whats the difference?

[johnyj]

have just noticed (yeah i know) that the s3 is a 18t what is the difference between that and the 18t a4
is it turbo ecu or something else?

 

[jcb]

about 45 bhp in quattro form

 

[aragorn]

the turbo is the KKK04 as fitted to the TT225 and the ECU map is different to suit. The injectors will also likely be larger than the A4 engines.

 

[Markey]

Not 100% correct above, depending on year etc.

The TT and S3 use the K03s turbos and have very different maps with steel pistons and i think the crank as well.