Magnaflow OEM "Replacement" Muffler

**Naaman** · 10-28-2016, 07:04 PM

So, my old Magnaflow was all busted up and needed to go. What I didn't realize was just how bad it was. Not only was it rattling (the pipes were coming loose and crap), but it had holes in the piping; the weld on one of the hangers failed, and one of the exit pipes was basically just loose inside the muffler. It was ungodly noisy driving down the road.

Anyway, I went to the exhaust shop and got the muffler, tail pipes and over-axle piping replaced (They resued my I-pipe since it was still in good shape... saved me $100). Also, they welded the exhaust together, rather than using band clamps, which they said was one of the problems with the exhaust that came off: it wasn't installed securely enough, which caused it to bounce around and eventually shake itself apart.

The car is much quieter now. Not only are the bumps and clunks gone, but the exhaust is quieter. At first it sounded very wispy and airy... kinda weak, really. However, either I have grown used to the sound, or it has "matured" a little bit, as after driving it a couple thousand miles, I am liking the sound more: it seems to be a fuller, more "Magnaflow" sound, though it is still quieter than the outgoing muffler.

Also of note: on the old exhaust I had a strange sputter/stumble at low RPM if I went to WOT too soon (below 2000, even in 1st). The replacement exhaust seems to have almost eliminated the sputter. I suspected that the "loss of backpressure" from multiple exhaust leaks may have reduced low end response/torque, but I wasn't sure that made any sense. Now, I'm sure that the stumble has been reduced: it's much smoother even from idle... or maybe it's a placebo effect... who knows?

Anyway, I am generally happy with the replacement, though, if I could have done it exactly the way I wanted, I'd have gone with a Madhammer, especially knowing that I would not have needed the I-pipe (could have saved some money).

I also went with the rolled tips: I think they look nicer than the straight cut tips.

**pajeff02** · 10-29-2016, 01:58 AM

The only way I can think of that the exhaust would cause a stumble is a plugged converter, bad front O2 sender, or an air leak upstream of the front O2 senders. I run a cutout halfway down the mid-pipe which, in essence, is one monster exhaust leak and have never experienced a stumble.

I agree, the rolled tips do look nice.

**Naaman** · 10-29-2016, 05:32 PM

Yeah, I don't know what the deal is with the stumble being reduced. Though, like I was saying, perhaps its just a placebo effect. I do notice it in higher gears still, but that's more or less normal as I understand it (lugging in too high of a gear). I've also thought that it could be the cam profile just not being set up for that range of operation, but it's out of a Silverado or Yukon or some such, so I would figure (all other things being equal) that it would have favored the lower end grunt.

I had the cats tested while the car was getting the exhaust done. They said they were fine. If it was an airflow issue, maybe it was some obscure perfect storm of leaks and turbulence that just worked out to muck things up... ?

Now if I could just find the time to swap the fuel filter...

**pajeff02** · 11-02-2016, 03:14 AM

Other than getting under the car, the fuel filter swap is pretty darn quick and easy. In addition to logging it in my maintenance records, I have gotten in the habit of writing the date on the filter housing so that I have an easy reminder whenever I am under the car of how long it has been in service.

**Naaman** · 11-02-2016, 05:05 PM

That's a good idea.

**Naaman** · 01-01-2017, 09:40 PM

So, here is an update on the low rpm stutter issue:

I changed out my fuel filter last week and had my first chance to drive on the fresh one today. The car feels noticeably more responsive (not any more "powerful," just more like it's "supposed to feel") and I'm pretty sure the stutter is altogether gone... I'll still have to test this out with a little more stop and go driving. It does seem to lug below 2k in 6th gear if I get on it too hard (like casually overtaking on a wide open freeway), but that may be normal.

One indicator that I seem to be experiencing is the low rpm behavior during braking/stopping. On the old filter, when braking, if the engine got below ~1000 rpm in high gear before disengaging the clutch, I'd get the stumble or imminent "stall" effect. It did not seem to happen this time. I was not particularly attentive to this on my way to work today, but will be paying more attention to it on the way home.