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Thread: Knock retard

  1. #1
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    Knock retard

    Can someone please tell what the deal is with logging kr on these xr6 turbos I haven't had a lot to do with them tuning wise Iv come from the LS world. Now when you see kr on a LS in a log it means the ecu thinks there is knock. Now I have done some logging on 3 stock xr6 turbos and every time they come on boost there is some kr getting logged. Is this normal? And if so how are you identifying real knock (apart from a 3rd party devise).

  2. #2
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    Although secondary knock monitoring is what I use. You could try taking timing out at that load/rpm or adding fuel. If the knock retard stays the same I'd be inclined to say it is false knock.
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  3. #3
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    So in other words if it is showing kr in the log the ecu thinks there is knock and will remove timing just like a ls ecu. Has anyone else experience kr on a completely stock car, is it common.

  4. #4
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    you are most likely seeing this as a - negative value, which means it is adding timing.

  5. #5
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    Yes it is a negative value, that's weird how timing getting added through other tables shows up as negative kr in the scanner.

  6. #6
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    So it looks like negative kr is knock, turn the knock sensors off and you don?t get negative kr in the scanner.

  7. #7
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    Also interested in this topic. On a 3rd gear pull, I may see no knock retard, however if the car is at wot in first or when stalling and launching, I always see some knock retard. Is there a reason for this, and can it be eliminated? Seems rather odd as the car is quite happy in 3rd. Could it be related to boost control?

  8. #8
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    What fuel are you using?

  9. #9
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    Was using Costco fuel which is Mobil, but having switched to BP, it seems to be a bit better but still exists.

  10. #10
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    I think the stock calibration on the knock sensors are way to sensitive, so you probably need to D sensitise them, but in saying that I would always try and eliminate any chance it is in fact real knock.

  11. #11
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    I agree,

    I'm not too sure where to start re desensitising though. I've heard some say you need to increase gain (the map definition is incorrect) and I've heard to decrease gain. Then I'm not too sure how much to change the gain settings. I'm asking for 13 or so degrees at 12psi with AFR's around 12:1. I've seen tunes asking for 15+ at higher pressures so I do believe I've well below knock.

  12. #12
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    the factory IAT compensations are quite aggressive. don't be fooled into thinking 15 degrees is ok on big boost. from what I've seen as a rough ballpark a BA will take 7-8 at peak torque (4500) out to about 11 at 6k rpm on 18psi 98 pulp.

    a BF will take 4.5-6 at peak torque out to about 9/10 at 6k rpm. on 98pulp 18 psi

    FG F6 seem to take about 11 at peak torque out to 13 at 6k rpm 98pulp 18 psi

    that's what I find the car will actually take excluding all compensators. that example assumes a free flowing intake and exhaust with a capable cooler on factory turbo.

    a lot of the generic early tunes were rattle city.

  13. #13
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    You will get false knock from loud exhaust actually as the knock sensor picks up the sound