Audi has detailed its SQ8 TDI, equipped with a 4.0-liter biturbo V8 capable of delivering 435ps and 900Nm of torque between 1,250rpm and 3,250rpm. The TDI unit, paired with an e-compressor, propels the SQ8 from rest to 100km/h in 4.8 seconds and on to an electronically limited top speed of 250km/h.
In the eight-cylinder heads, the intake side is on the outside and the hot exhaust side with the two turbochargers is in the inner V. As a result, the gas travel paths are short, working in favor of immediacy of response. The turbos are operated according to the principle of sequential turbocharging. Only one charger is active at low engine speeds; the second charger exerts its influence from around 2,200rpm.
An electrically powered compressor (EPC) assists the turbochargers when starting off and when accelerating at low engine speeds. The EPC is located in a bypass behind the intercooler and is activated when the flap is closed. If the load requirement is high while the amount of energy available in the exhaust gas is low, the intake air flows into the EPC, where it is compressed a second time.
The driving force behind the EPC is the 48V main onboard electrical system. A compact lithium-ion battery serves as its energy storage unit. The belt alternator starter (BAS), which is connected to the crankshaft, allows up to 8kW of recuperation power to be generated during deceleration and can feed this energy into the battery.