DIY LTCC or similar system for LT1s

[vilefly]

So does that mean we need to figure out what is on that eprom? I would almost rather use the LT1 ignition module and then use LS coils. I believe that is what your original plan was, right?

we might need to in order to prove/disprove any theories. I have no intention of using the original ignition module. The ignition transistors only cost about $1.29 each last time I checked. Allows me to use any coil configuration I want. I am still undecided which coil setup I want, because I have been wrong before. I am only mildly curious as to what is on the eprom, so don't do it for me, do it only if you want to. It is still possible to figure out what they did without an eprom's data.

[Aroberson77]

we might need to in order to prove/disprove any theories. I have no intention of using the original ignition module. The ignition transistors only cost about $1.29 each last time I checked. Allows me to use any coil configuration I want. I am still undecided which coil setup I want, because I have been wrong before. I am only mildly curious as to what is on the eprom, so don't do it for me, do it only if you want to. It is still possible to figure out what they did without an eprom's data.

I forgot that you had found the transistor already...

[lionelhutz]

I wouldn't assume you can use any coil by simply driving it with a transistor. I'm pretty sure the GM ignition modules have current limiting, basically driving full-on until the current in the coil reaches the limit and then holding the limit.

[Aroberson77]

I wouldn't assume you can use any coil by simply driving it with a transistor. I'm pretty sure the GM ignition modules have current limiting, basically driving full-on until the current in the coil reaches the limit and then holding the limit.

Here's the coil schematic. Looks like it just needs a 5v signal

ls1_coil_schematic.gif

[vilefly]

I wouldn't assume you can use any coil by simply driving it with a transistor. I'm pretty sure the GM ignition modules have current limiting, basically driving full-on until the current in the coil reaches the limit and then holding the limit.

Not sure if you were talking to me or not. But I do know that the LS coils with the igniter built in are very basic. Hit one with a 5v signal and hold it. You will burn it out. Dwell time is controlled by the ECM. The pulsewidth of the 5v signal will prove it when you rev it up while watching it with an oscilloscope. It is not cost effective nor practical to install a dwell control circuit inside every coil. The size is a factor, not to mention temperature. More parts=more chances of failure. This is not a new concept for me at all. See it every day at work.

Now, you have to ask yourself.....do you want to pay $100 per coil or $45? Second, I will set up ion sense ignition feedback on mine, so I don't want any surprise circuitry in my way.
I have decided to use ordinary coils for mine, the rest can do as they will.

[lionelhutz]

I'd pay about $25 for 8 from the junkyard assuming they'd work with the LT1 PCM. It's loaded with LS engines these days.

Sure, the LS coils are simple and the LS controls do dwell, but so what? The LT1 PCM isn't a LS PCM. I don't believe the LT1 ignition module is as basic. I have no idea if a LT1 PCM does any internal dwell timing or not but I doubt it. I expect the LT1 ignition module is a current limiting HEI type design. So, if you run the LT1/TBI etc coil on straight switched power you'll likely just burn it out.

[Aroberson77]

I dont think we'll use an lt1 coil, i think the idea was to use the ls1 coil

[vilefly]

I'd pay about $25 for 8 from the junkyard assuming they'd work with the LT1 PCM. It's loaded with LS engines these days.

Sure, the LS coils are simple and the LS controls do dwell, but so what? The LT1 PCM isn't a LS PCM. I don't believe the LT1 ignition module is as basic. I have no idea if a LT1 PCM does any internal dwell timing or not but I doubt it. I expect the LT1 ignition module is a current limiting HEI type design. So, if you run the LT1/TBI etc coil on straight switched power you'll likely just burn it out.

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.

[lionelhutz]

I will not discuss this any further until I need to.

Getting a plan together first is better than going off half cocked with a "solution". But, you've got it all figured out so go ahead.

Still, this isn't your thread so it's not really your place to be pissy about my posts...

Personally, I will just buy a replacement sensor if it fails, or do a 24X conversion if I really want a change. So, I have no real incentive to design anything myself. I'd try to help but you apparently don't need it.

Still. thinking about it more I probably would have investigated using the combined rising or falling edges of the high and low res signals combined to clock a shift register chain of 8 flip-flops. Decode one of the pulse combinations to inject a 1 into the shift register each revolution. Then, the bit just passes through the chain at each TDC so there's you cylinder identification done and done. None of the AND gate decoding required and no latch required since the flip flops hold their state until the next low res signal comes along.

[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.