NAC..'00 VW Passat 4Motion...$7200 in repairs!!!

Dan Cordon cord4530 at
Fri Jun 10 17:21:26 EDT 2005

Not to be argumentative, or flamatory, but this post is way off. I don't 
think posts like this should be left in the archive w/o a subsequent 
post to help clear it up.

> Catalytic converters are a bunch of crap anyway! They do not work! Do what
> many people I know do on all their cars. Take a hole saw with a long
> extension, take out your cat, and drill the thing out. Or get a "Test pipe"
> if there is one made for your car. Ether way, nuke the thing.

How is 'crap' defined? Is it because they can hurt performance? Or 
because they don't improve emissions? Or because they have been eaten 
and subsequently expelled by something? While cat. converters were a 
significant exhaust restriction in mid 1970's cars, they are virtually 
transparent in more modern vehicles. Unless you're trying to push 
significantly more exhaust through a stock cat, hollowing it out won't 
make any performance improvement. However, if you cat has melted, then's a restriction. You may consider replacing it rather than 
hollowing it out. In some cases, the induced turbulence of a 'hollowed' 
cat can actually decrease performance of a vehicle.

> A number of newer cars now have multiple O2 sensors, one before the cat and
> another after. Unfortunately, our USDM car computers require an O2 input to
> run properly, so you cannot do away with the buggers altogether. However,
> the O2 sensor that is located after the cat is usually only there to monitor
> the cat and has nothing to do with fuel mixture. You can cut it out and buy
> a $30 O2 emulator to keep the Computer, the EPA and your Check Engine lights
> happy.

Every USDM new car since 1996 is required to have a pre and post cat O2 
sensor. In *most* cases, the rear O2 sensor is just to tell the ECU that 
the cats aren't functioning like they should. However, there's nothing 
unfortunate about 'requiring' an O2 input to the ECU. While a modern car 
will likely run just fine w/o any O2 feedback, it's also going to get 
worse fuel economy, or produce more of the undesirable exhaust species. 
Would you prefer your ECU to control the engine w/o any idea what the 
results are? I suppose you could just pull the O2 sensor wiring and put 
some black tape over the CEL. Maybe that's what we should recommend to 
everyone who'd having problems passing emissions. <joking>

> Every car that I have seen without it's cat's shows better numbers on the
> emission tests than it did with them. Those things are bogus, much like O2
> sensors, and only work under certain conditions for certain problems in a
> lab. In the real world, when they malfunction, they will cause more harm to
> your car and to the environment in a week than the benefits they supposedly
> provided over a lifetime. Japan, the most environmentally conscious country
> in the world, does not use cats or O2 sensors for just that reason.

I can think of very few cases where this would be true at all. What do 
you consider better numbers? Have you actually seen any tests where 
emissions improved after removing the cat? Catalytic converters aren't 
just for lab situations. They are completely passive, and only require 
reaching operating temperature to function continuously. O2 sensors also 
work after only seconds of engine operation. They are used in all 
conditions *except* high throttle acceleration (where a stoichiometric 
mixture isn't necessarily desired). These conditions have little to do 
with 'laboratory' environments.

Makes one wonder...if cat. converters *aren't* helping, why are we using 
them? Maybe it's a conspiracy...the EPA has a LOT of extra platinum it 
wants to cash in on to overthrow.....

> Ohh and the partial reason that some cats cost so much is because the
> leading tips of the honeycombs are now made of Platinum.

Yep...they are now, and pretty much always have been. Platinum is one of 
the more common catalysts. If they didn't have a catalyst, they would 
just be called "unreactive honeycomb sections" and not catalytic 
converters. :o)

Dan Cordon
Mechanical Engineer
University of Idaho - Engine Research Facility

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