Thy don't really get clogged. The ceramic honeycomb inside will melt if the things is abused or overloaded with too much raw HC. Keep the car tuned well and no worries.

 

Sometimes you can't help what you get when you buy a used 928 though. They aren't all perfect gems (sadly).

 

<rant>
Funny this came up. I just tried to smog my car with the motorsports high-flow cat on it. Clean tailpipe but didn't get past the visual. On reinstallation of a factory cat, it passed of course, but the emissions are dirtier than with the racing cat (and I am down big time on throttle response and power).

Nice work, C.A.R.B! I mean, I can see the logic if the 100% factory set up is cleaner than some aftermarket stuff, but to make my car legal to drive it has to be more harmful to the air. As a tree-hugging liberal I should be morally obligated to return my car to illegal status in the name of less LA smog!

*%#$ing stupid.

</rant>

 

Chris-

That's interesting. The guy in OC that I go to never even looks. He just asks if I've changed anything. Looks at the vacuum diagram, then at the motor, shakes his head and checks it as 'passed'. Never looks under the car, and couldn't see much anyway with the trays installed.

So what tipped them off that you didn't have the right cats on it? Different color than the rest of the pipes? Too loud?

 

Maybe no air injection?

 

Al Gore will wake up sweating, screaming, and clawing at the sheets at 3am.

 

The motorsports Y has threaded bungs for O2 sensors for the later cars - mine has none stock so both those are plugged. The fact that there were plugs in what looked like where an O2 sensor should go looked fishy to them. That, and the modern cat doesn't look like a 3-way cat from 1979 - it looks more like a pass-through muffler than anything.

The air injection system is actually intact - the lines from the pump go to the exhaust manifolds, which are original. So the car actually has all the required equipment (air injection, EGR valve, and catalytic converter) but since the cleaner cat is not 100% original (nor has it been CARB/BAR approved) it's technically not OK. In California, anyway...

 

gotta link?

 

I've seen them get clogged when the head gasket is slowly leaking and the car is driven. At leat that's what it looked like, some of the cells were clogged like a honeycomb.

 

Then I am all for it.

 

More power/pull above 3500rpm, less backpressure so less torque below 3500rpm. Anything that gives big Al fits is ok by me. My 928 is far less a polluter than his private jet. Chris that sucks, perfect example of bureaucrats screwing things up, and another reason why I love to visit California but don't live there.

 

Seems that there are a 3 philosophical camps here:

1.)No exceptions-Don't pollute-Keep the cats or replace when needed.

2.)No one will tell me what to do-Damn it all-My reasoning is (insert reason such as When chainsaws and back-yard grills have em, so will I. Or Global warming makes women dress more scantily).

3.) I am reasonably responsible and choose to compromise as long as I am not too abusive.

The differing opinions among all of us are always ponderous, amusing and/or sometimes even enlightening.



That being said and asside from the legal ramnifications of deleting a catalytic converter, what are the bottom line physical attributes or detriments to our cars if one were to remove a cat?

How does this affect:
Performance
Noise both in and outside of the cabin
Longevity of other parts
Need to adjust tuning
Wallet

Apparently the original poster's question has been answered to some degree and we (as we often do) have taken a question down many avenues to explore all related to even a shred of the original topic.
Just my too sense....


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Removing the cats on an '88 will give you 15-20hp more power and will make the car a good deal louder (assuming you are replacing with straight pipes). It will also probably make it pollute more, especially NOx. You will most probably fail emissions inspection.

What you should really do is buy an X-pipe and high-flow cats. It will cost you about $500. The X-pipe will add ~30hp and the new cats will take away maybe 2hp at most. The car will be slightly louder, you will have a noticeable increase in power/torque, and you will have a clean exhaust. Best of all worlds.

Dan
'91 928GT S/C 475hp/460lb.ft

 

I love exploring many trails. I am here to learn. This information is Great !!!!

 

I'm with you Dan. Maybe when the OEM supply of 928 cats run out we can go the aftermarket route.
I have a good friend who is a true guru with Aston Martins. Early AM V8's ran two GM air pumps into a pair of cats and also required a distributor that had an ignition retard built in to heat up combustion temperatures at idle. V8 's from this era were real turds. This was state of the art 1975.
Advance 25 years and conforming an engine is much easier with better results. My aston bud builds a completely new ignition system using a multiple spark system, new state of the art cats etc and is able to tune a much better running engine w/o the ignition retard. The head engineer at Ford wanted to buy this ignition system and make it an OEM Aston V8 part as the original lucas distributor was well Lucas. Oddly the head Ford engineer had no idea what the vacuum retard system was for which invoked a very sarcastic response from my friend.