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 bhp and 399.9 lb-ft of torque at the wheels, while during the third run (not filmed) the car pushed out 425 lb-ft of torque. Bear in mind this is a North American example of the Z4 for which BMW gives the following numbers: – 382 bhp and 369 lb-ft.
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 bhp and 467 lb-ft.
The situation is identical with the Z4’s technological twin, the new Toyota Supra, which uses the same B58B30 3.0-litre twin-turbo inline-six engine. When tested on the dyno earlier this year, the Japanese sports coupe registered 339 bhp and 427 lb-ft at the wheels. The numbers Toyota lists are 335 bhp and 365 lb-ft of torque.
Back to the Z4, given the higher output numbers than advertised, it’s not a surprise BMW corrected the 0-60 miles per hour time for the roadster earlier this year, claiming it goes from standstill to 60 mph in just 3.9 seconds instead of 4.4 seconds that was initially announced.