2002 S8 cat/exhaust - HELP!

[The_Laird]

Now I'm getting desperate! I can't find a 'type approved' nearside cat for my 2002 S8 anywhere and Audi want £740 plus fitting. I've also beem advised by Ben (ex AVP I think) that I should not replace just one cat or there will be 'issues'.
So far, I've had someone offer to get the cat under an earlier registration plate (so the type approval doesn't apply), but A4 Audi (independent Audi garage in Glasgow) say that will trip the warning lights, someone else say that an A8 4.2 cat will be OK (and I can get one on ebay), someone else says don't buy an aftermarket cat anyway 'cos they're rubbish, and (my only hope so far) MJC (I think) in Walsall offer 2 sports cats and a custom after cat system for around £850 (tempting, but I'm in Scotland!).
Jeez, I just bought the car and thought it was great....for a while... but there must be a better solution (although if all else fails, I'm taking a day off to drive 5 hours each way to MJC!).

If anyone has been here before,please pointme in the right direction. Thanks

[Conan_the_Librarian]

Remember all your cats do is reduce emissions and allow you to pass the emissions test at MOT time. It does nothing for your engine except give the ECU information about exhaust gas composition.

The Lambda probe before the cat tells the ECU how well the combustion process is doing and helps adjust the mixture accordingly.

The Lambda probe after the cat passes information about how well the cat is improving emissions. If this one is defective or passes out of tolerance information then the ECU will try to compensate.

If you put after market cats on then there is a good possibility duff information will go back to the ECU because it will not get the pre-set readings it's expecting, you could well be ok but the ECU doesn't know this. To overcome this people that use after market cats modify the Lambda housings so the probes are out of the exhaust gas flow.

I'll look for the topic and post back.

[sutherland]

Originally Posted by IceBlue8

Now I'm getting desperate! I can't find a 'type approved' nearside cat for my 2002 S8 anywhere and Audi want £740 plus fitting. I've also beem advised by Ben (ex AVP I think) that I should not replace just one cat or there will be 'issues'.
So far, I've had someone offer to get the cat under an earlier registration plate (so the type approval doesn't apply), but A4 Audi (independent Audi garage in Glasgow) say that will trip the warning lights, someone else say that an A8 4.2 cat will be OK (and I can get one on ebay), someone else says don't buy an aftermarket cat anyway 'cos they're rubbish, and (my only hope so far) MJC (I think) in Walsall offer 2 sports cats and a custom after cat system for around £850 (tempting, but I'm in Scotland!).
Jeez, I just bought the car and thought it was great....for a while... but there must be a better solution (although if all else fails, I'm taking a day off to drive 5 hours each way to MJC!).

If anyone has been here before,please pointme in the right direction. Thanks

That's expensive. Go to Simon's exhausts in East Kilbride. He put two sports cats one of my previous S8s for £400 and I then got Wayne's Angle Blocks to take the post cat O2 sensors out of the mix. They were less than £100.

[Conan_the_Librarian]

Originally Posted by sutherland

That's expensive. Go to Simon's exhausts in East Kilbride. He put two sports cats one of my previous S8s for £400 and I then got Wayne's Angle Blocks to take the post cat O2 sensors out of the mix. They were less than £100.

That's the jolly old dog's biscuit! Here is a photo of said block


Here is the thread I was referring to.

A photo of it in use.

[The_Laird]

Thanks loads guys!

Simon's Exhausts passed me on to Semtech Motors in Kirkintilloch, so I'm taking the car in for them to have a look and to quote for 2 sports cats and a cat back system. Any thoughts? They also queried what had caused the cat to fail, so they'll test for that too. But as I had it on PsYcHe's VAG COM last week, would whatever the problem is not have shown up then?

[Conan_the_Librarian]

If there were any injector issues or misfires it should have done.

[The_Laird]

The report from PsYcHe’s VAG COM had faults in 2 areas:

1. Centr. Locks Labels 2 faults
Key 2 adaption limit suppressed
Alarm Horn Internal Supply Voltage

2. Auto trans Labels 2 Faults
Pressure control valve 2: open or short to ground. Intermittent
Pressure control valve 3: open or short to ground. Intermittent

But everything seems to be working OK. Both keys work, the alarm works and the gearbox selector lights/ limp mode was only for a couple of minutes and has been fine now for over 500 miles.

Any ideas?

[Dezzy]

The first one is ust the alarms internal battery i think i remember reading about it before. Can't help others