It's more than the 'top speed' in speed traps. It's more about how it get there. Like from corner exit out. Top speed will be affected by drag, but the initial acceleration is all engine power. Or, 'drivability' in drivability speak.
Bottas has already gone on record about the Ferrari engine being more drivable than his old Mercedes engine.
Aston has focus on 'top speed', but they are almost always around the slowest around corners. They trade corner grip with top speed in order to not be passed on the straights. It has also been widely accepted that the Mercedes chassis has a lot of drag despite the spaceship look, for a given power level, the Mercedes will go slower than most.
Between Red Bull and Ferrari, there are numerous on-boards that shows Leclerc might be right there entering a corner behind Verstappen, but Verstappen simply gained more in the corner and basically disappeared at the exits, Leclerc doesn't quite get back to the tail again at the end of the straights before braking.
One way to explain that is that the Ferrari makes more ultimate power, but the Honda power plant in the Red Bull has more 'area under the curve'. Not a new concept, Porsche had been doing that during their 919 days, big power down low to exit the corner faster, and make the other guy playing catching for the whole straight. 918 follows the same principle, P1 and LaFerrari has higher ultimate power and faster terminal velocity, but those extra speed are playing catch up for the whole straight simply because those other cars are slower out of exits. For racing purposes, area under the curve rules.
The old Mercedes engine, from 2014, has higher ultimate power, but they also make more power all throughout the whole curve. It's just simply a much more powerful engine. The current Honda engine, maybe some would argue it isn't make meaningfully more power at the very top, but it makes more throughout for the whole curve.
Maybe I can't be bothered with having my own Youtube channel, or a internet website discussing stuff, or being asked to be a commentator, I don't quite believe I know less on certain subjects. The basic physics on how a car goes doesn't change, and I know science.
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