Still have a kit available, PM box has been cleaned up.
Still have a kit available, PM box has been cleaned up.
if anyone is desperate i have a kit too and i doubt i'll ever use it due to lack of time and other proects...prove it'll be used for a good cause and for productive testing and i'll send 'er to you for postage.
Hey steveo why don't you hang on to that for someone in Canada. Or, just use it as a paperweight - as I said I wanted to express my appreciation in some way. The cost and hassle of getting it back through customs would be shamefully wasteful.
I do have one more unassembled kit I was hoarding for an emergency, and I will make it available if the right person comes along. I also have an assembled spare for myself so it's not going to cause me any difficulties.
Once these are all gone I will make some revisions and get another batch of boards made. In addition to wanting to add an ICP header, the coil indicator leds need to be omitted because I believe they're overtaxing the AVR's power capabilities. I've yet to confirm this scientifically, but one of my chronic problems has been running extremely rich. I believe this has developed over time due to the AVR's internal current shunt burning out causing the output voltage to drop which I suspect results in very weak spark. When I got this running at first it was running phenomenally, but the more I ran it the worse it got now to the point it won't idle b/c the iac is pegged open. I'm waiting for pushrods to get my engine back together before I can confirm. Once I can I'll post a revised assembly guide to address this.
EDIT: By the way - for anyone intending to test I thought it would be a good idea to mention that you try and locate the board / case in the coolest location possible. There's a post somewhere that demonstrates where mine is mounted below the battery. Inside the passenger compartment couldn't hurt either but may be overkill. Whatever the case, I wouldn't advise mounting it where the ICM was - right behind the radiator's airstream. The 328P (microcontroller) is rated for a maximum operating temp of 125C. Some of the other components aren't quite as robust.
Last edited by spfautsch; 07-11-2019 at 12:30 AM.
i appreciate it for sure, the effort you've put into this is pretty insane.
honestly i do plan to build one but it might take a few years since i don't have a vehicle to use it on, and it probably wont be an LT1 so i'll have to redesign large chunks of it, but most it will be workable.
Anyone with a kit who's intending to use it, particularly NomakeWan and F-Body you guys will want to drag your heels a bit on your plans with that. If you haven't noticed my other thread, I'm having driveability problems since summer and the accompanying humidity have arrived, and a lot of my problems seem to point to consistently weak spark. See discussion thread here.
In the process of trying to track down the problems I discovered the coils I have are not the higher energy truck / corvette coils that only require ~4ms, but in fact normal 6ms coils. The firmware on all the AVRs I've shipped is using the 4.5ms dwell target. This is easy to fix by simply un-commenting the dwell targets you want and re-flashing the AVR.
Last night I had a chance to do some testing with a scope and was able to confirm that the dwell time is correct - commanded 5.8ms at idle is giving exactly that according to my antique test equipment.
What I'm concerned with is the current draw the coil's igniter circuit is drawing. As I mentioned previously the coil indicators LEDs may be causing problems as well, but I didn't get a chance to measure their current draw. Measurements indicated the coils are only drawing 0.000425 amps (425 microamps). This seems low compared to what I've seen others mention. But it could also be nothing if the igniters have very sensitive FET inputs. I'm going to be experimenting with smaller resistors in the circuit to see what happens. If I can find enough 100 ohm resistors I hope to report back this weekend. Otherwise I'll have to wait for the parts from DigiKey.
Sorry for any problems this might cause those of you who are actually planning / working on installing.
Last edited by spfautsch; 08-09-2019 at 07:25 PM.
Thank you for the update! I wasn't planning on starting the project until this month anyway, so if I just hold off a little longer that's fine. I'll wait to see what your experiments with current draw find, then get to trying to adapt it to my car. That way if I have to build a driver circuit or something I can do it all at the same time.
Best of luck, as always!
If you haven't assembled the PCB you're probably fine. Desoldering the RC network resistors on the coil outputs was kind of a pain. I lifted several of the pads but luckily none that required traces to be repaired. If I had a soldering iron that wasn't made by fischer-price I might have been able to do better.
The coil indicator LEDs are probably not a dangerous amount of load for the AVR if you're using the same coils I am. More details on the coils later.
I'm posting my math for everyone to double check, please don't hesitate to do so and post any corrections.
Voltage drop over the 1k ohm current limiting resistor driving the red LED indicating the spare output (I configured it for a tach driver) measured about 3.2 average - peak of 3.6 at turn-on. Sticking with average that's 3.2 / 1000 = 0.0032 A or 3.2 ma. If my math is correct there's no worries here. With that said I'd still eliminate / omit the coil indicators - they were really only intended for experimental / diagnostic purposes. If anyone thinks they'll prove useful I can split their grounding network on a re-designed pcb so they can be configured with a removable or soldered jumper.
Moving on to the coil igniter circuits, I replaced the 470 ohm resistors with 100s. Previous testing showed 0.425ma draw. Getting a clean sync on the signal was difficult but I was able to get a faint image about every other engine revolution. Across the 100 ohm resistor I was seeing 60 millivolts. This waveform had a surge at the beginning then settled down to a flat voltage level - the peak was probably 80mv but I'm going to use 60mv. So 0.06 / 100 = 0.0006 A or 0.6 ma. This is well within the capabilities of the AVR even with coil indicator LEDs and still leaving headroom for other loads.
I am somewhat baffled by this current figure. The reason I decided to research this topic further is because I was afraid the coil igniters weren't getting driven into saturation and spark energy was suffering as a result. Unfortunately this critical piece of data doesn't appear readily available on the interwebs. What would really be useful here are some standardized specification data. Search as I might, I've found nothing similar to a datasheet on any of the GM CNP ignition packs. All I have to work with are anecdotal reports.
My primary source of data was the oft-mentioned megaquirt 2 sequencer manual [link]. In all references to the igniter circuit draw, "a few dozen milliamps" is given. Also salient is the mention of 1000 ohms in series (internal to the sequencer) with the output circuits being used to drive the igniters.
Another tidbit I found in the beginning and then re-discovered a few days ago is [this] post on allaboutcircuits.com's discussion forum by a college student struggling with a very similar project for his 99 Infiniti. Seems like he had problems with connected and / or induced interference. But the recurring theme seemed to be 20ma at TTL levels on the igniter pin.
So, barring someone coming forward with veritable treasure trove of technical data on coil packs, I suppose what's needed is independent testing not only for igniter current but ignition energy relative to dwell time.
Based solely on appearance, I purchased 8 coils off eBay for a very reasonable price that I believed to be these LS2 "hot" car coils.
GM PN: 12573190
AC Delco: D514A
But I found just a few days ago they are in fact these.
GM PN: 12658183
AC Delco: 12674754
Based on application data it seems like the coils I have might be a considerably newer design than the 4ms "hot" coils. But the current draw on the igniter input indicates they're anything but similar to the 12573190 coils if the anecdotal data mentioned previously is accurate (20 to several dozen milliamps). This is a huge difference indicating the coils I have utilize a shielded FET igniter instead of a more standard IGBT.
I've found a source for some of the D514A coils on A website for about $20 apiece so I'm seriously contemplating buying a set. Also logical would be testing the "legacy" LS1 coils with the exposed laminated core.
For those of you planning to install the test setups I'd recommend you pull the brakes if you've already chosen a coil pack, as I'd really like to test the controller driving at least one of each of the variants, especially these beasts.
GM PN: 190005218
AC Delco: D585
So barring any volunteers willing to loan me hardware I guess I'm going to build a test platform and start collecting parts.
I was able to drive it some today and it was better, but not absolutely impressive as back in May. I'll try to post more info relevant to drive data in the "humidity" thread [link], but it may be several days.
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