All chassis dyno give you the net reading (true HP to the rear wheels), not the gross reading like the factory uses on there adds to the flywheel.
Sorta. Gross and net refer to the test conditions when they were originally rated- net is still a flywheel number, but it includes things like the alternator, the water pump, the fan, the full exhaust system with representative backpressure, etc.. The gross ratings were not realistic. Both of them will still be higher than the rear wheel horsepower number. Depending on manual vs. auto, or the type of converter, you could see losses in the vehicle anywhere from 12% to 22+%, below the net rating.
Dynos also have 2 correction factors - SAE and standard. SAE is also more representative of real world conditions. STD corrects to completely dry, 60* air, with a density altitude of near 0, so the STD number will always be higher than the SAE. SAE corrects to 77* air, a little lower barometer, and more reasonable humidity (it's closer to 2000' density altitude). This applies to both engine dynos and chassis dynos.
