When diving into the specs of a performance vehicle like the BMW M240i, the horsepower figure is always a key point of interest. Enthusiasts and potential buyers alike want to know just how much power is under the hood. But understanding exactly what that horsepower number means, and how it’s measured, is crucial. Especially when considering the BMW M240i and its impressive engine.
To clarify, official horsepower figures from car manufacturers, including BMW, are determined at the engine’s output shaft, using an engine dynamometer. This measurement is taken directly from the engine itself, not from the wheels after power has traveled through the drivetrain. Over the years, various engineering standards have been developed for this process.
Historically, “brake horsepower” (BHP) was a common term, particularly during the muscle car era. This was under the SAE gross power standard, testing engines largely without ancillary components like alternators, radiator fans, and water pumps. Sometimes even stock exhaust manifolds were replaced with headers for these tests. However, BHP was superseded in the early 1970s by the SAE standard J1349. This newer standard measured “net power,” accounting for all power-consuming accessories such as the water pump, emissions controls, exhaust system, and air cleaner.
Further refining the process, in 2005, “SAE Certified Power” was introduced. For automakers seeking SAE certification, testing now had to occur in accredited labs, witnessed by an accredited third party.
Image: An engine dynamometer setup, illustrating the direct measurement of engine power at the crankshaft, the standard for official horsepower figures like those published for the BMW M240i.
Another standard exists, the German DIN (Deutsches Institut für Normung) standard, which is quite similar to the SAE net power standard. Like SAE standards, DIN measurements are taken at the crankshaft with all ancillaries connected, and power is expressed in PS (Pferdestärke), a metric horsepower unit. Essentially, all car manufacturers’ horsepower measurements involve crankshaft readings. None are derived from measuring power at the wheels.
This distinction is important when considering chassis dynamometers, often used in aftermarket tuning. While chassis dynos are valuable tools for tuning and establishing baselines for modifications, they measure power at the wheels. For turbocharged cars like the BMW M240i, standard chassis dyno readings can be unreliable and often inflated. This inaccuracy stems from “correction” factors for temperature and elevation frequently applied by dyno operators, which can significantly skew results for turbo engines.
Therefore, when assessing the Bmw M240i Horsepower, it’s best to rely on BMW’s official figures. These figures are meticulously measured at the crankshaft using industry-standard practices. Chassis dynos serve a different purpose, primarily for tuning adjustments and monitoring changes, not for absolute horsepower verification against manufacturer specifications. Trust the manufacturer’s stated BMW M240i horsepower for the most accurate representation of engine output.
