Originally Posted by trademaster
Different dyno manufacturers use different methodology to derive horsepower and torque. Especially with turbocharged cars you will see different results with water-brake, inertia, and electric dynos. Load will affect spool and thus impact charge air temperatures at peak boost as well. You can do all the calibrating in the world and not get inertia and load-bearing to read identical without seriously fudging some numbers, especially on high horsepower turbocharged cars.
I'm fully aware that a vehicle with a power adder that requires load to operate will read weird on different dynos. What I'm saying is that I take dyno numbers with a grain of salt these days. Too many people want either money shot numbers, manipulated numbers (claiming to do more with less) and those who want real world figures. Thanks to the first two the last one is quite rare as most operators have settings to suit the most popular bullshit numbers.