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(Post Link) post #1 of 16 Old 05-03-13 Thread Starter
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Smash that pre-cat!!

Hey guys,

I have a 156 JTD M-Jet 150 which is the last of the CF3 motors I think. I have been thinking about replacing the turbo down pipe with one from J.S. Tuning but it would be much cheaper to knock the guts out of the standard part. Has anybody done this and does it sound okay? Also, my car is lowered so there is no chance of DIY, how much labour is involved?

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There is metal mesh in the downpipe which is very hard to knock out. I seen some guy cut the window, take out the mesh and weld it back. But welding cast iron doesn't sound good to me.
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I've done it. You can get all of the cat material out from the downpipe connection end. I don't think lowering would cause too many issues as a lot of the work to get the cat off is done from above. The V band was a pain getting off and back on again.

The most effective method of removing cat material was using a hole saw from the downpipe end. It was useful to have the lamda sensor hole in mine for extra access.
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Hi, I've done it to my old 156 and my 159.
In both cases I bought a second hand cat to smash the middle out of so I could return it to standard if needed.
the 156 used the same cat as many jtd fiats, I used one from a stilo for about £25 and the 159 uses the same cat as a vectra, £30 verses over £100 for exactly the same part listed for a 159.
I used a large masonry drill and some steel tubing that I sharpened and then pulled the remainder out with long pliers.
The car does feel more responsive and is slightly better on fuel, and both passed the mot without issue.

A word of caution, the cats contain some nasty metals that you dont want to be breathing in so wear a mask and tie a bag around the bottom of the cat to collect the bits that come out

Last edited by JON156VELOCE; 06-03-13 at 13:12.
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(Post Link) post #5 of 16 Old 06-03-13 Thread Starter
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Okay, this is a dumb question but how do I work under a car with less than half a foot of ground clearance? I presume that I don't jack it up on a kerb with the standard Alfa jack in the boot and risk crushing myself?

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You'll be working from above almost the whole time to get the pre-cat off. From underneath you'll only need to undo the 3 bolts for the cat to downpipe flange, i did this on my GT without even jacking the car up. Once the pre-cat is disconnected from the turbo (hardest bit) it comes out from underneath. It only just fitted under the front bumper.
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(Post Link) post #7 of 16 Old 07-03-13 Thread Starter
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So how long do you think it would take me armed with a spanner and a drill? What needs to be removed so that I can get to it? I gave up on changing the air filter so I 'm guessing this is even less accessible and more tricky...

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Not changed the air filter yet but I'd imagine the cat would be a fair bit harder than doing the filter. Took ~3hrs to do.
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iv been thinking about replacing my pre-cat and cat. is it just was gd smashing these bits out of the original cat's , rather than spending a couple hundred quid on the new ones.
anyonw know where is can get really cheap second hand cat's for my gt 1.9 jtdm?
would rather smash them to bits off the car so i can do a better job and not have to rush it all.
cheers
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(Post Link) post #10 of 16 Old 10-03-13 Thread Starter
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My thoughts exactly. I suppose I'd better call around the scrapyards to find one, that said, I might just pay my mechanic to do it. Once I have bought axle stands and found a day off I might as well have worked overtime and paid him, plus he has all the right tools to sort it easily. I don't fancy poking it with a screwdriver...

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Originally Posted by marky89 View Post
iv been thinking about replacing my pre-cat and cat. is it just was gd smashing these bits out of the original cat's , rather than spending a couple hundred quid on the new ones.
anyonw know where is can get really cheap second hand cat's for my gt 1.9 jtdm?
would rather smash them to bits off the car so i can do a better job and not have to rush it all.
cheers
pre cat and cat?

I really think you only have one, which moved from under the car on older engines to behind the turbo on the newer ones...

I smashed the innards out of my 2.4's cat but that was mounted under the gearlever... the second half of the cat was actually only an absorption silencer, left that bit in... I'm sure if there's a box under your gearlever in the center section it's just that and not a cat.
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How hard is it to actually trash a cat then? i have an arsenal of pointy bashy things, and a cf3 petrol precats on their way to me, just thought it might be easier than doing the welding thing....?
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ah right, i thought my car had two cats. didnt relise the centre section was just a silencer. thought it was odd a car having 2 cats. a bit OTT.
think ill give this a go one day. get the car up on ramps, take it off so i can do a proper job n see how it goes from there.
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Originally Posted by marky89 View Post
ah right, i thought my car had two cats. didnt relise the centre section was just a silencer. thought it was odd a car having 2 cats. a bit OTT.
think ill give this a go one day. get the car up on ramps, take it off so i can do a proper job n see how it goes from there.
Should have two cats - small pre-cat on the turbo and a large cat/silencer assembly underneath the car. All the diesel 156/147/GT 1.9 16v diesels have this setup.
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Should have two cats - small pre-cat on the turbo and a large cat/silencer assembly underneath the car. All the diesel 156/147/GT 1.9 16v diesels have this setup.
Have to agree this is what I found when searching ePER earlier. I plan to pull the innards out of both and replace the rear silencer with a straight pipe. Some VAG diesel modifiers call this a 'mufflerectomy'

Hopefully it won't sound too loud. The turbo should do a fair amount of noise dampening. We'll see if it smokes more.
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Quote:
Originally Posted by DG_ View Post
Have to agree this is what I found when searching ePER earlier. I plan to pull the innards out of both and replace the rear silencer with a straight pipe. Some VAG diesel modifiers call this a 'mufflerectomy'

Hopefully it won't sound too loud. The turbo should do a fair amount of noise dampening. We'll see if it smokes more.
Love the sound of this. Ill be taking a day off work when the weather gets better to take both cats off n do a decent job.
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