Gutting the pre-cats

Anonymous · March 30, 2004, 08:59

Ive read i few engine problems on this site and it all seems down to the pre-cats (or thats what i can make out)

as ive not got very much knowledge in engines i dont even know what the pre-cats do s:oops: :oops: s:oops:

it seems that is has been mentioned to gut the pre-cats to prevent any futre problems.

so if i gut the pre-cats what advantages and disadvantages are there??

has anybody done this?? if so is the car still running ok??

how hard is this to do??

thanks

Alan

markiii · March 30, 2004, 09:06

easy to do,

remogve manifold, and knock out teh honeycomber with a screwdriver or similar.

downsides, none that I can see. You may need to get warm before emissions test. Personal experience I doubt it.

Upsides, remove biggest chance for engien to go bang.

reason for being there, to ensure exhaust gasses are clean before main cat is up to operating temp.

Anonymous · March 30, 2004, 09:12

what i dont understand is if its just a case of removing the honeycomber then why does it cause engine faults?? cos surely when it cracks and breaks up its just doing the same thing as removing it??

Alan

Anonymous · March 30, 2004, 09:14

When you remove the precats yourself you will remove the honeycomb stuff... when it does it itself the bits of precat 'could' get sucked back into your engine which is where the damage is caused (im sure mark will explain it better than me s:oops: :oops: s:oops: ).

Anonymous · March 30, 2004, 09:17

oh right i see.

all starting to make sense.

as anybody on here gutted the pre-cats??

i think i will ask for a 2nd opinion from my local garage (as the do my MOT) just to see what they think of the idea.

Anonymous · March 30, 2004, 12:25

I'm seriously thinking of doing this too, as my 2000 has just come up to 50k, and I'm not going to be in any position to sell it on for a while.. the last thing I want is to pay for an engine rebuild due to the pre-cats breaking up!

Doesn't sound like something I want to attempt myself however, what do people think the chances are of convincing a local garage to do the deed? Any chance of further problems caused by someone hacking the manifold around?! s:? :? s:?

I'm almost tempted to let sleeping dogs lie though... sound reckless?!

Cheers,
Tim

markiii · March 30, 2004, 12:47

pretty much as Kris said, If the precat disintegrates in situ, it will either get sucked back into the cylinder or drop down into the main cat.

neither are good news.

as for a local garage doing it. Iwouldn't think a Toyota dealer will want to oblige, but a local garage should be ok.

Anonymous · March 30, 2004, 12:49

so that's all thats in it then? just removing the honycomb? i thought i would need a different manifold that didnt use the pre-cats and hooked up straight to the main cat!

markiii · March 30, 2004, 12:58

imagine a normal manifold made up of 4 pipes that then go into 2 pipes.

it;s the main cat pipe where they go from 2 to 1 pipe.

now at the 4 to 2 junction imagine the pipes going into a baked bean can.

the can is filled with honeycombe. All your going to do is knock out the contents.

Anonymous · March 30, 2004, 13:28

but surley if you knock out the contents, they will be siting at the bottom of the pre-cats and can still disintegrate and be sucked back into the engine?

is there anyone who has done this on here yet? im really tempted as im out of warranty

markiii · March 30, 2004, 13:30

think of teh bean can as an open can with honeycombe suspended across it. You will of course need to remove the manifold to do this. Then teh contents will drop out onto the floor.

Anonymous · March 30, 2004, 13:43

i too am seriously thinking about doing this but would feel much better if somebody has already attempted this and been successful

markiii · March 30, 2004, 13:45

there have been many in the US that have done this. Once out of warranty, I will either fit a header, the turbo if it's ready or gut mine.

GSB · March 30, 2004, 13:54

I'm gutting mine as soon as I can be bothered to strip the manifold out. Warranty or no warranty, it's got to be done really. If it came to it, there will always be someone on here I can buy, beg, borrow or steal a stock manifold from for warranty purposes.

Plus, with a unichip pending, (never seem to have the time though s:roll: :roll: s:roll: ) I'd rather have the exhaust in a de-catted condition so the mapping is done correctly.

markiii · March 30, 2004, 13:56

fancy offering a swap out facility if we can find a spare manifold? once we have one gutted could run an exchange program?

Anonymous · March 30, 2004, 14:06

that idea sounds good to me

GSB · March 30, 2004, 14:09

As in, we send off a gutted, cleaned and particulate free manifold, in exchange for one with pre-cats, so that there is always a decent manifold somewhere that can be got at quickly if the need arises? Not a bad idea...

I did have a used manifold coming in, but the guy who was selling it was a total messer, and never answers his phone...

markiii · March 30, 2004, 14:18

Adam has a spare if he could be persuaded to allow it's use.

Anonymous · March 30, 2004, 14:37

this is beginning to sound better and better. makes perfect sense for all concerned to have a normal one on standby.

Slacey · March 30, 2004, 15:31

Sounds good to me. I'd gut mine now if we could organise an exchange facility.

aaronjb · March 30, 2004, 15:33

Ditto.

Perfectly willing to help anyone out who doesn't want to take their own manifold off etc too.

mph · March 30, 2004, 15:46

markiii: just because you have my manifold, doesn't mean you can practise on it. s:x :x s:x s:!: :!: s:!:

While I'm running the turbo, I have no need of the stock manifold, which can be considered 'spare' if one were needed.

Personally I think taking a screwdriver to the pre-CATs isn't going to be (easy) enough to be able to remove all of them well enough to be effective. Still, that's not my problem s:wink: :wink: s:wink: I'd much rather just go for a replacement 4-2-1 instead.

Anonymous · March 30, 2004, 17:52

Count me in, I am thinking of doing this precedure next week if the weather is good, If I could recieve a pre gutted Cat that woud be fantastic, then I would simply swap them and gut mine to send on.

If you want a clearer understanding of the process why not visit Spyderchat.com?

Anonymous · March 30, 2004, 22:29

Quote from: "keninski"i too am seriously thinking about doing this but would feel much better if somebody has already attempted this and been successful

I have done it.

More torque, small gain in hps.

Anonymous · March 30, 2004, 23:28

This sounds very promising, I think I'm going to have to do it soon!

Is there any chance somone could post up some kind of tutorial, possibly with pictures - or a link they've found on Spyderchat?

I'd be much more confident in taking the car to pieces if I had a better idea which bolts were likely to shear off, or what tools were best to remove all of the pre-cats..?

Cheers!
Tim