TXAV2003
Full Member
This is an informational post for those who might be considering purchasing either a Magnaflow 12579 or 12589 and want a layman's input on these single-in/single-out straightflow mufflers. Now I'm no mechanic or anything close to being a technical expert like some on this board, and 11H in particular. Moreover, the only dyno I've used is my rear-end (aka "seat-of-the-pants" feel). However, within the last three weeks, I've had occassion to try both the 12579 and 12589 on my '03 1500 AV and found significant enough differences to post my thoughts about them.
LOUDNESS -- As 11H has mentioned in previous informative posts (see e.g., this great post) and Magnaflow has confirmed, the 12579 muffler was designed for our 5.3L engine. It is louder than stock (by maybe 10-15db's, my best guess), but definitely quieter than the 12589 (by at least 10-15db's). The 12579 has a nice sound, but I doubt you will be able to tell how loud it is to the outside world unless you go WOT in a tunnel or a parking garage or something. I've driven around town with my windows down and I can't really hear it that much. ON THE OTHER HAND, the 12589 has an awesome louder sound that you can definitely hear, especially when you drive under freeway overpasses. It leaves no doubt that you've done a muffler mod to your AV, and it really sounds great (sort of sounds like a cigar speedboat exhaust). From a pure exhaust note standpoint, I'd vote for the 12589 (the AV also sounds less strained under WOT with the 12589, whereas the 12579 is sort of higher pitched and makes other drivers think you're winding up your engine to race or get ahead of them -- a layman's observation).
RESONANCE -- The 12579 beats out the 12589 here, but still has a surprising amount of resonance when driving @ 70 mph (approx 2200rpm w/4.10's). At 65 mph or 75 mph resonance is not a problem (you hear none @ 65, and you hear a nice higher pitched humming noise @ 75+). But right @ 70, the resonance is noticable and irritating, at least to me. The 12589 has resonance from about 65 mph on up, but it is lower in pitch -- like a subwoofer. To be honest, my wife didn't even notice it that much compared to my '00 Dodge Dakota Quadcab w/5.9L engine and Gibson Single Sideswept catback, but I did and had to turn up the stereo.
PERFORMANCE -- The 12589 wins hands down. I noticed a definite low end performance improvement from say 5mph - 45mph and I felt the engine & tranny were less strained when getting up to speed. There is an improvement with the 12579's as well, but my observation is that my AV likes to downshift more, or when it does, the exhaust noise pitch is higher than the 12589, and thus makes the engine sound more strained or like one of those Japanese Racing Motorcycles. The 12589 sounds like a V-8 truck ought to sound.
CONCLUSION -- Both mufflers are an improvement over stock, unless you can't tolerate any cabin resonance. I'm still undecided whether I'm going to keep the 12579 on or go back to the 12589. All things considered, it wouldn't be an issue but for the 12579's resonance @ 70mph -- if both of them buzz at this speed, I start to wonder what's the advantage in keeping the lower performing, less awesome sounding 12579 muffler? Still, the 12579 may be the best compromise for those who are looking for a more aggressive exhaust note with little increased cabin noise (except as noted above). My AEM Bruteforce intake should arrive this week. I'll probably wait and see how much louder things get with this installed b/4 making my final decision.
LOUDNESS -- As 11H has mentioned in previous informative posts (see e.g., this great post) and Magnaflow has confirmed, the 12579 muffler was designed for our 5.3L engine. It is louder than stock (by maybe 10-15db's, my best guess), but definitely quieter than the 12589 (by at least 10-15db's). The 12579 has a nice sound, but I doubt you will be able to tell how loud it is to the outside world unless you go WOT in a tunnel or a parking garage or something. I've driven around town with my windows down and I can't really hear it that much. ON THE OTHER HAND, the 12589 has an awesome louder sound that you can definitely hear, especially when you drive under freeway overpasses. It leaves no doubt that you've done a muffler mod to your AV, and it really sounds great (sort of sounds like a cigar speedboat exhaust). From a pure exhaust note standpoint, I'd vote for the 12589 (the AV also sounds less strained under WOT with the 12589, whereas the 12579 is sort of higher pitched and makes other drivers think you're winding up your engine to race or get ahead of them -- a layman's observation).
RESONANCE -- The 12579 beats out the 12589 here, but still has a surprising amount of resonance when driving @ 70 mph (approx 2200rpm w/4.10's). At 65 mph or 75 mph resonance is not a problem (you hear none @ 65, and you hear a nice higher pitched humming noise @ 75+). But right @ 70, the resonance is noticable and irritating, at least to me. The 12589 has resonance from about 65 mph on up, but it is lower in pitch -- like a subwoofer. To be honest, my wife didn't even notice it that much compared to my '00 Dodge Dakota Quadcab w/5.9L engine and Gibson Single Sideswept catback, but I did and had to turn up the stereo.
PERFORMANCE -- The 12589 wins hands down. I noticed a definite low end performance improvement from say 5mph - 45mph and I felt the engine & tranny were less strained when getting up to speed. There is an improvement with the 12579's as well, but my observation is that my AV likes to downshift more, or when it does, the exhaust noise pitch is higher than the 12589, and thus makes the engine sound more strained or like one of those Japanese Racing Motorcycles. The 12589 sounds like a V-8 truck ought to sound.
CONCLUSION -- Both mufflers are an improvement over stock, unless you can't tolerate any cabin resonance. I'm still undecided whether I'm going to keep the 12579 on or go back to the 12589. All things considered, it wouldn't be an issue but for the 12579's resonance @ 70mph -- if both of them buzz at this speed, I start to wonder what's the advantage in keeping the lower performing, less awesome sounding 12579 muffler? Still, the 12579 may be the best compromise for those who are looking for a more aggressive exhaust note with little increased cabin noise (except as noted above). My AEM Bruteforce intake should arrive this week. I'll probably wait and see how much louder things get with this installed b/4 making my final decision.
