How much will the Porsche 963 have to be slowed down to bring back exciting competition in the IMSA SportsCar Championship? Following the 1-2 finish at the 12 Hours of Sebring, officials are bringing out the heaviest hammer in their arsenal.
For the first time in the history of the entire Hypercar/GTP regulations, a car is receiving the most unfavorable power-to-weight ratio possible: 480 kilowatts at 1,100 kilograms. The maximum additional weight for LMDh cars was increased to a maximum of 70 kilograms by the International Automobile Federation (FIA) ahead of the 2024 season, at the time due to the Toyota GR010 Hybrid dominating the World Endurance Championship (WEC).
Now, the negative maximum rating is being applied for the first time in IMSA. Porsche Penske Motorsport will have to compete in the critical speed range up to 190 km/h (different reference values apply on street circuits than on permanent race tracks) with a power-to-weight ratio of 2.292 kg/kW, or 480 kilowatts at 1,100 kilograms. In contrast, the Aston Martin Valkyrie continues to receive the most favorable power-to-weight ratio possible of 1.981 kg/kW.
The weight penalty compared to Sebring is no less than 45 kilograms or 99 pounds for Porsche. With its dominance, Penske has now pushed the officials to the limit, as the regulations do not allow for more than 1,100 kilograms. It will be interesting to see what happens with this balance of performance in the urban canyons of Long Beach.
For the first time, there is also a separate BoP for JDC-Miller Motorsports’ previous-year Porsche. It receives a significantly more moderate BoP than the 2026 963s of the Penske factory team. The “you’re all in the same boat” principle no longer applies. The different homologation statuses of the cars make this possible.
Classification up to 190 km/h: BMW benefits the most
In terms of power-to-weight ratio, the weight allocation for the GTP cars at Long Beach is as follows:
1. Aston Martin Valkyrie - 1.981 kg/kW
2. BMW M Hybrid V8 - 2.057
3. Cadillac V-Series.R - 2.070
4. Acura ARX-06 - 2.117
5. Porsche 963 (2025) - 2.123
6. Porsche 963 (2026) - 2,292
Of course, Porsche’s power reduction is dominating the headlines. There has never been a blow like this in the history of the Hypercar regulations. Even the private Porsche must take a hit.
It’s almost easy to overlook that Acura is also taking quite a hit. The ARX-06 will be eight kilograms heavier and receive ten kilowatts less power. With a 15-kilogram weight penalty and one kilowatt more power, the Cadillac V-Series.R almost stands out as the winner.
BMW, however, comes out on top: While the M Hybrid V8 must add 11 kilograms, it also gains nearly 7 kilowatts of power.
The reason for the weight gain of the other GTP cars is likely the Aston Martin Valkyrie, which couldn’t really keep up at either Daytona or Sebring. As mentioned earlier, its classification remains at the best possible power-to-weight ratio of 520 kilowatts at 1,030 kilograms.
Changes for the 2026 12 Hours of Sebring. It’s important to note that the low-speed range there went up to 230 km/h, not 190 km/h as it does now:
1. BMW M Hybrid V8 -0.006 kg/kW
2. Aston Martin Valkyrie +-0.000
3. Cadillac V-Series.R +0.025
4. Porsche 963 (2025) +0.047
5. Acura ARX-06 +0.057
6. Porsche 963 (2026) +0.215
The BMW M Hybrid V8 is thus the only GTP car to receive a better rating than it did at Sebring. The Aston Martin retains its ideal rating, while all other GTP cars receive a less favorable power-to-weight ratio.
Of course, Porsche’s 0.215 kg/kW stands out. Neither in IMSA nor in the WEC has there ever been such a drop in performance between two races.
In 2025, Porsche dominated the race in a battle with BMW, while Cadillac and Acura remained in the shadows. Here are the changes from the previous year, though they should be taken with a grain of salt because all LMDh cars received updates last winter. Additionally, the 230 and 240 km/h speed limits were still in effect in 2025, so direct comparability is limited.
1. Cadillac V-Series.R -0.072 kg/kW
2. Aston Martin Valkyrie -0.070
3. Acura ARX-06 -0.042
4. Porsche 963 (2025)+0.008
5. BMW M Hybrid V8 +0.057
6. Porsche 963 (2026) +0.177
Cadillac tops this list, though this is largely due to a rather unfavorable classification in 2025. The same applies to Acura and Aston Martin, which was still relatively new at the time. Although BMW is better classified compared to Sebring, its classification at Long Beach is actually significantly worse than the previous year.
Within just three races, a remarkable gap has emerged between the individual vehicles: While at the season opener in Daytona, all vehicles in the low speed range up to 230 km/h were within 0.017 kilograms per kilowatt, the difference between Porsche and Aston Martin is now a maximum of 0.311 kg/kW.
Classification above 200 km/h
Due to the low threshold of just 200 km/h, this range is quite relevant, especially on the long full-throttle section across the start/finish line:
1. Aston Martin Valkyrie - 1.981 kg/kW
2. Cadillac V-Series.R - 2.095
3. Acura ARX-06 - 2.097
4. BMW M Hybrid V8 - 2.102
5. Porsche 963 (2026) - 2.115
6. Porsche 963 (2025) - 2.123
Once again, the significant gap between Aston Martin and the other manufacturers is striking. The Valkyrie has high aerodynamic drag and therefore requires a lot of downforce. As a result, the power-to-weight ratio increases for most of the other GTP cars.
Compared to Sebring, the changes are as follows, again with the caveat that these values apply here starting at 200 km/h, whereas in Sebring they apply only starting at 240 km/h:
1. Acura ARX-06 -0.001
2. Aston Martin Valkyrie +-0.000
3. Cadillac V-Series.R +0.010
4. BMW M Hybrid V8 +0.026
5. Porsche 963 (2026) +0.026
6. Porsche 963 (2025) +0.034
Acura is the only manufacturer to receive a slightly better rating above 200 km/h than at Sebring. Aston Martin retains its ideal rating, while all other GTPs are further restricted.
And the changes compared to last year, again with the previously mentioned limitations (updates, speed ranges):
1. Aston Martin Valkyrie -0.062 kg/kW
2. Acura ARX-06 +0.043
3. Cadillac V-Series.R +0.053
4. Porsche 963 (2026) +0.058
5. BMW M Hybrid V8 +0.059
6. Porsche 963 (2025) +0.066
The 2026 Porsche swings from one extreme to the other in terms of engine power: it is allowed to draw the maximum permitted 520 kilowatts above 200 km/h. As a result, the previous year’s Porsche actually loses slightly more in power-to-weight ratio in the upper speed range than the current Porsche.
Translated from German
GTP BoP Values at a glance
Values in parentheses = Change from Sebring 2026/Long Beach 2025 (Note regarding power specifications: The limits were set at 230 and 240 km/h for both Sebring 2026 and Long Beach 2025)
Acura ARX-06
Minimum weight: 1,059 kilograms (+8/-1)
Max. power <190 km/h: 500.24 kW (-9.88/+9.24); 680 hp
>Max. power at 200 km/h: 504.92 kW (+4.16/+13.92); 686 hp
Max. RPM: 9,512 revolutions per minute
Max. energy per stint: 901 megajoules (+3/-2)
Fuel flow during refueling: 22.525 megajoules per second (+0.075/-0.050)
Aston Martin Valkyrie
Minimum weight: 1,030 kilograms (+-0/-8)
Max. power <190 km/h: 520.00 kW (+-0/+14.00); 707 hp
Max. power at 200 km/h >: 520.00 kW (+-0/+14.00); 707 hp
Max. RPM: 8,400 revolutions per minute
Max. energy per stint: 913 megajoules (+1/+11)
Fuel flow during refueling: 22.825 megajoules per second (+0.025/+0.275)
BMW M Hybrid V8
Minimum weight: 1,059 kilograms (+11/+29)
Max. power at <190 km/h: 514.80 kW (+6.76/-0.20); 700 hp
Max. power at 200 km/h >: 503.88 kW (-3.00/-11.12); 685 hp
Max. RPM: 8,000 revolutions per minute
Max. energy per stint: 908 megajoules (+8/+9)
Fuel flow during refueling: 22,700 megajoules per second (+0.200/+0.225)
Cadillac V-Series.R
Minimum weight: 1,058 kilograms (+15/+2)
Max. power at <190 km/h: 511.16 kW (+1.04/+18.16); 695 hp
>Max. power at 200 km/h: 504.92 kW (+4.68/+18.16); 686 hp
Max. RPM: 8,800 revolutions per minute
Max. energy per stint: 906 megajoules (+11/+3)
Fuel flow during refueling: 22.650 megajoules per second (+0.275/+0.075)
Porsche 963 (2025)
Minimum weight: 1,060 kilograms (+5/+11)
Max. power <190 km/h: 499.20 kW (-8.84/-9.80); 679 hp
>Max. power at 200 km/h: 499.20 kW (-5.72/-11.83); 679 hp
Max. RPM: 8,158 revolutions per minute
Max. energy per stint: 906 megajoules (+4/+7)
Fuel flow during refueling: 22.650 megajoules per second (+0.100/+0.175)
Porsche 963 (2026)
Minimum weight: 1,100 kilograms (+45/+51)
Max. power <190 km/h: 479.96 kW (-28.08/-29.04); 653 hp
>Max. power at 200 km/h: 520.00 kW (+15.08/+8.96); 707 hp
Max. RPM: 8,158 revolutions per minute
Max. energy per stint: 913 megajoules (+11/+14)
Fuel flow during refueling: 22.825 megajoules per second (+0.275/+0.350)
