hey guys i got a 99 z28 and want to do the exhaust. I am trying to choose between Flowmaster American Thunder - Hooker cat back - or SLP Loudmouth. The sound i am looking for is a very throaty powerful true american made V-8 sound. i want it to be loud but not extravagant. and have absolutely no raspiness to it. would i be better with one of those catbacks? if so which one? also can i achieve this sound through just replacing the muffler? I dont want to do x-pipe or header or cat or cutout work. just basic catback or muffler . thanks again in advance


Mike

 

Don't do the flowmaster whatever you do. It's the worst flowing muffler/catback out there. If your like me you want to get an aggressive sound and add some HP while your at it.

The loudmouth is a good choice but there are a few drawbacks. It tends to be a little raspy and causes interior drone at around 2000 rpm's so in A4's at least highway travel can be brutal on your ears. And the loudmouth is often referred to as way too loud with headers and could cause you several tickets with your local police on noise violations. But if you don't have or plan on headers and you either have a m6 or you don't do much hwy driving then the loudmouth is an excellent choice since it's the best flowing catback on the market, loud as heck, stainless steel and a good price.

Hooker is a great choice too. It's deep and throaty but a tad on the quiet side. You'll notice very little improvement at idle over stock sound, cruising sounds just a tad better then stock but not by much. WOT runs are where you can hear the difference as night and day between a hooker and a stock muffler. There is no rasp, no drone and good HP gains for an excellent price. Only downside is it's a little too quiet for some until LT headers are installed and it's not stainless steel so it can rust after a few years especially if the car sees rain and or snow.

But I have to recommend GMMG if you have lots of money as it costs $700 in a GP but is worth every cent. Very bad a$$ sounding exhaust with no rasp and excellent gains. Top of the line IMO.

But if you are on a budget then I have to recommend Dynomouth 100%. I did it and absolutely love it! Here are the facts,

Catbacks offer you 3" stainless steel mandrell press bent pipes. Your stock pipes are 2.75" stainless steel mandrell press bent. Although you will gain a little from upgrading the pipe size .25 of an inch it's hardly worth the extra money spent on a catback IMHO. 95% of HP gains from a catback are in the new muffler/resinator not the new pipes.

So what you do is buy a 12" Dynomax bullet race muffler (if you have cats and no LT headers) or a 18" dynomax bullet race muffler (if you go catless and or have LT headers). The muffler costs $36.00 new so about $50 bucks shipped to your door. Then you find an exhaust shop that will do two things. First they cut out your stock muffler and fab in a pipe to take it's place just to keep dual out continuity. Then they weld the dynomax bullet race muffler in your I-pipe right behind the rear axel. If you don't like the stock tips you have now it's a good chance to replace them. Just buy a pair of tips from somewhere online and bring them with the bullet muffler. Or if you like the stock tips then your good to go.

The muffler shop that did mine charged me $100 for the parts and labor including swapping out my tips for ones I brought with me. The car will be almost as loud as the loudmouth but toned down a tad with no rasp. If there is drone I can't really notice it so having a conversation in my a4 on the hwy is no problem. The HP gains are just as good as loudmouth since the bullet flows the same as the resinator (2200 cmf). And the sound, OMFG it rules. loud at idle, mean at acceleration (but just under the point where cops take extra unwanted notice) and it screams at wot. I turn heads everytime I go wot with pedestrians outside.

And $100 for labor, $50 for muffler = $150 which is less then the catbacks and someone else had to do the work. I know a lot of folks like working on thier cars but not many enjoy exhaust work. It's just not as glamorous as engine work. Even with new tips I was at $250 which was still cheaper then a hooker or loudmouth catback. But I really like z28 tips so if you do too then $150 and your set.

I hope some of this helps. Good luck with whatever you decide.

 

2.75" stock "I" and Over axle pipe + muffler restricts 20 HP in my application (dyno proven) vs. open cutout.

Just get a full 3" Cat back like the Hooker.

 

I did the Magnaflow Muffler I think it was #16427. Great sound, very deep and no raspiness. Its the only mod to the car so far. I has now drone, and you can get it from hottexhaust.com for about 100 bucks-its a stainless steel muffler too. I also have been getting about 2.5 better mpg so it should pay for its self in about 100 fill ups or so. lol. I have also heard that it gains you about 15 rwhp, but I havn't dyno'd my car, and I don't race it so I can't verify that with you. I think you'll be very happy with this muffler. I did just the muffler because it wasnt worth the extra 300 bucks to gain 1/4 of an inch all the way back.
Good luck.
Ed

 

Then why do most people only gain 7 rwhp from a hooker catback? or 13 rwhp from a loudmouth which is pretty much as free flowing as a cutout. I'm talking bone stock cars with exhaust added because modded cars can react differently. You will gain a couple of RWHP from the pipes but lets not get carried away here, .25" upgrade is not gaining a stock car 10 rwhp unless the dyno machine was a bit off. A full catback is still a great idea but most of your gains are in the muffler and just a few in the catback pipes.

But change out the y-pipe and add headers and now your talking some serious HP gains. The LT headers are where the big exhaust HP gains are found.

 

Thanks for all the replies, it has helped me out alot. I have decided to go with the 12" bullet muffler from Dynomax, and a local exhaust shop is mandrel bending pipe from the cats back with 3" stock for me. so i will have a cat back the way i want it. I will post pics when i get it all done. After that, i want to get the JET HOT L/T's and the Y-pipe. what do you guys think of that setup?????

Thanks again

Mike

 

One thing I've learned, when you mod, mod for the future.
Your argument is correct, but the flaw is that lots of us don't keep our cars near stock very long. I'm driving around with a big cam pushing air through straws out the back (at least I have a cutout). I should have gotten a full 3" catback instead of doing the muffler swap. Live and learn, 3" X-pipe on the hit list now.

PS. Big cam chosen for planned Stage II heads (again modding for the future).