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Right guys, I had some free time on Friday evening and again yesterday so I decided to have a bash at making a de-cat for my HDI 90. Here’s my story:

I started of by disconnecting the exhaust clamps. One where the front pipe meets the manifold and the other where the front pipe meets the centre section. The Haynes Manual suggests that after loosening these clamps the front section should easily slide out of the back section. This is not the case. I had to remove the front section mounting and batter away with a hammer for a good few minutes to get them separated. To my despair this is what I was left with.







As you can see from the pic’s my exhaust was done and had holes in several places. At this point I should have scrapped it and looked for a replacement from a breakers yard but I decided to have a go at mending it and continued on. I was able to buy a flexible piece, some flexible tubing and a new clamp from my local motor factors for £29.

I started off by cutting off the flange and welding it to the new flexible piece. Next I had a go at patching the area around the mount. I did this by cutting and flattening two pieces of the new pipe so I had good metal to attempt the patches either side of the mount bracket. Next I removed the CAT section and welded in the new piece of pipe, I cut a slit at either end of the new pipe so I could flatten it and slide it inside the original exhaust making it easier to weld and stronger too.



Now with everything welded I attached the new flexible section to the manifold. Knowing how difficult the exhaust was to get off as one section, I kept the flexible downpipe piece separate from the straight pipe. With the flexible piece secured, I was able to slide the straight pipe into this and secure it with a clamp. It also made it easier for me to get it slid back inside the middle section. With it all secured I sealed the joints with some exhaust gum and tightened the clamps. Job done!



Video of exhaust note: http://www.youtube.com/watch?v=NDSYEhEZ2m0

First impressions: It’s a great little mod, I de-cated my 106 and was impressed and I’m even more impressed with the results on the 406. What I’ve noticed is a more responsive, freer revving engine. Acceleration in 3rd and 4th gear is now much improved and there’s a lot more urgency when you press the accelerator. Also there isn't a really an increase in noise inside the cabin, maybe more turbo whistle and you can hear a beefer note from the exhaust when standing behind the car. Hope this has cleared up some of the de-cat questions that often come up and hope you’ve enjoyed reading it.

thanks for letting people know about this

That's great, it's a bit Heath Robinson like but very effective so well done!

Where did you source the new flexi section?

I firmly believe now that almost every HDi has got a broken flexi

I wish i had the equipment and the know how to do stuff like that ,

in fact just the equipment, i reckon i could steal the know how from places like this ,

oh but then there is the ability factor too bugger i reckon im sh1t outta luck with that one too.

Still great write up mate and Im glad its doing the business for you

as for the flexi pipes, every polski motor factors ive been to seems to have them on the shelf here,


but then this is much more a "make do and mend" type of society than "disposable Britain"

Ditto here, that's why everything costs so much, it has to last forever

Same sort of deal when they put a new cat in my 2.1 - cut the old one out, weld the new one in. I'm sure you'd be able to find a similar garage in your locality (do what I did, find one that speaks English and make friends ) I did ask about leaving it out but they said the tried it and the car was as flat as a pancake.

Was thinking I might invest in a welder when i head back to the UK next time,

Machine Mart porn time

I have the space and at the moment the time, to start practising my welding, it would give me something to do come the long dark winters out here,

the in-laws garage is heated too, so its gonna be a nice bolt hole for me when the nights are long and the weather cold.

Hmmm..... comedy twin pipe exhaust anyone??

Feel like creating a decat pipe for me?

Welly wrote:That's great, it's a bit Heath Robinson like but very effective so well done!

Where did you source the new flexi section?

I firmly believe now that almost every HDi has got a broken flexi

Haha, cheers. I very nearly scrapped it when I saw how many holes were in it.

The flexi section I got from a local motor factors, they stock universal type parts and pieces for the most popular cars in the locality, generally peugeots/citroens and anything that has a turbo diesel.lol. I just walked in with the whole front section of exhaust and showed them what I needed.

Captain Jack wrote:Feel like creating a decat pipe for me?

I think I'll put my welding mask up for a while. Provided your exhaust doesnt have all the holes mine did then its just a matter of cutting out the CAT and replacing that section with some 2" pipe. If you have a friend with a welder and a grinder I'm sure you could do the job in a couple of hours

Exhaust place replaced my cat when the flexi went.

Wish they had just replaced the flexi, as now the car has strange vibrations from the aftermarket cat

Excellent write up

Thats going to be my next mod........ Only trouble is I can't weld, well I have never tried so this looks like a perfect time to learn

Looks a good mod i did it on wifes MX5 import when cat went as thats 1992 car no probs with mot but how will it pass on say a 2002 diesel.
alan

The NI MOT just seems to be a smoke test for diesels.

Was confused by this as it is taxed quite reasonably according to CO2s.

so if i decated my car then the price of the car tax wouldnt change at the next emissions test?

406executiveHDI wrote:so if i decated my car then the price of the car tax wouldnt change at the next emissions test?

No, the emissions figures used for tax bandings are specified for the model and not those recorded by your specific car at the MOT station.