Help on part throttle knock

[BoostKillsStres]

When rolling at low speed say 30-45 and giving about 1/3 throttle, just enough to whistle the turbo but make no boost say just below 0 psi, my knk gauge is going nuts. This is only when in a non PE situation. I can get it to go into the red of I hold it at right around 0 psi for about 2 seconds but I can't hear anything noise related over the turbo air whoosh into the air filter.

It does this around 2000-2400 rpm, I added 6 units of fuel to 2400, pulled 2-4 degrees of timing in the 31-63% LV8 range but no change. I've tightened and loosened the tiedown strap, all exhaust is tight and DP isn't hitting frame. I checked the flywheel bolts last yr they were tight. I turned the key on and tapped around the knk sensor and it doesn't seem overly sensitive, I've tested it in the past and it seems to take about the same amount of tap to set the knk gauge off.

It doesn't knock at all once I get above about 3 psi and can run right aroung 17-17.5 psi with no knock through 2nd gear. Once up to hwy speed I can't even make it do this. It will do this in 1st, 2nd, 3rd and 4th at low speed aka <52 mph.

Any ideas appreciated.

 

[Rollin]

Mark, let me move this to tech for ya

 

[John at J&S]

It's that dreaded part throttle false knock.

I've been building knock controllers since '85. I've found that engines that are in decel or lightly loaded make more noise than when they are in moderate to full load. I call it piston slap, but I don't really know if that's what it is.

In our units, I keep the knock sensor disabled until the vacuum drops below 5 inches. This is usually a high enough load so that piston slap isn't a problem.

Have to ask Dave or Bruce if the ECU ignores the ESC under low loads. You didn't say that the car was nosing over, just that the knock gauge lit up.