Removing Pre-cats

[v8 mark]

I realise there have been other posts prior to this but once and for all.....
I want to remove pre-cats and possibly main cat, but leave lambda sensors in place...Will i still need a re-chip???? As the sensors are only after the pre-cats, sureley you can remove main cat, without any hassle anyway...So what do you think......

[gerjo]

Best is to remove the pre-cats only (that's what the experts told me); you don't need a re-chip. I removed them recently from my Griff 500 because I'm getting an ACT plenum etc. I think removing pre-cats is only useful if you're upgrading the engine, otherwise don't bother. Sound is a little better, but if you want better sound do an exhaust sport conversion.

[v8 mark]

Thanks for that gerjo, i will remove pre-cats tommorrow. Weather permitting.Did you just pull out the packing or need any other equip?

[mack]

I've just removed all three cats on my car-what a b*stard of a job to remove the manifolds(it was a tad easier to do last time with the engine out!)Cut the 'Y' piece in half,then drilled/bashed/cursed/
destroyed the main cat,and had it rewelded.Precats were just as tough as the main one and,after getting nowhere fast,decided to cut and reweld these as well-made them simple to knock out and guaranteed all the bits were removed.Seems some people are lucky their cats just break up easily-mine were very solid and it would have taken me ages (I went through enough drill bits as it was!)It may not be the recommended way of doing it but,as long as the cutting/welding is done precisely,it saves a lot of time.Just got to refit everything tomorrow now!
Good luck.

[gerjo]

Someone did it for me. He had to bang them out but this seems to vary from car to car: some fall out almost by themselves, others have to be "persuaded".

v8 mark said: Thanks for that gerjo, i will remove pre-cats tommorrow. Weather permitting.Did you just pull out the packing or need any other equip?

[budd]

Removed all three cats from my Griff500, bought the cat replacement pipe(Y section)from Act products (to avoid cutting the std Y section)and knocked out the pre-cats and like Mack said it's a pig of a job.
You will need a re-chip and different value tune resistor to select the correct fuel map.These parts are easy to fit and available from TVR (I have the part No's for 1995 Griff 500HC).
Not had the car on a dyno yet(clutch now slipping)but the car is much quicker than before,and sounds fantastic! no regrets (apart from the extra power frying the clutch)
MOT my prove a problem a you don't have a tame tester (another reason to retain std Y pipe for refitting if needed) hope this helps.

[IPAddis]

The Y piece isn't an unboltable item so how do you do a cheap and easy replacement for MOT? It is bolted to the manifolds but surely the other part of it is welded to the rest of the exhaust?

Ian A.

budd said: Removed all three cats from my Griff500, bought the cat replacement pipe(Y section)from Act products (to avoid cutting the std Y section)and knocked out the pre-cats and like Mack said it's a pig of a job.
You will need a re-chip and different value tune resistor to select the correct fuel map.These parts are easy to fit and available from TVR (I have the part No's for 1995 Griff 500HC).
Not had the car on a dyno yet(clutch now slipping)but the car is much quicker than before,and sounds fantastic! no regrets (apart from the extra power frying the clutch)
MOT my prove a problem a you don't have a tame tester (another reason to retain std Y pipe for refitting if needed) hope this helps.

[2 sheds]

IPAddis said: The Y piece isn't an unboltable item so how do you do a cheap and easy replacement for MOT? It is bolted to the manifolds but surely the other part of it is welded to the rest of the exhaust?

Ian A.

The "Y" piece is attached to the manifolds by a "V" clamp and at the exhaust end a "u" clamp, see no welded parts, probably a bXXXXD to remove though
Tim

>> Edited by 2 sheds on Friday 15th November 17:45

[david beer]

My "Y" piece came out ok and enabled me to knock the pre cats out without removing the manifolds. I think it is common for it to be said there is a "hollow" sound around 2.5k rpm, but you dont stay around there for too long! Overall, worth it everytime.I have a ACT super sports exhaust,tickle the throttle on overrun to compliment the great sound getting up there!

[budd]

IPAddis It's not a big job swopping the Y pipe, couple of hours no problem,slacken one manifold remove the two V clamps and the U clamp and its off ,put the one containing the cat back in and off to the MOT station,pass the test and swop back to cat free motoring.
Might sound alot of hassle but it's worth it.

[dai capp]

I have an email from a Chim owner who did it which I'll forward on to you...

I spoke to a mate of mine who knew him and the conversation went a bit like 'It was a right pig of a job, but when he enquired about the price of new cat free manifolds he decided there was a few more hours labour in it'

I'll get the mail sent over if I can get the thing to work right!

Cheers

DC

[v8 mark]

Thanks for (Dai) I will trying this later, looks like mine are corregated sheets (like cardboard effect) Could be fun...

[IPAddis]

budd said: IPAddis It's not a big job swopping the Y pipe, couple of hours no problem,slacken one manifold remove the two V clamps and the U clamp and its off ,put the one containing the cat back in and off to the MOT station,pass the test and swop back to cat free motoring.
Might sound alot of hassle but it's worth it.

Hey might investigate this further, especially since I am running sans lambda sensors anyway. When you say slacken the manifold, I presume you mean to slacken the manifold from the heads not from the Y piece. Can I then get flames?!

Ian A.

[yiw1393]

Mine has stainless mainfolds sans cats - and a tame tester You're right though, The 'real' things cost an absolute fortune - luckily mine had them fitted before I bought it, but I've seen the bills