Transmission losses on dyno

If you aren't changing the rolling resistance of the transmission, then your loses would stay the same at 65hp.

 

Everywhere I've ever seen a dyno run done it's by percentage. Most shops and CAT use 15% driveline loss with the engine fan on. The newer trucks with there high flow fans are 20% power loss. The fans can decrease power from 25-50 hp depending on blade pitch, diameter, and the number of blades

 

I ran a dyno and we always figured drive line loss at 18% you get 82% of engine HP to the ground that is in direct in the transmission. That is a steady pull and if you drop the load down 50 HP it will pick it back up. That is not the BS way of putting it in OD and top RPM then dumping a huge load on it and when the graph hump goes to the max giving that as the HP. when it is on the dyno and you get a base with the fan in you can cut it out and see what it gives without the fan, remember a dyno is very hard on everything. You do not get adequate cooling,

 

I've always used 50hp loss for the drive train and 25 for the fan when dynoing a stockish pre Acert engine, once the engine is no longer stock and you are not chasing factory type low power complaints the engine horsepower is irrelevent anyway, all that matters is how much power it puts to the ground as thats whats available for pulling the load.
You can get huge diffenences from one dyno to another, altitude can make a diffenence and wheel slip plus many other factors. There are whole websites on how to set up a car to perform its best at a dyno comp, even alot of ways to cheat and fool a dyno, same applies to trucks just on a bigger scale.
Target horsepower shouldn't realy be the deciding factor in turbo choice, it should be more based around the engines desired air flow capability, engine capacity and intended use.

 

I just meant there are other factors other than desired HP, but engine capacity does have an effect on turbo choice, a 16 liter engine can take a larger turbo than a 10 liter because it has more capacity to spin it up, the big turbo may still work on the 10 liter but it may be way to slow spooling up to be of any use in all but dyno comps.