DIY LTCC or similar system for LT1s

[Joshie225]

I'm sorry. How did the wheels come off? I'm not understanding what's happening.

I'd like to be one of the people with a running setup, but the world as it is gives me scant opportunity to use the car so my motivation to improve it is nil.

[NomakeWan]

I'm sorry. How did the wheels come off? I'm not understanding what's happening.

I'd like to be one of the people with a running setup, but the world as it is gives me scant opportunity to use the car so my motivation to improve it is nil.

It’s a figure of speech. He means everything went to shit.

[Joshie225]

Hmm. How can I say this nicely? ...I can't so...

What I'm interested in knowing is what went wrong.

[spfautsch]

How did the wheels come off? I'm not understanding what's happening.

Let me clarify. The problem I'm having with the current development branch seems to be intermittent / aphasic (is that even a word?) / possibly temperature related. It's also possible the board I'm currently running in the car has had something happen to it - it's the first of the manufactured boards I put into operation and I later changed the coil driver resistors to 100 ohms thinking there was an electrical problem that was purely imaginary (one of the joys of being an un-educated country bumpkin with an uncontrollable penchant for tinkering). If I end up pulling all my hair out with the current development branch I'll temporarily mothball it and verify that 0.9.17 still works as well as I remember it.


The project in general is not doomed.


I've just put too much effort into this very full-featured branch (it senses coolant temp, has 2x 3d tables for dwell with temp and map compensation, calculates dwell from time to degrees on the fly, etc.) to backport all the bug fixes I've added since then (0.9.17).

I think I've devised a way to monitor what I believe the problem is (noise on the EST input) and let me dump the recent controller activity after several misses have been picked up. But instead of driving it I'm posting here because it's threatening to storm and I feel no reason to push the envelope (yes, it's my garage queen and I don't drive her in the rain, or worse).

... the world as it is gives me scant opportunity to use the car so my motivation to improve it is nil.

I suppose I can understand, depending on what your motivating factor is (fear, loss of income, loss of a loved one). Loss of income would wipe anyone out. Loss of a loved one may make one long for the distraction of a project (my father passed away a few weeks before I first drove the car over 100mph with the prototype breadboard duct-taped to the windshield). I don't mean to sound like a complainypants, but my current situation is that my employer handed us a 20% pay cut ten days after laying 40% of the company off. I get it. Luckily gas is almost as cheap as I remember it when I first filled up my '74 Camaro in 1987. If it weren't for the price of gas I probably wouldn't even be driving it, and there would be no progress on testing.

I'm going to stop now before I get into a discourse on political matters. Let me just summarize my thoughts about cornavirus thusly - I never knew I had Tourette's syndrome until this hit. It takes phenomenal restraint each morning to resist throwing my coffee mug at the television, even though I'm fully aware it is an inanimate, soulless object. All I want is the goddamned weather forecast, and when you commute a minimum of 115 miles a day the "app for that" sucks balls.

[Joshie225]

You've coded an ignition system that is far more complex than I thought necessary. The coil needs a certain amount of time to charge fully. If the voltage is low it needs more time. If the MAP is low less spark energy is needed, but why add the complexity? Component life? Before considering dwell vs temperature I would want to see that the coil and driver are significantly temperature sensitive across what -40°C to 120°C? Forgive me if all this was explained and I've missed it. I don't understand how the project arrived here and it's not really my business so don't feel the need to explain.

My motivation for playing with cars was that I found it fun. With driving so little, and not feeling much desire to drive, the car simply gets less of my attention.

I'm sorry you've lost your father. I'm grateful that my father is in good health as he approaches 80 this June.

I wish you luck. Much of my working life a 20% pay cut would have been rather painful. Shit, it was painful. I once was laid off and then worked for 70% of what I'd been earning. It was precisely enough to pay the bills with nothing left over. You might call it economic social distancing as there just wasn't any money for going out.

[spfautsch]

Before considering dwell vs temperature I would want to see that the coil and driver are significantly temperature sensitive across what -40°C to 120°C? Forgive me if all this was explained and I've missed it.

See the spreadsheet in this post. <link>

I know there's a lot of off-topic discussion here so to summarize, I found that different coils react differently to both temperature and voltage. Implementing a voltage vs temperature vs dwell time table that can be specific to each part # seemed to be the most intelligent way to accommodate anything and everything ppl might want to use this for.

I don't understand how the project arrived here

It's all here, and there's a lot of it. If you choose not to read, what purpose does complaining serve?

[Joshie225]

Thanks for the spreadsheet. Indeed there is much more dwell variation with voltage than with temperature.

Expressing not understanding isn't complaining. I better understand now. And with the understanding I'm dropping out.

[spfautsch]

Thanks ... Indeed there is much more dwell variation with voltage than with temperature.

Had you read any of the surrounding data you might have noticed where kur4o and I discussed how the D585 (aka hot truck coils that everybody wants to run) are significantly more non-linear with temperature. Also, and a whole lot more important is they lack "soft" dwell limiting circuitry. This means when you give them too much dwell time, they fire the plug with full energy regardless of what the PCM is commanding. This poses a huge problem, and also explains why the Bailey LTCC setup that uses fixed dwell without temperature compensation (or the ability to customize the dwell target / table) was not recommended for use with these coils. Google: "bailey ltcc kickback".

Expressing not understanding isn't complaining. I better understand now.

I've been married to a half Phillipino, half Irish woman for going on 27 years. I'm pretty sure I can identify complaining. It's sometimes what we do as foreplay. I respect people that complain - means they're thinking for themselves. Seems a lost art these days.

And with the understanding I'm dropping out.

That's your choice, but I hope you will reconsider once sanity returns to the general population.

Testing yesterday with some rudimentary misfire detection revealed an ignition event where subsequent to a massive "hiccup" at ~2200 rpm, a coil was "fired" 3 times, starting at 39 degrees, then again at 31, and then finally at 30 - where the spark advance tracker and eehack were showing spark advance was at the time. All within the same combustion event on #3. I'm extremely happy to see logging data to show me this because it's indicative of a noise situation on the EST circuit. Minimally, this gives me an idea of what area the problem lies.

I have a more robust debouncing algorithm for the EST line ready for road testing tomorrow, as soon as the rain, and the massive pond in my back yard dissipate.

[spfautsch]

Well I'm back to replying to myself here... but, couldn't help but share my enthusiasm.

Sorry it's taken so long but life events and weather have been less than conducive to data collection efforts.

The multiple firing event thing seems to have been easily fixed by oversampling the EST input on the falling edge. This explains all the seemingly random detonation I was seeing at high ambient temps while cruising in 6th gear @ 75mph.

Unfortunately this still wasn't the last remaining bug. After more work profiling the program execution I was able to clearly identify there were dwell charging events being mysteriously missed. It took several days of testing and lots of pulled out hair to discover what I believe was a race condition between calculating dwell and initiating dwell. Building a buffering / queuing mechanism seems to have resolved the problem, and concurrently made me wonder why the hell I didn't implement one from the get-go.

The evening commute was almost flawless with the fix in place. The "almost" qualifier deserves the explanation that I haven't fine-tuned IAC vs A/C pressure tables so when the compressor engaged I felt surge. I also felt / heard something strange when I wound it out to 5800rpm but that could have been any number of things.

I still need to test all the functional modes to make sure it works as well with and without logging and / or profiling disabled, but I'm pretty sure this was the last major turd left in the punch bowl. If things go well tomorrow I hope to upload a release.