Quote:I wonder if any of the perceived power / response increase is all in the mind or a sort of placebo effect.
Absolutely, you got it. Firstly the names, ultimate, super, v-power etc, premium products that you pay more for - they must be better - right?
Wrong. 92RON petrol contains the same amount of energy or bang as 99RON. What 99 RON offers is better 'knock' protection or a slower burn.
It's all about ignition, timing and a controlled burn. ie - at what point in the cycle the fuel is lit. The fuel is ignited before Top Dead Centre (TDC) as the fuel is being compressed. If it is ignited too soon it will start to explode before TDC, which will give you knock, and if you keep getting that you'll get a heat build up and burn't oot valves.
High compression engines, or many of those running turbos need a higher octane fuel (often 98RON), if you run them on a lower octane fuel like 95 or 92 RON you risk 'knock' or 'pinking'. Note that most if not all cars that require 98RON today have knock detection that will adjust the timing to prevent engine damage.
As for my bike a GEN1 Fazer Thou. It's timing is set for 92RON. In the UK our standard fuel is 95RON. If you use 98RON, it's like igniting the fuel too late, you are getting the big push just slightly further down the stroke.
So in summery if you use a higher octane than recommended, then the engine will run absolutely fine but will make very slightly less power.
And never use an octane less than recommended.