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YOUR RESEARCHMagnaFlow cat sound vs. 200 cell sport cats?
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Performed · outcome unconfirmed · Original poster
Not a super picture since it's installed already, but here you go:
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The part numbers I installed are 444066 and 444067.
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I recently replaced both cats and all 4 O2 sensors on my 2003 Coupe.
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Stock cats failed and replaced those wtih TopGear 200 cell sport cats, and that is good on the track, but too loud and obnoxious for street, and requires O2 sensor spacers to keep from getting CEL.
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Mufflers failed out so I replaced with Milltek, still on stock cats, and that was very good.
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Stock cats failed and replaced those wtih TopGear 200 cell sport cats, and that is good on the track, but too loud and obnoxious for street, and requires O2 sensor spacers to keep from getting CEL.
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This is a long shot, but anybody had MagnaFlow cats and also 200 cell sport cats and can compare the sound? My story has been:
Original exhaust was too quiet, but came free with the car, so no complaints
Mufflers failed out so I replaced with Milltek, still on stock cats, and that was very good.
Stock cats failed and replaced those wtih TopGear 200 cell sport cats, and that is good on the track, but too loud and obnoxious for street, and requires O2 sensor spacers to keep from getting CEL.
I'm wondering if the Magnaflows would be a better fit and allow me to use the throttle more without feeling like such a jerk in non-track environments. There seem to be very few options out there other than stock, which is obscenely expensive, or sporty aftermarket things, which I"ve found to be a bit too ragged for my taste. I don't feel like spending $2000 on an experiment though; I'd like to know for sure it's going to make an improvement in enjoyment of the car.
I recently replaced both cats and all 4 O2 sensors on my 2003 Coupe. The magnaflow cats have a more pronounced throaty sound vs OEM original cats. For me this increase is just about perfect without being obnoxious. The added bonus of being CA/CO compliant is also nice.
FYI I got the MagnaFlow cats in the mail today and am unimpressed with the build quality so far. There is welding spatter all over everything, including in the O2 sensor threads. Even after cleaning that stuff off, all 4 O2 sensor bungs needed to be chased with a thread tap to make them accept a sensor, as they seemed distorted and threads would only go in one or two turns before feeling heavy resistance. Some of the bungs are noticeably off-perpendicular to the pipes by a few degrees. Also there is a random M8x1.25 bung near the upstream end of each catalytic converter, which serves no purpose on the 996. Maybe a space for an exhaust gas temperature sensor? No hardware is included to seal off those bungs if they are not needed.
Will report back on fit and sound once they're installed.
I have been running Magnaflows for a few months after my original ones failed. I can't comment on the difference between them and 200 cel cats, but can tell you that they sound awesome with my Fister mufflers, much nicer than stock. Unlike the previous poster, mine had no issues with quality, well made and well finished.
I remember when I went from the OEM exhaust to FVD 200 cell cats and sport mufflers back in 2006. The sound was an eye opener at first in comparison to the muted oem sound. Took a couple of weeks to get used to the extra sound and how to control it in the neighborhood so the neighbors wouldnt run me out of town.
Yeah, and I would never go back. Then I worked on improving the air induction sound. Nothing better than an exhaust and intake sound under different levels of aggression with the throttle.
My cats also had the upstream bung. I simply plugged them with a bolt. The quality of the set was fine. Soundwise, I feel no need to follow up with the Fister mod since the cats alone sound awesome.
I did get the converters installed today, and I'd give the MagnaFlow + Milltek combination a thumbs-up. Overall, the sound is much better, at least to my ear, than the TopGear catalysts. I work in the field of vibration and acoustics, so I'm probably more sensitive to the character of vibration that most people, and louder is not necessarily better to me, although there's no doubt the 996 needs something louder than the OE exhaust, which was was much too quiet. The MagnaFlow has a "rounder" sound, while the TopGear has a sharper, raspier, more percussive sound, that I find kind of unpleasant. To me, the MagnaFlow sounds like a Porsche should, while the TopGear sounds kind of hacky and more like a kit car, less polished, like the car might rattle itself to pieces over time. Again, it's not necessarily about overall volume, it's about the frequency signature. The replacement has transformed the car and made it more fun to drive, because I can drive it as authoritatively as I want without feeling like I'm waking every cop in the county, or making my own eardrums cringe. With the TopGear kit, I was making driving decisions based on whether an input was going to sound unpleasant, whereas now I can just drive the car and enjoy it 100% of the time. I'd probably like the MagnaFlow to be 10-20% louder overall, but the character of the sound is a lot better. Another tiny benefit is that the O2 sensors seem to be closer to the OE positions, so the wires and connectors can sit in the factory locations. With the TopGear cats, that was not the case, and some zip-ties were needed to relocate the wires and support the connectors from flopping around.
The main things I don't like about the MagnaFlow are workmanship:
Welding spatter all over everything, including mating surfaces and internal O2 sensor threads.
Hardware provided that doesn't really fit (flanged heads on bolts interfere with rather large-radius welds holding pipes to flanges, along with even larger washers that had zero chance of fitting.
O2 sensor bungs needed to be re-tapped to let sensors thread in freely.
Extra unneeded bungs and no hardware provided to plug them.
The muffler end of the pipes are a couple inches too short, and a short ~4" extension sleeve piece is included to fill the gap. It must be that some similar 911 models use shorter pipes, and this is MagnaFlow's solution to get the same converter to fit additional models? But it's annoying that it is an extra clamp, some extra weight, and some extra places for it to possibly leak.
None of these are a problem once installed, except the additional clamp complexity and potential leak points.
Great to hear, would definitely be interested in a sound clip if possible. Also, would you mind posting a part number for the cats? Not sure why I'm having a tough time finding them online.
Not a super picture since it's installed already, but here you go:
The piece is in the center of the photo. Going from left to right is the muffler (rusty), then the extension piece, then the cat. The middle clamp is an extra one provided by MagnaFlow to attach the extension piece to the cat. It's a pretty simple piece, with a swage and 4 slits cut longitudinally from the big end to let it clamp onto the cat. Tolerances seem pretty sloppy. The one on the left of the car fit snugly and clamped down easily. The one on the right was super loose and required torquing the heck out of the clamp to squeeze it down tight.
In their product photo of the converter, which shows an exploded drawing of all the hardware, this extension part and clamp are not shown, so I was surprised to find them in the box, and thought maybe I didn't need them, but when I laid a new converter next to the old one on the garage floor and saw the new one was much shorter, it became obvious that I had to use those parts.
This photo also shows the unnecessary port in the MagnaFlow cats (top left), plugged with an M8x1.25 bolt.
Maybe I got lucky with mine as far as weld quality is concerned, mine are well finished. BTW,
@dkraige
, nice write up on the sound quality., I agree that somehow the new cats have increased my driving enjoyment much more than I expected.
What are the part numbers of the magma flow cats? I received one that did not fit due to interference with the other unit. Also, BTW, I had a guy tig weld a 3” piece onto the outlet pipe as I thought that extra clamp and extension are a cheap abomination.
BTW if anybody wants the TopGear cats, please DM me. They are in great shape, have about ~7k miles on them, and have no issues; the sound just wasn't for me. Great set for a track-only car that needs to pass emissions, or somebody who likes more noise than me on the street!
I wish I'd seen this earlier - Magnaflow cats are a last-ditch effort to pass smog, they don't last long in my experience. I've tried several times. Best of luck.
A nice HJS cat costs 3x as much but is built even better than OEM.
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