DIY LTCC or similar system for LT1s

**spfautsch** · 07-20-2023

The latest "official" release is 0.9.43 which is linked in my .sig. Today I added the gerber outputs to this zip archive at the request of another user wanting to produce their own PCBs.

Looking back, I have a forked folder on my dev machine named 0.9.44 dating to Oct 2021 but I would have to diff the changes against 0.9.43 to know what I was doing there. It appears to be the version I'm currently driving.

I'm not sure if you sent previously but I'd really like to have a copy of the dwell tables you're currently running for your coils to add to the official release tree.

Incidentally, I'm coming up on 25k miles since gutting the factory ignition system and splicing the DIY-LTCC in it's place. I've driven it daily quite a lot over the last ~36 months, but it's recently been compulsorily appointed my dedicated daily driver since putting my C5 in storage back in early April of this year. The only complaint I have is when it's hot and idling it smells so pig rich it causes eyes to water. I feel like this is caused by the cam + headers, since it's averaged around 21 mpg over the past 2-1/2+ years of completely turn-key driving with extremely negligible tune changes. Not to say it runs poorly, I've recently spanked a 6.4L N/A Scat Pack Challenger as well as what appeared to be (in my rearview mirror) a 2021 Jeep Trackhawk.

I changed the oil in the test mule over the weekend and discovered the seal between the cam and distributor was leaking. So I'm going to have to fix this sh*t bisquit at some point soon. Thinking I'll tackle this over the winter and possibly switch to a new billet cam while simultaneously refreshing the double-wound valve springs, lifters, etc. Maybe make a few additional horsies in the process.

I guess I need to revisit this project and get it to a 1.0.0 release status.

**kur4o** · 07-20-2023

Thanks for the update,

Here is a copy of d514a dwell + the map muptiplier table I used[guess for some 2-3k miles]

I can only refresh your memory that 9.43 had some unresolved bug you were talking about in the thread, that was figured but an update never got issues. I can only speculate that 9.44 was some beta fix for it. I can give a shot at that 9.44, since currently I am running some older version, but have no way to check which one.

I too got tired of tuning. Last was hacking some evap code, and just let it run as is, even stopped logging and let the CL do its job.
I might need to check MAF signal for consitency too.

**spfautsch** · 07-20-2023

Thanks for the tables.

After having spent the last several hours re-acquainting myself with the project (I literally haven't given the code side of it 10 minutes worth of thought in more than 2 years), I'll try to update 0.9.44 with some new defaults and documentation and get it posted later today or in the next few days along with the gerber outputs.

After mulling over diff outputs I don't find any fixes between 0.9.43 and 0.9.44. If you didn't enable logging (I probably told you not to initially) then you can't get the firmware version of what's on the board without dumping the flash and comparing the dump to a compiled binary. Sorry. This is one of the things I'm going to change - defaulting to logging enabled and preload the locBuf[] array so the controller minimally spits out the firmware version and voltage divider constants including regulator voltage fine-tuning at power-up. I'll probably add the means to dump the name of the coil-specific dwell table used as well.

Anyway, there was a bug in 0.9.42 where an unchecked bounds in a table lookup would have caused issues at higher RPMs. Aside from that I haven't experienced any other problems I believe were caused by the controller.

I will include your dwell table for the D514a coils in the official release. I won't be using your map_v_rpm_mult.h multiplier table as that shouldn't be used to accommodate differences in coils.

I'm somewhat ashamed to admit I'd completely forgotten how much work I put into getting this to the stage it's currently at. Life has contributed it's necessary distractions and detours, and for the majority of the past 2 years I've dismissed the idea of improving it and resigned to driving it. I probably won't change that methodology much unless I hopelessly break something in the next few days and can't drive the car. In a nutshell, since about the middle of 2021 I've been getting in and turning the key to the car starting and running well, and have treated it like that was the expected outcome. In that time period it has not complicated my life whatsoever. In that time period there were maybe 3 or 4 starts when the ambient temps were low where it flooded during cranking. I'm not going to attempt to fix this with dwell since it did this when I was still running the stock optispark so it's completely unrelated to the ignition controller.

So you drew me back in... will make an effort to implement some changes before my attention span diminishes. Have already made a couple changes I'm about to head out to the car to test. Curse you kur4o (kidding)!

Anyone who's PM'd me wanting boards please re-connect as I'm starting to get my bearings again. I'd like to get this running on an eeprom car with the required tach driver output and potentially different ECT sense table. You're going to be made into my guinea pig / test pilot, so be careful what you ask for.

**spfautsch** · 07-20-2023

Latest build, 0.9.45 now in .sig. Preliminary testing is good, plan to drive ~60 miles round trip to golf in a bit.

**kur4o** · 07-21-2023

Sounds great. I will test in next few days. Need to refresh my flashing skills with arduino.

I hate unfinished projects, so expect some extra motivation to continue with code polishing and engine tuning.
I have some tbi SBC that is in bad need for some coil on plugs. Will test as much as needed, till engine blows.

**spfautsch** · 07-22-2023

Instructions on building / flashing firmware are relatively well-documented in README.txt

Originally Posted by kur4o

I hate unfinished projects, so expect some extra motivation to continue with code polishing and engine tuning.

I'm feeling your peer pressure. I just sat down and spent 2+ hours taking pictures and writing verbiage for a homepage for the project. It's hard to believe I've been driving this acid trip around for 5 years, but it's already a historical fact.

Drove it to work today as usual (110 miles round-trip) and nothing adverse to report. I got phenomenally stupid with the car on yesterday's return trip, and it did not disappoint. I'd so love to get this thing on a chassis dyno to have some independent data to back-up my "butt dyno numbers".