Engine knock diagnostic
A knock diagnostic module having a knock module that increments a sample count when a cylinder firing signal corresponding to a first cylinder is received and selectively increments a knock count based on a knock detection signal that corresponds to the cylinder firing signal of the first cylinder A knock analysis module analyzes the knock count of the first cylinder when the sample count of the first cylinder reaches a predetermined value and selectively generates an excessive knock signal when the knock count exceeds a predetermined threshold. A remedial action module selectively performs a remedial action based on the excessive knock signal.
1. A knock diagnostic module, comprising:
a digital signal processor (DSP) that performs N Fast Fourier Transforms (FFTs) during a knock window around a firing event of a first cylinder based on output from a vibration sensor measured during N different periods during the knock window to produce N sets of FFT points, respectively, wherein N is an integer greater than or equal to 2;
a data reduction module that:
selects one of the N sets of FFT points;
selects one of M ranges of interest within the selected one of the N sets of FFT points, wherein M is an integer greater than or equal to 1; and
determines a single intensity value based on ones of FFT points within the selected one of the M ranges of interest in the selected one of the N sets of FFT points;
a processing module that determines whether knock occurred based on the single intensity value and an average intensity value determined for the first cylinder;
a knock module that increments a sample count for the first cylinder in response to the firing event of the first cylinder and selectively increments a knock count for the first cylinder based on whether knock occurred;
a knock analysis module that analyzes the knock count of the first cylinder when the sample count of the first cylinder reaches a predetermined value and selectively generates an excessive knock signal when the knock count exceeds a predetermined threshold;
a low variation module that determines a variation for the first cylinder based on a difference between the intensity value and a second intensity value determined for a previous firing event of the first cylinder;
a low variation analysis module that selectively generates a low variation signal for the first cylinder when an average of the variation and at least one other variation of the first cylinder is less than a predetermined value and that determines the predetermined value based on an engine speed and an engine load;
an abnormal range module that selectively generates an abnormal range signal when the intensity value is outside of a predetermined range and that determines the predetermined range based on the engine speed and the engine load; and
a remedial action module that selectively performs a remedial action based on the excessive knock signal, the abnormal range signal, and the low variation signal.
2. The knock diagnostic module of claim 1 wherein the remedial action prevents a spark control module from advancing spark timing beyond a predetermined threshold.
3. The knock diagnostic module of claim 2 wherein the remedial action further includes generating a trouble code.
4. The knock diagnostic module of claim 1 further comprising a counter module that stores the sample count and the knock count of the first cylinder.
5. The knock diagnostic system of claim 1 wherein the data reduction module determines the M ranges of interest based on an engine speed.
6. The knock diagnostic system of clam 1 wherein the data reduction module sets the single intensity value to a maximum one of the FFT points within the selected one of the M ranges of interest in the selected one of the N sets of FFT points.
7. The knock diagnostic system of claim 1 wherein the data reduction module sets the single intensity value to an average of the FFT points within the selected one of the M ranges of interest in the selected one of the N sets of FFT points.
8. The knock diagnostic system of claim 1 wherein the data reduction module selects the one of the M ranges of interest within the selected one of the N sets of FFT points based on an engine speed.
9. The knock diagnostic system of claim 1 wherein the data reduction module selects the one of the sets of FFT points based on an engine speed.
10. A method of knock detection, comprising:
performing N Fast Fourier Transforms (FFTs) during a knock window around a firing event of a first cylinder based on output from a vibration sensor measured during N different periods during the knock window to produce N sets of FFT points, respectively, wherein N is an integer greater than or equal to two;
selecting one of the N sets of FFT points;
selecting one of M ranges of interest within the selected one of the N sets of FFT points, wherein M is an integer greater than or equal to 1;
determining a single intensity value based on ones of the FFT points within the selected one of the M ranges of interest in the selected one of the N sets of FFT points;
determining whether knock occurred based on the single intensity value and an average intensity value determined for the first cylinder;
incrementing a sample count in response to the firing event of the first cylinder and selectively incrementing a knock count for the first cylinder based on whether knock occurred;
analyzing the knock count of the first cylinder when the sample count of the first cylinder reaches a predetermined value and selectively generating an excessive knock signal when the knock count exceeds a predetermined threshold;
determining a variation for the first cylinder based on a difference between the intensity value and a second intensity value determined for a previous firing event of the first cylinder;
selectively generating a low variation signal for the first cylinder when an average of the variation and at least one other variation of the first cylinder is less than a predetermined value;
determining the predetermined value based on an engine speed and an engine load;
selectively generating an abnormal range signal for the first cylinder when the intensity value is outside of a predetermined range;
determining the predetermined range based on the engine speed and the engine load; and
selectively performing a remedial action based on the excessive knock signal and the low variation signal.
11. The method of claim 10 wherein the remedial action includes preventing advancement of a spark timing beyond a predetermined threshold.
12. The method of claim 11 wherein the remedial action further includes generating a trouble code.
13. The method of claim 10 further comprising:
storing the sample count and the knock count of the first cylinder.
14. The method of clam 10 further comprising setting the single intensity value to a maximum one of the FFT points within the selected one of the M ranges of interest in the selected one of the N sets of FFT points.
15. The method of claim 10 further comprising setting the single intensity value to an average of the FFT points within the selected one of the M ranges of interest in the selected one of the N sets of FFT points.
16. The method of claim 10 further comprising selecting the one of the M ranges of interest based on an engine speed.
17. The method of claim 10 further comprising selecting the one of the N sets of FFT points based on an engine speed.
18. The method of claim 10 further comprising determining the M ranges of interest based on an engine speed.