The iRacing GTP hybrid MGU-K system has been completely overhauled in the latest season update. Drivers quickly noticed that manual hybrid controls such as Quali, Attack, and Build are now unavailable. Even with keybindings set correctly, the option is grayed out in the control menu, and the black box display no longer shows MGU-K mode adjustments.
This change isn’t a bug — it’s part of a major update designed to make iRacing’s GTP cars behave more like their real-world IMSA and WEC counterparts.
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➡️All Things GTP Hybrid Project
Why the iRacing GTP Hybrid MGU-K Was Changed
In previous seasons, GTP hybrids allowed limited manual control of energy deployment. That system, while fun, didn’t match how the actual LMDh machines operate.
Real cars such as the Porsche 963, BMW M Hybrid V8, Acura ARX-06, and Cadillac V-Series.R use automated hybrid logic. Their control units constantly manage energy harvesting and deployment, leaving no reason for drivers to adjust the system manually.
With the latest build, iRacing removed manual MGU-K adjustments to replicate this real-world design. Drivers can now focus entirely on racing while the software handles hybrid management in the background.
How the iRacing GTP Hybrid MGU-K Works Now
The new system automatically harvests and deploys electrical power. During braking, energy is recovered through regeneration. When accelerating, the hybrid motor assists until the state of charge (SoC) drops. If energy runs low, deployment automatically decreases to maintain stability.
This setup also reduces engine output by an equal amount when hybrid power is added, keeping overall horsepower within regulation limits. The end result is smoother, more realistic hybrid operation — and no need for driver-controlled boost modes.
Comparison to Previous Hybrid Systems
Earlier cars like the Porsche 919 Hybrid and McLaren MP4-30 offered manual MGU-K maps, giving players full control over energy recovery and attack modes. Those systems suited the prototype and Formula 1 eras they represented.
However, GTP cars run under newer rules. The latest iRacing GTP hybrid MGU-K update brings the sim closer to current IMSA standards, where hybrid use is standardized and controlled automatically by each manufacturer’s Energy Recovery System (ERS).
What Drivers Should Expect
If you’re used to adjusting hybrid settings mid-race, the change may feel restrictive at first. But it simplifies driving and levels competition across all four GTP models. You can still monitor hybrid deployment in telemetry, but manual control is no longer part of the experience.
The update removes any need for button assignments or black-box management — the car takes care of itself. Focus on braking precision, corner exit balance, and fuel strategy instead.
Realism Over Flexibility
This move reinforces iRacing’s commitment to realism. The GTP class now mirrors the technology and rules of real IMSA and WEC racing. The system ensures consistent energy deployment and prevents unrealistic “boost” advantages.
For endurance racers, the benefits are clear: fewer distractions, more authentic performance, and consistent hybrid behavior across every manufacturer.
