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Marc Haibeck · 10-01-2019

Hi Dominic,

For a typical stock engine and stock calibration.

If a run is made from first gear through to third gear to 70 mph. About 50% of the time there will be a tip in knock of about -3 degrees when the throttle is opened at 2000 rpm or so. Then there could be a -3 to -5 degree knocks in the area of peak torque at about 5000 rpm in one or two of the gears.

If a second run is made soon after that there is a 50% chance of a tip in knock. The other knocks are typically lower in intensity.

On a third run, tip in knock probability is about the same. The other knocks may be be as low as -1 degree or none as the combustion chambers are cleaned out by the heat.

Typically a healthy engine will not knock when over 5500 rpm or so.

My observations are with 93 octane fuel. A 500 hp modified engine will behave similarly. I never use over 11.5:1 compression on a modified engine that will be running on pump fuel.

I hope that Graham gives us his insight.

10-01-2019	#2
Marc Haibeck Join Date: May 2007 Location: Addison IL Posts: 252	Re: Knock. A question for Graham or Marc Hi Dominic, For a typical stock engine and stock calibration. If a run is made from first gear through to third gear to 70 mph. About 50% of the time there will be a tip in knock of about -3 degrees when the throttle is opened at 2000 rpm or so. Then there could be a -3 to -5 degree knocks in the area of peak torque at about 5000 rpm in one or two of the gears. If a second run is made soon after that there is a 50% chance of a tip in knock. The other knocks are typically lower in intensity. On a third run, tip in knock probability is about the same. The other knocks may be be as low as -1 degree or none as the combustion chambers are cleaned out by the heat. Typically a healthy engine will not knock when over 5500 rpm or so. My observations are with 93 octane fuel. A 500 hp modified engine will behave similarly. I never use over 11.5:1 compression on a modified engine that will be running on pump fuel. I hope that Graham gives us his insight.