Catching car's ignition signal - Page 1
Forum section: electronics / projects

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 03, 2020, 07:48:51 am
content: Hey guys.I have 12V and 2 signal wires coming out of the ECU into the ignition coil pack. To my understanding, they are active low signals, which means they get activated by the ECU with low signal (ground). I'd like to catch that signal (individually) and I have problem reading them.If I just connect the scope to a signal wire, it looks like this:Spark is active for 3-ish milliseconds and then it bounces back to 12V and repeats the ignition again.If I cut the wire and connect the wire coming out of the ECU to 12V using a pullup, I get 12V like I should (I get 12V without the pull up as well) and it does not change when I crank. I tried different resistor values, even pull down - no change. Just as if ECU is not triggering it. What could be the issue?

author: Benta
author_rank: Super Contributor
timestamp: August 03, 2020, 11:08:25 am
content: ECUs are very often smart enough to detect a wrong load, eg, your resistor.

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 03, 2020, 01:09:48 pm
content: Good point - but i guess ECU would try at least once?

author: Benta
author_rank: Super Contributor
timestamp: August 03, 2020, 03:37:58 pm
content: Quote from: cmcraeslo on August 03, 2020, 01:09:48 pmNot necessarily. It'd normally do a system self-check when starting. If it finds something wrong, odds are that the ignition won't be released.

author: David Hess
author_rank: Super Contributor
timestamp: August 03, 2020, 08:32:56 pm
content: If it is driving the ignition coil directly, it could be looking for the series resistance of the primary; use that for the value of your pull-up resistor.

author: Circlotron
author_rank: Super Contributor
timestamp: August 03, 2020, 11:47:21 pm
content: Quote from: David Hess on August 03, 2020, 08:32:56 pmI think you’re on the right track, but modern coils often have a primary resistance of something like 0.5 ohms but they get switched off for the spark at 7-10 amps or so. So a resistor of 1.5 to 2 ohms might be about right. Lots of watts though.

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 04, 2020, 06:06:55 am
content: I tried with 3 ohm resistor (didn't have any lower at hand) and it started showing something so it's definitely the right way to go. Because I only want to get the signal out of the ECU and not waste power (unless needed), is there any other way to detect this signal? (if we ignore that ECU detects the error in the coils) ?

author: Circlotron
author_rank: Super Contributor
timestamp: August 04, 2020, 06:28:40 am
content: If the ecu is detecting a lack of current in the switched load then it must be switching it to ground to measure it. Perhaps the negative going pulse is only very short and you are missing it with the timebase the scope is set on. Speed it up a bit. Make sure you use some kind of pull-up resistor, say 100 ohms for this test.Maybe it pulses just once then locks out.

author: Labrat101
author_rank: Unknown
timestamp: August 04, 2020, 08:35:24 am
content: Hi we help develop a car diagnostic system . about 5 years back.What you are looking at is just part of the story .. Car ignition varies from make / Model /year / engine size/ compression ratio / altitude / O2 % .. etc .The ignition system is controlled by the central computer which measures about 8 sensors from the engine and fuel .The pulse you are seeing is about what you will see . from a GP scope . be careful your scope is mains grounded ..you have to use the diag plug with a loop back to tell the on board computer to output the correct signals .and you need the the manufactures data for you Car as every model differs .You need to use the correct Diag equipment .The signal you are seeing will not be of any use as this is only 1 fire pulse without the time from TDC -8 -10 deg.Have funBTW if you really like your scope Don't use it on a car ignition system without Isolated clap over probe .Update .. 2 quick details ..1 . remove the plug from the engine connect it to the lead and rest the case of plug on chase on engine ground.if there is a spark its good. Clean all plugs.2 60% of engine problems are caused by the immobilizer system .. check first

author: mikerj
author_rank: Super Contributor
timestamp: August 04, 2020, 09:27:21 am
content: Quote from: Circlotron on August 03, 2020, 11:47:21 pmWith an ignition coil the primary current will (relatively) slowly ramp up to the desired final value, with a dummy load resistor it will be immediate. If the ECU has closed loop control of coil dwell time this could cause it problems.

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 04, 2020, 09:35:05 am
content: Hello.@Labrat101 - I'm not trying to diagnose the car's issues with this.What I'm trying to do is to build ignition cut device, that is catching the signal, "processing it" and then output it. I have the device working on a car with ignition drivers built in the coils, but not when coils are directly driven.Device uses very sophisticated cutting strategies, so it's not just "coil off" cutting so I need to have clean signal coming in constantly so I can process them correctly.@mikerj - that is very advanced control. Do you know how many cars use this? This could be a deal breaker for me for sure.

author: Labrat101
author_rank: Unknown
timestamp: August 04, 2020, 10:06:33 am
content: Ok that you can do by using an induction pick up .There are clamp over that can be bought ..But as you are building it . I would use ether a Hall effect transistor or a ferrite ring with a few turn .I don't fully understand why you are doing this .. you are supping up an old carif so you have to add the N02You are getting into to some heaving stuff . good luck

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 04, 2020, 10:53:42 am
content: @Labrat101 - You don't understand. I need to cut the signal coming out of the ECU. I can do pickup reading on connected coil, but it's not connected in my case. I dont know how to explain it otherwise

author: Labrat101
author_rank: Unknown
timestamp: August 04, 2020, 11:28:34 am
content: Quote from: cmcraeslo on August 04, 2020, 10:53:42 amOk .I think I know what you are trying to do .But I have this feeling your are working on a industrial Project .By they way you are keeping 95% of what you are reallydoing Not told . You have already invested some very expensive equipment in this update to a ignition system.QuoteTo break a signal is really not Hard but if this is for commercial gain and NOT a hobby etc.Sorry I am out . TTFN

author: HighVoltage
author_rank: Super Contributor
timestamp: August 04, 2020, 11:38:20 am
content: Best to use is a current probe to watch the ECU signal.Most of the time it is around 10 mA to 20 mA but some latest systems have less than 1 mAAlso, some systems use the amount of current from the ECU to the coils as a signal to get thecoil in to different mods. And others use the current as a feedback from the coils to tell the ECU how the last spark performed.There are many different systems around these days.What car is it and what is the coil being used?

author: Circlotron
author_rank: Super Contributor
timestamp: August 04, 2020, 12:01:27 pm
content: Quote from: cmcraeslo on August 04, 2020, 09:35:05 amAre you making a rev limiter? If so, it might be easier to cut the drive to the fuel injectors instead. Easier on the catalytic converter too. No unburnt fuel going out the exhaust and no bangs and pops.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 04, 2020, 12:08:54 pm
content: Quote from: cmcraeslo on August 03, 2020, 07:48:51 amQuoteI'm not too surprised by your first post. I had made an engine simulator for my bike. Getting the ECM not to fault out on the ignition coil took some effort. Attached a couple of pictures of the that load which was a custom made pot core that I mounted inside an aluminum housing and mounted to the case to draw the heat away. The driver basically is a HV FET that can load the secondaries to cause the ECM to fault under software control. This ECM is fairly low tech and I wouldn't be surprised to find the load requirements for an auto to be more critical.Are you trying to make some sort of governor (2-step, studder box...)? Is the car injected? If so, are you handling the fuel as well?In most of my setups, I am using aftermarket electronics which provide a kill signal input. In the case of this stock ECM, I am using some changes to the OEM software to perform the kill. The simulator in this case allows me to test different software without the need of running an engine.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 04, 2020, 12:10:19 pm
content: Quote from: Circlotron on August 04, 2020, 12:01:27 pmWhere's the fun in that??!!

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 04, 2020, 12:57:36 pm
content: Quote from: HighVoltage on August 04, 2020, 11:38:20 amIf I understand correctly, you mean current probe on the wire from ECU to a 10k (as an example) pullup?Test car I have is Mercedes Benz A160.I have successfully tested this on a coilpack that has integrated drivers (VW).

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 04, 2020, 12:59:30 pm
content: Quote from: CirclotronNo, I'm making flatshift (ignition cut) device. I have it working on a coilpack that has integrated drivers, but when ECU is driving the coils directly, it doesn't work.

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 04, 2020, 01:03:47 pm
content: Quote from: Labrat101I'm building an ignition cut device (that will allow me to shift while on full throttle on racing gearbox) and it has very sophisticated algorithms to cut it so I need to process the ignition signals very precisely and time it. I have it working fine on a coilpack with integrated drivers, but it doesn't detect the input signal on cars that ECU drivers the coils directly.

author: Labrat101
author_rank: Unknown
timestamp: August 04, 2020, 01:40:04 pm
content: you have a few choices Hi voltage IGBT or FETI think IGBT maybe a better choice and have them oil mount cooled .There was a post a few up used Hi voltage Fet's Both will give you the fast response time.I have never tried this we only build the plug module for diag plug 5 yrs back for standard cars . Auto Test.if its for racing is it a 4 or 8 cylinder just for interest ..Photo's word help as wellMr joeqsmith maybe more your Man ..Have fun

author: Circlotron
author_rank: Super Contributor
timestamp: August 04, 2020, 01:40:34 pm
content: Quote from: cmcraeslo on August 04, 2020, 01:03:47 pmYep, you definitely don't want to interrupt the coil while it is charging and consequently get a spark way to early! What about a single relay contact that cuts power to the fuel injectors, controlled by a microswitch on the clutch pedal? Why wouldn't that be good enough? Would the ECU throw an error with that?

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 04, 2020, 01:57:49 pm
content: Quote from: CirclotronIt's for racing application where perfect engine cut is needed to unload the gearbox properly. It's for racing gearboxes so no clutch between the shifts. This has to be timed perfectly. What you're describing is a full cut which is something that hasn't been used in this industry for the last 10 years or so (at least the proper ones). Fuel cut on the other hand is very slow and not really useful in my case.My device is capable of retarding timing of the original ignition pulse, then cutting the spark partially, depending on the configuration and load and making sure that the active spark is evenly distributed among the cylinders and then ramping the restore back to the original ignition timing. It's capable of doing this on up to 6 cylinders parallel, either wasted spark or sequential ignition.Now, I have this working perfectly on low power/current signal, but when I tried this on a stock car, with regular ignition coil, there was this issue i'm having. So I need to somehow catch this signal's timing when it's not connected to the coil directly.Driving the coil (output) is not a problem.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 05, 2020, 01:01:40 pm
content: Quote from: cmcraeslo on August 04, 2020, 01:57:49 pmIf we spun the motor at say 20,000RPM, or 333revs per second, or 3.0ms for one rotation. Using a fixed kill time of 20ms, that's 7 crank rotations. With your six cylinder we get 3 power strokes per rotation or 21 power strokes. For this example, it seems long enough that there may be some gains.My bike bike shifts under full load with no kill during the start (Robinson transmission). After that, it shifts at 9800 with a 20ms kill. So 20ms/6.12ms or 3 rotations. It's an in-line 4, giving us only 6 power strokes to work with. It's a 5 speed, so only 4 shifts on a pass and again, not all require the kill. Actually, with this type of transmission, using kill could damage it. Similar, if you chop the throttle, you can expect repairs.Your particular ECM may be looking for a certain combination of di/dt, peak currents and back EMF. I would just measure the coil that is known to work and replicate it as a starting point.

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 05, 2020, 01:15:41 pm
content: @joeqsmith - Like everything in life, having anything fixed is bad. Usually, you monitor the gear position and let it cut for as long as needed. So it differs from gear to gear. Also, retarding the ignition, rather than cutting it, is much smoother and effective.

author: mikerj
author_rank: Super Contributor
timestamp: August 05, 2020, 01:34:59 pm
content: Quote from: cmcraeslo on August 04, 2020, 01:57:49 pmWhy would fuel cut be any slower than ignition cut? With either one a cylinder could be cut for a single firing cycle if needed.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 05, 2020, 02:24:37 pm
content: Quote from: cmcraeslo on August 05, 2020, 01:15:41 pmThere are many many things in life that I like constant but I thought you were working on an ignition kill and not your philosophy of life.On the older bike, the ignition timing, boost, shift points and kill times are all fixed. It's KISS and reliable. The gains from the shift down track would be small compared to say adding another PSI of boost or just going on a diet.I assume you have data showing the effects of the shift using various techniques. That would be very interesting to see. No need to disclose anything proprietary about what you are doing but rather just show the end result.

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 05, 2020, 02:47:52 pm
content: Quote from: mikerjOn full throttle, the amount of fuel going into the intake is huge, basically, you could fire all injectors at once all the time and it would not make a difference (would just be more fuel consuming). It takes some time for the air and fuel to mix so cutting 1 or 2 cycles of the injector, does not make a a lot of difference in reality. This is needed when shifting gear because the reaction needs to be instant and the longer you unload the engine, the harder it will shift. Ignition on the other hand is what drivers the car so every interruption in that, disturbs the car, which is what is needed.

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 05, 2020, 02:57:27 pm
content: Quote from: joeqsmithLOLQuote from: joeqsmithUnfortunately, I cant show you the graphs as this is the knowledge we've gathered in the last 15 years in motorsport industry.It's not just about the shift speed gain - the duration of the "cut" (and the cutting strategies used) determine other factors - stability of the bike/car in tricky conditions, smoothness of the shift (engine likes smoothness and so does the gearbox and all other components). If you have 24 hour race rough fixed shifting, you'll probably end up failing the race.If you're too long on the cut, this brings all kind of troubles, so does cutting too fast. Each gear is different - let say you start loosing a gear in a race. Once this starts happening, with fixed timing, you'll just destroy everything and not finish. Cutting the engine (with combination of rev matching) helps on downshifting as well, cutting too long will drop the rpm and make it rough as hell, possibly loosing the grip. This can be a huge problem in the rain. Just to name a few.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 05, 2020, 04:41:42 pm
content: Quote from: cmcraeslo on August 05, 2020, 02:57:27 pmI collect a very little data compared to say an F1 team but it would be trivial to show you what I have. You've never mentioned what the application was. Maybe you are not allowed to log the data. I wondered that with the control. I've seen in some racing were the do not allow for any type of electronics control. Don't ask me how that would even work today.My hobby is a fair bit different. You have 24hours of racing, I have a few seconds. You have to be concerned with downshifting. The only time I think about that is going from third back to first after warming the tire. The air cylinder can only upshift. Any downshifting is done manually. I've damaged transmissions before I switched to using the Robinsons. Because of the auto, as I mentioned they can be damaged by backing off the throttle. In one of your 24 hour races, you would have traveled more miles that I would put on my bikes for their entire life.Interesting to hear more about your team and what they are doing. Do you have a website?

author: joeqsmith
author_rank: Super Contributor
timestamp: August 06, 2020, 03:14:47 am
content: Quote from: cmcraeslo on August 05, 2020, 02:47:52 pmWhat about diesels and HCCI?

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 06, 2020, 05:37:53 am
content: Diesels have very precise fuel timing so it's different of course. In that case, fuel cut is the way to go. But I'm doing this for a petrol engines

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 06, 2020, 07:31:33 am
content: Quote from: joeqsmithWe do not have a team (although it started with me racing and doing stuff for myself).We manufacture high performance paddle shifting (currently only pneumatic actuation) for various teams and automotive sports. Including 24 hour races, drag racing, hill climb like pike's peak etc.Our web page ishttp://www.mme-motorsport.com

author: joeqsmith
author_rank: Super Contributor
timestamp: August 06, 2020, 12:37:45 pm
content: Looks like you make some very nice products.I wonder if you do any sort of HIL testing? This like shows a bit of my simulator. It's basically all digital and can provide timing data for the injectors and ignition. I can't use it to tune an engine but for testing out various shift algorithms, it works great. You can program things like clutch slip.https://youtu.be/q_89qoFMivg?list=PLZSS2ajxhiQBvWvqMVLdRQMjGofKpQUJr&t=2313With this setup, both the injectors and ignition are modeled from standard parts. The ECM had no problems with the fuel injectors but it wants something fairly close for the coils. This engine doesn't use wasted spark like my older ones. I was able to simulate all four coils with a common core and not have it fault out. It was a bit of a surprise as they obviously couple but their firmware must ignore the signals except when the selected driver is active. Obviously there's no need for any high voltage so I think I stayed with a 1:1 turns ratio. There is a zener/FET to simulate the plug's breakdown.You may need to try several cars you plan to target and just see how they work. Maybe there is a generic solution.

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 07, 2020, 07:04:31 am
content: Nice setup you got there. The fuel system simulator - is that your own creation?I usually deal with aftermarket ECUs, this is the 2nd or 3rd time that I'm trying to do anything "ignition like" on the standard ECU. I have engine simulator, that is able to generate wheel triggering and if you hook up original ECU, it does the cranking, firing up the coils etc. I cant use it in this case as this particular ecu has immo so it doesn't fire up and I wanted to make it simple. As I said, when ecu is operating with low power signals, I can handle that and I'll probably just make an external box that will catch high power signals and convert them into low power (and vice versa).I'm going to try few other ideas from this topic next week and report if i'm able to get anything on the scope. Current measuring seems pretty good idea although catching correct dwell will probably be tricky in this case due to different firing ramp. What I dont want is to have this tweaking for every other car. Seemed very straight forward job from the distance

author: mikerj
author_rank: Super Contributor
timestamp: August 07, 2020, 08:08:24 am
content: Quote from: cmcraeslo on August 05, 2020, 02:47:52 pmGreat in theory, but popular motorcycle quickshifters such as the Power Commander manage to work perfectly well by cutting fuel.

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 07, 2020, 08:21:39 am
content: Motorcycle has never been hard to shift at full throttle. They're very light, basically no load on the gearbox, low torque and very high rpm - you can shift that as long as you're able to disturb it a little. With cars, it's a lot different. Add a turbo with huge load and it will very different scenario. That's why, the solenoid shifters work well on bikes, but struggle with cars.

author: mikerj
author_rank: Super Contributor
timestamp: August 07, 2020, 10:19:21 am
content: Quote from: cmcraeslo on August 07, 2020, 08:21:39 amNo load on the gearbox because the quickshifter cuts fuel to remove loading!A friends rally car has a 2L engine making around 285bhp at ~9k RPM with a Sadev sequential gearbox which uses fuel cut for shifting as well, so car engines are not really different. However with a monster turbo pushing large quantities of fuel into the cylinder I can understand how this could be a problem.

author: cmcraeslo
author_rank: Regular Contributor
timestamp: August 07, 2020, 11:26:13 am
content: @mikej - would love to see your friend's parameters for the flatshift. Does he only uses fuel or adds fuel cut to the ignition cut/retard combination (that would be my guess).