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Motorsport

Heiko Stritzke

IMSA BoP update for Watkins Glen: Who has an advantage?

Porsche Aston Martin BMW BoP (Organization) Cadillac IMSA Acura Watkins Glen

Once again, IMSA has found a pragmatic solution to a lingering problem. Following the BoP separation of the private Porsche 963 from JDC-Miller Motorsports from the factory entries, a GTP/Hypercar receives a weight specification outside its original homologation parameters for the first time ever—unless Aston Martin previously ran lower than 1,030 kg in WEC competition, where the BoP remains strictly confidential.

To aid the Aston Martin Valkyrie for the 6-hour race at Watkins Glen International, its minimum weight has been reduced to 1,020 kilograms, breaking the standard 1,030 kg GTP/Hypercar homologation floor.

This adjustment should boost the THOR-run Le Mans Hypercar (LMH), which is the only car on the grid that did not receive updates over the winter. After a podium finish at the 2025 Petit Le Mans, an 8th-place finish at Laguna Seca Raceway stands as its best result of the season so far.

This change also introduces a power-to-weight ratio below 1.981 kg/kW for the very first time in the history of the class.

Below 230 kph (143 mph): Huge break for Porsche

The low-speed power-to-weight ratios for the 6 Hours at The Glen are as follows:

Aston Martin Valkyrie - 1.962 kg/kW
BMW M Hybrid V8 - 2.005
Porsche 963 old - 2.035
Cadillac V-Series.R - 2.044
Acura ARX-06 - 2.044
Porsche 963 - 2.143

Aston Martin enters uncharted territory and can be expected to be highly competitive in this setup. With the project now in its second year, the British brand seeks its first joker updates for the upcoming winter. https://www.motorsport.com/wec/news/aston-martin-evaluating-first-major-upgrade-for-valkyrie-hypercar/10830807/

Comparing the values to Detroit reveals why the Porsche 963s lead the adjustment charts. The German cars received a vital weight break for the long, sweeping corners of Watkins Glen compared to the short, 90-degree slow-speed corners of the Motor City:

Porsche 963 -0.108 kg/kW
Porsche 963 old -0.071
Aston Martin Valkyrie -0.019
BMW M Hybrid V8 +0.014
Cadillac V-Series.R +0.017
Acura ARX-06 +0.023

Apart from Porsche, the low-speed changes are relatively minor. Acura takes the largest hit with a nearly 9 kW reduction, while Cadillac loses just over 7 kW, though both American cars shed 6 kilograms each.

BMW loses 1 kilogram and 4 kW, while Aston Martin capitalizes on its 10-kilogram weight loss while retaining its full 520 kW allocation.

Comparing this BoP to the 2025 Watkins Glen event shows a surprising picture, though it is important to remember that all four LMDh cars (except the 2025-spec Porsche) received technical updates over the winter:

Porsche 963 old -0.174 kg/kW
BMW M Hybrid V8 -0.099
Porsche 963 -0.066
Aston Martin Valkyrie -0.019
Cadillac V-Series.R +0.047
Acura ARX-06 +0.048

Despite remaining the heaviest GTP entries in the field at 1,058 kg (2025) and 1,073 kg (2026), Porsche gains a significant boost in the lower-speed sections of the track.

This stems from the fact that the 963 was pegged at the minimum 480 kW limit back in 2025. This year, the factory cars receive 20 kW more, while the private JDC-Miller entry reaches the opposite extreme at 520 kW.

BMW also benefits from a massive gain of over 15 kW alongside an 18-kilogram weight reduction compared to 2025. With Aston Martin keeping its 10 kg advantage, the two American-built LMDh models face a demanding battle as the power reductions take their toll.

Above 240 kph (149 mph): More top speed for everyone!

For higher speeds at the 2026 Watkins Glen 6 Hours, the power-to-weight ratios of the cars are as follows:

Aston Martin Valkyrie - 1.962 kg/kW
Cadillac V-Series.R - 2.005
Acura ARX-06 - 2.018
BMW M Hybrid V8 - 2.044
Porsche 963 - 2.063
Porsche 963 old - 2.091

While the baseline order matches the Detroit standings, every car receives a significantly stronger high-speed BoP compared to the twisty street circuit:

Cadillac V-Series.R -0.092 kg/kW
Acura ARX-06 -0.083
BMW M Hybrid V8 -0.065
Porsche 963 -0.052
Porsche 963 old -0.026
Aston Martin Valkyrie -0.019

The massive gap between Aston Martin and the rest of the field shrinks considerably here, even though the Valkyrie still profits from its sub-homologation weight.

Substantial power additions for the rest of the grid—excluding the 2025-spec Porsche, which has its 5 kW loss offset by a 24 kg weight break—give all LMDh cars a much stronger power-to-weight ratio.

Acura and Cadillac even surpass their Daytona baselines, earning the biggest high-speed breaks after losing ground in the lower speeds. The 2026-spec Porsche receives its most favorable high-speed power-to-weight ratio since the season opener.

Concluding with the comparison to the 2025 high-speed figures, while bearing the winter updates in mind:

Porsche 963 -0.146 kg/kW
Porsche 963 old -0.118
BMW M Hybrid V8 -0.049
Aston Martin Valkyrie -0.019
Acura ARX-06 +0.022
Cadillac V-Series.R +0.024

Porsche sweeps the highest gains once more. BMW also makes major steps forward after a difficult race at The Glen in 2025.

However, the track characteristics of the 2026 Porsche will contrast sharply with its 2025 predecessor, utilizing the maximum 520 kW instead of the 480 kW floor, despite carrying 13 kg more.

BMW enjoys a break on all fronts with 3 kW more power and 18 kilograms less weight. Aston Martin holds onto its 10 kg weight break, while Cadillac and Acura remain nominally ahead in raw power-to-weight ratios but see their gap to Porsche and BMW heavily reduced.

Conclusion

The complete swing in the behavior of the Porsche 963 from one extreme to the other will be fascinating to watch. It represents a complete black box with its features inverted from the 2025 event. Will the extra power compensate for the weight increase, or will the Penske cars struggle with 1,073 kilograms in the long, demanding corners?

Both the older-spec Porsche and the BMW M Hybrid V8 are prime contenders to watch as well given their massive steps forward since last year.

Cadillac and Acura look weaker on numbers compared to 2025, when they were the dominant force at The Glen. With the 2026 Cadillac V-Series.R running a significantly lower-downforce configuration, it remains to be seen if it can stay competitive on a track where downforce is vital.

Meanwhile, Aston Martin's record-low weight looks more spectacular on paper than its actual on-track advantage warrants, given the sweeping improvements handed to its rivals. However, Watkins Glen shares clear traits with Road Atlanta, where the Valkyrie registered its strongest performance to date.

We are looking at an unpredictable race with major year-over-year adjustments. On paper, BMW looks like the favorite and we could also brace ourselves for another Laurin Heinrich masterclass in the 2025-spec Porsche.

But whether these numerical advantages translate into pure cornering performance at Watkins Glen International remains the ultimate question. This weekend promises to be a thrilling spectacle.