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Thread: DIY LTCC or similar system for LT1s

  1. #46
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    I agree with you about some of the so called "Pros". As far as the average tinkerer goes, one example for the trials and tribulations of the LT/LS swap that can screw up a tune is the injection timing. Stock LS1 engines have no overlap, LT1's have varying degrees of overlap, if it isn't corrected you get a false rich condition when the engine is actually lean. You have the injectors spraying into an open intake valve while the exhaust valve is still open.
    Most novice tuners trying to DIY, wouldn't know that and will be chasing their tail trying to get their VE corrected. This is just a single example, there are many other parameters that need to be addressed. My philosophy is to the best of my ability, to make the car hobby more enjoyable than frustrating for all involved. Sometimes the time and expense of these various upgrades is just not worth doing. Sensible, cost effective solutions on a case basis are usually the best way to proceed.

  2. #47
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    Quote Originally Posted by Tom B. View Post
    I agree with you about some of the so called "Pros". As far as the average tinkerer goes, one example for the trials and tribulations of the LT/LS swap that can screw up a tune is the injection timing. Stock LS1 engines have no overlap, LT1's have varying degrees of overlap, if it isn't corrected you get a false rich condition when the engine is actually lean. You have the injectors spraying into an open intake valve while the exhaust valve is still open.
    Most novice tuners trying to DIY, wouldn't know that and will be chasing their tail trying to get their VE corrected. This is just a single example, there are many other parameters that need to be addressed. My philosophy is to the best of my ability, to make the car hobby more enjoyable than frustrating for all involved. Sometimes the time and expense of these various upgrades is just not worth doing. Sensible, cost effective solutions on a case basis are usually the best way to proceed.
    The overlap is really a non-issue with these PCMs. I have run the same values on 4 different cams. The factory Vortec 5.7 Express van tune offers a great starting point for most LT1 setups.

    FWIW the LS1 engines DO have overlap. It just happens to be at lower valve lifts than the LT.

    I see your point though.

    I also have a history table I setup to log gms/cyl vs RPM vs KPA and can recreate any Map based spark map in the LS controller. I run a Ramjet 350 crate engine based timing map in my Express van.
    Last edited by Fast355; 09-14-2017 at 08:12 PM.

  3. #48
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    Finding the right chips to talk together is annoying, especially when a toddler is constantly attacking you and your paperwork. I may have to rework a few counting strategies.
    LT1_distributor_optical_disk.jpg
    My 8 channel analog multiplexer/demultiplexer chip had to be switched to a 16 channel one, due to a different counting strategy. (all low inputs make a count, leaving me with 7 outputs, not 8 to use with my ripple counter) The 24 pin dip version is obsolete and no one stocks it. So, I will use the CD74HCT4067-Q1 chip.
    cd74hct4067-q1 pinout.pngcd74hct4067-q1 logic table.png
    You can see how I tie in the ripple counter. To the uninitiated, a binary counter turns on certain output pins on the chip to express a number. a 7 would use 3 pins, 1+2+4. So, it should be a small matter to tie the proper value pins together from the counter directly to this chip. (basically, an electronic rotary switch).
    I am being attacked again. be back when I can.
    Attached Images Attached Images
    Last edited by vilefly; 09-15-2017 at 07:23 PM. Reason: update truth table

  4. #49
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    Quote Originally Posted by Fast355 View Post
    FWIW the LS1 engines DO have overlap. It just happens to be at lower valve lifts than the LT.
    Valve overlap is purely a function of cam timing (lobe separation angle), duration, and lobe ramp rates. You and Tom B should take your LS vs LT p###ng contest elsewhere, it's not contributing to the essence of what the OP is trying to accomplish, which is cooler than you're capable of comprehending.

    vilefly: - killer idea. I can't wait to see how it pans out.
    Last edited by spfautsch; 09-15-2017 at 06:37 PM.
    '95 C4 LT-1 ZF-6, Polo Green
    Comp 467 / XFI 280, UltraProMag RRs, LE1 Heads, Lunati 73925 Springs

    Somebody stole the spark plugs out of my other car, yet it still runs???

  5. #50
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    Quote Originally Posted by Aroberson77 View Post
    More rambling, but could you basically make a trigger wheel with 360 slots and one with 8 slots for the LS sensors to pick up? would whatever crank sensor is used in the LS engines work? Im gonna sketch something up today
    No reason you couldn't have a new optispark disk laser cut to your specs and installed in place of the original. Then "analog up" the signal to simulate a reluctor. Oh, wait.....forgot the magnetorestrictive sensor has a digital output like a hall effect sensor. No analoging needed.

    Neat post on the alternate opti-conversion, just wish they weren't trading one problem for another.....such as debris damaging those tiny teeth and crank sensor. The crank sensor would have to be a hi-impedence type just like an ABS wheel speed sensor to make it sensitive enough to work.
    Last edited by vilefly; 09-15-2017 at 06:53 PM.

  6. #51
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    Hey now! We did get a little off topic for a minute. Anyways, I am committed to help you guys find a good, reliable, economical solution. I'm sure Fast 355 will be just as generous with his time and expertise. (P.S. we know exactly how camshafts function).
    Last edited by Tom B.; 09-15-2017 at 06:50 PM.

  7. #52
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    Quote Originally Posted by Tom B. View Post
    (P.S. we know exactly how camshafts function).
    Then you should know it has nothing whatsoever to do with the engine it's installed in. It doesn't matter how many cylinders there are, if it's an inline or v60 or crossplane v90. In a four stroke engine the intake stroke occurs immediately after the exhaust stroke. End of discussion.

    This is a thread discussing the possibility of interfacing a cop setup to a PCM designed for for a distributor. Let's get away from the LS swap economics discussion. The subject has been beaten to death. Let it rest in peace.
    '95 C4 LT-1 ZF-6, Polo Green
    Comp 467 / XFI 280, UltraProMag RRs, LE1 Heads, Lunati 73925 Springs

    Somebody stole the spark plugs out of my other car, yet it still runs???

  8. #53
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    I will say this once and then I am done with it. Valve overlap has a lot to do with the way it affects how an engine runs. If your position is to the contrary, I can only surmise you are less experienced than some of us that know better. You and I don't know each other or our personal abilities and experience, so lets not to try to play school teacher.
    Back to the subject at hand. As far as this project goes, Andy should have the convertor box I sent him dissected in a timely fashion, and he and Vilefly will have a viable solution.
    Last edited by Tom B.; 09-15-2017 at 07:29 PM.

  9. #54
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    VF, I know those hall effect sensors might be more durable than the optical sensor, but Im not sure. It was hard to find one that had high enough frequency. I think a well sealed opti with no HV will live just fine. Im glad you found a chip that will work so easily.

  10. #55
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    Quote Originally Posted by Tom B. View Post
    Valve overlap has a lot to do with the way it affects how an engine runs. If your position is to the contrary, I can only surmise you are less experienced than some of us that know better.
    Valve overlap is a measurement in crankshaft degrees of how long the intake valve and exhaust valve are open at the same time. It is entirely controlled by the camshaft, and for most factory cams it's zero or very nearly. Let's get back to discussing what's relevant here. Overlap, whether in an LT or LS block, is not.
    '95 C4 LT-1 ZF-6, Polo Green
    Comp 467 / XFI 280, UltraProMag RRs, LE1 Heads, Lunati 73925 Springs

    Somebody stole the spark plugs out of my other car, yet it still runs???

  11. #56
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    I can only hope I will ever have time alone to myself to make a prototype. Hard enough to concentrate these days. I at least hope to post a schematic someday that works.
    It still would be cool to have interchangeable optical disks for various computers and such. Laser cut sheet metal. Sounds pretty cheap to me.
    Nissan uses such discs, too.
    Last edited by vilefly; 09-15-2017 at 07:37 PM.

  12. #57
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    Quote Originally Posted by Aroberson77 View Post
    VF, I know those hall effect sensors might be more durable than the optical sensor, but Im not sure. It was hard to find one that had high enough frequency. I think a well sealed opti with no HV will live just fine. Im glad you found a chip that will work so easily.
    Years ago, when HEI was all the rage, I had epoxied spark plug towers to HEI coils, had a mirror on the rotor and a IR detector/emitter in the cap. Everyone said I was crazy. I had found the 1-to-8 data distributor chip (as it was called) back then, but I didn't have squat for money, and the internet was not up.

  13. #58
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    The Opti without the high voltage running through it will be just fine. Just clean it up and seal it. The same sensors seem to run forever in the other cars they are installed in.

  14. #59
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    Nice project, I think it would be much easier just to use uP for coil switching, we are talking about frequencies of about 25kHz at 8k RPM, that's basically a slow signal for let's say AVR or STM32 running at a few MHz... But I appreciate your effort to make it discrete!

    Another point that comes to my mind is that almost all of the optis I had replaced had the optical sensor failing due to high temperature, NOT the HV part. It seems that over time temperature causes the LED and phototransistor to lost alignment somehow.

    I think a good solution would be to use vortec style cover with CKP sensor for hi-res signal (180 tooth wheel), and only low-res sensor in the opti. The question remains if the CKP sensor is capable of picking so dense teeth.

  15. #60
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    Quote Originally Posted by Tom B. View Post
    The Opti without the high voltage running through it will be just fine. Just clean it up and seal it. The same sensors seem to run forever in the other cars they are installed in.
    I'll agree with you on this one. The optis I've seen fail died in two different fashions. One was the cheap chinese junk replacement off eBay with the Chrysler optical sensor installed that loses high resolution signal when it gets hot. I have one of these and replaced the optical sensor with one from AIP Electronics that meets the specs of the original Mitsubishi unit. The others died because the optical wheel was destroyed by arcing from the high voltage side.

    As lionelhuntz mentioned, AIP Electronics makes a sensor that meets oem temperature specs. They're sometimes out of stock, but I've been running one in my triple-c opti from eBay (previous owner installed it) for going on 3 years now. No problems up to 6800 rpm rev limiter.
    Last edited by spfautsch; 09-16-2017 at 03:58 PM.
    '95 C4 LT-1 ZF-6, Polo Green
    Comp 467 / XFI 280, UltraProMag RRs, LE1 Heads, Lunati 73925 Springs

    Somebody stole the spark plugs out of my other car, yet it still runs???

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