Gotcha, so it's just to cover their ass, which is what I assumed from the get go. There's no real scientific reason to back down based off of a certain HP # if timing, boost, etc are all at safe levels for the octane. Maybe this is a recent thing they're doing with their tunes, as I've never heard any of the tuners say they won't tune over a certain amount of HP on a particular octane.A rated torque output probably has a specific energy requirement that must be met to get to said output. Given the nature of automotive reciprocating piston power, rapid compression and ignition of pressurized air and fuel is inherently an inefficient way to harness energy.
Direct injection offers engineers and tuners a much more stable fuel system to control detonation. Injecting fuel into the combustion chamber literally milliseconds prior to ignition via spark allows for far higher boost pressure on pump fuel. Youre pressurizing LIQUID fuel in the fuel rails and injecting it, and not exposing fuel VAPOR to compression with air on the compression stroke. Youre nowhere near at risk for detonation compared to a port fuel injection setup if the fuel goes in effectively, at the timing point of ignition. Of course, a direct only setup has a ton of drawbacks real world.
Scientifically, there is no reason x octane at its max spec Y cylinder pressure with max spec Z timing at T temperature would need to be backed off. You wouldn't dial it back if the fuel's known quality was 93. Regulated intake air temp, regulated coolant temp etc would also be needed. You would take it to its limit with the known power breaking point of your engine mechanicals.
What we are saying is real world, its never always 93, air temp is always varying, youre still compressing air AND fuel at the same time. Boost pressure could be off and parts rated for 800lbs reliably could have a bad day, develop micro fractures in their structure and at 743 lb of generated torque fail. Cover ass mode engage. Thats literally the reason reputable tuners are stating power figures with pump fuel that seem lower than what possible.
The last time I saw one of these motor combos dyno'd on 93 octane (I'm assuming) was @dale.baker 's thread from a couple years ago. If my memory serves me correctly he made a little over 800rwhp at only 12* of timing. He was still on the stock fuel pumps, and those were the limiting factor. If he wasn't running out of fuel they could've turned it up even more. So to say that we're going to dial it back to 750 just seemed a little unreasonable....ignition timing would have to be severely retarded to hit that #. Of course, I will do what the tuner wants....