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Ion-sensing w/knock control


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My understanding is an ION-Sensing system is very sensitive and able to make adjustments as necessary for each combustion cycle. Using a small electric current running through the spark gap, it can sense combustion efficiently, and detect knock with extreme accuracy. Again my understanding is this type of system is superior and less costly then a "knock box". Try and put yourself in the manufacturer's place. My guess is since Link has created their own seperate detection system and need to realize a return on their investment, it does not make sense to engineer a new strategy, even if it's better and more cost effective then their existing design. I was really hoping LINK was going to engineer ION sensing ignition system. Ashley, thanks for responding to my earlier post, and please let me know if I'm on the mark here. Best regards, Mo-

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I've had a look at the information you have provided. Seems like a good idea, but i  disagree with "Again my understanding is this type of system is superior and less costly then a "knock box"." for the simple fact that 99% of vehicles on the road do not run CDI from factory which means this would need to be installed before even considering the costs of the knock controller. Installation would also be far more difficuilt as each spark plug needs its own interface, where with the standard method one knock sensor can be used to detect individual knock on up to four cylinders using data windowing techniques.

We appreciate the suggestion but I don't think any development will be done on this anytime in the near future.

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  • 1 month later...

Hi Morris,

   Thanks for taking the time to look into ion sensing.  We appreciate your feedback.  As with all feature requests, your ideas will be added to our requests list.  All requests are prioritised based on customer and dealer feedback and scheduled for development.  Should ion sensing become a highly sought after feature you can be assured that it will be added to our ECUs in good time...

Ashley

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  • 1 year later...
  • 7 years later...

+1 for this suggestion! knock detection, particularly on older engines where a suitable location for your joe average piezo sensor is not provided, is made difficult. sure, there are plenty of free softwares online to do a bit of signal conditioning but it's still compromised. given that smart coil packs with ion sensing technology is now common place (since the late 90s!) and that these coils are a cheap and easy upgrade an old distributed spark setup (for the old donk enthusiasts especially!) when fitting a Link ECU, it'd be great to be able to use this to our advantage!! :D certainly a lot cheaper and more convenient than fitting pressure sensing spark plugs! 

as a bit of an adjunct to this, is there any way we can log the ion sensor signal at the ECU? 

 

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  • 2 years later...

Just read about this technology and I'm excited. My understanding of the probmems is pretty basic of course, but It seems that it just needs some work work on software side to support certain smart coils / hardware and should be pretty usable. 

I saw some open source projects experimenting with this quite successfully!

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I think it is interesting technology when you look at prospects of closed loop peak cyl pressure angle control, but I think that is still a long way off the aftermarket world.  As for ion current knock control, it is not very useful in anything but OEM applications, there are just too many combustion irregularities to allow it to be implemented in a DIY scenario.   On the moderm BMW's with it for instance even a small change to the fuel mixture completely upsets it.  

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From what I read by now there are OEM components these days that output signals that are ready to be used. Like Saab's Trionic 8 system. Ionisation module gets 4 ignition inputs from ECU an 4 inputs from ion sensing coils and generates three digital output signals to the ECU - knock and combustion event signals for cyl 1-3 and 2-4.

With ionisation module and separate coils, I assume that this system it already can be used instead of external knock sensing device, for example. 

I'm not sure if combustion signal is interesting and useful for other things instead of detecting misfires, but as I can see what people trying to achieve now is to use raw ion sensing signal processed by ECU to determine peak cyl pressures.

I kind of suspect that right now I'm closing to the peak of Mount Stupid, but seeing what is being done now by diy community, with this technology in use theese days by many major manufacturers and being proven by Saab since 1993... I think it has good potential.

I just tried to setup knock control on my Subaru and I understand that it's efficiency veeery dependant on settings. I'm closer to Valley of Despair with this one :))). First I had quite aggressive settings and it pulled a lot of timing because I got lots of noise up top. Now I sort of quiet it down so I can see anomalies that look like real detected knock events - I can't hear any knock via wideband knock sensor connected to headphones and confirm it. Up top engine is quite noisy so frankly I can't understand how anyone can hear anything there... Also I gave a problem with false knock on transitions or gear changes...

Honestly, earlier I thought that getting good ECU with knock settings like windowing and stuff will be a silver bullet and can rely on it as a safeguard, but now I understand that it is only as good as (probably) the rest of the map is :)

This system to me looks superior (in term of knock detection) because it's solely based on combustion process analysis and free of noise from other engine components. Other potential applications are just a bonus.

I'm just a bit afraid to fry my ECU :unsure::D

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3 hours ago, HomebuiltRacing said:

From what I read by now there are OEM components these days that output signals that are ready to be used. Like Saab's Trionic 8 system. Ionisation module gets 4 ignition inputs from ECU an 4 inputs from ion sensing coils and generates three digital output signals to the ECU - knock and combustion event signals for cyl 1-3 and 2-4.

Yes, and it will work well when the spark plug is inside an unmodified Saab engine with exactly the same combustion characteristics that it is expecting to see.  

 

4 hours ago, HomebuiltRacing said:

I'm not sure if combustion signal is interesting and useful for other things instead of detecting misfires, but as I can see what people trying to achieve now is to use raw ion sensing signal processed by ECU to determine peak cyl pressures.

The crankshaft angle that peak cylinder pressure occurs at is the fundamental variable in achieving peak torque/efficiency.  It varies slightly from engine to engine but generally around 14Deg ATDC.  The whole reason for your ignition map is to try to make that pressure peak occur in the right place under all operating conditions.  But typically measuring it (cylinder pressure) requires very expensive and fragile equipment so it is usually limited to very highend engine development or OEM's.  

 

4 hours ago, HomebuiltRacing said:

This system to me looks superior (in term of knock detection) because it's solely based on combustion process analysis and free of noise from other engine components. Other potential applications are just a bonus.

I suspect it is when highly optimised by an OEM - but first you will need probably 100's of hours of development to first get the combustion stable enough so that ion current from event to event is predicable (and you need ICPM to do that) - then many 100's more hours to tune the ion sensing to know what is normal and what is not - and this would probably be mapped in 1 deg crank increments in an OEM application.  But the problem is if you change anything that effects the combustion pressure and/or chemistry it will no longer be accurate.

Audio knock detection is very reliable, far less sensitive to mild changes in tune and will work well for most road car engines.  Yes, there are exceptions where audio knock detection doesnt work well (gravel rally cars and superbikes for example) but generally it is the best option for road car engines.  Like anything tuning related you need significant experience to get the most out of it.  

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7 hours ago, Adamw said:

Audio knock detection is very reliable, far less sensitive to mild changes in tune and will work well for most road car engines.  Yes, there are exceptions where audio knock detection doesnt work well (gravel rally cars and superbikes for example) but generally it is the best option for road car engines.  Like anything tuning related you need significant experience to get the most out of it.  

Thank you for clarification and your understanding to overexcited beginners like myself :)

Regarding audio knock sensing, can you advise any commonly available knock sensor with good known calibrations to start with? To be an upgrade for 97 Subaru with (fresh) 1-wire  sensor? I'm progressing with settings on my setup but I still can't rely on it 100% especially on high rpm where engine becomes noisy. Btw, is there different practical rpm limit for different sensors? Like if newer wideband ones are better in any way? Probably simple solution will be to get external knock box, but in my understanding it's basically the same thing but with fixed settings that someone did for specific sensor.

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