Programmable digital knock filter?

Ecu Hardware Modifications
VX L67 Getrag
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Re: Programmable digital knock filter?

Post by VX L67 Getrag »

There a GREAT thing & can't talk highly enough of it not only for making an 808 upmarket with knock sensing but just the knock LED or LOG triggering!

GREAT WORK FESTY!!!!
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festy
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Re: Programmable digital knock filter?

Post by festy »

Here's a quick log of me mucking around with the filter module's settings.
The engine is idling, and by adjusting the module's parameters the knock being reported to the ECU varies from intense, constant knock to no knock being reported at all.
knock_settings.png
knock_settings.png (16.15 KiB) Viewed 11403 times
A LED connected to the output helps get the settings in the right ballpark to start with, a quick knock isn't always visible in the logged knock count like here - the knock retard is increased but the knock count isn't obvious:
knock_counts.png
knock_counts.png (5.82 KiB) Viewed 11403 times
Attachments
knock_settings.xdl
12P log of knock settings changes
(309.45 KiB) Downloaded 448 times
robertisaar
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Re: Programmable digital knock filter?

Post by robertisaar »

i believe that would be due to only the MSB of the knock counter register being transmitted over ALDL.
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festy
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Re: Programmable digital knock filter?

Post by festy »

It could also be related to the slow old laptop I was using to log, it's so gutless that it can't update the monitor window and log packets at the same time - I'll try it again with a faster machine and see if the log looks any better.

Things like this don't make much sense to me - the knock flag is clear and count is 0, but in the second line the knock retard increases so my guess is that knock was probably detected between sample 2126 and 2127, but was gone by the time packet 2127 was sent?

Code: Select all

Sample	Time	Knock	Count	KR
				    flag
2126	234.417	Clear	0		7.4
2127	234.524	Clear	0		8.1
2128	234.629	Clear	0		8.1
The knock filter would have processed heaps of samples between those two messages, so maybe a message6 would show more granular detail... not that it really matters because the KR value shows what's going on anyway.
VX L67 Getrag
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Re: Programmable digital knock filter?

Post by VX L67 Getrag »

Had the ECU been diss connected before logging?

If it goes into areas it's learnt knock before it could just be from ram memory?
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festy
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Re: Programmable digital knock filter?

Post by festy »

Yep, I'm in the habit of isolating the battery whenever it's not being run.
And the engine was holding a pretty steady idle, so shouldn't have been moving in and out of learned areas?
I think it's just similar to what you were seeing with your logs - sampling at 10Hz is going to miss some fast events.
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VL400
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Re: Programmable digital knock filter?

Post by VL400 »

12P does not have learned knock, its purely reactive on knock at that instant. Its just that the knock detected flag is set and cleared every 12.5ms that you can miss it while logging.
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festy
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Re: Programmable digital knock filter?

Post by festy »

Thanks, the log makes perfect sense in that case ;)
Is the knock count cleared at the same rate?
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VL400
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Re: Programmable digital knock filter?

Post by VL400 »

Yeah knock counts are the same 12.5ms, the flag is just a zero check of the knock counts to clear/set it.

Am sure you have worked it out from testing, but 16 knock counts = (very close to) 1mS of knock duration sampled every 12.5ms.
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festy
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Re: Programmable digital knock filter?

Post by festy »

VL400 wrote: Am sure you have worked it out from testing, but 16 knock counts = (very close to) 1mS of knock duration sampled every 12.5ms.
I hadn't done the maths, but that certainly matches up with the max knock count being around 200 in the logs.

I was mucking around with a sig gen the other day and found that with very high integration time/low gain set, the detected knock bandwidth got as narrow as 250Hz :shock:
I don't think those extreme settings would work too well in the real world though...
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