Jaguar World Monthly Forum - Clogged downpipe cats ??

Leo_Denmark

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Clogged downpipe cats ??
09.04.2011 at 22:07:32

Hi

I took a look into the downpipe of my car and found this :

That does in my opinion look bad !! Shocked

How will the engine react, if resistance in these downpipe cats is to high ??
I have a weird hissing sound from the engine at kickdown and some hesitation until appr. 4000 rpm

Next question: How will the ECU react, if I simply remove the internal matrix of the first set of cats ??

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Leo Jensen, Denmark XJ 40 3.2 1992 - Citroën 2CV 1975

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2jagsDoug Senior Member Offline Posts: 1456 United States Gender:	Re: Clogged downpipe cats ?? Reply #1 - 10.04.2011 at 02:53:42 Knock out the converter matrix? On a 1992 XJ40? The ECU won't know and the engine will thank you In the 'States we call that a "catalytic converter overhaul". Not that I'd know from pesonal experience, mind you. It's just something I've heard mentioned from time to time. Cheers DD
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Leo_Denmark

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Re: Clogged downpipe cats ??
Reply #2 - 10.04.2011 at 07:09:50

These downpipe cats looks like metallic catalytic converters and not ceramic.
If I decide to knock it out, will everything come out easily, or will I end up having to cut it open to get the remaining bits out ?? As there is one more set of converters under the floor, I do not expect to get problems at the MOT-test.

I would really like to have a response from someone, who have actually done this....

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Leo Jensen, Denmark XJ 40 3.2 1992 - Citroën 2CV 1975

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2jagsDoug Senior Member Offline Posts: 1456 United States Gender:	Re: Clogged downpipe cats ?? Reply #3 - 10.04.2011 at 07:52:52 Not sure what luck you'll have but I've never had to cut one open myself. I just use a metal rod or long screwdriver and a hammer. Don't breathe the dust. Cheers DD
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Leo_Denmark

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Re: Clogged downpipe cats ??
Reply #4 - 11.04.2011 at 16:24:26

2jagsDoug wrote on 10.04.2011 at 07:52:52:

Not sure what luck you'll have but I've never had to cut one open myself. I just use a metal rod or long screwdriver and a hammer.

Don't breathe the dust.

Cheers
DD

I have now cut it open, and confirmed what I expected: Its not ceramic, but metallic. Thin metal sheets shaped and rolled to give a lot of channels with a lot of surface.
It will take a lot of aggresivity to get all of that out, and after looking closer its not so clogged. I compared to a race-cat from my shelf, and it has much larger channels and thereby also much less area.

What would you do from here

Knock cats out (and replace by tube to improve flow in downpipe) ?
Buy a 'new' downpipe on Ebay ?
Just weld it up again... ?

Picture of my Jag-cat:

Picture of new (and smaller, maybe 60mm) race cat from Kemira:

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Leo Jensen, Denmark XJ 40 3.2 1992 - Citroën 2CV 1975

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2jagsDoug Senior Member Offline Posts: 1456 United States Gender:	Re: Clogged downpipe cats ?? Reply #5 - 12.04.2011 at 06:11:44 Personally, having gone that far, I'd get agressive and knock it all out. Cheers DD
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Jacqueline Senior Member Offline Posts: 1756 Cleckheaton, West Yorkshire Gender:	Re: Clogged downpipe cats ?? Reply #6 - 12.04.2011 at 18:49:34 Thats a first for me as never seen what a catalytic converter looks like let alone had to replace one on any of the cars I have ever owned
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Leo_Denmark Senior Member Offline Posts: 462 Middelfart Denmark. Gender:	Re: Clogged downpipe cats ?? Reply #7 - 12.04.2011 at 20:40:47 2jagsDoug wrote on 12.04.2011 at 06:11:44: Personally, having gone that far, I'd get agressive and knock it all out. Drilling round the circumference and some levering did the trick. I have decided to find a piece of tube to make the gas flow better. No reason to have a chamber there...
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Leo_Denmark

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Re: Clogged downpipe cats ??
Reply #8 - 12.04.2011 at 20:43:17

Jacqueline wrote on 12.04.2011 at 18:49:34:

Thats a first for me as never seen what a catalytic converter looks like let alone had to replace one on any of the cars I have ever owned Wink

Also a first time for me. I did not expect to run into problems with catalysts, but after looking into the downtube I had to do something...

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db Senior Member Offline Posts: 511 Gender:	Re: Clogged downpipe cats ?? Reply #9 - 13.04.2011 at 11:11:06 Did you have any symptoms from the blocked catalyst? David
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Leo_Denmark

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Re: Clogged downpipe cats ??
Reply #10 - 13.04.2011 at 12:38:31

db wrote on 13.04.2011 at 11:11:06:

Did you have any symptoms from the blocked catalyst?

Maybe... Hard to say until I have tried the car without clogged cats...
I had poor mileage, a weird hissing sound during acceleration and hesitation when accelerating. I hope some of it will be cured. I will change the lambda sensor as well, so it will be hard to say, how much that influences mileage.

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Leo_Denmark

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Re: Clogged downpipe cats ??
Reply #11 - 15.04.2011 at 20:28:31

Leo_Denmark wrote on 13.04.2011 at 12:38:31:

db wrote on 13.04.2011 at 11:11:06:

Did you have any symptoms from the blocked catalyst?

Maybe... Hard to say until I have tried the car without clogged cats...
I had poor mileage, a weird hissing sound during acceleration and hesitation when accelerating. I hope some of it will be cured. I will change the lambda sensor as well, so it will be hard to say, how much that influences mileage.

OK, have done the first run now w/o downpipe cats.

The hissing sound and hesitation is gone, and it clearly feels like I have more power. Acceleration at 180 km/h is pretty strong Cheesy

The car is of cause more silent without the leaks at the manifolds, even though the rear mufflers still needs replacing.

It is really good to have the car back on the road Grin

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Jacqueline Senior Member Offline Posts: 1756 Cleckheaton, West Yorkshire Gender:	Re: Clogged downpipe cats ?? Reply #12 - 15.04.2011 at 23:41:21 180 KPH OMG what speed limits do you get over in Denmark Glad to hear progress is being made though
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Leo_Denmark Senior Member Offline Posts: 462 Middelfart Denmark. Gender:	Re: Clogged downpipe cats ?? Reply #13 - 16.04.2011 at 07:52:57 Jacqueline wrote on 15.04.2011 at 23:41:21: 180 KPH OMG what speed limits do you get over in Denmark Glad to hear progress is being made though He, I did just accelerate up to feel if it was OK and then lift off. Limit is 130 on motorway, so I hope noone took notice...
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apax Senior Member Offline Aged to perfection! Posts: 4376 Heathfield, East Sussex Gender:	Re: Clogged downpipe cats ?? Reply #14 - 16.04.2011 at 11:34:42 Sounds like a very good engine. The 3.2 XJ40 that I had (no catalyser) was at maximum at 120 mph, so 'strong acceleration' at 112 mph is impressive. Cheers, apax.
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