The Audi engines behind GP Turbos' hybrids
Grant Parker has been tuning cars since the early 1990s. By his account, around 2000 he built a Mk1 Golf with quattro four-wheel drive and an Audi 20-valve five-cylinder turbo engine, and around 2019 he was also running an Ur-quattro 20v. In November 2021 the website Engine Swap Depot reported that the Golf had run 10.65 seconds at 128 mph at Santa Pod Raceway's Doorslammers event.
The 20-valve five-cylinder
The 2.2-litre 20-valve five-cylinder (engine codes 3B, AAN, ABY and ADU) powered the S2, the RS2, the original S4 and S6 and the 200 20v with a turbo from KKK, which stands for Kühnle, Kopp & Kausch and is now part of BorgWarner. GP Turbos' hybrid for this engine was based on the factory K24. It had uprated main bearings, a large-pad thrust bearing, an extended-tip billet compressor wheel in a cover re-profiled to match, and a cut-back turbine wheel. The listing said it could also suit other high-powered 1.8 to 2.2-litre builds.
The 1.8T 20v
In the S3 8L and TT 225 (engine codes BAM, AMK, APY and APX), the 1.8T used a KKK turbo with part number 5304-970-0022. GP Turbos' hybrid for it combined an extended-tip billet wheel, a trimmed and lightened turbine wheel, a staggered oil seal and a gas-flowed turbine housing. The lower-output 1.8T in the A3 and TT used the smaller K03 (5303-970-0052), which had a hybrid of its own.
The 3.0 V6 TDI
The 3.0 V6 TDI (turbocharged direct injection) in the A4, A5, A6, A8 and Q7 uses Garrett variable-nozzle turbos, with part numbers including 769705 and 776469 across engine codes such as CAPA, CASA, CCWA and CDYA. GP Turbos listed several hybrid stages for it, some made to order. The most detailed paired a new ten-blade billet compressor wheel in a machined, matched cover with a lightened and trimmed turbine wheel, a heavy-duty journal bearing, a 360° thrust bearing and collar, and an uprated oil-seal ring.
Twin-turbo pairs
For the RS6 4.2 V8, GP Turbos listed a pair of hybrids built on its K04-based KKK turbos (5304-970-0028 and 0029), and a pair was also listed for the B5 S4 2.7 V6. The RS6 listing pointed out that the same turbos could instead be repaired to standard. Those are the two routes open to any worn turbo: turbo rebuilds covers the standard route and hybrid turbos the upgrade.
Several of these engines were shared with Volkswagen and SEAT models. GP Turbos is independent of Audi, and model names, engine codes and part numbers appear here only to identify parts.