2001SaxsterS

Hey all! Thanks for taking the time to read this and hopefully offer me some advice. The secondary cats on my 01' S have been rattling for a while and my CEL finally got tripped as a result. I'm looking at various options to fix this including using new OEM parts, used OEM from a dismantler, new aftermarket, or possibly just taking them off altogether and putting in bypass pipes. I am leaning towards the used OEM parts, of which I've found several available (at a very wide range of prices) from multiple dismantlers. My second choice would probably be the aftermarket parts. I'll be honest, at this point, with 125k on the odometer and the car showing its age in other respects I can't see the point of spending a ton of money on new OEM parts, even if I loose a little HP as a result. I guess my logic is that at a fraction of the cost, even with labor, I could replace them multiple times if I had to and still be under the cost of new ones. Just wondering what thoughts were on this. Anyone done this? Good experience or bad? What's a reasonable price? Thanks for your input.

Macster

Never done this but I face a similar situation.

First, though, the secondary converters if I understand your terminology correctly are not monitored. Only the warm up converters are monitored by O2 sensors (one after each converter) for performance.

If the secondary converters are rattling they are probably bad though. Be sure the rattling is coming from them and not some other place or source.

I have not yet had to face the decision to replace any exhaust system components. I do know the factory parts are expensive. I have a weak converter on my 02 Boxster (which is probably "weak" because the converter brick has come loose for I hear noise from that general vicinity but not loose enough to fail outright and stay failed) and I have priced a factory converter. $!000 (and maybe more now) and $200 or more to install. Ouch.

The problem is an after market setup requires I buy both banks and make other changes to the car's exhaust. Also, I'm not all that current on what is the best system, one that bolts on, works right and honestly is as quiet as the stock system, and is CA CARB compliant. Any that meet all of the above requirements will probably be expensive and a factory converter could be the lowest cost solution.

Or and this is probably what I'll do when (if) the time comes, and that is buy a replacement from a Porsche salvage yard.

As long as the thing doesn't rattle and is not damaged from whatever caused the car to end up in the salvage yard in the first place it should be ok. I mean the other side is ok and it has the same number of miles (almost 270K miles) and the same wear and tear on it as the side that is acting up.

2001SaxsterS

Hey Macster, thanks for your input!

I am curious in particular about one thing you said, that being "secondary converters if I understand your terminology correctly are not monitored". So are you saying that failure of the secondary cats could not cause a CEL? If this is true than obviously my CEL is either due to another problem or a mis-diagnosis of the noise. I am pretty certain that my mechanic came up with the correct source for the noise and he referred to the "secondary cats" as the problem. He showed me where both sets were while it was up on the lift. This was a while ago, so I don't recall exactly the order of parts in the exhaust system, but I do recall that they were the ones closer to the rear of the vehicle. His choice of terminology of "secondary" my not be entirely correct though.

Macster

Maybe the confusion arises from this: IIRC early Boxsters had only one pair of converters. But how the lone pair of converters can be referred as secondary (secondary to what?) is beyond me.

Now, at some point (MY 2000?) "warm-up" converters were added. These are part of the exhaust manifold proper.

The exhaust manifold runners from the head/exhaust ports converge and where they converge there is an O2 sensor (the #1 sensor). Then there is a large diameter section with another sensor after. (This is the #2 sensor.)

Now if one follows the exhaust on he will spot another large section which is another converter, one per bank. To me these are the secondary converters.

The exhaust then continues to the mufflers.

Note the secondary converters are not monitored by any 02 sensor. The assumption is if the warm up converters are operating ok -- they are monitored for performance -- then the secondary converters are operating ok too. Now if an exhaust emissions test finds the emissions levels out of spec and if the DME has no error codes, and all readiness monitors are complete and there are no other errors or signs of trouble this could be interpreted as the secondary converters being bad. What else (rhetorically speaking) could account for the unsatisfactory emissions?

Which prompts a non-rhetorical question: Was the secondary converter diagnosis made on the basis of an emissions test and its results?

Anyhow, given the above, to me with my 02 Boxster secondary refers to the converters which are located downstream of the warm up converters.

If there is some way the 1st pair of converters (one per bank) with 2 converters per bank can be referred to as secondary I'm not aware of it.

Mighty Shilling

sounds to me like you are assuming that is the cause of the check engine light. What codes are you getting when you scan for the trouble codes? Rattling could also be lots of things how did you determine that the catalyst is the cause?

being certain can save you lots of money and time and prevent you from throwing parts at it. OBD is a great tool. use it. go to an auto part store and have them scan it for you.

I do know that the dual mass flywheels can rattle at low speeds if they are wearing.

I'm also fairly certain that putting used catalysts on your car isn't legal. double check that with your town... Junk yards will also let you know fairly quickly if you try to buy one...

5CHN3LL

Macster, I'm assuming the secondary cats were added to bring the average emissions down, since Porsche were busy adding SUVs and 4-doors to the lineups. Adding some weight to the Boxster to get the emissions down is probably a tradeoff to accommodate the larger displacement motors in the Panamera and Cayenne...but this is just conjecture.

My '03 Boxster with the secondary cats deleted still passed CA emissions tests with flying colors.

Byprodriver

2000 brought on many more stringent emissions laws that nearly cut CA allowable tailpipe emissions in half.

MikeBat

I had an error which was vexing. The code referred to O2 sensors, but after changing them, the problem was still there.

Turns out it was one of the primary cats, which are expensive. I got a used cat from a local who was building a race car.

No issues since.

Plastikos

Considering doing the Fabspeed 2' cat delete myself. Did you notice any drop off in low-to-mid range power? On that note, do you think you noticed any benefits (other than sound!)?