Damn,WTF

[grt08g8]

:wtf:is going on. Had new exhaust put on today, stainless mag's with X-pipe, now at idle, s.o.b. sounds like a 4 banger.is this norrmal? is it due to the dod or what, if so can I cut it off? also, what is engineering mode?:charlie2:

[Weldon]

give it a day or two for the pipes to wear in

[GRRRR8]

It should only sound different at cruise with AFM/DOD active.

[09PBMGT]

Its possible the muffler shop you went to, put a shoddy product together. Your right...... it shouldn't sound like that. Good luck on getting it resolved.

[-Ray-]

We need sound clips.
I had that configuation with an x pipe, and it sounded really mellow.

[Andy@Livernois]

:wtf:is going on. Had new exhaust put on today, stainless mag's with X-pipe, now at idle, s.o.b. sounds like a 4 banger.is this norrmal? is it due to the dod or what, if so can I cut it off? also, what is engineering mode?:charlie2:
was this an actual kit? or a "custom" made piece? the reason I ask is MANY exhaust shops will custom make exhaust using o.e. sized piping, but when bent it is actually smaller then stock. This changes to tone, DB level, and performance. Now you said stainless "mags" are they actually magnaflow branded mufflers? or just stainless mufflers the shop put on? all of these can play a role in the performance/sound of the exhaust...

[grt08g8]

IT is not a kit, custom made x- pipe with stamped, polished magnaflo's. I've determined what I'm hearing is the afm on & off, sounds great at start-up and when i'm laid into it but at part throttle it sux,also sux to come to a stop at light,sitting there idling in gear, I guess afm is still active and doesn't come back til I mash the gas again. Is this something I can manage with the dashhawk or do I have to have it progrrammed out with a custom tune. Oh yeah! charlie, I know you are lurking in there sum where, you were right, it is a part throttle issue. I believe I posted a soundclip on another thread can;t wait any longer.

[macgto]

IT is not a kit, custom made x- pipe with stamped, polished magnaflo's. I've determined what I'm hearing is the afm on & off, sounds great at start-up and when i'm laid into it but at part throttle it sux,also sux to come to a stop at light,sitting there idling in gear, I guess afm is still active and doesn't come back til I mash the gas again. Is this something I can manage with the dashhawk or do I have to have it progrrammed out with a custom tune. Oh yeah! charlie, I know you are lurking in there sum where, you were right, it is a part throttle issue. I believe I posted a soundclip on another thread can;t wait any longer.

AFM is not active at idle. AFM is only active at cruise and light load/throttle. If you are using over about 15% throttle, AFM will deactivate. If AFM is active and you are off the throttle and coasting down, it will stay active until you get down below 30 mph and will deactivate by itself. Again, no AFM at idle.

What you are hearing is something else, but not AFM, not under those conditions.

mac

[grt08g8]

Well then, WTF any ideas like I said it sounds good as long as i'm mashing gas

[macgto]

Well then, WTF any ideas like I said it sounds good as long as i'm mashing gas

Well, the only thing I can say it that is has to be the configuration of the system.

I did some testing on some axle-back mufflers from Pypes. They are not out yet, but I offered my car as a developmental test mule for these. They have mocked up two sets, using off the shelf mufflers that they have.

The first prototype used their Violator straight thru muffler. Here are links to the sound clips.

http://www.youtube.com/watch?v=dVWQE7jFlTs

http://www.youtube.com/watch?v=jvprkAd6-tE

The second set of prototypes used their Street Pro 3 chamber muffler. I don't have sound clips for these, as they did not sound good. At idle, they had a nice low rumble, but at WOT they produced an odd "flutter" caused, I suspect, by the chambered design. The techs at Pypes were not happy with the sound of those, so they went with the Violator for the production design.

I had the Street Pro set on my car for about a month, and then took them off. They were fine around town, but on the highway, produced a drone that got tiresome after a while. Also, there is a distinct difference in the tone when the AFM activates on the highway.

As I said, these are axle-back. No other changes were made to the system, and there is a lot going on under there. Cats, mid muffler, resonators, and the rear mufflers. That's a lot of chit! I can't even venture to guess where the AFM sound control lies in the system, but it seems that the rear mufflers have a lot to do with that.

I think any aftermarket muffler design is going to have to address the AFM/non AFM issue if they are to be successful. I don't know how they will do it, I'm not an engineer. But, as a G8 GT owner, it is an issue from the driver's seat.
I would almost think that in an aftermarket exhaust, there would need to be some sort of built in cut out (like on the Corvette) that can change the internal configuration of the airflow inside the muffler when AFM is active. I know that's asking a lot, and I'm sure it will be $$$.

I know this is a lot of bs and doesn't answer your question, but maybe it will help you understand what's going on under the car.

mac

[EcoBrick Bob]

Did they use the factory mounts or create their own? Is it possible something is touching/rubbing? Did they replace all the pipes from the x pipe rearward?

I have SF's Axleback Magnaflows and an H pipe where center muffler was. After 5K, it is a bit louder and DOD is noticeable, especially between 55-62 mph, but not annoying. Mostly notice when it comes on and off. Also did Charlie's mod of removing insulation on top of manifold so have maxed out my DOD noise! Think we will have to learn to live with DOD as it will be on most if not all GM V-8's soon..

Good Luck...

ANY COMMENTS FROM OTHERS ON X-PIPE VS H-PIPE EFFECTS ON DRONE...????

RRM

[grt08g8]

everything was cut out, all that remains are factory cats,and they used all factory hangers to rehang new.