Audi needed a reliable V8 engine for their new DTM program at the time. Neil Brown Engineering is the confirmed enginebuilder/rebuilder for AudiSport which tuning was done inhouse by Audisport using a DTM mandated Bosch Motorsport ECU. Apparently Audi contacted Honda for a solution because of their performance, reliability and dominance in IRL (Sound familiar now). Also Audi was able to reduce center of gravity in the R11/R12 chassis since the IRL platform derived V8 sat so low in the Dallara & Panoz chassis's used. Unconfirmed is if Audi took the Mugen design further for the R13 platform DTM car. Interestingly enough is Audis 4.2 litre engine in the B7 RS4 was designed with 4 valves per cylinder much like Hondas V8, which replaced the older 4.2 litre 5 valve per cylinder design from the V8 in the B6 Audi S4 (similiar in design to Ferrari's V8 used in the F355 and funny enough Both the S4 & F355 were plagued by similiar transmission troubles and were made by ZF Engineering).
Considering Audis recent use of the Lamborghini V10 in Audi vehicles this information unconfirmed goes along with a timeline of development & use in road cars by Audi.
This is the original Honda/Mugen MF308 in 3.5 litre form:

Here is the Audi Sport 4.0 Litre version and Article:


