When you hear BMW reporting that its car has certain output figures, you better suspect that it’s actually more potent than they say. The German automaker has underreported its vehicles several times, with the latest one being the 2020 BMW Z4 M40i. It’s pretty impressive that a recent run on an all-wheel-drive dyno in Florida proved that the range-topping variant puts out much more torque than what BMW claims.
The Z4 did three dyno runs with the second one being shown in the video at the bottom of this post. The roadster developed 373 horsepower and 399.9 pound-feet of torque at the wheels. We don’t see the third run as it’s not filmed, although we do know that during the last pull the Z4 made 425 lb-ft of torque. Now compare these torque numbers to the one published by BMW and you will find a big gap between them. For the US market, the Z4 is officially said to offer 382 hp and 369 lb-ft of torque.
From the video we can conclude that BMW’s figures are at the crank, which explains why it’s different from the actual power and torque at the wheels measured on the dyno. Now let’s do a straightforward calculation; assuming the transmission loss is only 10 percent, then the actual output figures at the crank could be 410 hp and 467 lb-ft.
Since these numbers are higher than advertised, we think BMW has the right to revise its claim about the vehicle’s acceleration time like it did earlier this year. Initially, the Z4 was said to be able to dash from zero to 60 miles per hour in 4.4 seconds. However, later BMW corrected the time to just 3.9 seconds, which is much faster.
Another vehicle that has a similar case to the Z4 is its mechanical cousin, the Toyota Supra, which comes with the same B58B30/01 3.0-liter twin-turbo inline-six engine. A dyno testing earlier this year reported that the Japanese sports car delivered 339 hp and 427 lb-ft at the wheels. Again, these actual figures are different than the official ones listed by Toyota, which are 335 hp and 365 lb-ft.