Help removing Cat



  • Hi guys, Ive run into a problem, I cannot no matter how hard I try get the damn nuts off the cat on the engine side, there isnt enough space to do anything, not only that, but the nuts are so heavily corroded/heat damaged that they are stuck so tight I have been unable to get any give on them at all. What do people reckon I should do? I though about getting an angle grinder, but I dont have a pit so would be seriously dangerous, I also only have access to the rear off the bolt with an angle grinder, and I dont think that would sort it as the bolts thread into the cat dont they?



  • **These rule. Hard_!_

    They grip onto the bolt head by cutting into it, even if the bolt is rounded off. You'll need new bolts afterwards, mind.**



  • Ok thanks, is going decat going to be crazy loud?



  • depends alot on the exhaust system from the cat back. decatting my alfa is stupidly loud so i will be putting it back on



  • @20480cd383=Jesta:

    Ok thanks, is going decat going to be crazy loud?

    It will be loud but not too much, might get a bit boring on longs journeys and yes dont do anything untill you have bought some new exhaust bolts and gaskets etc. We did it very slowly turn by turn with a huge extender breaker bar :)



  • I've got a dog?

    Oh, wait…..... :lol:



  • They are an absolute bitch to remove, how we did it was

    jack the car up onto 12" high wooden blocks under the front wheels

    get an exact 6 sided socket
    (not a multi side one with 12, this will be needed as the others will round it off, even a 6 side ring spanner will do if the bolt is in the correct place)

    get a scaffold tube

    get another person underneath to hold the socket onto the nut

    other person bounce on the scaffold tube to break the seal and it will suddenly go, when it does, it just comes off normally.

    TIP
    When replacing bolts on decat pipe, plenty of copper grease and use stainless steel nuts, split washers, bolts and penny washers, you will never have them seize up again then, so its easy to put the cat back on for MOT



  • @a2ab919f9c=RustyMx3:

    I've got a dog?

    Oh, wait…..... :lol:

    lol you barking mad you now



  • @1fc3a1a273=jay:

    lol you barking mad you now

    Just to continue going off the subject, I think you'll find it's my dog that's mad :lol:

    He's watching you!

    Oh wait he's asleep

    NO, he's watching you!!!!



  • all sorted, took it to a garage thats old school friends with my fiancee's dad, £15 to get the stripped bolts off and fit the decat, dont mind that cos its cheaper than them stripped bolt socket things and I didnt have to do anything. Didnt really have a choice as I couldnt get the car more than about a foot of the floor even on the railway sleepers, so couldnt get my breaker bar on it, thats all he said he did.



  • Simples :wink: Car sound nicer?



  • yeah im curious on this as well as i never decat mine and would like to know if there is any gains in performance (probably 5-6hp at a guess max) and any difference to the noise



  • yeah im curious on this as well as i never decat mine and would like to know if there is any gains in performance (probably 5-6hp at a guess max) and any difference to the noise



  • dj said it should give an instant 15bhp, dunno if thats based on fact or speculation, but he knows his stuff so I guess it cant be far short. Could be +/- on that though depending on engine condition and state of tune. The car is quick anyway, so hard to guage on accel alone, but on the dual carriageway it lifted the front end up in 5th at 60mph.

    Yes, it sounds fkin awesome like you wouldnt believe! My mpg is gonna flop massively cos I cant resist booting it all the time just to hear it go psycho hehe. Oddly, it makes only a tiny difference to idle loudness, but the tone is definately different, sounds like a much bigger engine. That said, I have a straight through 4" zorst, not that the 4" makes much odds as its practically just trim. So it was pretty zesty sounding before the decat anyway, sure if you went from stock zorst to what I have itd be like night and day in comparison.

    Im super happy with it, (thanks to Lori for selling me it ;)) at idle it isnt intrusive, I leave home at 5am and Im sure my neighbours wont have any gripe with the noise it puts out, but once you get to about 2.5krpm or WOT then it just unleashes itself on the world. Certainly get attention, which may or may not be to your liking, depends how strict your local policing is, our town is filled with chav's, so here they dont really bother, atleast with the K8 it actually sounds like something powerful, not just a bean can on a 1.2 I4. It doesnt sound like its straining or being forced to produce the sound like so many cars with exhaust mods do. I did take a very short video on my phone of it with the 4" on before the decat before I took it to the garage, but the engine was cold so I only revved to about 3k, when it stops raining I will take another video with the engine again cold and rev only to 3k with the spacing between camera and zorst about the same as before. Youll then be able to see how loud it is when the IAC is operating cos when its warmed its not that audible at idle but my IAC takes it to 1.5k which is where most peoples will be first thing in the morning, which for me, is when I need to be concerned most, not a fan of upsetting the neighbours and thereby sh*tting on my own doorstep.



  • I noticed a small increase with my decat and now I have gone fully stainless its a better note and much smoother feel with the engine, with standard center and stainless rear it still seemed to have a bit of back pressure holding it back

    the 10 bhp is spectulative and when reading through google on this it was pretty much the same on all sites about it, that and the induction kit on a dyno put the engine back to factory standard BHP, I would have expected it to lose 10-15bhp after 15 years and 120,000 miles so just those together have gained it



  • the decat, stainless and cold air infeed on my alfa have made a great deal of noise but with relatively small (if any) performance gains. it does feel more eager once i get past 6000rpm and will rev cleanly now until the red line where it struggled before but i would say a max of 5 bhp for me. that said it is a home made decat pipe (by me) which is not made of stainless steel, just some old exhaust and flange that i had lying around. after seeing that 1.6 for sale yesterday i want one even more now :( really miss my mx 3



  • if you miss it, why not go back?



  • at the moment its because my girlfriends dad bought the alfa for me so i have to keep it for at least 6 months lol. dont worry i will defo be back to an mx3 very soon. :) it was more exciting to drive and had more power than the alfa and the sad thing was i didnt modify the mx 3 lol.


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