[Audi A3/S3] decat or sports cat?

[hus99]

hi, im having trouble in deciding whether to go for a sports cat or a decat for my mapped s3. considering a milltek sports cat im lookin at the region of 700 quid but a local powerflow dealer said they will fix me a up decat pipe for a reasonable 160. can anyone tell me why the sports cat is so much compared and what benefits are offered. thanks

[Paul]

re decat.

firstly you need a cat for MOT, & roadside checks to stay legal.

IIRC its a £1000 fine without one.

secondly...

if your car has before and after cat lamda sensors, its highly likely you will throw a fault code and go into limp mode.

This is because the ECU is expecting an improvement in the quality of the exhaust emmisions, and will shut the car down if its not within its expected tolerances.

Easier if you only have one lamda before the cat, but it doesnt make it legal.

thirdly, the exhaust and cats are not the restriction, its the turbo and manifold.

Its widely known that sports cats on the S3 cost dearly and add next to nothing in terms of performance.

Some sports cats have also been known to throw error codes because of the lamdas, so thats not even a certanty.

If it were me, id spend money elsewhere.

[hus99]

yes i understand that is no restriction there but as i have just ordered a garret uprgrade and eventually a new ecu will be installed . thias problem with the ecu is somewhat irrelevent to me. also could you thell me what limp mode is?

[Paul]

With a big turbo in mind , then you should see a benifit.

limp mode is where the car shuts down onto a less powerful map to protect the car.

think of it as a limp home injured mode.

[sitas3]

let us know how you get on as I'm interested in doing this myself.