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Thread: DIY LTCC or similar system for LT1s

  1. #526
    Fuel Injected! spfautsch's Avatar
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    I had a chance to do some preliminary testing on the D580 and D581 coils over the weekend, and the results were very promising. I wasn't able to perform any measurements other than observing the timing and quality of spark produced, but nothing thus far leads me to believe any of the common GM coils have significantly different igniter current requirements.

    Quote Originally Posted by kur4o View Post
    Someone knows a good, DYI method of measuring dwell time and the current that the coil draws from the pcm.
    I think that the resistors are kind of current limiting device protecting the chip. So how much is needed to ignite the coil and can that be measured reliably without a scope or some fancy equipment.

    I managed to confirm the resistors value on the 1mb pcm with blue color. It is again 430 ohms.
    Those resistor values are only relevant for the igniter circuit - think of it as a low-level trigger. These draw an incredibly small amount of current at TTL levels (0 to +5v). On the other hand, the current being referenced in what you quoted is primary current (the 12v input) on the coil and this is the amplified signal that results from the igniter IGBT / MOSFET and will register a significantly larger power level. This is what puts power into (aka "charges") the coil and is fed by the circuit I was mentioning might need a larger fuse due to more than 2 coils being charged at one time.

    I have a methodology mostly fleshed out for testing things, and will try to document my process very thoroughly. And believe it or not I actually have some formal training in electronics engineering, unlike all my other "skills" which are completely self-taught.

    I have an adjustable power supply on it's way (from China) and the v1.1 circuit boards should be here tomorrow, so with any luck I should be able to do some fairly thorough testing this coming weekend and through next week.

    The method you quoted for measuring charge time until what they refer to as "current limiting" is mostly accurate, but somewhat flawed. Most of these coils have built-in dwell limiting logic that takes into account all the variables (system voltage, temp, etc.) and starts to clamp charge current after reaching some pre-determined maximum charge state (measured in Joules). Ideally, we want to find the amount of charge time (dwell time) that provides the maximum discharge energy well before incurring the coil's dwell limiting. So to jump off on a tangent, with coils that have built-in dwell limiting it would be incredibly hard to actually cause a coil to fail due to over-dwelling. It's not clear whether the D580 coils have this function, but I intend to test and hopefully determine scientifically for these as well as all the others.

    I wish I had the time and patience to try to convey everything I've learned about how inductive discharge systems work over the past year, but it's been a long day filled with idiots complaining about their inability to make phone calls, so I'm going to decompress now with a double (ok, quadruple or sextuple) bourbon. But believe me when I say I'll do my best to clear up all the mystery after I've been able to give all five of the coils I have a thorough shake-down with instruments and what-not.

    Quote Originally Posted by kur4o View Post
    The baseline of measuring is 12 volts. At 12volts the voltage correction must be zero. Below 12 volts the correction is positive and above 12volts the correction is negative.
    We're making the tables from scratch, so it doesn't really matter what we consider "nominal" system voltage - 12, 14.4, 13.7, etc. it's all a linear equation that arrives at the same result. As evidenced by the GM dwell vs temperature tables, using 0.864 (the 2014 corvette bin) as a default dwell multiplier is evidently more meaningful than 1.0. So clearly I'm stupid in this regard. But I have two twenty-something children, so I've become fully accustomed to being "stupid" since each of them turned fourteen.

    Quote Originally Posted by kur4o View Post
    You can be suprised but the end of injection target calculations in ls1 pcms is borrowed from $ee code, so it is continuous code upgrade in the years. If you missed the beginning, it will be very hard to understand the later code.
    That doesn't surprise me at all. I've worked with computer-illiterate types for the past 25 years, and learned first-hand how "we've always done it this way" becomes scientifically acceptable conjecture in such scenarios.

  2. #527
    LT1 specialist steveo's Avatar
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    it's definitely an evolution but also a case of it being really hard and taking a really long time to reinvent the wheel. 'we've always done it this way' is valid logic if you have a working system/product/whatever, there are reliability risks in ground up re-engineering. you should know that since you've so far successfully developed a distributorless ignition system that is exponentially less reliable than the optispark. i still love this project though and i'm sure you'll figure it out. the plastic black box that is the LTCC probably went through similar growing pains.

    just out of curiousity, does anyone know what the coil driver circuitry in the LSx ecms looks like? is there something in hardware that's more gentle with their coils? they never seem to burn up

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    Quote Originally Posted by steveo View Post
    you should know that since you've so far successfully developed a distributorless ignition system that is exponentially less reliable than the optispark.
    How so? The only major issue I recall him reporting ended up having nothing whatsoever to do with the LTCC, and everything to do with the optical disc in his optispark slipping by 30 degrees. That's not an LTCC problem, that's an opti problem.

  4. #529
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    Quote Originally Posted by steveo View Post
    that is exponentially less reliable than the optispark.
    Eh?

    We had a bit of a coincidence where my opti trigger wheel slipped, and vilefly burned up a logic pulser trying to drive some coils I hadn't personally tested yet and I jumped to the wrong conclusion in thinking the igniters were drawing more current than I thought they were. I will know for certain tonight, but I'm fairly positive his logic pulser died of natural causes or the lack of a capacitor to absorb the spikes when the coil discharged.

    Because of that scare I've chosen to buy test examples with the intention of verifying their function with the controller as well as to attempt to determine engineering data on their operational characteristics, because frankly there's no information out there that I trust. Not even the GM calibrations.

    Quote Originally Posted by steveo View Post
    just out of curiousity, does anyone know what the coil driver circuitry in the LSx ecms looks like? is there something in hardware that's more gentle with their coils? they never seem to burn up
    kur4o posted some pics and info a few pages back. There's almost certainly no problem with the circuit design - factory was using a 430 ohm resistor in series with the driver IC output pin, and I'm using a 470 ohm, both at TTL voltage levels.

    Nobody's burning up coils here, at least yet.

  5. #530
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    Just wanted to drop in with an update.

    First, the new rev 1.1 circuit boards came in last week. I built one out to use on my coil testing rig.

    After that I started working out the instrumentation I'll be using to test with.

    Digging through my toolbox I found some toroids (circular core transformer) I'd wound for an inductive power meter project that never got off the ground. These are essentially identical to a clamp-on inductive ammeter, except the core is one piece instead of split so the wires for the circuit to be measured need to be passed through the transformer. I'm using one of these to measure coil charging current - the power leads for the two different connectors are passing through it. I'll have to devise a way to calibrate it's voltage output into units of current (amps).

    For measuring the igniter current I simply soldered some leads across the 470 ohm R13 (see schematic).

    Today I had time to finish up a generic pulser sketch that uses timer1 and allows the user to change dwell and overall loop time through the serial "console".

    I decided to re-test all the coils I have for igniter current, and attempted to determine where dwell limiting starts based on primary current.

    Keep in mind the igniter current here is very low and the differences were small and difficult to pinpoint due to the noise being picked up on the leads (it seems to be the AVR clock signal). With this said I feel confident about the numbers in general. On the other hand, the dwell times are based on the best waveform I could get with the toroid in it's current configuration. I should be able to acheive more stable waveforms with some with fine-tuning of the toroid. Overall loop time was 50ms and the system voltage was a constant 12.9v provided by a big ass AGM boat battery.

    D580
    igniter current: 0.514 ma
    dwell limiting starts at: 4.6 ms

    D581
    igniter current: 0.471 ma
    dwell limiting starts at: 4.7 ms

    D514a
    igniter current: 0.471 ma
    dwell limiting starts at: 5.2 ms

    8183
    igniter current: 0.492 ma
    dwell limiting starts at: 3.7 ms

    D585
    igniter current: 0.471 ma
    dwell limiting - indeterminate

    I was intrigued by the D585 coil's behavior. I'll need to change the testing configuration to determine if the coil actually fires before the igniter signal is driven low. I tried dwell times up to 10ms, but couldn't tell if the dwell limiting caused the coil to fire. Unlike all the other coils, the primary current seemed to increase when dwell limiting came into play. This was confusing to say the least. Whatever the case, judging solely from the sound from the spark plug, spark energy increased proportionally to dwell up to about 4.6ms.

    Hoping to see the variable power supply next week so I can start testing across a range of voltages. In the mean time I'll work on adding another current transformer for the secondary side to measure spark current.

    vilefly - I don't know what killed your logic pulser, but I don't think it had anything to do with the igniter current drawn by the D581 coil. Perhaps it was reflected noise, old age, etc.

    Whatever the case, none of these coils present the slightest problem for the AVR's output pin capabilities. I don't know how any of the sources we looked to for igniter current came up with their "a few dozen milliamps" numbers, but it was clearly dead wrong.

    Edit: This afternoon I tried different divider resistors on the current transformer, and added one for the secondary side - fits around the plug's insulator nicely. I'm now getting a decent waveform of primary current, and an "okay" waveform of secondary. Of particular interest is the D585 coil. Dwell limiting on this unit is what I would call "absolute". Unlike all the others which demonstrate marked primary current reduction and oscillation at their limit point, the D585 coil just fires. At 12.8v that's happening around 4.6-4.8ms. This is dangerous - any calibration that's targeting more than this dwell time will ultimately have the coil firing ahead of the desired time, resulting in an increase in realized spark advance.

  6. #531
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    Hmm. Perhaps it was time for the 30yr old logic pulser to die. One too many abuses over time. Probably kickback voltage along the ground path. I wish I had more time these days. Don't know how you do it during the holidays, but this is good info.

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    I made some progress on ls1 disassembly.

    There are 3 dwell values calculated but it is not clear where they are used. It must be again some TPU usage.

    The first value is the BASE dwell. It is derived from the IGN vs rpm table.
    It is multiplied with the coolant vs ign multiplier and than multiplied with the map multiplier.
    Than it is stored as BASE_dwell.

    From the BASE_dwell a maximum and minumum allowable dwell variation is calculated.

    The MAX_dwell is base_dwell * max dwell vs rpm table and is stored.
    The MIN_dwell is base_dwell * min dwell vs rpm table and is stored.

    The coolant scalar is a coolant value scaled for the table. There isn`t any fancy conversion there.

    I am really interested in a hot coil test. Warming the coils to 80-100 degrees and run the test. I am still puzzled with the correlation from dwell times and coolant temperatures but they seem to be very important.

    I also have a running code for 68hc11 to calculate dwell based on the ls1 tables. I used it for another GM pcm that was retrofitted to run ls1 coils. On that pcm I can change dwell via obd and can run some experiments with engine running. The code can be transferred to lt1 pcm and based on my calculation the pcm can run dwell upto 1.5-1.8ms at 6000+rpm without overlapping coils.

    If you are willing to make a more close integration between LTCC and PCM we can setup dual mode. A cruise mode where the pcm calculates dwell and a power mode where LTCC commands dwell. The trigger will be from pcm pulling low a pin on the LTCC. In that case we can safely run the more dwell needed on startup.


    Since I am short on coils now, I will need to buy a new set. I made a furhte investigations on different coils and there are roughly 5 different types.

    1. square ls1 car coils made by denso.
    2. square truck coils made by mitsubishy form 99-06
    3. round truck coils[d585] made by Delco 00-06
    4. square coils from 07-18, I managed to find 3 different stamps on them through out the years.a delco stamp , a GM stamp and one with p/n stamp.
    5. round coils 07-18. couldn`t find much info on them.


    I suppose you have option 5 in your setup. Is that the best coil to have. Based on earlier round coil design I think they will have the best output with the shortest dwell times.

    I found somewhere that aftermarket coils have some crappy igniters that can cause all kind of problems. I also found some reviews that running too much dwell will damage the igniter and make it to preignite on shorter times. I am sure these are the myths that needs busting just like the few dozen milliapmps.
    What we might miss with the few dozen milliapms is that they might run the coils without the 430ohm resistor to limit the current. The igniter might be hungry for more amps if it is not limited.

    Did I mention that I managed to run the coil through a led and resistor. If we put leds on the circuit that might reduce the noise on the avr.

  8. #533
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    Quote Originally Posted by kur4o View Post
    The first value is the BASE dwell. It is derived from the IGN vs rpm table.
    It is multiplied with the coolant vs ign multiplier and than multiplied with the map multiplier.

    The coolant scalar is a coolant value scaled for the table.
    That was basically what I gathered from looking at the calibrations, minus the min / max value.

    For me, the takeaway from looking at the factory dwell tables was:

    1) the factory calibrations for all intents and purposes implement zero dwell compensation for MAP
    2) they seem to be reducing dwell as rpm increases
    3) temperature matters

    A little research led me to this page [link] which contained some information I hadn't found previously.

    I recalled from ee 101 30 years ago that temperature changed the resistance of copper but had long since forgotten the direction and magnitude.

    Quote Originally Posted by dtec.net.au
    Temperature will increase the resistance of the coil and wiring, ‘0.393 % per ºC’ is copper’s temperature characteristics so at 100 ºC its 39% higher, drivers actually have lower losses at higher temperature (semi-conductor materials used) and so help cancel out some of the temperature effect on losses.
    And I assume this is why the GM cals are reducing dwell with rpm (though at a relatively marginal rate).

    Quote Originally Posted by dtec.net.au
    about 0.6 ms of spark time is sufficient at high engine speed for good combustion due to the excellent mixture formation in the cylinders.
    Quote Originally Posted by kur4o View Post
    I am really interested in a hot coil test.
    As am I.

    Which is why I ran all the tests I mentioned previously with the coils at room temperature (~21c) and then repeated after letting them let them sit in my oven at ~80c for a half hour. I didn't post any of that information because I really want to get a more complete picture at different voltages. But since you asked, here's what I observed.

    Code:
    data format: [dwell time in ms],[system voltage],[coil temp deg c]
    
    D580 - dwell time before current limiting evident
    4.5,12.8,21
    5.0,12.8,80
    
    D581 - dwell time before current limiting evident
    4.6,12.8,21
    5.2,12.8,80
    
    D514a - dwell time before current limiting evident
    5.3,12.8,21
    7.3,12.8,80
    
    8183 - dwell time before current limiting evident
    3.6,12.8,21
    3.8,12.8,80
    
    D585 - dwell time before coil fires
    5.0,12.8,21
    6.0,12.8,80
    This is compelling evidence that temperature compensation would be a good feature to add. But as always, there's a catch - depending on mounting location, underhood airflow conditions, etc. coolant temperature simply can't be relied on as an accurate representation of coil temperature.

    Quote Originally Posted by kur4o View Post
    ... On that pcm I can change dwell via obd and can run some experiments with engine running. The code can be transferred to lt1 pcm and based on my calculation the pcm can run dwell upto 1.5-1.8ms at 6000+rpm without overlapping coils.
    Again, I mean this in a light-hearted way, but I think you might have a patching addiction. Also, 1.5-1.8ms of dwell at 6000 rpm should quite clearly explain the stern way I'm going to answer the next question.

    Quote Originally Posted by kur4o View Post
    If you are willing to make a more close integration between LTCC and PCM we can setup dual mode.
    I'm no more interested in discussing this than I was when you mentioned it previously. It seems very pointless. If you want to control dwell in real time you could more easily modify the controller code, or implement a feedback loop, etc. Integrating this into a 25 year old ecu via patches just seems like the wrong direction. But, as I shouldn't need to mention again the source is freely available. Fork your own version and call it something else if you so desire.

    By the way, "LTCC" is a product of Bailey Engineering. Let's stop calling what we've done here that please. Lest a cease and desist letter arrive in my mailbox for something I'm doing in a non, or more accurately, "negative" profit manner.

    Quote Originally Posted by kur4o View Post
    ... there are roughly 5 different types.
    Part numbers make that list meaningful. Without them you open the door for assumptions to be made, which breaks the scientific method.

    Quote Originally Posted by kur4o View Post
    I found somewhere that aftermarket coils have some crappy igniters that can cause all kind of problems. I also found some reviews that running too much dwell
    If you look hard enough you can find pretty much anything you (may or may not) want on the internet. Use much discretion in what you choose to believe, or believe nothing.

    Let me jump off on a slight tangent here - and rant a bit. When I publish my test data I fully intend to disclose the source of the coils I tested. There is one that came in a Delphi box, but could easily be counterfeit. The rest are asian knock-offs with the exception of the 8183 coils which I hope are the genuine article, but were sold as "scratch and dent" and didn't come in original packaging. My point here is that I'm funding this adventure with my own money, and not one of you has made a monetary contribution to the project in any manner even after I've asked repeatedly to borrow coils to test. So while I'd like to be testing only the genuine article, they're goddamned expensive. Testing salvaged parts of unknown condition introduces another variable in the scientific method. So I've bought the cheapest stuff I can, because at some point the notion of spending money from my own personal toy budget is going to get sour. In fact, I'm starting to taste it now. Stepping off the soap box now.

    Quote Originally Posted by kur4o View Post
    What we might miss with the few dozen milliapms is that they might run the coils without the 430ohm resistor to limit the current. The igniter might be hungry for more amps if it is not limited.
    I'm currently running 100 ohm resistors in place of the 470 in my car. I think I posted the igniter current at that configuration, but if I didn't I have it on paper somewhere. The difference was negligible, still well under 1 milliamp. So the 20ma number and "a few dozen" were clearly complete bullshit derived from non-scientific methods.

    Quote Originally Posted by kur4o View Post
    Did I mention that I managed to run the coil through a led and resistor. If we put leds on the circuit that might reduce the noise on the avr.
    I wouldn't use an LED inline with a system critical circuit. LEDs are made to emit light, not protect the driver circuitry. Not to mention, you're going to create a huge voltage drop across them. There are no diodes inline in the ecu pics you shared, so I think you're inventing a fix for a problem that is imaginary until proven real.

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    Quote Originally Posted by kur4o View Post
    The code can be transferred to lt1 pcm and based on my calculation the pcm can run dwell upto 1.5-1.8ms at 6000+rpm without overlapping coils.
    That seems to defeat the whole point of allowing overlapping dwell between coils if/when it's necessary.


    Quote Originally Posted by kur4o View Post
    The igniter might be hungry for more amps if it is not limited.
    You can easily find out by checking voltage drop across the resistor.

  10. #535
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    Quote Originally Posted by kur4o View Post
    The igniter might be hungry for more amps if it is not limited.
    Quote Originally Posted by lionelhutz View Post
    You can easily find out by checking voltage drop across the resistor.
    Unless it increases spark energy or decreases dwell time, there would be little point. It should be easy to test so I will - if dwell limiting happens at the same time then there would be zero benefit to changing the resistor size / igniter current.

  11. #536
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    Tested a D580 and a D514a coil today with a 100 ohm rc network resistor.

    Side tangent (again). The purpose of this resistor isn't technically aimed at limiting igniter current. It's the buffer component of an R-C network, designed to absorb induced or reflected voltage spikes when the igniter circuit turns off and the comparatively massive amount of current running into the coil's primary winding suddenly halts and then attempts to change direction. The capacitor, which is fully charged in what we'll effectively call a "positive" direction quite effectively absorbs the reversed voltage spike when the circuit turns off. The resistor is a protection and buffer mechanism that limits positive charge current into the discharged resistor when the circuit initially turns on (goes from 0v to 5v) and then provides a similar buffering function when the negative spike is received.

    Anyway, the D580 coil's igniter current increased from approximately 0.514 milliamps to approximately 0.600 milliamps. Likewise, the D514a coil's igniter current increased from approximately 0.471 milliamps to approximately 0.514 milliamps. More importantly, at the same system voltage of the previous test (12.8) there was no measurable change to observed dwell limiting with either coil.

    In summary, it appears there's absolutely no benefit to messing with the value of the 470 ohm resistor. Going forward I'm considering this avenue of investigation a dead-end.

    Funny story... I started to test this setup with the D585 coil until it occurred to me I'd have to re-arrange leads to observe dwell limiting with it and instead picked up the D514a. Anyway, in my haste forgot to disconnect the clamp from the positive battery terminal when I plugged the 4 pin connector into the coil. Sonofabitch did that "tickle"! Got the palm of my hand real good. I felt my teeth tingle, and when I began to gather myself started to wonder why I wasn't smelling my flesh burning. I do not recommend anyone try this unless you really hate life. It's a damned good thing the coil body is wrapped in a piece of grounded sheet metal, or instead of typing this I might instead be lying in a puddle of drool and urine, dead on my basement floor.

  12. #537
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    Quote Originally Posted by spfautsch View Post
    Anyway, the D580 coil's igniter current increased from approximately 0.514 milliamps to approximately 0.600 milliamps. Likewise, the D514a coil's igniter current increased from approximately 0.471 milliamps to approximately 0.514 milliamps. More importantly, at the same system voltage of the previous test (12.8) there was no measurable change to observed dwell limiting with either coil.
    So in summary, with this resistor, the D580 drew roughly 0.580 milliamps...and the D514a drew roughly 0.514 mA. Yay, fun with numbers!

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    I am about to get the SPFcop system tomorrow and start playing with the code. I doubt I will go anywhere but will give it a try.

    You`d better start adding code for temperature compensation since my test vehicle run 100 times better with stock gm dwell tables with temp compensation, than the initial average settings with the stock code.

    I wonder if the ls1 pcm can monitor ignitor current and readjust on the fly with the MIN and MAX dwell settings.

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    Voltage regulator showed up yesterday and I was able to do some preliminary testing. Looks like it's going to work great. Hoping to do some room temperature tests later this evening.

    Quote Originally Posted by kur4o View Post
    You`d better start adding code for temperature compensation since my test vehicle run 100 times better with stock gm dwell tables with temp compensation, than the initial average settings with the stock code.
    Wow, well since you put it that way, let me just drop everything!

    I feel a bit reluctant to have to explain this to a guy that probably dreams in motorola assembly, but there are a number of ways to get the right amount of dwell over the majority of engine running conditions without monitoring ECT to compensate for coil temperature. Since the engine (in this instance I'm referring generally to all the powertrain components under the hood) spends the vast majority of it's time in one of two thermal states - cooled to ambient, or at full operating temperature, and because we're primarily interested in dwell at full operating temp, the simplest way to get ideal dwell is to target operating temperature. This is most likely what the Bailey setup did / does, and this provides a better explanation of why they didn't officially support the D585 coil. All the other coils will do no harm once their internal dwell limiting is initiated, but the 585 fires the coil and that's a big problem. I'm confident doing this would be perfectly adequate for all coils other than the 585s, and I'm certain it won't cause the engine to run 100 times worse than having one fixed dwell for all temperatures and RPM ranges. But nice try with the "100 times better" hyperbole.

    With that said, it's something I'm going to investigate because I have a similar level of OCD and it would allow the 585 coils to operate at their maximum capability (which is extreme overkill in my opinion). Let me propose this - I'll trade you one temp vs dwell time compensation routine and accompanying circuit design, for one $EE lean cruise patch!

    Whatever the case here, I think you might be aiming to emulate the factory coil per cylinder setups so closely that you're losing sight of what this is, and isn't. If it's that important to you to have all these tables for something like dwell you're probably better off doing a 24x conversion. Because dwell really isn't that big of a factor. To use your own hyperbole against you, getting to a decent startup fueling table is 100 times more sensitive than providing adequate dwell.

    Quote Originally Posted by kur4o View Post
    I wonder if the ls1 pcm can monitor ignitor current and readjust on the fly with the MIN and MAX dwell settings.
    Monitoring the igniter current wouldn't tell the ecu anything. It would need to monitor the primary current powering each coil, and we know the required circuitry for that doesn't exist. Edit: (in the factory wiring harness)

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    I got the mail and stuff looks really good. Nice work done with the board design. One downside might be that capacitor is not between controller and resistor{AS per PCM design}, but is between resistor and coil. Do you think it will make any difference.

    In your case the temp compensation might be negligable. The coils you are running have only about 3-5% temperature compensation. The coils I have can have upto 20-40% change in dwell time, so it is a huge improvement.
    The most noticible is with the first design truck coils. Totally unlinear on both axis.

    Also the temp compensation is tied with voltage, so in the end there is 3d matrix of adjustments. If it was so unimportant I doubt GM will make an effort to dial those tables. Fact is the car run much better with the proper data.

    I am not a fan of `kind of worked` approach or it will work only at room temperature approach. It either gets done the right way or goes underground.

    Now why it is so imprortant I have no idea. It also might be related not with coil temperature but air fuel mixture temperature. Discharge time on colder mixture and residual coil charge. I don`t think the coil with get any hotter than 50-60*C on the hottest summer day.

    I am not a patch fanatic as you have supposed. Just improving GM code and adding new feature not availble back in the days some 30 years ago. It is nice to make the pcm behave the way you want it. The PCM is more than capable of calculating dwell, just 2 3d tables added, compared to current code it might be even more efficient.

    The patch exchange looks good idea. I was already planning to add the lean cruise mode, since my cuurent experience with moster spark energy output.

    I came to the conclusion that the fat spark from these coils can ignite leaner mixture so good that the adverse effects of the lean mixture can be overcomed completely.

    On my test vehicle I got improvement all over, and that is with almost shot plugs. I can`t imagine the result with new plugs and dialed spark tables.

    Now I need a firmware for SPFcop that runs dual mode based on rpm threshold. All the time it will calculate dwell as needed but on lower rpms based on threshold it will run as sequencer. I think it will be a piece of cake to add sequencer mode with a rpm switch on top of the existing code.

    I think the dwell lowers on higher rpms for better spark control on rapid rpm and spark advance changes. Especially on auto trans cars when it downshifts it goes to red rpms in a split second. That will be the ultimate test for the SPFcop system. Too bad you have a manual and can`t test a downshift.

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