BMW is one of the companies in the industry known for underreporting the output numbers of its engines. We’ve seen several examples of that, and now there’s a new one and it’s quite impressive. During a recent AWD dyno run somewhere in Florida, the Z4’s range-topping version, the M40i, registered way above what the manufacturer claims in the official figures. Let’s take a look.
The video at the top of this page shows the second of a total of three dyno runs of this red Z4. The stand measured 373 horsepower (278 kilowatts) and 399.9 pound-feet (540 Newton-meters) of torque at the wheels, while during the third run (not filmed) the car pushed out 425 lb-ft (576 Nm) of torque. BMW gives the following numbers for the U.S. market – 382 hp (285 kW) and 369 lb-ft (500 Nm).
There’s one minor detail that explains a lot here. BMW’s numbers are at the crank while the dyno measurements show the actual power and torque at the wheels. Doing the simple math, if we assume the drivetrain loss is just 10 percent (which is not possible in an AWD car), this would mean the actual power figures at the crank are 410 hp (306 kW) and 467 lb-ft (633 Nm).
The situation is identical with the Z4’s technological twin, the new Toyota Supra, which uses the same B58B30 3.0-liter twin-turbo inline-six engine. When tested on the dyno earlier this year, the Japanese sports coupe registered 339 hp (253 kW) and 427 lb-ft (579 lb-ft) at the wheels. The numbers Toyota lists are 335 hp (250 kW) and 365 lb-ft (495 Nm) of torque.
Back to the Z4, given the higher output numbers than advertised, it’s not a surprise BMW fixed the 0-60 miles per hour (0-96 kilometers per hour) time for the roadster earlier this year, claiming it goes from standstill to 60 mph (96 kph) in just 3.9 seconds instead of 4.4 seconds that was initially announced.