The wait is over. With the 2025 Season 4 release, iRacing has shipped a completely overhauled hybrid system for its most advanced racing cars. The changes are less about flashy new knobs and dials, and more about making the system accurate, seamless, and invisible—just as it should be in modern prototype racing.
The New Hybrid Architecture
The hybrid system has been fully integrated into iRacing’s latest power unit code. What this means for drivers:
- Blended ICE + MGU output: Power delivery is smoothed so that you don’t feel a “drop” when the hybrid motor switches off. The car just delivers consistent, rule-capped wheel power.
- Locked deployment strategy: All GTPs now operate in a balanced mode, targeting ~50% state of charge. There are no user-adjustable deployment maps—because the real cars don’t offer that kind of freedom.
- Better braking feel: Regeneration and friction braking are blended in the source code, eliminating edge cases like sudden lockups.
GTP Cars: Just Drive
The BMW M Hybrid V8, Cadillac V-Series.R, Porsche 963, and Acura ARX-06 all now behave identically from a hybrid standpoint. Drivers no longer need to think about when energy is being deployed—it simply happens automatically within the rule limits. BoP also becomes easier to balance across manufacturers because iRacing can directly control wheel power output.
Ferrari 499P: The Exception
The Ferrari 499P Hypercar includes an extra rule-driven constraint:
- 190 km/h threshold: The front MGU won’t deploy below this speed.
- 100 kW max output: Electric drive is capped, just like the real car.
- Rear-wheel drive at low speeds: At corner exits under the threshold, the car drives like a GTP without hybrid help.
This fundamentally changes how the Ferrari feels compared to its peers. Setups and driving style will need to adjust.
What’s Not Included
Some features were intentionally left out:
- No Virtual Energy system — iRacing decided not to reframe fuel in “joules” or “percentages,” since it would mostly change the display, not the driving.
- No driver-adjustable hybrid modes — at least not yet. The GTPs and 499P are locked to balanced deployment for now.
Other Hybrids
- Mercedes W12 & W13: Now feature a “fast recharge” mode and smoother brake blending.
- McLaren MP4-30: Nearly unchanged from before.
- LMP1s (Porsche 919, Audi R18): Still run much the same, but you can now manually cut hybrid deployment when you want to avoid unwanted corner-exit understeer.
Why It Matters
For the first time, iRacing’s hybrid cars behave the way their real-world counterparts are designed to. You won’t feel “magic push-to-pass” or awkward power cuts anymore. Instead, the system is invisible—you just get in, drive, and race, knowing that your car’s performance is aligned with IMSA and WEC regulations.
TL;DR
- GTPs: seamless ICE + hybrid blending, consistent capped power, balanced strategy locked.
- Ferrari 499P: capped at 100 kW, no hybrid deploy below 190 km/h.
- Mercedes W12/W13: fast recharge added.
- LMP1s: manual cut fix improves drivability.
- No Virtual Energy, no adjustable maps—this update focused on realism and stability.
