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Old 09-09-2011, 10:47 AM   #41
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Quote:
Originally Posted by djp0623 View Post
That is where retarding the timing based on where the theoretical optimum timing is based on knock. If research suggested that knock occurred 5 degrees past the optimal timing configuration, then retard timing by at least 5 degrees after knock is detected.
Unfortunately, research makes it clear that there's no fixed angle between optimal timing and the knock threshold. Some cars (Subarus are Exhibit A) have the MBT timing ahead of the knock threshold. Some combination could have MBT 20 degrees or more behind the knock threshold - I suspect a NA Miata running on methanol would fall into that category, for example.
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Old 09-09-2011, 11:03 AM   #42
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Unfortunately, research makes it clear that there's no fixed angle between optimal timing and the knock threshold. Some cars (Subarus are Exhibit A) have the MBT timing ahead of the knock threshold. Some combination could have MBT 20 degrees or more behind the knock threshold - I suspect a NA Miata running on methanol would fall into that category, for example.
That's unfortunate. So is a speed sensor method the best solution?
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Old 09-09-2011, 11:11 AM   #43
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Yes, a knock window is easier to do in software. The first SafeGuards were a combination of analog and discrete digital, made from '88 to '91. It didn't do individual cylinder control, but it did have a knock window. The knock window was controlled by a PLL clock synchronized to the ignition trigger. Two counter chips set the window start and end points. Dip switches on the front set the counters for 4, 6, or 8 cylinder.

I love doing layouts, but they take a fair amount of time. Good layouts can be works of art. I've found that if they don't look pretty, there's probably a better way to do it, so I start over.

This is part of the Interceptor layout, showing the Altera CPLD chip and the 9S12 processor. The CPLD contains I/O, trigger detection, and retard logic for eight channels. A single line to and from the processor is all that's required to individually control eight ignition channels.

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Old 09-09-2011, 11:23 AM   #44
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John, how come you know so much about J&S? Is it your business? ex Employee?

just curious!
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Old 09-09-2011, 11:31 AM   #45
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Coming to you from World Headquarters.
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Old 09-09-2011, 11:40 AM   #46
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Old 09-09-2011, 11:50 AM   #47
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Not THAT whq. Looks like something from the Great Whole Earth Catalog (pre-internet era).
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Old 09-09-2011, 03:50 PM   #48
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Thanks for chiming in, John!

So current the SafeGuard uses a similar processor to the MS2? Interesting.

Ben and I have been testing some of the future MS knock detection stuff on the dyno today. We're not going to sacrifice a Miata engine for it, but we've got an old beater Sentra sitting around to try this out on.
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Old 09-09-2011, 04:40 PM   #49
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Change is hard. I finally made the transition from HC11 to 9S12 in 2007.
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Old 09-09-2011, 05:00 PM   #50
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That's unfortunate. So is a speed sensor method the best solution?
Adaptronic method seems best outside of a dyno.
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Old 09-09-2011, 05:11 PM   #51
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Adaptronic method seems best outside of a dyno.
Does it combine it with some sort of cruise control so that any observed acceleration/deceleration is due to the timing adjustment? Obviously we would be assuming this would be done on a level road. Mounting an optical sensor system to one wheel doesn't seem like it would be that difficult. Add an input where you can lock the pulsewidth of the injectors. Pick a long level road, or inclined for boost cells. The boost cells seem like they would pose the most trouble, but they are the most important in my eyes.

I think the optical speed sensor idea might fall apart while you are under heavy acceleration to begin with trying to get into boost. How could one tell if the acceleration was due to timing or accelerator pedal movement.

Ok, so here is an idea.

The software would require you to do record multiple acceleration runs. This would log data that related TPS to acceleration through different rpm points. Done on the same road as the tune and you might be able to pinpoint the data changes due to the timing adjustment alone. This would require the user to treat it like an absolute calibration, meaning Temp, pressure, road used, etc all need to be monitored an held somewhat constant between the baseline data and the adjustment data.
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Old 09-09-2011, 08:06 PM   #52
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No it looks at the RPM. It dithers the timing continuously, rather quickly (several times per second) at some frequency. It looks for an FM signal with the same frequency in the RPM. The sign and magnitude of that signal tells you if there was an increase in torque from the increase in timing.
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Old 10-07-2011, 12:59 PM   #53
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Re: KNOCK WINDOWING

I just had a realization.

The time windowing should be BEFORE the filter.

The reason is that a bandpass filter rings like bell when stimulated by a noise with in-band frequency components. And the reason knock is hard to detect is that engine noise has some in-band components. Therefore to maximize discrimination, you don’t want engine noise reaching the filter outside of the crank-angle window where knock isn’t possible.

If the ECU had an output that simply went high when crank angle is “in window”, that signal could be used by the analog circuitry.
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Old 10-07-2011, 05:03 PM   #54
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Quote:
Originally Posted by JasonC SBB View Post
If the ECU had an output that simply went high when crank angle is “in window”, that signal could be used by the analog circuitry.
Uninformed question;
Could one of the cam wheels be modded so a hall sensor could go high/low during the knock window (if a section of the 720 degree cycle would be good enough, i.e. fix window in relation to rpm/load/TPS etc).
That way you could window the knock signal at the source.

Software is still needed to figure out what to do when,but even with simple knock check, you could stop listening during the times when there "cannot" be knock.

But uninformed, as I said.
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Old 10-07-2011, 06:36 PM   #55
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A spare cam wheel? If you could make your own window, yea.

Reverant could add this functionality, if we could find out what crank angle range knock is valid. Obviously it has to be <90*, else it would be meaningless, unless one were doing per-cylinder knock detection and spark adjustment.
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Old 10-09-2011, 08:05 AM   #56
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The one and only ECU that had a "best timing finder" feature is the Adaptronic, and mysteriously, nobody was interested in the feature. Such that they removed it in later revs...
They ditched it? I'm amazed. That was the one really cool feature that made me regret not buying an Adaptronic.
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Old 10-09-2011, 01:19 PM   #57
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