Knock Retard

Will

Core Member
Quite an interesting article. It says that knock detection frequency for an LS1 is around 6kHz, which is surprising, but can change with cylinder bore. Dan, I can't recall if you only stroked your engine or had it overbored too? Unless I missed it, it doesn't specifically mention valve train noise but does mention false knock detection (which they probably mean is valvetrain noise).
Can you adjust the gating of when the ECU is monitoring the KS for knock? If so, I was just wondering, unless the knock is occurring at exactly the same time as a particular instance of valve train noise, if the knock sensor was only gated for when knock was likely to occur, the ECU wouldn't be listening for knock outside of the gated period? Although, I know there is the valve gear noise of the other cylinders to consider.
The article also says about single and two wire KS's and the set up method for each. I think you said that yours are single wire (resonant) ones?
Seems it's quite a science :geek:
 

Stephen CA

Core Member
I think I saw Knock Retard on the other stage at Glastonbury in about 1998. I went off them after their difficult third album..... 😀💿
 

TransAmDan

Forum Admin
Staff member
Don't some tweaking last night on the spark tables, not programmed them in as been working on other stuff in the garage.
 

TransAmDan

Forum Admin
Staff member
I have some additive to reduce knock. It changes the octane rating of the fuel.
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Running super unleaded reduced knock. Wanting to go that step further to see if it can be eliminated everywhere. As if knock is detected the ECU remembers where that happened and will reduce spark in that cell until you fill up again and then it resets this table to relearn again.

I have put in half the bottle as it will treat the amount of fuel I have in it. We have the Breakfast run in the morning, so I'll do some data logging on the way back. Hope Sarah doesn't mind a few bursts of acceleration to test things out. :LOL:
 

TransAmDan

Forum Admin
Staff member
Well with the octane booster I'm still getting knock at low loads.
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Spark advance is 3.6 degrees when this happened with is around 5 degrees lower than when it happened before. Therefore I believe it is false knock and more like something else causing it.
 

TransAmDan

Forum Admin
Staff member
Tank full of V-Power, and also the whole bottle of the octane booster.

Still getting knock. So I think we have pretty much proved its not duff fuel. The AFR is 12ish, so not too lean. Knock retard is in 3rd gear but not 4th or 5th going through the same rev range.
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The knock must be caused by another source of vibration, or sensors getting duff.

So as a positive, we know what its not.

Nice doing the data logging and driving the car.
 

TransAmDan

Forum Admin
Staff member
My main aim for tweaking the spark timing and looking into this graph is the bucking at low loads. Which is why I started looking into knock. Fuel ratio is perfect, lean cruise turned off. I'm well happy with performance at WOT. If anything tuning at lower loads is more tricky. The knock retard is falsely going off at lower loads as retarding the timing and using high octane fuel there should be no knock. So it's gotta be vibration from elsewhere. So needing to ignore the knock sensor in some places.
The bucking at lower loads, I could be cruising at 30mph, if going up a hill it's perfect. If on flat ground it's like it dosn't know to accelerate or slow down, surging and bucking. If you come out if gear and back in, it's fine for a few seconds. I need to find the best spark advance for this area.
Now this may never be perfect, many people in the states say you will never get the cam to be 'streetable' but I like a challenge. So I will keep tuning in this area.
 
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