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XfireZ51 · 10-01-2019

Graham,

A very illuminating explanation. If I could, I’d like to explore this a bit further w u and Marc. My question relates to part throttle, as I have found performance to be as u describe under WOT conditions.

1. If the stock LT5 does present knock at certain low MAP/low RPM areas of the Spark table, are there specific points where that was universally true? Or did it depend on the individual motor?

2. As u state, modifications to the motor/drivetrain may introduce other noise that could be interpreted by the KS as knock even tho it may not be. It would seem to me that the only way to verify whether knock or not is by visually inspecting the plugs. If this were to reveal that it was “false knock”, what would u suggest could be done to either minimize or eliminate it, if anything?

3. The reason I ask #2 is that if it is “false knock”, the retard that is being employed I would think is still affecting the motor in a way that would be detrimental to performance during daily driving situations. As an example, I see some random knock occurring even in steady state cruising situations at somewhere between 1800-2400rpm and 45-70kPa. It seems to occur with very slight variations of MAP. Also some on/off throttle transitions.
My motor is modified with porting and cams, but I wonder if knock in areas such as I describe is something inherent in the LT5 architecture.
Your answer Graham certainly suggests that there are inherent inadequacies to
the knock detection employed for the LT5 and it is a noisy motor. No doubt made noisier w the modifications.

Thanks again for any additional clarifications u can provide.

10-01-2019	#5
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,686	Re: Knock. A question for Graham or Marc Graham, A very illuminating explanation. If I could, I’d like to explore this a bit further w u and Marc. My question relates to part throttle, as I have found performance to be as u describe under WOT conditions. 1. If the stock LT5 does present knock at certain low MAP/low RPM areas of the Spark table, are there specific points where that was universally true? Or did it depend on the individual motor? 2. As u state, modifications to the motor/drivetrain may introduce other noise that could be interpreted by the KS as knock even tho it may not be. It would seem to me that the only way to verify whether knock or not is by visually inspecting the plugs. If this were to reveal that it was “false knock”, what would u suggest could be done to either minimize or eliminate it, if anything? 3. The reason I ask #2 is that if it is “false knock”, the retard that is being employed I would think is still affecting the motor in a way that would be detrimental to performance during daily driving situations. As an example, I see some random knock occurring even in steady state cruising situations at somewhere between 1800-2400rpm and 45-70kPa. It seems to occur with very slight variations of MAP. Also some on/off throttle transitions. My motor is modified with porting and cams, but I wonder if knock in areas such as I describe is something inherent in the LT5 architecture. Your answer Graham certainly suggests that there are inherent inadequacies to the knock detection employed for the LT5 and it is a noisy motor. No doubt made noisier w the modifications. Thanks again for any additional clarifications u can provide.