Since our previous article Black Smoke Racing has continued to develop their Mercedes W203 Wagon drift machine. One of the most obvious changes is the 2012 W204 Black Edition body kit. Under the hood still sits a Mercedes 3.2 L OM648 diesel inline-six however it now holds modified factory pistons, custom camshafts, and custom injectors. The team also switched from a single Holset HX40 turbocharger to a compound twin-turbo system capable of 4.5 bar (65.2 psi) or 750 horsepower using a Holset HX27 and Holset HX50 turbocharger. The drivetrain still consists of a TEXracing T101 four-speed manual and Toyota Supra rear end.
Source: Black Smoke Racing FB page
My biggest doubt about compound turbos: Does it really reduces turbo lag, or it just adds more pressure to make more power?
From what I understand a properly built system would deliver both. It delivers the extra boost needed over a single turbo but also cuts down on “lag” that a single large turbo would create. The drawbacks are it’s a more complicated system.
Like all turbos they need to be selected carefully for the desired fuel/power level, with compressor, intercooler and volumetric efficiencies in mind. Then they need to be tuned optimally.