How much should I advance the ignition timing to improve performance?
You can only advance the timing safely if the octane rating of the fuel is increased. Otherwise you will place the engine at serious risk of suffering piston damage as a result of high speed detonation – which is not always audible before striking. To put some perspective on this Jaguar officially recommend that the 12.5:1 compression European HE V12 (1981-88) should have the timing retarded by 5 degrees in order to safely use 95 octane (RON) unleaded fuel instead of the 97 octane originally specified. We think this is probably a bit over-cautious and that 3 degrees of retard should be adequate, conforming to the general guide that reduction of 1 octane number in the fuel requires approximately 1.5 degrees of retard. 27. What is the difference between detonation, knock and pre-ignition and how might it effect my engine. This a very deep subject. A concise explanation will be found in our “Introductory Technicalities” section. Note that harmful knock does not necessarily give audible wa
