DIY LTCC or similar system for LT1s

[Fast355]

I am not so sure the lt-1/vortec ignition module is auto dwell or not. Guess we'll find out. Not one of the most challenging problems ever, you know. You are putting cart before the horse. We need to get back to decoding and counting, otherwise we will get nowhere.

Here is a dwell calculator for you. Stretching the trigger signal from the ecm should pose no real problem.
http://www.useasydocs.com/theory/setdwell.htm

I will not discuss this any further until I need to. I have more important things to do. You have a better idea, draw it up and show us. That is why this forum exists. To share ideas and solve problems. Offer us something.

PCM controls the Dwell on a Vortec atleast. Guessing it is the same on a LT1 since I believe atleast the OBD2 LT1s used the same module.

[lionelhutz]

The LT1 never used a black block PCM. I'm quite positive the OBDII LT1 PCM was unique to that engine the same as the OBDI PCM was. You can swap between the OBDI and OBDII PCM's pretty much directly. Just the knock sensor changed and the OBDII had read O2's.

[vilefly]

PCM controls the Dwell on a Vortec atleast. Guessing it is the same on a LT1 since I believe atleast the OBD2 LT1s used the same module.

They sure look the same, and have the same wiring to them. But just in case, I have a smart ignition driver IC ready to intervene for the bargain price of $4.89 each.
http://www.mouser.com/ProductDetail/...klZFEN1w%3D%3D
It will come in handy for the future. I will order 8 of them in case. If not, I will use them in my bag of tricks at work used to save/convert old classic vehicles that intermittently show up.
The datasheet is available on that page.

[vilefly]

Sorry about the delay, guys. Here's what I've got so far. not fully accurate, since I am missing a reset for the 4-bit counter, but it should get the idea across.
Attachment 12115

Hope this clears up any misinterpretation due to my horrible way of explaining things due to constant distraction. Nothing is set in stone, yet. The LOAD input on the 4 bit counter tells it to preset a value, and start counting from there with every LOW-RES leading edge. It is positive edge clocking.
This is the datasheet on the CD54ACT161 presettable 4-bit synchronous counter.
http://www.ti.com/lit/ds/symlink/cd74act161.pdf

[vilefly]

Hey Aroberson77,
How's the delteq schematic decoding going?
I have a theory on how it converts the optispark signals to a northstar reluctor signal. And the eprom theory, of course. A northstar reluctor has 32 teeth total, unevenly spaced....or so I thought. 24 slots are 15degrees evenly spaced, and 8 more slots 7.5 degrees spaced between the 15 degree slots at various points. I imagine you can take the 360 degree signal from the optispark and double it, and use it as a clock signal for the circuit once it is synchronized. so now the 7.5* becomes an integer at 14*.

The crank sensors are spaced 27 degrees apart. This can be simulated by 2 outputs separated by a 27 count counter. Now it is a 54 count, since we doubled everything. Hope this helps if you use an arduino with a for-next loop that is 720 counts incremented by the doubled hi-res input.

The eprom method would consist of raw sensor readings digitized into memory that is accessed by a binary counter coupled to the synchronized Hi-res signal.

[Aroberson77]

Hey Aroberson77,
How's the delteq schematic decoding going?
I have a theory on how it converts the optispark signals to a northstar reluctor signal. And the eprom theory, of course. A northstar reluctor has 32 teeth total, unevenly spaced....or so I thought. 24 slots are 15degrees evenly spaced, and 8 more slots 7.5 degrees spaced between the 15 degree slots at various points. I imagine you can take the 360 degree signal from the optispark and double it, and use it as a clock signal for the circuit once it is synchronized. so now the 7.5* becomes an integer at 14*.

The crank sensors are spaced 27 degrees apart. This can be simulated by 2 outputs separated by a 27 count counter. Now it is a 54 count, since we doubled everything. Hope this helps if you use an arduino with a for-next loop that is 720 counts incremented by the doubled hi-res input.

The eprom method would consist of raw sensor readings digitized into memory that is accessed by a binary counter coupled to the synchronized Hi-res signal.

I've been too busy trying to get my car back together to look at the delteq too much. Hopefully this week I can spend some time with it. Your theory sounds pretty good since it is easy to just change counts

[spfautsch]

Just to try and catch up, is the goal here to ultimately piggyback the optispark signaling with the OEM wheel?

I'm wondering if the arduino platform might be capable of this. I'm somewhat reluctant to bet the farm on a microcontroller like the Atmel 328 in the thermal and EMI environment encountered under the hood, but is it even fast enough? 360 rising edge signals per 2x (edit: crank) revolutions, right? Also, what would "limp home" look like with something like this - the ECM can function quite satisfactorily without the high res signal. (edit: perhaps the second half of this sentence should be phrased as a question)

[vilefly]

Well, we've got 3 projects going on. 1) my minimalist hardwired electronic "decode optispark signals for 8 ignition coils using oem computer timing"
and 2) Aroberson's "decode with arduino and possibly have limp mode operation"
and 3) "reverse engineer the Delteq unit", which converts the optispark signals to Northstar dual crankshaft signals and sends them to a stock northstar ignition module and coils. This is a waste-spark system with 4 coils for 8 cyls.
Although, not nessesarily in that order.

My system should behave like the OEM design....synchronize during starting only, switch coils using leading edge of Low-Res signal from then on. No restart on loss of Hi-Res signal. You could do the same thing with the Arduino I bet. Speed shouldn't be too much for it in that mode of operation.

As for synthesizing a northstar signal using an arduino, I have to wonder about the speed factor, too. Not well versed in the arduino stuff.
Any other ideas/strategies are most certainly welcome. Plenty of room for more projects.