No luck in LT1tech, so ill try here

"I am thinking about adding another ultra flow muffler in series with my current Ultra flow(straight through). any idea how much this will cut down on noise?"

I know I am looking at diminishing returns, but any hands on data that would prove/disprove this as being a good idea?? thanks!

 

Hey Jordon, you know Jason added a bullet muffler (ipipe) before his ultra-flow round muffler (stock location). I bet he can tell you what you want to know .


Ryan

 

Jordon, I had a hell of a time with my car when it was still rotary powered, because rotary engines "complete the burn" in the exhaust, and turbo rotaries are nearly as loud. Non-sequential with the stock twins, the car would wake the dead and blow flames out the exhaust when it backfired. On my third attempt at an exhaust, I ended up with a single tip (3" inlet, 4" outlet) from PFS that was still too loud. I eventually had a Borla XR-1 muffler (12" long, 3" in, 3" out) welded into the mid-pipe and it dropped the noise considerably without affecting performance. I then switched back to an aftermarket twin tip and the car was much more livable in daily driving, but I still noticed everyone fleeing the building when it was on the dyno.

Brian Richards, who owns M2 Performance in CA recommended the XR-1. He runs three of them in series on his race cars to keep the noise down for certain tracks and tests have shown that they affect overall power very little.

If you're looking for a compact muffler to place in series, Borla makes a round "bullet" style and an oval, in 12" and 18" lengths, I believe. They're very compact and easy to tuck up into the place of a stock catalytic converter. I'm probably going to end up putting another Borla in my new mid-pipe with the LT1 just to keep the noise down somewhat. I don't think that the twin tip cat-back mentioned in my header post is going to keep the car quiet enough to avoid attracting the wrong kind of attention, if you know what I mean.

Hope that helps!

 

I've got one of those 12" Borla XR-1 mufflers in the stock location and a Dynomax 3" bullet on the intermediate pipe. With Hooker LTs and !cats, it is quieter than my friend's car with a Dacoma cat-back and shorty Edelbrocks. It's fairly loud when you get on it outside the car, but cruising around it's quiet.

If you are going to do a second muffler in series, I'd get a different type of muffler so that it dampens different frequencies. That was Mufflex's advice when they made me this set-up at their shop.

 

Putting 12" XR1's in the y pipe in place of the cats sounds like a great idea. Didn't think of that one. I'm guessing it could fool quite a bit of people when they look under the car. And then put one in the back of the car in the stock location but I'm sure it becomes a pricey option.

 

I have a dynomax bullett inline before my flowmasters and it quieted it down some. There is less high rpm rip that was there (miss it too ), but over all it is quieter by a few dbs. There is less drone on the highway, but in general, people still think my car is loud, it just not LOUD anymore.

 

I'd be most concerned about space constraints.

I'd run two Dynomax bullets, one on each side of the Y pipe.

I had dual Borla XR1's they sound nice but they are pricey.

 

Do you have any sort of crossover like an H or I pipe? That may help a little bit. Otherwise, I'd look into one of Spintech's mufflers or and XR-1.

 

Adding another muffler in series should theoretically double the backpressure (negligable with a good muffler) and drop the noise by 3 or 6 dB (which one, I can't figure out as my brain was numbed by a week's worth of vacation).

 

Has anyone tried the Dynomax "cone" noise reduction inserts?

I ran the 3" Borla XR-1 shorties in place of the cats, with a Mufflex 4" catback, and it was extremely quiet. I know George Baxter ran the same system up to about 1,000HP, when he decided the Mufflex 4" weighed too much. His car was also deceptively quiet. I think this is a good example of using two differnt types of mufflers to help cancel a wider frequency band.

I've since switched to a system consisting of the Borla XR-1 hanging on each header collector. Loud . The local track (Englishtown) now requires 90db at 100-feet, in tech, and under load on the track. They also require that the exhaust extend beyond the rear of the door. I was thinking of running 3" pipe straight back from each Borla, and putting a Dynomax 3" turndown with cone on the end of each pipe.

Wondering if anyone has measured the "cones" for performance loss? If not, I guess I will have them make up a set of plain turndowns, and the "cone" turndowns, and test both of them for HP and noise levels next time the car is on the dyno.

 

When you're thinking about exhaust system design, you need to remember that the farther back you can get the muffler, the less restriction it will induce. It probably makes the mufflers' job easier too (which translates to quieter). Balance pipes help too, but a y-pipe sorta subverts that.

 

Really? I thought that dual exhaust would weigh more. What's lighter than the 4" mufflex?

 

This is a question which gets into exhaust system design, and how different silencers interact with each other. If the two silencers are identical and placed close to each other, you will see a small improvement, but not much. If you put them at different points in the system, you will see more of an improvement. If you know the frequencies that you want to attenuate and can place the silencers at the quarter-wave point associated with that frequency, you will see the maximum effect, assuming the silencers are tuned to that frequency.

Without testing to find out, I suspect that you could get decent silencing by putting a larger silencer in the stock muffler location and putting a resonator further up the system. I plan to try this in my system. Size matters. More volume attenuates better if it is properly configured inside the silencer. If you want straight through performance, a silencer that uses some sort of packing (steel wool, long fiber glass wool, basalt) is effective. Fred's comment about widening the frequency band is correct. OEM's have been doing this almost from the beginning. If you see multiple elements in a system, it is either to hit multiple problem frequencies, or because one makes the other work more effectively. There is usually some separation between the elements.

As a general rule of thumb, the silencer is more effective the further upstream you move it away from the exit (unless it's at a node). A muffler at the back would likely be much more effective if moved closer to the front. I have heard people say they'd give up 5 cc's of volume in back to gain one up front. It's not always possible due to packaging constraints, but it illustrates the point.

 

One Borla XR-1 shortie attached to each collector flange, a turndown on the outlet of each muffler and NOTHING else, weighs approx 50# less than the same mufflers PLUS a 4" Mufflex catback.......

 

While the muffler might be more effective further upstream, I would be concerned that it could restrict power more than if it were further downstream. I'm no engineer, but aren't the exhaust gases much hotter upstream and therefore more in need of a voluminous exhaust than they are just before system exit after they have cooled and the gas molecules have moved closer to one another? Isn't this the reason that a cutout is much more effective if placed up near the collectors rather than just before the rear muffler?