In Poland dyno operators won't pull cars with automatic gearbox. They say that automatic cannot be controlled well throughout the RPM-band and the graph will not show the actual performance of the engine. Also - after the engine has reached maximum RPM they need to go to neutral gear to measure the drag - so that the engine HP is known - and that's not healthy for automatics. How do You Guys cope with that issue in the USA?
Automatic cars can be dyno with same accuracy as manual transmission.
Dyno does not know what i driving the rear wheels and only cares if the rollers are turning.
Best type of dyno for accuracy is load dyno which applies load to rollers against rear wheels.
Inertia type dyno has rollers that spin freely which wheels drive.
Usually best to dyno in gear that gives 1:1 transmossion ratio.
I find that on M103-12V with 722.3 auto best to dyno in third gear.
This allows max rpm without turning tires to 140+ mph.
Dyno operator starts car then accelerates to max RPM.
He starts dyno read about 2500-3000RPM.
No need to go to neutral as dyno reads torque real time as wheels turn rollers.
Horsepower is then mathematically calculated by dyno based on torque
This is my automatic twin turbo on dyno.
This pull gave RWP torque of 302. which equates to about 390 torque at the crank.
Baseline pull prior to TT install gave 145 torque against published 188 torque for a 30% drive train loss.
Click on picture to watch pull