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Ok, so I have been asked a couple of times recently and thought I would post this information up. Please correct any inaccuracies in my understanding of this information, but I have stolen the prices from AMD's site, although there are many other supplier/installers

There are basically two options available for the RS4

RS4 DUAL SYSTEM, B5 2000 – 2002, CAT back
RS4 HI-FLOW CAT ASSEMBLY, B5 2000 – 2002 Full system

Both have the Pulse twin exhaust pipes

Basically one is Cats back and will just give a louder sound of exhaust note, sweet although actual performance increase is minimal

The second is the full system with new CATs, this gives a much higher gas flow and will ultimately improve performance up to 458 as stated by MTM, similar for AmD etc. However if you have the full system it will need a remap to ensure fueling is correct and so avoid mechanical failure. But this is a nice upgrade and IMHO is what the car should have been built to. Excellent

Hope this helps, any other comments anyone?

Also just a thought they have made some different CATs, 100 cell and 200 cell which refers to the density in the exhaust, the less dense the higher the gas flow so performace is increased, as is the noise!

I believe the OEM Cats are 400 cell but of a different material, hence the 200 cell still give the same emmisions

Full Stainless Steel Exhaust System (CAT back), £680 Supplied, £750 Fitted
Stainless Steel Sport CAT's & Downpipes £1140 Supplied, £1450 Fitted


Cheers

Bushy

Bushy,
from my digging about I discovered that the cat back takes the quoted 420bhp stage one (i.e just chipped/remapped) to 428 bhp stage two.
Not sure what it does on its own but to give the 8bhp increase when combined with a map it ought to do something.

The full system with remap is known as stage three, or better known by mtm as 458.

Also, the 100 cell cats have been known to give 'check engine' lights.

Cheers,
John.

The engine check light issue has been overcome by moving the lambda probe location I believe.

I also had the cats back before the full system and did notice a marginal gain but as I had no proof didnt post it, sometimes the noise can give you the sensation of going fast. The kids sometimes ask me to go fast, so drop down a gear and go yee har and they think you have got faster whereas in fact you are still going 40mph

Anyway if the cats back gives another 8bhp I wonder if there is a gain by having the 100 cell cats?

Thanks for the input John

Bushy wrote:The engine check light issue has been overcome by moving the lambda probe location I believe.

I had heard that too, but just thought I'd mention it.

I also had the cats back before the full system and did notice a marginal gain but as I had no proof didnt post it, sometimes the noise can give you the sensation of going fast. The kids sometimes ask me to go fast, so drop down a gear and go yee har and they think you have got faster whereas in fact you are still going 40mph

, do you have to put your cowboy hat on too

Anyway if the cats back gives another 8bhp I wonder if there is a gain by having the 100 cell cats?

I would assume they do, otherwise why bother to change them ?
(assuming its not simply a case of the new downpipes wouldn't mate to the existing cats of course...)

Thanks for the input John

No problem

OK, so if you go for the full system, you need a remap anyway, to avoid mechanical cockups. So if you've got to pay for a remap, is it not worth paying that bit extra and having the full chip to put you up to 458hp? Is that chip upgrade an entirely new chip or just a remap of the standard one? I am a total newbie in the world of chipping if you hadn't noticed!

I definately agree that the full system is worth having though, as I've been driven in a car with standard and full system exhausts within 10 minutes of each other, and the difference is amazing. Of course the remap might have helped a bit!

Sam

I'm heading for Bicester on Thursday to have the budget version fitted
I only wanted a bit more sound, not interested in big power increases and additional maintainence, hard enough to keep one of these things on the road standard
Many thanks to Bushy who has supplied the info and contacts I needed behind the scenes to get this sorted, and to RS4.Com who have created a solid database for owners to work from, and allow us to avoid the mistakes others might have made in the past

runrowsam wrote:OK, so if you go for the full system, you need a remap anyway, to avoid mechanical cockups. So if you've got to pay for a remap, is it not worth paying that bit extra and having the full chip to put you up to 458hp? Is that chip upgrade an entirely new chip or just a remap of the standard one? I am a total newbie in the world of chipping if you hadn't noticed!

I definately agree that the full system is worth having though, as I've been driven in a car with standard and full system exhausts within 10 minutes of each other, and the difference is amazing. Of course the remap might have helped a bit!

Sam

Exactly, it is more cost effective to go for the full remap and new system

Basically the concept of chip is not strictly true to cover all available offerings.

It would imply by the name that a new chip is installed whereas several tuners remap the existing chip, although some do fit anotehr one

The point is to get correct or optimum combustion the fuel and air mixture needs to be correct, so if the exhaust increases gas flow of air out, the air in is also increased, so to meet this the ECU needs to adjusted to meet this, hence the chipping/remapping requirement

Hope this is clear as mud

Regards

Bushy

Mine is fitted and is the Mutz Nutz.....shame I waited so long! And AMD, superstars of the Audi world, what a pleasure to deal with real people who do not hide in their glass offices pretending to be doing their next £m deal And the job was perfect from the off, no return trips to get things adjusted.........I'll be going back for all my servicing.

Anybody know if the Miltek system meets the 100db noise test at Castle Coombe? Tubi sports exhaust on Ferrari doesn't
Does not seem much point in going to one these track days with RS4 if it can't pass the test

I guess it does as when we were all there last year there were plenty of modded RS4's.

Cheers

Ben

yep, they do.
I was behind Bushy during the noise testing, think he was 98.6 or 96.8 eitherway below 100db.

In fact even the TVR Chimera just snuck in, and they are proper noisey

Good to know
There were a few there which did not pass even extra box bolted on tailpipes Testarossa with sport exhaust, my 328, a challenge 355 and several 360's

Whit's all this nonesence about a race track having a sound limit - Who came up with that ?

The RACMSA came up with this to comply with planning regs about noise polution. It only applies to non competative cars being used on non race days

As pointed out I have been to Castle Coombe a couple of times, no probs with noise, at least it is at 4000rpm, under full steam, well that is a different matter!!