OxyCat - Page 2 - PeachParts Mercedes-Benz Forum

Johnhef · #16 06-19-2008, 11:45 PM

eh well maybe I have another problem, it developed a pretty pronounced knock today. Its going to sit out from autocross this weekend and I'll try to get time to mess with it next week. this car was great for the first 4 years with almost no problems so I guess it's overdue.

C Sean Watts · #17 06-20-2008, 08:12 AM

Quote:

Originally Posted by babymog

The recall replacement is under the car in the downpipe, right? I'm not sure of your post.

Mine is under the car, down stream from the turbo.

UPDATE: Stay tuned for photos.

C Sean Watts · #18 06-20-2008, 08:28 AM

Quote:

Originally Posted by ForcedInduction

Why not just put a straight pipe in placeof the cat?

That would be an instant annual inspection failure. I forget the exact verbiage but in NC, at least, it's something like, "Emission control equipment must be correctly installed, not bypassed or defeated." Even if the car is not subject to exhaust gas testing.

sixto · #19 06-20-2008, 01:12 PM

Quote:

Originally Posted by babymog

The recall replacement is under the car in the downpipe, right? I'm not sure of your post.

The recall should at least replace the pipe from the exhaust manifold to the turbo and everything south of the turbo.

It sucks that they went from a 3-bolt to 4-bolt flange between the downpipe and midpipe. They might even have shifted the location of the flange so a catless downpipe isn't a bolt-on replacement. I guess if you find a catless midpipe you can get the rest of the exhaust system. Or is this rustless California thinking?

Has anyone checked what a new cat costs from MB or Timevalve? I'm only asking for the benefit of those who won't consider a straight pipe.

Sixto
87 300D

Carson357 · #20 12-31-2008, 09:00 PM

removed mine today, car was somewhat more powerful, the unit that was removed was partially clogged, for the first few hard accelerations there were huge clouds of residual soot from the exhaust. apparently removing allowed more flow to remove the build up

Carson357 · #21 01-01-2009, 12:40 AM

wanted to post a follow up post after driving this evening, the car now appears to emit alot less exhaust smoke, the heavy smoke i used to see was not smoke directly from the engine, but rather soot what would accumulate in the oxy cat, and blow out during hard driving. i guess these units become inactive overtime, as i said in previous post mine was partially clogged

#22 01-01-2009, 03:27 AM

The particulate filter is passive. It requires hard driving to get exhaust temperatures up enough to burn off the trapped soot.

Carson357 · #23 01-01-2009, 04:01 AM

Quote:

Originally Posted by ForcedInduction

The particulate filter is passive. It requires hard driving to get exhaust temperatures up enough to burn off the trapped soot.

i had previously performed many "italian tune-ups" for several miles with no change, i dont think it was doing what it was intended due to age and limited exhaust flow, the huge clouds during the first drive tells me that the exhaust flow was reduced or all that crap would not be present, it only did it for 3-4 hard accels from stop then was gone

#24 01-01-2009, 04:16 AM

Right. Once a channel is plugged off with soot, its dead.

Even the modern filters used on trucks are often replaced because they fail to regenerate completely.

Carson357 · #25 01-01-2009, 04:17 AM

Quote:

Originally Posted by ForcedInduction

Right. Once a channel is plugged off with soot, its dead.

Even the modern filters used on trucks are often replaced because they fail to regenerate completely.

more than 1/2 the channels were plugged

JimFreeh · #26 01-01-2009, 07:29 AM

Our 87 300TD suffered a significant loss of power, coupled with huge anounts of black smoke.

This was several years after the warranty replacement of the trap oxidizer.

I found a very high backpressure, using the port in the front of the exhaust manifold, then verified the problem by loosening the downpipe from the manifold. Car ran like gangbusters after pipe was loosened.

Removed the oxy cat and found it plugged. Chucked it in a large vise and sharpened a piece of rebar to look like a flat screwdriver. Broke out the ceramic matrix and left the hollow case. One of the flanges is close to the oxy cat material, easy enough to do.

Car ran better than ever and appeared to be stock when inspected.

Jim

Johnhef · #27 02-06-2009, 10:22 PM

Quote:

Originally Posted by JimFreeh

Our 87 300TD suffered a significant loss of power, coupled with huge anounts of black smoke.

This was several years after the warranty replacement of the trap oxidizer.

I found a very high backpressure, using the port in the front of the exhaust manifold, then verified the problem by loosening the downpipe from the manifold. Car ran like gangbusters after pipe was loosened.

Removed the oxy cat and found it plugged. Chucked it in a large vise and sharpened a piece of rebar to look like a flat screwdriver. Broke out the ceramic matrix and left the hollow case. One of the flanges is close to the oxy cat material, easy enough to do.

Car ran better than ever and appeared to be stock when inspected.

Jim

Jim--- BINGO!

I actually did just that tonight after resurrecting the car a few days ago, its been a slug and I noticed the boost reading (8psi) was much lower then I remember when I last drove it almost a year ago (15psi). Got a little too happy with the air chisel and poked though the upper part of the other end of the cat.. whoops. peened it all back down again after removing the guts and I'll weld it shut some time next week.

Holy freaking crap batman!! the car runs like a raped ape now. Started to head home but decided to go back to the shop and turn the boost back down since on my 0-15psi gauge, it was now pegging at the underside of the peg at the 0 mark.... now at 12-13psi under max load and eveything is dandy.

deanot442 · #28 02-08-2009, 09:25 PM

Hi all, while browsing through this thread, I thought to myself (the SDL seems more sluggish lately). So, armed with a 12mm ratcheting combo wrench, a BFSD and a BFH, pulled the SDL up on the ramps, put the rear on jack stands and began to remove the pipe and converter. Once apart, I inspected the Cayalyst material from the side closest to the flange. This being the outlet side I expected it to be fairly clean (it was nasty). I assumed that this was causing extra back pressure, so it had to go. Several hard blows to the catalyst was enough to start it crumbling. I needed a needle nose pliers to break up some of the larger pieces to allow them to exit the outlet. I then reassembled the flanges and took her for a test drive and WOW WHAT A HUGE FREAKING DIFFERENCE!!! I wonder how long it had been building up the crud in there. Well she's breathing much better now thanks to the thought provoking ideas seen here. Thanks to all who dare to try out their ideas and post their results here.

C Sean Watts · #29 05-16-2009, 09:42 PM

We finally found the pics.

See if you can figure out the upstream from downstream sides.

We removed the 'obstructing' material and welded it back together. On start up, I immediately noticed a smoother and quieter idle. Throttle response was faster and turbo spool was much faster. It also ran a bit cooler. I then did an Italian tune up and briefly made a THICK smoke/particle cloud bad enough to be a visual obstruction out on the two lane country road I was on.

compu_85 · #30 05-16-2009, 10:26 PM

I have to wonder how bad the ox cat on my TDI is... They usually don't plug that bad. Perhaps they've made some improvements since they were introduced.

When did the recall to fit the ox cat start? I know the first VW to get one was in 1991.

-J