Is there any possible reason a 5.5t motor would run COOLER going from locked timing to 15dg of boost ?

I have a D413 running a rsx and d413 and indoors I was running 10dg on the can and locked timing in the esc. Esc stayed cool but motor got pretty hot indoors. Took it to my outdoor track and ran it with some boost and the motor didn't get anywhere near as hot as it did indoors. Was it just the increased air flow , the lack of constant acceleration , or an efficiency thing ?