K03 to K04..... What do i need?


Registered User
Hello, New to the site so hi to everybody. I purchased a 99 a3 1.8t, agu engine. Its all standard apart from the forge 007 i fitted to it. Now i knew it wouldnt be long before i wanted more horses. I can perform the conversion myself i just need to know a few things. Ive been weighing up getting a k03s or a k04 I know the k04 can handle a bit more power than the k03s but im looking for approx 225 hp (stock s3 power) but potential for more if needed. Anyway, What im asking is, If i go out and buy a k04-001 turbo and bolt it onto my a3 what would the power be (approx?) and could i run it / drive it right away?? What else would i then need to get the 225hp, what kind of map? Injectors? Also will it bolt on with the standard exhaust. ? Hope you understand my words. Thanks in advance. Nick. :arco:

S3 Paul

Well-Known Member
Regional Rep
How do mate
Right... k04 on a agu...
Been there and done that on a mates golf.
I would say go k03s for the ease of fitting and such,
The k04 option is a bit more of a ball ake.
the k04 needs a tt/s3 exhaust manifold, TT/S3 injectors fuel pump and a new custom downpipe. the "tip" needs changing too. but i think you need to swap that even if doing th k03s swap. You need to run a tt/s3 turbo intake pipe and then sort a 3inch maf housing... We used a golf vr6 maf housing fitted with the agu maf probe fitted to it. The boost pipe to the turbo is... im sure different so you would also need the red hose from the tt/s3.
This is just a quick run down as ive been out and have had a few drinks.
We did run the car without a remap but this was just for about 50 miles... the car was making huge boost figures so was nowhere near safe.
The injectors will fit the stock inlet manifold but need to be fitted to the agu injector rail not the s3/tt item as they will not fit and seal like that. the injectors need to be fitted in the manifold then use washers to space them out so the bolt to the agu rail. also dont forget the s3/tt preasure reg.

In short for 225 power i would go for k03s and a good map with a sports exhaust.


Registered User
Hi paul, Thanks for the reply, That sounds like a fair bit of work and i havent got much of a budget, approx £500, I think i'll go with the k03s for now ..

Is the k03s just a straight swap for my k03, Fit a full exhaust system and get it mapped? Would i have to ask for a specific map or is there just one basic map and its the actual turbo that adds the extra horses?

Appreciate your reply paul, Thanks.


Registered User
how much work is involved to replace the K03 turbo with the K03s? im aware you dont need any other parts but what needs to be removed to gain access to make the swap?


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