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Thread: DIY LTCC or similar system for LT1s

  1. #1
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    DIY LTCC or similar system for LT1s

    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?

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    Quote Originally Posted by Aroberson77 View Post
    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.
    Last edited by vilefly; 2 Weeks Ago at 02:15 PM. Reason: more info.

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    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

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    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.

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

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    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.

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    EFI connection 24x swap with an 0411 is how I would fix the optispark in a LT1. The only non factory part at that point would be the reluctor ring itself.

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    definitely a great hobby project.

    i would consider building a more general purpose piggyback ignition controller.

    make it accept many types of signal.. opti, various reluctors. make it work for arbitrary number of cylinders.

    make it able to drive coil per cylinder, waste spark, -or- single coils for distributors.

    give it a loadable config file. add two analog inputs for a map or tps.

    give it tables for add/subtract advance, dwell, multiple sparks per cycle, cut and retard options for nos n rev limit....

    arduino for a brain should be able to do it

    if its worth doing its worth doing well

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    Fast 335,
    Sounds too expensive for me. $1200 just to run like it normally does anyways. Add to that obd2 tuning program and programmer for the new ECM to get it running right for another $1000 + time. I could simply drop in a LS engine and computer instead.

    My ulterior motive is to make my ignition system into an ion sensing ignition system. That way, I can directly measure cylinder pressure and produce the most optimal spark timing for any condition on the fly. The optispark signals will need no decoding to produce a 1 degree accuracy for my system. The LS system provides me with no such decoding output that I can splice into.
    Last edited by vilefly; 2 Weeks Ago at 07:30 PM. Reason: addressing an individual

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    steveo, check this chip out.
    https://www.google.com/url?sa=t&rct=...2A8bwU5MCqf9UA
    Also, there is the NanoEFI project, which uses an arduino to run things. https://www.google.com/url?sa=t&rct=...X5-zzu0MGJKJLg

    I have the single chip 1cyl engine controller IC on backorder, should arrive next month or so. it contains its own reluctor signal processing and is programmable. It even resolves the signal to a tenth of a degree. So, I just had to have one to poke at and prod.

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    Quote Originally Posted by vilefly View Post
    Fast 335,
    Sounds too expensive for me. $1200 just to run like it normally does anyways. Add to that obd2 tuning program and programmer for the new ECM to get it running right for another $1000 + time. I could simply drop in a LS engine and computer instead.

    My ulterior motive is to make my ignition system into an ion sensing ignition system. That way, I can directly measure cylinder pressure and produce the most optimal spark timing for any condition on the fly. The optispark signals will need no decoding to produce a 1 degree accuracy for my system. The LS system provides me with no such decoding output that I can splice into.
    0411 runs better and the Blue/Green 1 meg runs even better and there was a 16 rwhp power gain at redline in my Vortec 5.7 going to the Coil Near Plug setup. I am currently running a Flex Fuel sensor and E85. Fuel change alone netted me an additional HP/TQ gain on the dyno.

    I had used 6.0L D585 coils at my disposal but the rest of the parts were relatively cheap. I only bought the coil brackets, mounting hardware, the crank reluctor, crank sensor and the distributor cap from EFI connection. Seem to remember my bill being less than $500.

    I already had HP Tuners and at the Time I bought it was under $700 with credits to tune 4 GM vehicles.

    If I had a LT1 to start with I would not consider anything under a 6.0L and that engine would cost you $2500 for a high mileage engine needing some work. You would need another $1000 in parts to swap it in on top of the pullout engine with harness. I am right in the middle of a LS 6.0L swap as I type this and it is time consuming and $$$$.

    The F-car LT1 I messed with put down 320 rwhp and 340 rwtq through a M6. 150K mile stock longblock with a spring/retainer/guide plate/pushrod/1.7:1 rocker/24x coil per cylinder 0411 swap. The car had a Moroso CAI kit and a catback exhaust.
    Last edited by Fast355; 2 Weeks Ago at 06:27 AM.

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    I will also not get into the fact this engine also gained 27 hp and 6 ft/lbs from a valve spring and retainer change. Lets just say I had a local machine shop pickup and install 2.02/1.60s in these heads and somehow ended up with 0.100" longer than stock valves and shimmed stock springs that did not even have 70# at the seat. With 1.7:1 rockers my small 395' cam had .489/.511 lift on stock Vortec springs at a 1.8" installed height. Between 5,100 and 5,300 it lost more than 20 rwhp mostly from valve float. I went from 230 rwhp to 257 rwhp changing to LS6 springs and Comp 787 retainers and using hardened .030" and .015" shims stacked to get to a 1.755 installed height.
    Last edited by Fast355; 2 Weeks Ago at 06:23 AM.

  13. #13
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    Well fast355,
    You've been having some fun lately. I am jealous.
    My rough pricing was for starting out with a '95 LT-1, which requires a later model timing cover, which I do not have. The kit that has it costs $865.00 without the computer. The computer costs $395.00 w/o programming, which they will not do for you. EFI live flashscan and tune costs $899.00. Without the wiring harness, that's about $2159.00. +$675 for the wiring harness. Grand total = $2834.00 without bargain hunting on ebay. So.....I was way off. It would be much cheaper if I started out with a distributor-equipped 5.7L vortec.
    Anyways, this journey is mostly about learning and honing my electronics skills, which are dreadfully out of practice. 25yrs in the automotive tech field barely kept my electronics skills alive, and I have forgotten a few basics in the logic circuit area.
    The LS motors bug me. I am seeing cam bearings walking out of place, and blocking oil from the lifters, sludge plugging the pickups, oil pump pickup o-rings failing, and Displacement-On-Demand roller lifters fail often. Oh, and I hate having to remove the cylinder heads to gain access to the lifters. They run great, but don't have much staying power without synthetic oil. (350,000 if synthetic is used)
    Oh crap. I'm ranting. Somebody stop me.

  14. #14
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    might i suggest not turning a really cool hobby electronics project discussion (which is why this forum is awesome) into some kind of horsepower estimating, shoulda used this ecm instead, lsx-is-better bullshit

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    Thank you steveo for slapping me. And now, back to the project.
    I think I will use the CD74HC4024E 7-stage ripple counter to count the pulses. It counts on the negative edge, though. (all ripple counters seem to, for some reason) I should mind my counts just in case.

    The single chip engine controller has a Variable Reluctor decode output that you might like. The arduino should like it nicely. I will have to get with the program, and learn more about this handy little device.

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