Lexus LF-NX turbo...Akinson...Otto...Turbo ?

I think it is just the just time you've seen it published that way. Horsepower is calculated from torque and engine speed. Depending on how quickly the engine's torque drops off after reaching peak horsepower could lead to a peak horse power range. Torque goes down, rpms go up, and the calculated hp remains the same. Or just close to the same.

Below is a chart of the torque and horsepower of the Sonic RS. Notice the curve after peak hp appears nearly flat. The actual measured horsepower along that line is probably close enough that marketing could could label peak hp with a rpm range.

. The reported peak for cars isn't where the engine operates at most of the time to begin. Just knowing maximum output is generally enough. Knowing that you can go past that peak rpm without losing power might be helpful in a few cases, but what it really tells you is that you can make the same power while burning more fuel. That's better than making less while burning more, but these engines will be spending most of their time



Powertrain Overview

 

I haven't looked at many power graphs, but knew hp was calculated from torque and rpms. Between all the engine types and drivetrain configurations, I just figured this couldn't have been a true first of peak horsepower having a range. The first graph my search came up with was for a F150 Ecoboost dyno test. They reported 302.7 peak HP, but the curve was shallow enough there that could call it 300hp over 500rpms.

Torque is value most people should be paying attention to anyway. It is what they are feeling during acceleration, and with most driving an automatic here, they probably will never get their car to peak hp on anything near a regular basis.