Pre Cat Removal

vocky

be very careful with the lambda sensors, I unplug the looms and leave them in the downpipe.

the lambda sensor wiring can be damaged when the downpipe is 'dragged' out from under the car, be careful cheers..

Sjdickso

Right i have just been outside vocky to have a look.

I did not remove the heat shield but the main cat is nearly next to the join where the centre section joins. I could see the flexi pipe but could not see a buldge afterwards (heat shield was blocking my view what the chances i have got a pre cat then?)

JohnnyN

If the cat is at the centre section and you've a got a flexi, I would think that you have a pre-cat. My engineering manager had a 53 plate Astra 2.2 and that didn't have a cat at the centre section nor a flexi in the downpipe.

Sjdickso

Thats somthing else i now have to add to my list to do.

Sjdickso

Quick update, just booked my car in with my mate to get oil and filter changed and pre-cat removed at the same time.

I just hope the first mechanic was wrong and it has got one LOL.

My only concern is if he has issues getting the centre section off from the cat as the back box flange is very delicate to say the least.

louise6515

vocky said:
be very careful with the lambda sensors, I unplug the looms and leave them in the downpipe.

the lambda sensor wiring can be damaged when the downpipe is 'dragged' out from under the car, be careful cheers..

did the pre cat mod last week , got the foil out ok took about 45 mins - just left me with 2 small holes where the pre cat seemed to be welded to downpipe (about 5mm) filled these with chem metal but after 33 miles engine management light back on and now at 65 miles has blown the chem metal off 1 hole! :cry:
seems i need to take off again and do proper weld on these holes , don1t know if it will cure the light though dunno..

vocky

you should not get any holes in the exhaust from removing the precat, the metal is very thick notsure.gif

still, get any holes welded up and perhaps get the ecu codes read 🙂

Round

Just to check. ppl are removing the right part arn't they?

some of the comments sound like they are removing parts of the braided/flexi section..

louise6515

Round said:
Just to check. ppl are removing the right part arn't they?

some of the comments sound like they are removing parts of the braided/flexi section..

mines definetly the pre cat. as vocky said its thick metal right at the top flange were it joins manifold ,but it was welded in place which surprised me as all the pics seen haven`t been :shock:
51 sri 150

Sjdickso

Just had a phone call from my mechanic, he has got toasty hands from removing my system only to find that it deff has not got a pre-cat in mine :lol: :lol:

One thing is that it's all good that i have not got one

but few bad things

I have to pay for some labour for his time
My car does not pop like you guys talk about 🙁
Got to look at more options now to get more power :lol:

edbutler

Is a De-Cat wise on these cars?

I must admit im a little used to Turbos (Petty and Diesel) where reducing more back-pressure was generally for the better. VAG engines you could also fool the lambda probe so the EML didnt light up.

Does anyone know if its wise on my my VX? Would it provide any real gains over the the pre-cat (i suppse 2kg is a gain!!). Would there also me a slight increase in noise in the standard exhaust i guess... I obviously know about MOT implications 😉

vocky

I would fit a sports cat 🙂

removing the main cat causes too many issues with the z22se, plus some have lost power due to too little back pressure dunno..

JohnnyN

Here's the pics from this afternoon. Now I can officially say i've done a pre-cat removal. My pre-cat was metal substrate. Not sure if all pre-cats are the same? notsure.gif

Anyway, from my experience I would not recommend drills for this operation. I tried with various Cobalt drills and TicN Coated drills and it wasn't very easy. I ended up using my Dads long screwdriver and a deadblow mallet. Down the middle, round the edges and then unravelled the remaining outer bits. The waste is sharp as hell. What's all the powdery yellow stuff thats coating the cat??

vocky

nice job Johnny 😃

JohnnyN

Thankyou! What's all the powdery yellow stuff??

notsure.gif

vocky

sand blasting grit notsure.gif dunno.. :?

or some strange metal coating dunno..

either way make sure it's all out before fitting :roll:

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