Presently I am in the process of collecting baseline performance data on the twin Borg-Warner K03 turbochargers that were equipped on the B5 S4 as delivered from Audi.  Once I have completed this process I’ll be removing the K03’s to install a different turbocharger.  The upcoming posts in this blog category will touch on some of the considerations and decisions I made during this process.

There are quite a few turbocharger options now available for the 2.7T twin turbocharged engine found in the Audi B5 S4.  Twin turbochargers aren’t even a requirement anymore as single turbocharger setups are becoming more common.  From the get go I’ve decided to stick with the twin turbocharger set, the main reasons being familiarity and ability to continue to use components that I have already acquired.

One process I have followed during upgrading has been to make incremental changes to the car, building on what already exists and only replacing parts when a weak link has been identified.  By following this process I am able to keep an eye out for opportunities to obtain upgraded parts at a discounted price, either through sales or used part classified ads.  One downside to this method is that if I decided to drastically change the car’s setup, for instance swapping from the dual turbochargers to a single turbocharger setup, there may be parts already acquired that would be overcome by events (OBE) and no longer of use.

In terms of cost and performance and single versus dual I have not felt there is a significant benefit one way or the other and with total cost a consideration, meaning I am not going to go crazy building a motor capable of setting world records for the 2.7T platform, the currently available dual turbocharger options meet my requirements.

Decision One: Twin Turbocharger configuration

Next: Turbo Size Decision