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The Lexus D4-S system combines direct fuel injection (DI) and port fuel injection (PFI) to optimize combustion, power, fuel economy, and emissions. On engines such as the 1UR-FSE and 2UR-GSE, each cylinder is fitted with a high-pressure direct injector and a low-pressure port injector. The direct injectors operate at pressures up to approximately 13 MPa (about 1,885 psi), allowing precise fuel metering during high-load operation. The port injectors operate at a lower fuel rail pressure, typically around 380 kPa (55 psi), and are especially useful during low-load and idle conditions to reduce particulate emissions and help keep intake valves clean. D4-S switches between injection modes depending on operating conditions: port-injection during light loads, combined direct and port injection during moderate loads, and direct-injection under high-load and wide-open throttle conditions. Injector flow rates vary by calibration and engine application, but the direct injectors are sized to support the engine’s target air-fuel ratio across its operating range. For 2026 Euro 7 emissions compliance, injector spray targeting, sealing, and deposit control are important. When replacing injectors on D4-S equipped Lexus vehicles, use OEM or certified components, follow fuel system pressure-relief procedures, and perform any required injector coding or calibration updates. Always consult the factory service manual for exact specifications and diagnostic steps.