So after several months I’m finally getting fed up with the excessive drone that the 3” Magnaflow catback has added to my Legacy GT wagon. It sounds really, really nice when I’m on the throttle… but it’s just too loud while cruising. This is the system I have:
https://www.rallysportdirect.com/part/cat-back-exhaust-system/mag-16747-magnaflow-cat-back-exhaust
I figured adding a baffle to the straight section of 3” pipe right before the “Y” might work well to quiet things down. Something like this looks perfect:
http://www.carchemistry.com/silencer-insert/
The problem is that these seem to be plain steel. I would really prefer one in stainless steel, so that it lasts as long as the rest of my stainless catback.
Anyone seen something like this in stainless?
I haven't seen a stainless one, but that one you linked is kinda pricey. This is more like it.
ebay.
Those seem like a horrible restriction to me. What about adding a resonator or small muffler in place of a straight section of pipe?
NEALSMO
UberDork
11/14/17 1:58 p.m.
rslifkin said:
Those seem like a horrible restriction to me. What about adding a resonator or small muffler in place of a straight section of pipe?
This.
My experience with loud exhausts is that resonators improve drone and sound quality with the least amount of restriction.
Thanks for the link to the cheaper version. I saw those too, but they look more prone to rattling… opinion only of course… they might work just fine. The one I linked looks like it should fit nice and snug in the pipe, almost like a stack of freeze plugs. I do wish it was cheaper though...
I could add a resonator in theory, but in my experience they really don’t reduce volume very appreciably. Plus it would be more work than slipping something inside the pipe and tightening one bolt (or applying a tack weld or two). Also very difficult to undo if it doesn’t help!
Adding an “actual muffler” would be problematic due to lack of space. This is what the stock center muffler looks like… no one makes a muffler that’s offset like this, at least not that I could find. There is very little clearance on the driver’s side of the pipe.
http://legacygt.com/forums/attachment.php?attachmentid=128293&d=1347230830
I’m not super-concerned about adding a little restriction at this point. The car has 210K miles on the original short block, and is still running stock boost levels. I’d still be running a stock exhaust system if it hadn’t rotted out… got a good deal on a lightly used magnaflow system & decided to go for it since it was stainless.
If you have an RPM specific drone maybe look into a tuned 1/4 wave resonator.
RPM where it drones * 0.066 = Frequency of drone
1075 feet per second / Frequency of drone from above calc = Length of wave in feet
You want the quarter-wave tube to be 1/4 of the wavelength so multiply that wave length by 0.25
Maybe drone was the wrong word – it’s not RPM specific, it’s just much louder than I would like with low throttle input.
It’s tolerable during my short daily commute, but having driven it 3 hrs to Maine and back recently…. It gets old quickly on the highway
