spark knock WTF ????

In an OBD-II system with electronic spark
timing, the PCM continually reads a number
of input signals, including base timing,
throttle position, intake manifold pressure,
transmission gear and vehicle speed. Some
PCMs will even read a rapid change in throttle
position, indicating the driver wants to
accelerate quickly. Based on its programming,
the PCM advances spark to a preset level for
different conditions. The preset spark advance
is typically close to the knock point because
the system relies on the knock sensor as a
warning device.
Most knock sensors send a base or “no
knocking” reference signal to the PCM.
If knocking occurs, the sensor detects the
increased vibration and increases its signal
to the PCM. The PCM then slightly retards
timing until the sensor signal returns to the
reference level.
If a temporary condition caused the knock,
the PCM will set spark timing to the
programmed advance. If the knock returns,
the PCM will cycle spark timing, advancing
timing until knock is encountered and then
retarding timing until the knock is gone.

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A too lean condition, such as a PCM, fuel
system or a vacuum leak problem, can also
cause knocking.

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Bravnik said:

I noticed the same this weekend using the latest build. I actually saw a 6 on mine in one run, but most were 3.2/3.5. I have never noticed more than a 1.0 before.

My AFR's run perfect as well and look as almost a solid line following the Commanded. I don't see how you can have such high Knock with such good AFR's.

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dadasracecar said:

I think the stock knock sensor is reacting to the injectors. I removed the foam under my intake solely for looks and my car started throwing 4.5, 6.0, 7.0... usually when I would let off of the throttle while cruising. I could even rev it in neutral and make the knock sensor go off. There is no way to cause knock with no load on this motor and I only started seeing this after removing the foam. It looked better though lol...

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shadrag said:

I think the knock sensor is over sensitive. I've occasionally seen "knock" when maintaining a low, constant speed. Either our ECU is a POS or it's a false reading.

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nypest said:

Tru-boost did you happen to DL spark advance to see if the computer was pulling timing due to the onset of the knock?

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astraelraen said:

From what Ken over at th dashhawk forums said the knock retard could just be a minus from spark advance.

So the spark advance shows total advance, and the knock retard is what the ECU is subtracting from advance. Knock retard won't make spark advance decrease on the dashhawk display.

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nypest said:

Have you see that the car pulls timing due to the knock and can we find out how much is too much ?

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matsuda said:

The ECU parameter that is being read is KNOCK TIMING RETARD.

Isn't that self explanatory?

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ok you must have it set up wrong.....just like i did !!
when you set up the command and actual AFR you should not use the "command AFR pid from the mazda specific section. it will give you the wrong reading. to get the proper AFR command reading you must use the PID for it in the regular "fuel" settings. i changed mine and found that most of the time my car is calling for 10.5:1 and i am actually at 11.5:1 . still plenty safe but for sure not what the car is asking for !

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tru-boost said:

hey guys, i got my DH and have been playing around with it. i did some logs monitoring command A/F, actual A/F, RPM, and knock retard. i was impressed with my A/F. the car follows the command at all times....i mean perfectly !! but the knock has me worried. 3rd gar by itself looks OK. 4the by itself is slightly higher but still OK i think.
the run through 3rd and 4th is when it gets scary !
in 4th gear the knock retard jumps up to 4.9 ! the car felt good and the rest of the parameters look good so,....... WTF ???

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