The history of the SQ8 is a narrative of two distinct engine eras, each
representing the pinnacle of technology available in its time and regulatory context.
Phase I: The Diesel Apex (SQ8 TDI, 2019–2020)
At the European launch in 2019, Audi made the bold decision to equip the SQ8 with the
most sophisticated and powerful passenger diesel engine in the world, the EA898.
V8 TDI Architecture
This 4.0-liter (3,956 cc) biturbo V8 engine was designed to deliver a relentless wave of
torque, ideal for moving the SUV's mass with effortless authority.
- Power: 435 hp (320 kW).
- Torque: 900 Nm, available from a mere 1,250 rpm.
- Complex Forced Induction: The system utilized two
sequential turbochargers. At low rpms, only one turbo operated. As
load and rpm increased (above 2,200 rpm), the second turbo came into
action.
The Electric Powered Compressor (EPC)
The "secret" to the TDI's performance was the third induction device: the Electric
Powered Compressor (EPC). Powered by the 48-volt subsystem, the EPC was located
in the intake air path, downstream of the intercooler.
- Operation: On standing starts or roll-on acceleration at very low
rpms, where exhaust gas energy is insufficient to spin conventional
turbos, the EPC would accelerate its turbine to 70,000 rpm in less than 250
milliseconds. This pressurized the air instantly, eliminating turbo lag and
ensuring that the 900 Nm were available at the slightest touch of the throttle.
The Decline of Diesel
Despite its technical excellence and efficiency (allowing ranges exceeding 1,000
km), the V8 TDI fell victim to increasingly stringent emissions standards and the shift in
public perception post-Dieselgate. The complexity of the after-treatment systems
necessary to keep the engine legal (dual AdBlue injection, massive particulate
filters) made its continuation unviable, leading to its global replacement in 2020.
Phase II: Gasoline Supremacy (SQ8 TFSI, 2020–Present)
Starting in late 2020, the SQ8 was unified globally under the gasoline V8 TFSI engine,
the same EA825 block developed in partnership with Porsche and used in the Panamera and
Cayenne Turbo.
V8 TFSI Architecture
This 4.0-liter (3,996 cc) engine represents a different philosophy: quick response,
high revs, and raw power.
- Power: 507 hp (373 kW).
- Torque: 770 Nm.
- "Hot V" Configuration: The two twin-scroll turbochargers are
mounted inside the engine's 90-degree "V". This drastically shortens the exhaust gas
path between the cylinder head and the turbine, improving thermal and
kinetic response.
Efficiency and Durability Technologies
- Cylinder on Demand (COD): Under partial load situations, the system
deactivates cylinders 2, 3, 5, and 8. The system closes the valves and cuts off
injection and
ignition, allowing the engine to operate as a balanced V4, reducing consumption while
cruising.
- Atmospheric Plasma Spray (APS) Coating: The cylinder liners
in the aluminum block are coated with an extremely thin and hard iron layer
via plasma spray. This reduces friction, wear, and improves heat
dissipation, essential for a high-power-density engine.
ZF 8HP Transmission
Both powertrains use the ubiquitous and acclaimed 8-speed ZF automatic
transmission (Tiptronic in Audi parlance). This torque converter gearbox is
preferred over dual-clutch transmissions (S-tronic) for high-torque and towing
applications, offering smoothness in low-speed maneuvers and the robustness
to handle up to 1,000 Nm of torque. Audi's management software adapts gear
shifts based on the selected driving mode, ranging from imperceptible
(Comfort) to aggressive with artificial "kicks" (Dynamic).
Direct Performance Comparison
The table below illustrates the technical evolution between the two phases of the combustion SQ8:
| Specification |
SQ8 TDI (2019-2020) |
SQ8 TFSI (2020-Present) |
Difference / Impact |
| Engine |
4.0 V8 Biturbo Diesel + EPC |
4.0 V8 Biturbo Gasoline |
Change of philosophy: Torque vs. Power. |
| Power |
435 hp (320 kW) |
507 hp (373 kW) |
+72 hp in favor of TFSI. |
| Torque |
900 Nm |
770 Nm |
-130 Nm on TFSI (less initial "punch"). |
| 0-100 km/h |
4.8 s |
4.1 s |
TFSI is 0.7s faster due to weight and power. |
| Weight (approx.) |
~2,440 kg |
~2,320 kg |
TFSI is lighter (aluminum vs. iron block). |
| Combined Consumption |
~12.8 km/l (7.8 l/100km) |
~8.3 km/l (12.0 l/100km) |
TDI was drastically more efficient. |
| Sound |
Synthesized (Soundaktor) |
Natural (Crossplane V8) |
TFSI offers authentic auditory emotion. |