We have to be careful with how excited we get about this, but an aftermarket shop in Illinois found a 2021 BMW M4 that was making a suspiciously high amount of horsepower.

The test, run by IND Distribution, found that the new M4 is making 465 hp on the chassis dyno. BMW rates the standard M4 at 473 hp. So far, that all sounds pretty normal. Except that automakers quote figures at the crank.

Assuming a 15% drivetrain loss, a very unscientific but oft-quoted estimate, the M4 in IND Distribution’s shop would be making around 547 hp at the crank! That’s a staggering 74 more than BMW’s factory estimate and 44 more than the Competition’s 503 hp rating. Impressive stuff.

We arrived at Performance Eurowerks early to give the BMW M G82 its first crack (pre-break in) on their new Dynojet 424x…

Posted by IND Distribution on Saturday, March 13, 2021

But as we said at the top, you have to be careful with these kinds of results. First of all, as Engineering Explained laid out back in 2017, comparing figures from different dynamometers in different locations is fraught with imprecision. The tool’s real use is comparing figures in repeated tests at the same location.

That’s because humidity, altitude, and more can affect how much power a car produces. Although it’s hard to know exactly where BMW measured this engine’s performance, we at least know that the engine is made in Munich. That city sits at an altitude of nearly 520 meters (1,700 feet), whereas Buffalo Grove (where IND Distribution said it conducted the test), is just 208 meters (682 feet) above sea level.

As Motor1 points out, the 15% rule is also challenged, with some claiming that modern cars lose closer to 10% of their power through the drivetrain. That’s not to say that IND Distribution’s findings are anything less than noteworthy or surprising, it’s just that there are a lot of variables here.

All the powertrain efficiencies, altitude differences, and relative humidity might not be enough to explain a 74 hp difference, but it’s hard to say for sure. At any rate, the good news for new M4 owners is that it that they are getting all the performance BMW has promised them – and, possibly, even more.