New Exhaust Built....Sounds Horrible!

fastsc92

Registered User
Alright, I finally got around to finishing my new exhaust after replacing the flowmaster/dynomax kit that I had before.

The new set-up consists of custom long tube headers, no cats, dual 2.5", magnaflow resonator, 3.5" center section, dual 2.5" into dual Borla Mufflers. The car sounds sooo bad. The drone on this is unbelievable. I cant figure out why. I figured that the car would sound decent, but I almost cant live with it and i'm ashamed to drive it.

I'm not new to these cars and i did my research before i started this project. I didn't cut any corners when i built this system and used all mandrel bent parts and top, name brand mufflers. Its very very simlar to a Honda. I've gone the route of running no resonator and it sounds just like that, but this time, I'm running three mufflers.

I'm just really frustrated now, after I've been at college and come home once in a while to work on this and after almost 3 months of making headers and the exhaust i start it up, and I'm stuck with this sound. Any ideas of what i can do. I can live the tone, but its got this deep, mellow drone to it that'll give you a headache really quick. I dunno guys.....
 
I'd say get some cats. I have 2cats longest magnaflow resonator that will fit and no mufflers, true dual. Sounds great
 
I wish i could fit some cats in there with those long tubes but i cant........The only thing i can think of is those dynatec header insert cones.....But its not loud, its just the worst Honda drone you can think of.
 
I would say its something with your headers than because I have no mufflers so in theary i should have more drone than you
 
i dont see how the headers would cause anything. Its just the weirdest deep deep mellow tone that'll give you a headache driving around. I mean, its just a kick in the b@lls when i took the time to get the right parts, do some research, order the longest res that would fit, and two mufflers that i thought would be great quality, cut no corners, and spent a pretty penny on this stuff. What else is new with this car.... :rolleyes:

Oh and these are the insert cones i'm talking about: http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=4312&prmenbr=361
 
I'de lose the cones. They might work just fine on an open exhaust header. But I think there causing problems reflecting sound waves around in your collectors. Droneing is really what audio people reffer to as hetrodyning.
Thats 2 objects resonating at the same freqiuncy but with a slight time delay.
The phenonom happens when the engine RPM's rise thus causing higher exhaust temps that inturn decreases the time delay(because sound waves travel faster in hotter enviroments) and the 2 objects begin to resonate with each other. The result is drone or hetrodyning.
You can recreate this with 2 tuning forks of the same octave. Strike them both and move them closer together then farther apart. The closer together they get the more they drone or hetrodyne.
 
After a Little Research and Thinking

Exhaust velocity is too slow (according to Borla), resulting in a droning exhaust.

Things to look at are the; shape, size, and length of the header collectors; and the use of a 3.5" center section.

If you have not done a lot of of mods to the intake and heads yet, then don't mess with the exhaust until you see what it will sound like with the added flow.
 
Hmm, I think I recommended a 3" center and 2.25" duals. ;) Anyway, doesn't help you now. You could try wrapping the pipes with header wrap. Keeping some heat in the pipes will help velocity. Other than that bigger mufflers in the back are probably the only thing you can do. What are the dimensions on the Borlas?

I have longtubes, a 21" Magnaflow (which in my opinion doesn't do much, it's loud as all heck with just the resonator) and some cheap turbo mufflers at the back. It was very quiet and sounded nice until the packing burnt/blew out of of the mufflers. Now it is too loud again and drones a little. I was just going to replace the cheap mufflers. I don't think a little restriction at the end of the system is that bad of a thing.

Sorry about your luck with this. :(
 
Noise

I would also agree with Dave on this I really think it is the 3.5" section. I went 3" and it has a deep sound but no Honda here.
 
I dont have headers, but my exhaust system consists of 2.5" to summit glass pack on each side a 3" midsection and 2.5" out with hooker aerochambers. Its pretty dang quiet, but i guess its good with power. I have cutouts before the glasspacks and i opened them on the dyno and lost 10HP. I'd get rid of the 3.5" midsection and just go 3. It will sound pretty good too.
 
Sorry to confuse anyone, but I dont have those cones in there.....This was just a thought of something i could do to stop the drone. I went with the 3.5" center pipe only because i wanted to keep the flow about the same with the dual 2.5" pipes. If i had to measure, the 3.5" section is probably only 2.5 feet long, and doesn't go far at all.

I could change the whole system over again, but I honestly don't think that the small length of 3.5" pipe would cause all of that.

The borla's are almost 15" long, center/offset 2.5". I based my system on what others have done. The SCP exhaust is nearly a clone of what i did with them using 2.5-3-2.5. I just used 3.5" instead and only went a distance of a little over two feet. I'll post some pics tonight and show you how the system looks. I think you'll all be very impresses with the quality of it, but that doesn't speak for much when it sounds like this.

I'd like to point out that there are no tips on the ends of the mufflers. No one had any turn-down style tips so all the exhaust gasses are pointing right into the rear bumper. Not sure if this will cause all that drone, but it might contribute to it somewhat.

The headers are Mac longtubes that i modified. The collectors on those are 3", but then they taper down to a ball and socket style that accepts 2.5" pipe. Each primary is about 27" long. One thing to point out as well is that the resonator is dual 2.5" single 3". I just added a reducer to make that out to 3.5" So once again, I might be stubborn, but I dont know if 2 feet of 3.5" pipe would be causing all of that. Header Pic:
drivedone1.jpg


I thank you guys for responding and giving me a lot of ideas to work with.
 
For what it's worth, my extensive drag racing experience, but I am suffering from oldtimes disease I would say the collectors are too short. Did they have to be done that way? Going back to my street racing days it seems to me that I used to bolt my mufflers directly to the collector's, maybe that is why I think the collectors should be longer???? I have no business offering my advice here cuz I am a throwback to 13 to 1 compression and 500 inch motors. God if we only had todays technology back then. WOW.
 
Maybe the collectors are too short, but i didn't design them. These headers are made by MAC to fit the 3.8 stangs. I've often heard stories of these headers giving those guys 25hp at the wheels over the stockers.

I just got some exhaust tips so now the sound should be dirrected under the car, rather than into the bumper. We'll see what that does..... :rolleyes:

Oh kind of an off topic question, but now that the exhaust is on there...it starts to break up really bad under WOT around 4000-5500. When i first started it up, it was running really rich and the wideband showed 12.6 at idle! This might be the cause of the break-up, however now it reads about normal with a 14.4-8 idle. I'm not sure if the o2 sensors have anything to do with that since they are so far from where they were before. Maybe i can change something with the exhaust pulse delay....any tips on this Dave..?
 
catwithboost said:
I would also agree with Dave on this I really think it is the 3.5" section. I went 3" and it has a deep sound but no Honda here.

Ditto. I'd ditch the 3.5" section and replace it with 3".

-Rod
 
That could be the reason, but it just doesn't seem logical. I just measured the center section and its exactly 24" of 3.5" pipe. I dont see how that small amount of pipe would change anything.

I'm not sure what anyone else is using for mufflers, but these are a straight through design and not a turbo style. So the resonator, and both mufflers are straight through, which might not help with the sound reduction.
 
Here I am sticking my old nose in here again. If my memory is serving me correctly headers equal a lean condition. At least with carburetion it would happen. Lean condition causes breaking up at higher rpm under load. But your "Greek to me" explanation of a rich condition caused me to really delay this response waiting for someone with FI knowledge to jump in with some suggestion.
 
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