CATs & stink bombs

[r13ras]

My RS2 smells when cold (like a stink bomb - H2S). Does this indicate a CAT problem?

If so can anyone suggest a source other than Audi (who want £495+VAT each)

Many thanks

R [img]images/graemlins/yellows4.gif[/img]

[Greg_S]

take the car for a bit of a B road balst. this should clear the cats out.

[s2driver]

Milltek high flow cats will be cheaper than stock I believe. Milltek also doing a more cost effective single cat conversion for the ABY (S2) and the ADU (RS2) which puts a single cat in the downpipe. Standard ones are very vulnerable to damage over speed humps as they protrude quite a bit below the floorplan. Miltek claim the single cat is as good as the standard setup and it heats up better as it is considerably closer to the turbo in its re-configured state.

Lee

[Greg_S]

Surely if the cat is moved closer to the turbo it will impede the gas flow from the turbo and put more back pressure into the system unless it can flow considerably more than the standard setup in the standard position

[s2driver]

You are correct Greg. Moving a cat closer to a turbo will affect turbo spool up due to the reduced plenum volume between the turbine housing and the (restrictive) CAT. But I am not sure what the effect of the configuration of the Milltek upgrade is. They firstly use a much less restrictive CAT and possibly change the downpipe diameter. I don't think it is located right next to the turbo but still down towards the gearbox somewhere...just in a less vulnerable position.

It is such a horribly complex dynamic problem that I wouldn't want to start speculating the effects of changing cat type/placement and downpipe geometry.

You 'might' affect transients (more lag?) with a closer CAT but steady state I would have actually expected more power if the single CAT is more free flowing than the two stock units.

I thought that this re-configuration of S2 CATs was developed with an Audi tuner anyway. I am sure Milltek would confirm. If they did develop with a tuner there must be some accompanying test data or something.

Besides, this is also a cost effective solution to replace failing CATs. It may turn out that there could be a slight performance hit (or gain) but not everyone out there is trying to max out and optimise their vehicles. The RS2 is horrendously expensive to run if you are not mechanically minded so this solution might appeal to many...especially those who might have bought the car just for the Porsche badge!!!!

Lee

[r13ras]

Turns our both the cats were removed when the car was upgraded to 360bhp (MTM by QuattroSports). Still seems to pass the MOT (!!).

In this instance the problem was traced (via diagnostics) to the lambda sensor. Purchased new audi part from VagParts @ GBP 89 + VAT (Audi GBP 147+VAT). Continue to be impressed by VagParts, no one else could supply.

Seems to be fine now - my friendly mechanic managed to get the mpg down to 11.6 during testing !!!!

Rgds, [img]images/graemlins/yellows4.gif[/img]Ratty