Well, I had a nasty feeling this was going to happen. You may remember me posting last year that my Piper CAT had failed and the car failed it's MOT due to emissions. Lots of flapping prevailed, ending up in me buying a new Pipewerx 200 CEL downpipe + CAT and flying through the MOT.

Just had this year's MOT and it's failed again. Gutted. Love to know what this is down to and how the CAT is getting damaged.

Trying a different tactic this year now it is apparent I didn't just have one dodgy CAT - booked into a custom exhaust place on Wednesday. They're going to chop up the Pipewerx and stick in a removeable section, then supply a de-cat section and a nice strong new-cat section that will be swapped in come MOT time. Quoted in the region of £350 which seemed pretty reasonable to me - plus I get the bonus of being able to run fully de-catted the rest of the year

both on the same remap??

if so maybe its running to hot and burning the cat material up. Myself and many others have used the pipewerx with zero issues. the fact that yours has done it to more than one exhaust says map to me. Its definitely not normal.

thought you were selling anyway?

Odd isn't it?

The first failed after running the Superchips stage2+ - the second was then run with the same map, switching to Sharkey's stage 3 in September time I think (so around 6 months on the SC) but plenty of people, for their sins, are running that Superchips map with no CAT issues - you very rarely hear about them failing.

It's still for sale, but I've only got it on here and Pistonheads - don't actually need to think about selling it in earnest until next probably when a new house might be on the cards. Had a load of part exchange offers from people modding their way up the BHP scale, but not a single cash offer. First one takes it

A common cat killer is too much fuelling. Though Bens Stage 3 map worked spot on in his car, so you might have a slightly defective lambda sensor and fuelling it slightly too rich? :think:

Yes that's a possibility - CATS seem to take objection to unburnet fuel I seem to remember from last year's investigation. Like you say, plenty of people using both Ben's map and the Superchips one so not map related.

Sorry to hear you are having a repeat of last years problems, but every cloud has a silver lining, post you views on the decat as I'm still in the market myself.

Very nearly went for the Pipewerx when I go a bonus last month until I realised it has gone up from £465 to £552 ........... I think there accountant needs a new VAT calculator.

Aghhh you've bust another!

Decat FTW

Yes I'm very careless

I'll still be bricking it that my bodge it in CAT will fail, but assuming I manage to actually get myself an MOT I'm quite looking forward to see what difference the de-cat will make - I've only heard good things about this mod.

Can you let me know how much they charge for the cat replacement please? I may do a similar thing to my decat.

Yup will do. £350 was a ball park figure, but £200 of that was for the CAT itself.

Yup will do. £350 was a ball park figure, but £200 of that was for the CAT itself.

Haven't you got your original exhaust? If so could you reuse that cat?

I spoke to my mechanic previously about de-cating the standard pipe, I think this is a viable option for me, it would be the same procedure as yours but obviously he would have to remove the pre-cat filter as well, then stage 2 map and job done..............?

Haven't you got your original exhaust? If so could you reuse that cat?

I spoke to my mechanic previously about de-cating the standard pipe, I think this is a viable option for me, it would be the same procedure as yours but obviously he would have to remove the pre-cat filter as well, then stage 2 map and job done..............?

Nope - I part exchanged it when I originally bought the Piper setup. It went on Lee's old VRS estate (FocusZetec) so I'd be interested to know what happened the first time that went through an MOT as in all likelihood I killed that one too

I guess you could chope the standard downpipe up, but what diameter is it? I thought most of the after market downpipes gave you the double benefit of a less restrictive CAT and a wider piper?

The standard downpipe is 2.5 inch. Im just going to take out the pre cat next week and leave the OE cat there. That should release a few more bhp and save me few pounds buying an aftermarket one.

Ive read articles on other mk5 forums with golfs using the AWE exhausts and seeing very good results from them. They are only 2.5 inch and not 3 inch. I have copied the explanation below as to why they use 2.5inch and not 3 inch.

Why did we choose 2.5 inch and not 3.0 inch diameter for our MK5 exhaust? Our first prototypes of this system were indeed 3.0 inch, but we found that the effort it took to move the large mass of air in the 3.0 inch system at lower rpms resulted in a loss of torque with very little offsetting gain up top. Take a look at our 3.0 inch prototype dyno sheets here and see why a 3.0 inch system is not appropriate for this car

Edited 13 February, 201115 yr by 56OctyVRS

The standard downpipe is 2.5 inch. Im just going to take out the pre cat next week and leave the OE cat there. That should release a few more bhp and save me few pounds buying an aftermarket one.

Ive read articles on other mk5 forums with golfs using the AWE exhausts and seeing very good results from them. They are only 2.5 inch and not 3 inch. I have copied the explanation below as to why they use 2.5inch and not 3 inch.

Why did we choose 2.5 inch and not 3.0 inch diameter for our MK5 exhaust? Our first prototypes of this system were indeed 3.0 inch, but we found that the effort it took to move the large mass of air in the 3.0 inch system at lower rpms resulted in a loss of torque with very little offsetting gain up top. Take a look at our 3.0 inch prototype dyno sheets here and see why a 3.0 inch system is not appropriate for this car

Interested in hearing the results from this, I have been swatting on the MK5 site as well.

I'm still thinking that this is the way forward...........especially if your friendly mechanic will pass an MOT if you leave the OE cat in the boot!

Edited 13 February, 201115 yr by vRS_Pagey

My old Mk1 FRS had a mongoose de-cat fitted at first and then I fitted the Graham Goode Racing Sports cat to pass the mot. Being honest there was no difference in performance and certainly no loss of performance by fitting the sports cat.

Once I have knocked the precat out, Im going back up to R Tech to have it rolling roaded. Last time I went I got 236bhp, but I also had an ongoing P0299 fault code, which has since been cured by fitting new boost hoses. I shall see what difference it makes and report back to the site. Once thats done I will see if Ben can do me a stage1.5 map to suit and then put it back on the rollers to see what the difference is compared to a full stage 2 map and downpipe.

I read a few interesting posts over at mk5GTI - slight loss of torque does seem to be on the cards, but a K04 conversion has always been around the corner really and the 3" system would put me in good stead here. Hurdy got some very impressive gains with his de-cat - not bhp related, but delivery wise. I've never pushed the button on the K04 simply because of the outlay and recently, my thoughts on getting rid of the car (and the Suzuki bike I'm planning on buying shortly ) but if the K03 popped tomorrow for example, off to JKM I would limp with my credit card ready.

Might get Ben's thoughts on the map situation and whether it might be worth a tweak to my stage 3.

Decat made quite a difference for me in spool up time, top end power seemed to end up the same on a stage 1 map. This was determined with VCDS not rolling road.

Well the decat is on - initial impressions show that it's slightly louder under load, sounds the same when idling and cruising. I'm sure it seems a bit livelier but will do my usual route to work tomorrow and decide then. Price was £360 in the end, so bascially true to the phone quote but the chap hadn't factored in the hole for the lambda sensor (on both sections, obviously) and I also asked for a spare gasket to be made - the material costs ~£160 a sheet - and it's a small sheet

Assuming it goes through the MOT (next weds) I'll put a new thread as I took a load of photos today of the process and the 2 swap-out sections - quite impressive.

If it fails then I'm burning the car.

Something to consider - I asked what a full turbo back system would cost including sports cat - £850 including fitting, vat and the standard lifetime warranty. Seems like a bargain to me...!

Hmm not as cheap as I thought, I think I'll be swaping my whole downpipe come MOT time :yes: