340 Pinging using 94

If you want to get an idea of how EFFECTIVE cylinder pressure is related to throttle position, just do a compression test with the throttle closed, and record the pressure on each stroke.
You might get a number like 90 psi on the first shot, then
120 , then then 140,150,155 and so on, but eventually, given enough compression cycles, you will get to the same number that you would get with the throttle at WOT. The difference is that on a good engine, at WOT, it might take half as many cycles, and the First shot will be significantly higher..

The same thing happens while you are driving, at various throttle settings and various rpms.

Knowing the specifications of the engine, it is possible to back calculate the Effective Compression Ratio from the cylinder pressure. When you do that, you will find out that;
your Effective compression ratio at IDLE might be just 5or6 to 1.
And at 2000 rpm , with the throttle closed and under decel, it might be a tad higher.
And at WOT at rpm of Peak Torque, you could be pushing 11:1 or more Effective, depending on the cam and combo.
And at Part Throttle, you can vary the Effective CR anywhere in between, just by adjusting the throttle position.
In fact, you could even hold the throttle at a steady position in a fixed transmission gear; and the Effective Compression could change everywhere throughout the rpm range as engine efficiency wanders around.
Why is this important?
Well, pressure makes heat, and heat makes power, so the more heat your engine can generate, the more power it can build ....................... right up until the design can no longer deal with the heat. When that happens she can get into preignition and/or detonation, which leads to destruction of parts. So the goal of the Builder and the Tuner, is to not let that happen, by keeping the chamber temperature under control. To do that, we have a number of tools in our toolkit that we can use;
1) anti-detonant,
2) reduced Effective cylinder pressure
3) retarded ignition timing
4) reduced load
5) a reduced cooling system temperature


As others have said, detonation under closed throttle deceleration is as good as impossible...................... because that eliminates all five of the things that can lead to detonation. Yes, it can, still happen, but it's gonna take a hot glowing spot in the chamber to initiate an uncontrolled and inappropriately timed, point of ignition