I saw this on Renntech's site:
https://www.renntechmercedes.com/index.php/crank-wheel-hp
Drivetrain Loss
The drivetrain loss is the power lost between the engine and the wheels. The drivetrain includes parts such as the transmission, torque converter, driveshaft, differential, axle, etc. Different vehicles have dramatically different components used to get the power to the ground. For example, one car with a particular engine may get a different transmission halfway through the model production run. Therefore, the drivetrain loss can vary dramatically between cars. Sport cars with rear-wheel drive have a more efficient drivetrain than all-wheel drive off-road vehicles. Based on our experience through our 28+ years in the industry and measurements from a huge variety of cars we have developed a system to calculate crank horse-power numbers based on a known drivetrain loss.
12% - Rear-Wheel Drive Sportscars
14% - Rear-Wheel Drive Cars
14% - All-Wheel Drive Cars equipped with 4MATIC+
17% - All-Wheel Drive Cars equipped with 4MATIC
18% - SUV’s equipped with 4MATIC
20% - Off-Road vehicles equipped with 4MATIC
Not sure if where we fall in the 14%-18% comparison
Any reaosnable way to estimate crank HP? The only way I can imagine is to dyno test a stock car and calculate the % loss vs the claimed 375, then use that differential to correct after you get the tune. I don't know if there's a better way. My understanding is that the 4matic is pretty lossy.