S4 Exhaust and cats query

[jeffw]

Apparently to change the manifold etc is a 6 hour job !!!!!!!!!

[jeffw]

And put them back come MOT time !

[Andiroo]

AmD of course [img]images/graemlins/wink.gif[/img] have you asked them mate?

Andiroo

[Andiroo]

I reckon they may well be interested in your project, if they think the power benefits will be worthwhile [img]images/graemlins/laugh.gif[/img]

If the benefits are there, and they are not interested, please let us know [img]images/graemlins/wink.gif[/img]

Andiroo

[DavidT]

APR do a system for the S4 which allows this:

http://www.goapr.com/Audi/products/apr_ ... _full.html

They call the cat replacement pipes 'test pipes'

I think this solution would have implications for the ECU settings because of the measurements taken before and after the cats for emmission compliance Andy ?

[Andiroo]

As long as this gives a performance benefit (and I'm not yet convinced to be honest [img]images/graemlins/tongue.gif[/img]) AmD can remap it to suit [img]images/graemlins/laugh.gif[/img]

There are ways [img]images/graemlins/wink.gif[/img] I mean I ran a decatted Cerbera 4.5, and it although it was way out on emisssions, the ECU was setup that way. Putting the Cats back in for say an MOT test would be fairly straight forward, and to be honest I reckon the car would drive OK.

Mind you I nearly got thrown off the TVR Trackday at Croft for being too loud (after the dB test I was instructed to slow down only for the start/finish straight, but after that go for ti coz it sounded wicked [img]images/graemlins/laugh.gif[/img])

Andiroo

[DavidT]

I'm sure your right mate, the better the exhaust flow, the more power and the cats are an obstacle in the exhaust flow.

Bear in mid though that the ECU has these as its first three priorites:

1) not to damage the engine
2) to meet the emmission requirements
3) to product torque and power

And there are measurements taken to confirm emmissions after the cats. If you take the cats away, these measurements will upset the ECU and you may end up with less power than with cats installed.

I'm sure I read a post on the old as-n about someone in South Africa doing this and he had to do ECU mapping to make it work.


David

[johneroberts]

Mind you I nearly got thrown off the TVR Trackday at Croft for being too loud (after the dB test I was instructed to slow down only for the start/finish straight, but after that go for ti coz it sounded wicked )

Good to see you givin the TVR boys with V8 and V12 a noise problem [img]images/graemlins/grin.gif[/img]
Keep up the good work
[img]images/graemlins/thumbs.gif[/img]Cheers
jr

[Crafty]

Hmm not too up on RS4s, but I know that some cars can have a problem with this..
If the car has two ( or more ) lambda sensors usually you find one before and one after the cat, in some cases cars with two cats have three sensors, before both, in between and after both.. if the ECU sees the same readings from two or more sensors it comes to the conclusion that the cat ( or one of them ) is no longer doing its job and flags the ECU light. Now, if the cat isn't there it comes to the same conclusion.
I know that VX220s have this problem (non turbo ones) and I have seen it resolved by changing the signal from the second sensor ( i.e. post cat ) with a bit of electronic trickery that fed the ecu the correct signal.

Its all this nasty emissions stuff that some collar decided would be a good idea [img]images/graemlins/rocketwhore.gif[/img]

Like I say I don't know if this would apply to the RS4 or not.