Ion Sense

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

Post by bill »

Another Ion Sense article...
with circuits and such

http://vvnet.fi/ville/ion/DIY-Ion-Sensing-2.pdf

and Mitsubishi patent

https://patents.google.com/patent/US5293129A/en
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kb1gtt
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Re: Ion Sense

Post by kb1gtt »

In slack @mck1117 linked this article about ION sense.
https://sci-hub.tw/10.4271/950004

SAE TECHNICAL
PAPER SERIES
Ion-Gap Sense in Misfire Detection,
Knock and Engine Control
John Auzins
Delco Electronics Corp.
Hasse Johansson and Jan Nytomt
Mecel
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Re: Ion Sense

Post by kb1gtt »

Also this one. https://sci-hub.tw/10.4271/1999-01-0204

SAE TECHNICAL
PAPER SERIES 1999-01-0204
Ion Current Sensing for Spark Ignition Engines
Jürgen Förster, Achim Günther, Markus Ketterer and Klaus-Jürgen Wald
Robert Bosch GmbH
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Re: Ion Sense

Post by saabnut »

https://www.researchgate.net/profile/Peter_Weyand

Peter works for Delphi europe, and has published some interesting articles that you guys may be interested in.
I believe is is mentioned in this thread, but if not, Delphi has moved processing to the coil itself.
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Re: Ion Sense

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Shy Mercedes owners are currently trying to stick some Saab magic without any Ferrari help
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Re: Ion Sense

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Pictured BMW in relation to cruely modified Saab
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Re: Ion Sense

Post by AndreyB »

BMW V10 S85 uses ion sensing right? Someone should try 7835108 - eBay has used singles, plug looks similar to v12 BMW?
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Re: Ion Sense

Post by OrchardPerformance »

I would like to make a note here that the 2002 paper on diy ion sense is fundamentally wrong in many areas, at the time of writing it seems the author did not understand either the fundamentals of combustion timing or the nature of the signal being sensed.

A quick Google of it also brings up the thread below where it is suggested when it was tested by a 3rd party the circuit failed upon the first spark.

https://www.msextra.com/forums/viewtopic.php?t=25725
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Re: Ion Sense

Post by OrchardPerformance »

To give a more positive update to this thread we have assembled a prototype DIY ion board based on a design MCK117 produced and have tested it using an R50 mini wasted spark coil connected to an MRE.

Result was no magic smoke escaping after 50+ sparks and a trace captured on a scope that was nicely capped at 7v.

The trace looks a little odd as its just the result of the plug firing in free air.
Hope is to test it in anger on an engine early next week.
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Vug1
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Re: Ion Sense

Post by Vug1 »

It appears that Mercedes has Ion Sense on some V12 engines (M137, M275, ..), some V8s (M113, M113K, ...), V6s (M112, ...) that have 2 sparkplugs/cyl. The magic is that one engine cycle one of the sparkplugs fires normally than quickly after, second sparkplug fires measuring combustion quality. Next engine cycle they swap places thus previously second sparkplug fires first and first sparkplug now fires second and so forth (In the video below given reason for alternatively swapping firing order is to eliminate piston hot/cold side).



starts 16:11
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Re: Ion Sense

Post by OrchardPerformance »

RusEFI now has some mazda ion coils for test.
Got me 4pc here and will be sacrificing one to see what we can learn about the internals.

Boots do come off if you pull hard enough and the inside of the boot is just a tube with a spring inside, zero ohms, dumb coil spring.
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Re: Ion Sense

Post by OrchardPerformance »

Time for a plug hunt boys. Basic dimension sketch below.

Pins are about 4mm down from the top inner surface
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Re: Ion Sense

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Plug pic for anyone needing a good view of it.
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Re: Ion Sense

Post by AndreyB »

@XDA says that Red Top Audi COPs could be ion-sense "compatible" same as our favorite saab/mazda COPs
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ssmith
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Re: Ion Sense

Post by ssmith »

I read through this thread, and am starting to process some of the academic papers regarding ion sense. So forgive me if I'm asking obvious questions.

BMW S85 (and presumably S65, but it looks like they moved the electronics into the ECU) use dumb coils, and have electronics that apply the bias voltage and amplify the ion current signal. Would that solution work with any other BMW dumb coil, or is there something specific to the S85/S65 coils that allows that to happen? The S85 coils are unique to that engine (and the S65 coils are unique to the S65) and aren't cheap, so if I could get away with the ones I have that'd be great (I have a BMW N20).

Mazda Skyactiv coils seems like another good choice, especially since they have built in ignitors. Do you know what kind of circuit is needed to read the current? Some Mazda documentation says "Pulls in current (4) increased by current amplification circuit (3) to the ignition coil from the PCM." Does that simply mean I provide an output with a pull up resistor, then measure the voltage to calculate the current drawn? Also do I just hope the coil is the right length for the motor or are there easy ways to make it fit (I saw reference to spark plug extenders, but google says that can change the effective heat range of the plug?)

I see the Saab CDM but I want my own interpretation on the ion signal.

My application: I would like to play around with closed loop timing, trying to map peak cylinder pressure to a specific crank angle. I generally only care about full throttle as this is for road racing. I currently have a BMW N20 in an E46 chassis run with a Link G4+ Force GDI ecu along with a secondary ECU that I built to control boost (electronic wastegate), valvetronic, and monitor some digital sensors (oil level, combo oil temp/pressure sensor, etc). Would love to use RusEFI if you had a GDI ECU but it looks like you're not quite there yet.
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Re: Ion Sense

Post by OrchardPerformance »

ssmith wrote:
Sun Oct 17, 2021 10:52 pm
I read through this thread, and am starting to process some of the academic papers regarding ion sense. So forgive me if I'm asking obvious questions.

BMW S85 (and presumably S65, but it looks like they moved the electronics into the ECU) use dumb coils, and have electronics that apply the bias voltage and amplify the ion current signal. Would that solution work with any other BMW dumb coil, or is there something specific to the S85/S65 coils that allows that to happen? The S85 coils are unique to that engine (and the S65 coils are unique to the S65) and aren't cheap, so if I could get away with the ones I have that'd be great (I have a BMW N20).
The S85 and 65 coils have a connection across the secondary winding while the other bmw coils I have do not. It seems most of the coils have a "spark booster" gap in them intended as an anti plug fouling measure. This makes reading a voltage across the gap in the secondary impossible.
You can check if it is possible to use a coil with a custom board by trying to measure the resistance of the secondary winding (plug tip through to connector pin).
ssmith wrote:
Sun Oct 17, 2021 10:52 pm
Mazda Skyactiv coils seems like another good choice, especially since they have built in ignitors. Do you know what kind of circuit is needed to read the current? Some Mazda documentation says "Pulls in current (4) increased by current amplification circuit (3) to the ignition coil from the PCM." Does that simply mean I provide an output with a pull up resistor, then measure the voltage to calculate the current drawn? Also do I just hope the coil is the right length for the motor or are there easy ways to make it fit (I saw reference to spark plug extenders, but google says that can change the effective heat range of the plug?)
We are a bit stuck with the mazda coils. I dissembled one to show the insides and it was a very simple circuit. We tried one on an engine and it gave no signal regardless of what we did with the signal pin.
We tried:
Pull up to 5v,
Pull down to earth
Various amounts of resistance

I managed to get some kind of signal out of one in free air by PWMing the signal pin up to 5v shortly before firing the coil, but it seems like that did not want to work on an actual engine.

We need to know what the mazda ECU is doing to the signal pin to be able to get the signal out of the coils. This probably means trying to scope a car or opening up a mazda ECU.
ssmith wrote:
Sun Oct 17, 2021 10:52 pm
I see the Saab CDM but I want my own interpretation on the ion signal.
Me too, I am not sure how practical this is but it would seem that first off we might need to get the saab CDM working and then replicate its functions or use it as a benchmark to build our own.
ssmith wrote:
Sun Oct 17, 2021 10:52 pm
My application: I would like to play around with closed loop timing, trying to map peak cylinder pressure to a specific crank angle. I generally only care about full throttle as this is for road racing. I currently have a BMW N20 in an E46 chassis run with a Link G4+ Force GDI ecu along with a secondary ECU that I built to control boost (electronic wastegate), valvetronic, and monitor some digital sensors (oil level, combo oil temp/pressure sensor, etc). Would love to use RusEFI if you had a GDI ECU but it looks like you're not quite there yet.
We are a little bit away from GDI for now. Maybe that is something we could hope to do in 2022 but no promises.
We have done a little bit of work towards the valvetronic on the N52, I pulled apart a sensor and we found the data sheets that give the data protocol. N series is something we collectively would like to do but there is limited resource to apply to it currently.
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ssmith
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Re: Ion Sense

Post by ssmith »

We have done a little bit of work towards the valvetronic on the N52, I pulled apart a sensor and we found the data sheets that give the data protocol. N series is something we collectively would like to do but there is limited resource to apply to it currently.
A little off topic, but: I don't know much about the N52 valvetronic, but for the N20 it's a BLDC motor with 5 hall effect sensors. 3 for major position (corresponding to the power leads) and 2 for "minor position," which I interpret to mean 1/4 steps between the major positions. I used three BTN8982's to power the motor and was able to open and close it without a problem. In practice I just open the valvetronic all the way and use the throttle body; I run speed density and thus need the MAP signal to regulate fuel.

I just took a quick look on newtis and it seems the N52 is a more traditional brushed DC motor, and as you say some digital sensor with a data protocol. Very different beast.
We are a bit stuck with the mazda coils. I dissembled one to show the insides and it was a very simple circuit. We tried one on an engine and it gave no signal regardless of what we did with the signal pin.
Did you try the 80V-300V bias? Or were you hoping the coil did that for you? At least the S85 module claims to provide that by capturing some spark energy.
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Re: Ion Sense

Post by OrchardPerformance »

So the mazda coil has some electronics in it but getting them out did some damage, we think the mazda coil is self charging for the ~300v.
We did get some info from a working CX-5 and it seemed to only be 5v on that signal line.
Its very strange.

It makes me think I should go destroy another one as I found a better way to get the epoxy off.


N52 is the older valvetronic, your n20 sounds like the newer version, our biggest challenge for the newer version is the BLDC motor and the required logic to control the valve lift.
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ssmith
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Re: Ion Sense

Post by ssmith »

OrchardPerformance wrote:
Tue Oct 19, 2021 9:33 pm
The S85 and 65 coils have a connection across the secondary winding while the other bmw coils I have do not. It seems most of the coils have a "spark booster" gap in them intended as an anti plug fouling measure. This makes reading a voltage across the gap in the secondary impossible.
You can check if it is possible to use a coil with a custom board by trying to measure the resistance of the secondary winding (plug tip through to connector pin).
Well, I tried that with a set of S65 coils and N20 coils; neither would read resistance from plug tip to any of the 3 pins. I also tried the diode setting and got nothing (which seems extra bizarre).

On the plus side, the S65 coils fit my motor just fine (though the connector is different, seems to match the hpfp sensor - Kostal 9-4413-91).
N52 is the older valvetronic, your n20 sounds like the newer version, our biggest challenge for the newer version is the BLDC motor and the required logic to control the valve lift.
As I mentioned before, three BTN8982 run it just fine. Though I only run it with the engine off. As for control logic, what I've found with the throttle body at least is that the % pressure drop across the throttle body depends only on engine speed and throttle position, not charge pipe air pressure. I actually use this to get short term boost control as an electronic throttle responds much faster than wastegate / spinning turbo, and thus means that you can spike boost more quickly without having to taper off the boost as you get close to your target. I imagine the valvetronic is similar in that the air flow depends on MAP Pressure * table(RPM, Lift), but I don't know for sure.
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Re: Ion Sense

Post by ssmith »

Hmm, seems S65 coils works differently. According to: https://ia801005.us.archive.org/11/items/BMWTechnicalTrainingDocuments/ST709%204th%20Generation%20M3%20Complete%20Vehicle/04_MSS60%2520Engine%2520Management.pdf
the ion signal is actually sent over the primary ground line, not over the secondary. I think I need to hook an oscilloscope up to my friend's car and see what I can figure out. It looks like the coils might have built in ignitors, in which case these are smart coils with only three pins.
OTOH the graph they show indicates the signal may not be able to show the peak pressure position, but instead may just be some amorphous integral of "quality."
daveblanchard
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Re: Ion Sense

Post by daveblanchard »

Hello all, I'm following this thread with interest. I would like to use ion sense ignition on an old engine powered by a wood gasifier. The gas generated by a gasifier varies widely in H2/CO content depending on many conditions, like type of wood used, operating temperature, engine speed, etc etc, and this greatly affects the burn rate and thus the optimum timing. With ion sense ignition, it should be possible to 'autotune' the timing automatically, greatly improving power, fuel economy, etc.

Would it be possible in theory to build an ion sense circuit that would work on a distributor ignition, with something like an old GM HEI ignition coil and CDI ignition? Or is coil on plug absolutely essential? What is the actual design difference between a standard coil and ion sense coil?

Thanks...looking forward to seeing how this thread develops. :)
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Re: Ion Sense

Post by daveblanchard »

Doing some more thinking on this--given that peak pressure detection is the main item of importance to my application, and knock detection is of no use whatsoever (with wood gas being around 120 octane), is there any reason why I couldn't use a basic single spark (or, if feasible, multi-spark) CDI ignition with standard HEI coil on a distributor, and then have a (shielded) probe wire going to a single spark plug terminal, which does PPP detection on that single cylinder after the spark has fired, and uses that information to adjust timing on all cylinders?
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Re: Ion Sense

Post by OrchardPerformance »

@ssmith - There does not seem to be any IGBTs in the MSS60 ECU which as you say would suggest smart coils. 3 wire is weird as you need 3 for the smart coil and a 4th for the ion signal.
So yeah, with you on that, not sure what is going on there.
Documentation for the S65 also seems to be junk compared to other/older BMW literature. BMW being trash after ~2005 is not a meme.

@daveblanchard - Ion sense of the kind we are talking about will not work with a distributor as you need an uninterrupted connection from the negative side of the secondary coil to the tip of the spark plug.
You can indeed do a positive side setup but you are looking at significantly increased difficulty due to having to deal with the spark energy and the need to switch the unit on and off between spark events, bosch did some work on ion sensing on the active side of the coil, might be worth a look into.
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Re: Ion Sense

Post by OrchardPerformance »

oh wait, I have just figured out what they are doing....

They are smart coils, the trigger line is also the ion feedback line.

I am not sure how we would interface with that based on the way RE ignition drivers work, it might make sense for you to take a look at the mazda or SAAB coils instead.
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