installation report - Magnaflow S54 header/cats

[MartyBtoo]

The back story: At about 80K miles the check engine (SES) light came on, but the car drove fine. Took it to PTech, who told me that it was caused by an error from the bank 2 catalytic convertor efficiency dropping. They said there was no harm in continuing to drive it, but it would be a problem at a smog check. Drove it for about a year, and the light would come on for a few days, then it would go off, sometimes for several weeks, before coming back again. I had PTech checking codes at every oil change, and bank 2 had more hits, and finally bank 1 joined in. So I researched cats for an S54, and discovered that you couldn't replace just the cats, as on an S54 they are part of the headers. I soon found that the only choice for a California-legal setup was two Magnaflow part numbers, 452415 and 452416, which sell for close to $900 each.

I was able to buy them on eBay for $850 each. Then I discussed the installation with PTech, and they recommended replacing all 4 O2 sensors at the same time. After negotiating on the price of the sensors, I scheduled the install. That turned out to be a chore due to the way the individual pipes were welded to the flanges. In a few cases they had to grind on the welds to get enough room for a nut on the stud, in other cases they had to grind the flange off of the nut to tighten them. Once the headers were on they found that one pipe was a little lower than it should be and was rattling on the crossmember; they fixed that by shimming the crossmember about an 1/8". I put about a thousand miles on them, then took the car back for the 90K Inspection 1 service. During that I had them check all of the nuts, and none of them were loosening up, so all is well. I did write an email to Magnaflow about the quality issues I experienced with their products. There have been no more warning lights, and PTech said there were no codes stored at all. The entire escapade cost me $3485 for all parts, new sensors and a lot of labor.

The one disappointment is the change in sound. The car no longer screams, instead it roars more. The reason is simple: The OEM headers, which now hang on the wall of my shop as a monument to the expense of smog compliance, have relative small diameter primaries that are carefully wound around to be equal length; the Magnaflows, on the other had, have larger primaries that go straight to a junction, so are no longer equal length. It sounds fine, but I miss the snarl that the OEM headers had.

Marty

[Mystikal]

Great review, Marty. I've seen the S85 V10 Magnaflow manifolds but didn't even know there was an S54 version.

What made you do this instead of buying used headers? I personally have a stockpile of good, used S54 exhaust manifolds sitting here as everyone wants to install aftermarket headers and leave these behind.

[BimmerBreaker]

Its illegal to sell used catalytic converters

If my cats go bad ill be doing ebay headers and aftermarket cats, but no CA smog to worry about here

[sjdennis]

Hmm,
My S54 M Roadster has about the same mileage but no issues yet. Just for kicks I went to the Magnaflow site and plugged in my make model etc and they said they had no compatible products. I then tried the same for an M Coupe and found the same result, so perhaps the fitment issues you experienced was related to this?

Magnaflow.JPG

[BimmerBreaker]

M coupe and M roadsters have no differences in the engine bay, so wouldn't have affected fitment.

[MartyBtoo]

(snip) What made you do this instead of buying used headers? I personally have a stockpile of good, used S54 exhaust manifolds sitting here as everyone wants to install aftermarket headers and leave these behind.

I never considered used OEM manifolds for one reason. When I bought the car at 26K miles they were still doing tailpipe emissions testing, and they just barely squeaked by. It didn't surprise me at all that they were done by 80K.

Marty

- - - Updated - - -

Hmm,
My S54 M Roadster has about the same mileage but no issues yet. Just for kicks I went to the Magnaflow site and plugged in my make model etc and they said they had no compatible products. I then tried the same for an M Coupe and found the same result, so perhaps the fitment issues you experienced was related to this?

Magnaflow.JPG

I don't know what you did wrong, as I just went to the site and put in a 2001 Z3 M Roadster and it came up with the same part numbers that I used.

Marty

[PbFut]

I think I would have tried swapping out the sensors first. The S54 motor is extremely efficient burning most of the fuel up in the chamber. I don't think it works the cats that hard under normal circumstances. What fuel are you using? Is the motor loose? Are you using oil?

[MartyBtoo]

I think I would have tried swapping out the sensors first. The S54 motor is extremely efficient burning most of the fuel up in the chamber. I don't think it works the cats that hard under normal circumstances. What fuel are you using? Is the motor loose? Are you using oil?

I use 91 octane Chevron exclusively, and I don't think the engine is loose at all, since I have never had to add additional oil between oil changes. I've no idea about the sensors, as the car seems to be getting the same gas mileage with the new ones as with the old. As the OEM headers (complete with sensors) are bolted to my shop wall, if I ever have an O2 sensor issue I'll just remove one of the old ones and put it back in the car!

Marty

[sjdennis]

I don't know what you did wrong, as I just went to the site and put in a 2001 Z3 M Roadster and it came up with the same part numbers that I used.

Marty

Aha, searched from the Performance Exhaust tab and got "no products". If you search from the home page and look for parts for our car, you get the CAT part numbers that you used.

Dennis