My car has always been cursed with loud exhaust. It's just a mild 306, maybe 260 RWHP, with 1-5/8 equal-length shorties, magnaflow spun-metallic cats in a custom 2.5-inch H-pipe, and a 2.5-inch cat-back with full LX tailpipes. Everybody says Super Turbo's are almost too quiet. Mine were louder than hell, so I replaced them with new ones. They were quiet, for about 2 weeks, then got louder than hell again. So I replaced them with some Borla ProXS, because they're supposed to be quiet. They were...for a little while, then got louder than hell. And here's what they looked like when I took them off, after less than 4000 miles (350 of them on road courses):
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So I just put some Walker Quiet Flow mufflers on it, #21548 for $55 each at Summit. They're basically small Super Turbo's without the "flow directors" at each end.
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And yeah, yeah, they neck down to 2.25 inches inside, but I don't feel a power loss, and they have a mild, almost stock rumble at idle, a nice rip at WOT, and are whisper-quiet at cruise with hardly any drone.
Before I took the Borla's off I downloaded the "SPLnFFT" Sound Meter App for my iPhone. It's developed by a signal processing expert who seems to know what he's doing. I did not officially calibrate it, so the readings may not be completely accurate, but the difference in readings is likely very accurate. I set it to the "C" weighting which doesn't filter low frequencies as much as other weightings do.
Here's the results. All measurements taken inside the car, windows up, radio and fan off, with the iPhone positioned the same and isolated from hard vibration-conducting interior materials. Bear in mind, a 10-decibel increase is perceived as approximately twice as loud.
RPM.........Borla.....Quiet Flow
Idle..........79 dB......69 dB
Drone.......85 dB......78 dB
WOT 3rd....89 dB......84 dB
That's some whopping differences at idle and in the drone zone, and a noticeable difference at WOT. Now the question is...will it last? Stay tuned, I have a track event the weekend after next. I'll measure again and see if they got any louder. I'll also likely have the car dyno tuned soon, we'll see if they cost me anything noticeable.
So I just put some Walker Quiet Flow mufflers on it, #21548 for $55 each at Summit. They're basically small Super Turbo's without the "flow directors" at each end.
And yeah, yeah, they neck down to 2.25 inches inside, but I don't feel a power loss, and they have a mild, almost stock rumble at idle, a nice rip at WOT, and are whisper-quiet at cruise with hardly any drone.
Before I took the Borla's off I downloaded the "SPLnFFT" Sound Meter App for my iPhone. It's developed by a signal processing expert who seems to know what he's doing. I did not officially calibrate it, so the readings may not be completely accurate, but the difference in readings is likely very accurate. I set it to the "C" weighting which doesn't filter low frequencies as much as other weightings do.
Here's the results. All measurements taken inside the car, windows up, radio and fan off, with the iPhone positioned the same and isolated from hard vibration-conducting interior materials. Bear in mind, a 10-decibel increase is perceived as approximately twice as loud.
RPM.........Borla.....Quiet Flow
Idle..........79 dB......69 dB
Drone.......85 dB......78 dB
WOT 3rd....89 dB......84 dB
That's some whopping differences at idle and in the drone zone, and a noticeable difference at WOT. Now the question is...will it last? Stay tuned, I have a track event the weekend after next. I'll measure again and see if they got any louder. I'll also likely have the car dyno tuned soon, we'll see if they cost me anything noticeable.
