LT1 PCMs have separate Tach output, so don't worry about that function.
LT1 PCMs have separate Tach output, so don't worry about that function.
The flash based LT1 PCMs do, the older chip based LT1 ECMs do not.Originally Posted by dzidaV8
Thanks, that's exactly what I was looking for! Shouldn't be an issue either way, there are plenty of open pins so I'm using the tach driver output to display the state of the EST input when in input test mode.
I think I've got it sorted out, it wasn't a power problem. I just didn't know where the 12v power to the opti was connected to so I wanted to eliminate any doubt about adequate power. The extra signal ground from the opti pigtail also wasn't the apparent cause of the noise.
I ended up with 4.7k pullup resistors on the opti pins with a 1000pf cap on the low res input, and a 10k on the EST line. Oddly, 4.7k on the EST line set a "EST Open" code - 41 if memory serves.
I'm opposed to growing part count unless absolutely necessary. When you test, if you can find a need for driving the coils w/ buffers we'll look into it.
The LS2 coils I have apparently have a very low current requirement on the igniter pin. I'm feeding mine through a 470 ohm resistor in series to the arduino pin. I'm also driving the sequencer leds from the arduino pins directly. I've noticed no issues thus far, but I'll save any further comment for when I've been able to bring the engine up to temp with the system.
Here's about a minute worth of video demonstrating cylinder #4 driven by the system with the opti running the other 7 cylinders. Once again, apologies for the shoddy camera work. I have no aspirations of becoming a videographer, amateur or otherwise.
Zip of logs here.
I have to agree to low parts count. Nice video. Got a question. Is your LS1 ignition coil hooked up the the same + lead that feeds the ignition coil? I know the ignition coil feed has a noise capacitor on it right at the coil. Other manufacturers do this too. Try using the V+ feed for the OEM ignition coil and see if your noise goes away. The inductance of he other coil may dampen some noise as well. The ignition module may have other noise-dampening circuits in it (on the shared positive side), such as a zener diode or something. No extra parts required.
Yes, and I'm relatively sure there's nothing like that on my '95. Last weekend I stripped the tape off the entire right side harness from the #8 injector to where the MAF sensor branches out including all of the ignition feeds and there's nothing but wires and connectors.
If I can find all my old spark plug wires I'll try firing it with the original ignition system disconnected tonight. Fingers crossed, bunghole clenched...
As my videography skills run, I accidentally deleted the crank / start segment from my phone. It was unimpressive because I'd already started it twice before - once so I wouldn't drop my phone in the event the engine came apart and I soiled myself, and the second time my wife was "helping" with the video. The valves had warmed up by #3 so it was a bit of a long crank as I suspect it flooded slightly. After the final video when ECT was around 60c I re-started it and it fired off just as vigorously as we're all used to.
At any rate, proof of concept at long last. Also, revel in my woodworking skillz (temporary coil brackets).
Short clip revving (haven't looked at the logs to see peak rpm).
90 second clip showing eehack when it switched to closed loop. At the end I walk around and pick up the disconnected ICM and coil connectors as well as the opti coil wire.
Logs
After disconnecting the ICM plug, DTC 41 set immediately as it did when I was using a 4.7k pullup. So I suppose I might need to try a zener diode or something on this pin to keep the ECM from freaking out.
I'm stoked to have gotten this far. There's still a lot of work, but that's all going to be dead nuts fun for me.
What still remains to be seen is what the Atmega will behave like the first time I get stuck in St. Louis traffic on a 95F day.
I'm going wander over to my neighbor's place, have a couple glasses of bourbon and come home and sleep like I haven't in a few months. I'll do some research tomorrow and try to decide how to publish the source code.
Last edited by spfautsch; 01-14-2018 at 04:21 AM.
Very awesome work! I commend you on beating me to the punch very soundly. I especially like the wooden coil bracket, seeing how most bracket kits cost $85 and up.
You are using the mega2560 unit, right? I imagine you can send a password-locked zip file. If legality issues concern you, you can draw up a patent-style Disclosure Document that proves you thought of the idea before you disclosed it to someone else, and have them sign it, and send it back to you. This will hold up in a court of law, but am not sure if you need to have it notarized. Should provide you with some code protection at least.
What I don't know, is how you can download what has been flashed to the AtMega so you can prove the code was stolen with a comparison. Should probably keep that secret to yourself, though. Just say if you can do it or not.
As to the code 41- I think the circuit impedence on the EST line is 10k ohms. Perhaps a 10k resistor in between the arduino and the EST white wire might fix it. (ignition module terminal "B")
95 corvette optispark.png
Just in case, I would check the alternator output for ac voltage and voltage drops from the positive lead to the alternator connection. Mine had some issues, and I added an extra positive connection to the underhood fusebox when I replaced and upgraded the alternator. Since the optispark runs off of 12V, I figure this could help.
I tested the optispark with a regulated 5v power supply, and it worked. It was a few months ago, so I hope I am remembering it right. With a clean power supply to it (grounded to the power supply of the controller), it could help eliminate any 12v entanglements.
I wonder if feedback was designed into the coil drivers like nissans do. One can hook an oscilloscope to a nissan's coil trigger signal and see a 5v representation of the secondary output. Kinda neat, but can cause problems if you are not ready for it. I suggest running your coil trigger outputs through a buffer IC with 8 input/outputs. I think the proper term is "unity gain amplifiers", but they will probably be sold as buffers.
Probably could use a big, fat capacitor right at the controller for anything else I missed.
Last edited by vilefly; 01-13-2018 at 10:18 PM.
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