Ion Sense

Hardware inside and outside of the ECU
mck1117
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Re: Ion Sense

Post by mck1117 »

All skyactiv engines with spark plugs have ion sense. I've personally scoped the ion sense line on my Skyactiv-G 2.0 in my ND2 Miata and it looks as expected.
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sepp2gl
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Re: Ion Sense

Post by sepp2gl »

Can you tell, what functionality is covered by IS on Skyactive-G?
Is it more basic misfire & knock detection?
Or does Mazda use advanced functions?
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sepp2gl
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Re: Ion Sense

Post by sepp2gl »

@mck1117:
...any reply? :?: :?: :?:
What do you mean by "...looks as expected"?
What was your expectation?
kr, sepp2gl
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Simon@FutureProof
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Re: Ion Sense

Post by Simon@FutureProof »

In this case "as expected" would be in regard to the conventional ion sensor systems as used by SAAB etc.
image.png
image.png (47.05 KiB) Viewed 1233 times
Very similar to what we saw here with the SAAB system.

https://github.com/rusefi/rusefi/wiki/Saab-Trionic-8-Combustion-Detection-Module-on-Mazda-Miata-running-rusEFI

The irritating thing with the Mazda coils is we/I was not able to get a decent signal out of them off the car. Still unknown as to the reason why.
Now keeping MRE and Proteus in stock in the UK - https://www.FutureProofPerformance.com
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sepp2gl
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Re: Ion Sense

Post by sepp2gl »

@OrchardPerformance:
Looking to the diagram, the black trace is the typical shape of an ion-sense native signal, with the blue trace being combustion pressure as reference.
It is important to know, that you don't get this perfect shape under all conditions of engine operation: mid/high load operation should be easy, low load or idle conditions I wouldn't rise my hand for it. In any case it is not a trivial task to isolate the characteristic values out of the signal.
Especially with the differentiated signal (magenta), you might get extreme issues with noise.

I went into the GitHub-Link. It is hard to analyse the observed signals, if you do not know any engine operating conditions or signals taken.
At least the yellow trace looks like a native Ion-Sense signal, but heavily disturbed.
As the ion signal is very sensitive, it should be processed with high care to noise cancellation.
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JohnP
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Re: Ion Sense

Post by JohnP »

The ion system for Harley Davidson was made by Delphi, but they went back to knock sensing in 2017.

"...the switch from ion-sensing knock sensors to cylinder-mounted ones dramatically increases the range of individual cylinder spark control the ECU has over the firing of the twin plugs, allowing as much ignition advance as possible. “So, you’re not creating heat by retarding the spark to keep yourself away from knock,” explains Bozmoski.

Since knock increases exhaust gas temperature (EGT) and in extreme cases can damage the engine, the Milwaukee-Eight’s ignition timing can be retarded right up to the point of the first signs of predetonation, which has no sound, and then be walked back until it stops. Managing ignition timing to the ragged edge of detonation delivers not only more power with less heat, but it also burns cleaner for fewer emissions..."

Apparently, HD says knock senors are more sensitive. This is the caption in one of the photos:
"Knock sensors mounted to each cylinder allow for the least amount of ignition retard possible without detonation."

Full article is here:
https://www.motorcycle.com/manufacturer/harley-davidson/2017-harley-davidson-milwaukee-eight-engines-tech-brief.html


Visteon is a Ford spinoff. They published a paper in 2008 on ion sensing for a "large displacement motorcycle engine", and showed their system was more sensitive than knock sensors.

It compares knock and ion sensing to in cylinder pressure sensing, as a reference:
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sepp2gl
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Re: Ion Sense

Post by sepp2gl »

@JohnP:
very interesting paper from Visteon.
The findings were mostly well-known state-of-technology.
If you only look at the pure detection of knock-occurrence, there is a lot arguments for ion-sensing.
There are three alternative solutions know: vibration-based (knock sensor), ion-current-based, combustion-pressure based.
They all have their pros and cons to be considered.
But after all it is a commercial decision about which way to go.
As criteria for the decision, there is always
- product-cost on top-priority (at least for mass-production) followed by
- development and investment cost
- technical risk (new, technology is always considered higher risk), good/bad experience/reputation, is the "old" solution sufficiently good or not?
- availability of components (second source available?)
- support by EMS supplier (can be a highly political issue)
- business model (especially the depth of OEM-involvement into EMS-development; Make-or-buy)
- timing, can it be developed on-time for SoP?
There must be good reasons, why there is still knock-sensors as mainstream solutions on the market.

The criteria are differently ranked in importance, depending on if we target for mass production or small-scale production.
So for small-scale we can find different solution selected.
Harley-Davidson might have had good reasons for doing ion-sense and they had good reasons for going vibration-based now.
And of course they found a good advertising strategy to claim "It is better now".

If I was intending to apply knock-detection to my motorbike, I might first consider ion-sense.
Why? First of all it can be easily implemented by just electronics in the ignition coil and the ECU. And I could do it on my own.
There is no need for a special bold on the engine block for the knock-sensor, which needs to be carefully selected to allow equal-quality knock-detection for each cylinder.
And I wouldn't even consider to drill a hole into the cylinder head for the In-cylinder-pressure sensor.

But if I was responsible for a mass-product, I would compare the cost of commodity ignitions-coils, igniters and knock sensors with a special coils, igniters and no knock-sensor.
Everything keeps being better ... ;)
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