cell phone.

I would leave the headers, and especially the cats, alone.... People take it for granted but the cats do a lot of sound deadening. These engines don't sound good raw.

Originally Posted by Ian_UK1

Couldn't agree more.

Whereas some engines sound amazing with almost no silencing (Ferrari flat-plane V8s are a perfect example especially in the 355/360) the Porsche 3.8 in the 997S.1 is extremely agricultural sounding by comparison. I'm not sure if it's down to the cam timing, the fact that it's in effect 2 x 3-cylinder engines or other factors The fact is that as Deputydog says, this engine will never sing to you if you open it up too much - it just sounds loud, flat and unrefined.

The best sounding exhausts for this car do seem to keep the standard cats. I just love the Tubis with the rest of the exhaust stock - amazing. It's just a shame it's the cats that are the key to performance as it seems much harder to get a really tuneful sound once the cats are replaced.

I usually agree with you two on alot of your posts,however,on these ones about the sound of the cats,I do not!
I had Fabspeed headers and mufflers with stock cats and really didn't like the sound and was seriously thinking about changing it.Which is why I purchased the AWE high flow cats.Figured I had nothing to lose and everything to gain!Yes it is louder with the high flow cats,but the sound is completely different from what I had,actually sounds like the car has some work done to it!
Please do understand that on every other car I have had has been built to be fairly quiet,except for my NSX,which I hated with aftermarket exhaust.
I cannot comment on the stock exhaust with high flows,never had it!
But with the above set-up.....I actually love the sound and as long as you aren't bagging on it,it isn't too loud!
Lets's face it if you are bagging on it....exhaust will be the least of your worries when the officer is righting you up,LOL!
I agree with you on the Ferraris and Lambos but to compare them to the Porsche......NO way,they sound WAAAY better!
The sound that eminates from those two is indescribable!

Sorry guys..just my opinion but keep posting I truely do enjoy the posts!

Stacy

PS By watching my tach it seems that the car gets through the RPM's faster.
The 5000-6000 RPM without a doubt goes by way faster now !
I need to revisit the same dyno I did before to get a comparison.