Beretta.net

Q:What is REAL KR and what is FALSE KR?
Real KR is KR that grows with engine RPM and engine load. It depends entirely on detonation, which is dependant upon throttle position, MAF, MAP, engine load, engine temperature, and RPM. As RPM and engine load increase, the chance for KR (or higher KR) increases. As the vehicle shifts to the next gear, KR will usually make a small jump up as well due to the higher engine load.

False knock is characterized by a sharp spike to an immediately high value of KR followed instantly by the KR Recovery Rate. It doesn't grow with engine RPM or load, it jumps to a high value on throttle input and then recovers to a low value, or zero perhaps, as engine RPM continues to increase. Note that this is exactly opposite to the characterization of REAL KR. Remember, knock is simply specific noise detected by engine microphones. Because it happens to fall with in the frequency of real KR does not necessarily mean that it IS real KR.

Q:What can cause FALSE KR?
Outlined below is a list of things that can cause false knock.
Sway bar hitting exhaust downpipe - This happens typically with the downpipe of headers because that configuration puts the downpipe in very close proximity to the sway bar … much closer than the stock downpipe. The banging noise from the two metal objects hitting may resonate through the frequency band that the PCM detects as knock through the knock sensors. The solution to this is to flip the swap bar over. Because of the curvature of the sway bar near the downpipe, flipping it will allow the sway bar to curve AWAY from the downpipe rather than toward it.

Transmission oil stick hitting exhaust crossover pipe - This typically happens with the crossover pipe of headers due to their large size and proximity as opposed to the stock crossover. The banging noise from the two metal objects hitting may resonate through the frequency band that the PCM detects as knock through the knock sensors. The solution to this is to carefully bend the trans oil stick away from the crossover pipe so that the two do not touch.

-Anything loose in the engine or outside the engine may cause noises that drift through the frequency range that the PCM detects as KR. Carefully check your engine! This is very vague and is intended to be vague because just about anything loose in or out of your engine that is making noise could cause this. This includes loose or noisy components in your transmission as well.

-Loose knock sensors, or knock sensors that are too tight. Double check that your knock sensors are torqued to spec (14 lb-ft).

IsaacHayes wrote:So are you positive the ICM bracket vibration was the culprit?

IsaacHayes wrote:So are you positive the ICM bracket vibration was the culprit?

3X00-Modified wrote:You referring to the timing chain? Its definitely a possibility but when it was so loose before it sounded like piston slap it never registered a peep... and it's not making a sound compared to the old cloyes setup I had run.

I put two rubber feet below the coil bracket and went for a quick ride... I did not get any KR on the highway when I was going only a few times at like 1800 RPM around town, which I can almost attest to bog knock since this engine is not happy that low. I can deal with that and accept it, its the 75mph on cruise control getting 18* of KR that is just unacceptable.