Originally Posted By: SteveSRT8
Originally Posted By: Nate1979
My understanding is that you cant hear all knock and ping and without looking at the actual data can you know if its alright. And not all cars can pull enough spark to get rid of all knock.
This is absolutely correct. Knock tolerance is wildly different by application and simply cannot be generalized. Odds are if you actually hear knocking there is far more pre-ignition occurring than you will ever know.
Many newer cars simply will not detonate under almost any conditions, but that is simply a function of sensitive knock sensors.
Yes, modern knock sensors and engine computers do a great job of reacting to the slightest knock. Back in the 1980s, you could gently tap the engine with a hammer, and the computer would retard the spark enough to bog down the engine. It would slowly advance spark back to normal. Now you have to use data logging or an oscilloscope to see what is happening when you tap the engine with a hammer.
In some Ecotec engines, there was no conventional knock sensor. Instead, the ignition coils would detect abnormal combustion somehow.
Some engines are programmed to ignore knock sensors under certain conditions. I remember mom's 1999 Honda CRV and 2002 Toyota Solara called for 87 octane fuel, but there would always be a few knocks at full throttle.
Anyway, you probably have an engine that will not be damaged by low octane fuel, but you will have reduced performance.
My dad's Pontiac G6 2.4 calls for 87 octane in the user's manual, so we never used anything else.