DIY LTCC or similar system for LT1s

[vilefly]

I figured this may be the best place to find any info. I have been having some issues with my ignition on my LT1 lately and am thinking about building my own LTCC type system that uses the optispark to determine crank and cam position, but uses individual coilpacks instead of routing the HV through the optispark. I assume I need to get the opti signals into a controller that has 4 or 8 outputs for each cylinder. has anyone tried this before?

Well, I am working on a similar project, but have very little time. Still in the planning stage. To start with, you need this transistor to fire your coils (8 of them) https://www.google.com/url?sa=t&rct=...qY24EtGtItbi9g

IRGB14C40L is a to-220 package protected on all sides with zener diodes, overcurrent protection, and can handle 14A with a proper heatsink. very tough and hard to kill, except for thermal destruction. A positive 5v pulse on the gate triggers it. dwell time is not controlled. Just a slave unit. All oem manufacturers use this one....ALL.
Newark or digikey or mouser should have some decent prices.

Read this page on LT-1 electrical specs and optispark decoding. http://chevythunder.com/lt1_electrical_page.htm
LOW RESOLUTION SIGNAL:
Cylinder # 8: 7 edge counts wide (from Hi-res signal)

Cylinder #3: 12 edge counts wide

Cylinder #5: 17 edge counts wide

Cylinder #2: 22 edge counts wide
The other cylinders between these (1,4,6,7)= 2 edge counts


The next item I intend to use is an 1-to-8 demultiplexer, sometimes called a data distributor. I will use this data switch to redirect the ignition module's FIRE signal to the 8 transistors listed above. That way, I can still let the ECM control the dwell time. easy-peasey.

The hard part: making a counter-convertor for the optispark signals. I can deal with the 2 signals by gating them to one another with an "and" gate. Then I decode the counts to decide which cylinder to switch to with a decade counter. Use an edge-trigger strategy for both positive and negative going pulses. The problem is that between the pulses is a single 2 count slot. Shouldn't be too much trouble if I switch the "and" gate off with the 1st decode, and count the starting edge pulses from then on as TDC.

My time is still limited by the fact that I am chasing a toddler around these days.

[Aroberson77]

Cool, I can definitely help out with this. Are you planning to use an arduino to write the program? I think that would be easy. Im not the greatest with programming but like wiring a lot so hopefully I can help

[vilefly]

nope. I think it would be like using a sledgehammer to drive in a nail. And there is the problem of propagation delay. Counters and gates. old school. I think an arduino might get cooked under the hood. I have yet to even use one....need time to learn more about them. Coding looks easier than in my day, but if I do it by hardware, I can make more in a cheaper fashion.

[Aroberson77]

I didnt know it could just be done with hardware, that makes it way easier.

[vilefly]

Well, I had a tough time finding ICs that were not surface mount only. How annoying. Makes prototyping difficult.
Step 1.........signal conditioning. I will use a positive edge triggered flip-flop with both outputs tied to an OR gate to double the pulse count from the low res signal.
This is because I couldn't find a dual edge triggered.....anything. So, for compatibility sake, I had no choice. (counters only see the positive-going edges)

I will have to check each signal output, to make sure I don't mess up the count, with an oscilloscope. Because I'm old and forget things when my child is eating the dog's food with too much gusto. Have to complete this thought later, I have to save the dog food.