ethan169

iTrader: (3)

Ok so I was curious if anyone with some experience on here could shed some light on this subject. Ive posted a log below and a graph of knocksum and knock voltage vs RPM.

How does the ECU decide when to show a "knock sum" value? Im more interested in spotting false knock. As a side note Id like to say that I dont really suspect this log to have any false knock it was just a good clean example with some light knock. I see the knock voltage begin to climb and then a 4 count is show that tapers down to 2, 1 then 0 again. The voltage does go down as well but by the time the voltage is in the same amplitude area of where there was no "knock sum" shown previously it is still showing 1-2 counts.

What about the 2 count shown right at the beginning of the log? There isnt much amplitude for the voltage there. I realize that I have only shown the window of the pull and you can see whats going on right before that 2 count but from what I recall it is pretty flat..

RPM	TimingAdv	Load1B	KnockSum	WideBandAF	JDMMAP	InjPulseWidth	InjDutyCycle	KnockVoltage
2468.75	19	92.4	0	14.4207	0.78413	6.656	14.04	0.936
2468.75	18	100.8	2	14.6412	0.9776	7.168	14.56	0.507
2375	17	102	0	15.9936	1.94495	7.168	14.37333333	0.6435
2437.5	17	102	0	15.9936	1.94495	7.168	15.30666667	0.819
2593.75	17	104.4	0	15.9936	2.33189	7.68	16.6	0.6825
2531.25	13	109.2	0	12.201	2.9123	7.936	16.53333333	0.4875
2468.75	11	111.6	0	12.201	2.9123	8.192	17.06666667	0.8385
2531.25	11	112.8	0	12.201	3.10577	8.448	18.48	0.6435
2656.25	11	115.2	0	12.201	3.68618	8.704	19.26666667	0.78
2625	10	118.8	0	12.3186	3.68618	9.216	19.92	0.624
2593.75	10	123.6	0	12.3186	4.26659	9.472	20.72	0.78
2687.5	10	124.8	0	12.3186	4.847	9.984	22.62	1.053
2718.75	9	129.6	0	12.3186	5.04047	10.496	23.50666667	0.819
2687.5	8	135.6	0	12.2598	6.00782	11.264	25.52	1.053
2750	7	141.6	0	12.2598	6.20129	12.032	27.88666667	1.1505
2781.25	5	150	0	12.2451	7.74905	12.8	29.66666667	1.131
2812.5	3	157.2	0	12.2451	8.13599	13.568	32.15333333	1.1505
2875	3	164.4	0	11.7894	9.29681	14.336	34.72	1.209
2906.25	2	174	0	11.7894	10.45763	14.848	35.96	0.9945
2937.5	2	182.4	0	11.7894	11.23151	15.36	38	1.3065
2968.75	2	188.4	3	11.5542	12.39233	16.384	40.96	1.365
3000	0	200.4	3	11.5542	13.94009	17.408	44.42666667	0.897
3062.5	-1	211.2	4	11.5542	15.68132	18.688	48.18	1.1505
3125	0	222	3	11.3778	17.03561	19.456	51.17333333	1.677
3156.25	0	228	3	11.3778	17.61602	19.968	53.04	1.7355
3218.75	1	231.6	3	11.3778	19.16378	20.224	54.77333333	1.1505
3250	1	235.2	2	11.025	19.35725	20.224	55.82666667	1.7745
3312.5	1	231.6	2	11.025	20.51807	19.968	55.64	1.8525
3375	1	226.8	2	10.8192	20.3246	19.712	56.46666667	1.833
3468.75	2	225.6	2	10.8192	20.3246	19.712	56.98	1.6965
3500	2	226.8	2	10.8192	20.90501	19.712	58.00666667	1.0335
3562.5	2	226.8	2	11.0838	20.71154	19.712	59.54666667	1.9695
3625	3	225.6	2	11.0838	19.93766	19.456	59.78666667	2.1645
3718.75	3	223.2	2	11.4219	20.71154	19.712	61.6	1.6185
3750	3	225.6	2	11.4219	19.93766	19.712	62.62666667	2.262
3843.75	3	225.6	2	11.4219	19.55072	19.712	63.65333333	0.8385
3906.25	3	225.6	2	11.4807	20.13113	19.968	66.56	0.936
4031.25	3	228	1	11.4807	20.13113	19.968	68.12	0.9555
4093.75	3	228	1	11.4807	20.3246	19.968	68.64	0.663
4156.25	4	229.2	1	11.3337	20.51807	20.224	71.62666667	0.624
4250	4	231.6	1	11.3337	19.93766	20.224	72.15333333	0.6435
4312.5	4	231.6	1	11.2749	20.51807	20.48	74.66666667	0.819
4375	4	231.6	1	11.2749	20.3246	20.48	75.73333333	0.5655
4468.75	4	232.8	1	11.2896	21.09848	20.48	76.8	1.131
4531.25	4	234	1	11.2896	19.93766	20.48	77.86666667	0.702
4593.75	3	236.4	1	11.2896	20.51807	20.736	79.92	0.6825
4687.5	3	236.4	1	11.3925	21.09848	20.736	81	0.78
4718.75	3	237.6	1	11.3925	20.3246	20.992	83.64	1.716
4812.5	3	238.8	1	11.319	20.51807	21.248	85.76666667	1.1895
4875	4	240	0	11.319	21.29195	21.248	86.87333333	0.7995
4906.25	4	241.2	0	11.319	20.71154	21.248	87.98	0.858
5000	4	242.4	0	11.3043	21.09848	21.504	90.72	1.053
5062.5	4	246	0	11.3043	20.90501	21.76	91.8	0.7215
5093.75	3	248.4	0	11.2455	21.29195	22.016	95.17333333	1.4625
5187.5	4	249.6	0	11.2455	21.29195	22.016	96.32	0.8775
5250	4	250.8	0	11.1573	21.87236	22.016	97.46666667	1.6575
5343.75	4	250.8	0	11.1573	22.2593	22.016	98.61333333	0.507
5406.25	4	250.8	0	11.1573	22.2593	22.272	100.92	0.9945
5437.5	4	252	0	11.025	21.87236	22.272	102.08	1.131
5531.25	4	252	0	11.025	21.87236	22.272	103.24	1.5795
5562.5	4	253.2	0	10.8633	22.06583	22.272	104.4	0.8385
5656.25	4	252	0	10.8633	22.06583	22.016	104.92	1.0335
5750	4	250.8	0	11.0838	22.06583	22.016	105.4933333	1.872
5781.25	3	250.8	0	11.0838	22.45277	22.016	107.2133333	0.9945
5843.75	3	250.8	0	11.0838	22.2593	21.76	107.1	1.833
5906.25	3	249.6	0	11.2455	21.67889	21.76	108.2333333	1.2285
5968.75	3	249.6	0	11.2455	21.67889	21.504	108.08	1.404
6062.5	3	246	0	11.4072	21.67889	21.248	107.9	2.0085
6093.75	4	244.8	0	11.4072	21.48542	20.992	107.6933333	1.4625
6187.5	5	242.4	0	11.4366	21.87236	20.992	108.7866667	1.716
6218.75	5	241.2	0	11.4366	21.29195	20.736	108.54	1.131
6281.25	6	238.8	0	11.4366	21.87236	20.48	107.7333333	1.3455
6343.75	6	237.6	0	11.4219	21.87236	20.224	107.44	1.8135
6375	6	236.4	0	11.4219	21.48542	20.224	109.5466667	1.794
6531.25	8	231.6	0	11.5248	20.90501	19.712	107.8	1.833
6562.5	8	230.4	0	11.5248	21.29195	19.712	107.8	2.1255
6562.5	8	229.2	0	11.5248	20.3246	19.712	108.8266667	1.677
6656.25	9	228	0	11.4513	20.90501	19.712	109.8533333	2.0475
6718.75	9	225.6	0	11.4513	20.3246	19.456	108.9333333	1.7355
6750	9	223.2	0	11.5248	19.74419	19.2	108.5	1.755

Any info is greatly appreciated!

Thanks,

Ethan

Evoryder

iTrader: (55)

I would say it's a combination of factors. Rpm /load/maf sensor/knock voltage/af...etc .the ecu will use all factors to determine when a knock sum is needed. There is code that allows you to adjust the knock sensor sensitivity.

Regarding your pull I noticed you have negative timing around 3k???

ethan169

iTrader: (3)

Good points. Im sure your right about the ECU using several factors to determine knock.

Regarding the negative timing. Im in the middle of a new tune and the timing map has just been rescaled and super conservative to get some knock control and straighten out my fuel. So the timing value in those load cells is 0 or 1 and since the ECU is seeing knock its retarding it down further..Its in the works....

Weird that my TPS values didnt copy over...hmm

JohnBradley

iTrader: (30)

Knock is frequency based, the voltage is amplitude.

On our motors its technically 6700hz and the secondary harmonic is checked to see if it "rings" and then decides its real. I have heard from the DSM disassemblers that its 6200 and 12400 (double amplitude) that they are checking but I dont have anyway to confirm that.

All that being said, I have seen 36 counts of knock register .7v and I have seen 3.94v be knock free. Depending on what fuel you are on (91 I would say its real) I would think you are seeing phantom based on knock V vs boost vs timing.

aaron

ODUB

iTrader: (8)

thank you for that explaination... do you think i'm having the same thing based on the logs I've posted in my thread?

IrightI

iTrader: (11)

Good thread, I had these same questions.

ethan169

iTrader: (3)

^- I saw your thread and took a read. Your knock count is much higher then mine and from what I thought was sporadic. Like just shows up with 15-25 counts and then goes away. Mine is transient which i thought was more like a real knock situation? I know that my AFR's are ok and timing is obviously low. But I do have some unsmooth parts in my map. Hopefully that is the reason for the knock as it seems to happen in the same area most of the time. I really dont want to get into playing with the knock filters and multipliers etc..