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Message: <blockquote data-quote="Acoustic" data-source="post: 126731" data-attributes="member: 728">HiKnocking ...... as mysterious as it may be - due to my limited knowledge .... is due to the fuel properties / qualities - as priority.high octane was once told to me as not more powerful, but when analyse closely, allows the slower expansion of the combustion explotion. It is actually less powerful, but more longevity friendly.regardless...... ignition mapping plays the 2nd more important role hence no amount of fuel ajustment will be able to solve this problem.fuel delivery timing, or should I say how early it spray at various RPM also affects knocking.i.e. at 1,000 RPM, it is generally set to 100 BTDC, while linearly increases to approximatelt 300 BTDC at 9,500 rpm = nearly one complete cycle advance - this is due to air-flow speed differences - the engineer who programmed the ECU will have to take into account of injector distance to combustion chamber.Hence, if you've modded the engine here and there, a little everywhere, all these things get affected......Hope this helps.Oh, you should realise by now, and I repeat, no amount of fiddling with the fuel will solve the problem....We should also consider the application of turbo, the way it uses injectors will be different from NA.i.e. turbo air flow may be more than NA, however it does not mean faster .... having a much bigger injector often means at low rev at low duty cycle the injectors shuts every quickly - if the particles were unable to follow the flow into the combustions - which always happens for all engines forced induction or NA, will suffer knocking... for reasons other than not enough fuel - right?Hmmm, I wonder did I say it right? anyway, just want to introduce the effect of the world of TIMING of various issues for your considerations. TIME DOMAIN.</blockquote>