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Thread: DIY LTCC or similar system for LT1s

  1. #346
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by kur4o View Post
    The greater the force needed to push the object down, the greater the tilting of the object, if the force is applied off-center.
    That way the valve will rub the guide sideways. So the higher the pressure, the more exact center location is needed. If the spring were softer you might even not get a failure.
    If I had the energy to further debate valvetrain geometry, it would be a discussion better suited for a "religion, politics & ford vs. chevy" sub-forum. After dumping another grand on a set of rockers and having bronze guide inserts installed, I'm patently sick of the subject at the moment.

    Quote Originally Posted by kur4o View Post
    I suggest you recalculate the spring rates and use the spring that can tolerate your RPM band and no higher.
    I discussed the subject in detail with Lloyd last year. All the research we could gather indicated that the XFI lobe design requires a lot more spring pressure than Comp specifies to control the valves above 6000 rpm. So if I go with softer springs the cam has to go. It's a really unique grind - basically capable of 480 crank hp in a 350/5.7 while having an idle lope that's less "conspicuous" than the GMPP hotcam.

    Anyway, back to the DIY-LTCC discussion - I don't think I snapped any pictures to share but when I built the prototype controller (the one I'll be more or less permanently installing in the car) I added another analog input to the harness for MAP. I'm hoping with the removal of all the floating point math from the code, the mcu will have enough overhead to monitor both system voltage and MAP (for accelleration compensation of dwell). The ADC section of the arduinos is a bit finnicky so I'm not very confident it will work well, but I thought it was worth a shot.

  2. #347
    Fuel Injected! Terminal_Crazy's Avatar
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    Quote Originally Posted by spfautsch View Post
    .



    I discussed the subject in detail with Lloyd last year. All the research we could gather indicated that the XFI lobe design requires a lot more spring pressure than Comp specifies to control the valves above 6000 rpm. So if I go with softer springs the cam has to go. It's a really unique grind - basically capable of 480 crank hp in a 350/5.7 while having an idle lope that's less "conspicuous" than the GMPP hotcam.
    .
    OOI, What specs have you got on the cam?
    I went with the high lift version of Lloyd’s 223,230 on a 112
    Lift I think is something like 0.598 0.610
    In a 383 it does not sound very lumpy but I need to pass emission sniff test which it does no problem so I know I can go bigger if needed ��
    Mitch
    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  3. #348
    Fuel Injected! spfautsch's Avatar
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    Code:
    CC P/N: 07-467-8
    Grind #: 280XFI HR13
    RPM Range: 2000-6000
    Valve Timing: 0.006
    Lobe Separation Angle: 113
    ICL: 109
    
            Intake    Exhaust
    Duration:    280    288
    Duration @.050    230    236
    Gross Lift:    .576    .570  (@ 1.6:1 rocker ratio)
    Lobe Lift:    .361    .358
    Would anyone be interested in designing a PCB for the controller? I've got my hands full at the moment and have zero experience in this area.

  4. #349
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by spfautsch View Post
    Code:
    CC P/N: 07-467-8
    Grind #: 280XFI HR13
    RPM Range: 2000-6000
    Incidentally, from what I've been able to gather this cam profile will make good power well into the neighborhood of 7000 rpm. Coincidentally, Comp doesn't sell a valve spring package that will fit the LT-1 that will keep the valves out of float beyond 6200 rpm. They do however sell sh 1 tty beehive stuff that will take you to right around 6200 - until they start to fatigue and break.

  5. #350
    Fuel Injected! vilefly's Avatar
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    A CHEAP OSCILLOSCOPE FOR ANYONE WITH A LAPTOP AND AN ARDUINO. Uses only 7 lines of code and the latest arduino software.
    https://www.build-electronic-circuit...scope-updated/

    The code basically sets up an input and sends it to the serial laptop cable. Use the new "serial plotter" tool in the software to graph the output.
    DO NOT EXCEED 5V AT THE INPUT PINS. Use a voltage divider if going above 5v. I suggest a 5v zener diode across the pins for safety against spikes.
    There. Now everyone can give us screenshots. ha.

  6. #351
    Fuel Injected! vilefly's Avatar
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    Would anyone be interested in designing a PCB for the controller? I've got my hands full at the moment and have zero experience in this area.[/QUOTE]

    I am looking into it, but this laptop needs replacing 1st. keeps crashing. PCB webdesigner looks promising as far as freeware goes. I will have to learn how to use it as well. A complete schematic is required before it maybe "optimizes" parts placement......I think. Reading between the crashes is a pain. I have a cpu fan ordered for the other laptop. I decided to fail on me, too. I blame the pets. PC board etching is pretty simple, just have to learn the software.

  7. #352
    Fuel Injected! sturgillbd's Avatar
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    I use EagleCad for pcb design. Cadsoft has changed the way they do licensing and I don't like the newer software. I may have a copy on an old laptop and can take shot at designing. I probably still have access to the LPKF Protomat pcb mill at my previous employer. If anyone goes ahead and designs the board, see if you can output a gerber file. If so I can get a board or two made free. Keep to max of two layer board because 4 layer sucks by how we had to assemble the boards.

  8. #353
    Fuel Injected! spfautsch's Avatar
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    I'll try to get the full schematic sans boarduino / arduino daughter board completed this week while I'm waiting for my heads to get done. It should be easy to do in a two layer, but it might even be possible to do single layer with a handful of shunts.

    Hoping to finish the prototype case tomorrow. It's not going to be very professional looking but I had to make do with what case options I could dig out of my parts bin.

  9. #354
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    This is how I built my pc oscilloscope https://m.facebook.com/profile.php?i...content_filter

  10. #355
    Fuel Injected! vilefly's Avatar
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    I have always been suspicious of the accuracy of the soundcard oscilloscope. The input is supposed to be 1v p-p, and this one is regulated at 5v, which would allow distortion to crab up the readings, and the arduino based one can display more that two inputs at a time. It's very handy for more than 2 traces, even though it is primitive. Just add more input pins/variables. The limit is how messy the graph turns out.

  11. #356
    Fuel Injected! spfautsch's Avatar
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    Last night I put waterproof connectors on my prototype's pigtails and it's ready to go in the car after I seal the case with some silicone. In finishing all this I wanted to test out the extra input I wired for the MAP sensor. I'm happy to report that it looks like manually interfacing to the ADC section of the microcontroller yielded much more reliable and faster results than I had using the arduino analogRead() function with other projects using multiple analog inputs. Unless there's some other unforeseen issue I think this will work very well. And since I retooled the code to eliminate floating point math pretty much everywhere, I built a bash script to convert the raw datastream to human readable values (voltage and rpm, map will follow).

    pic1
    pic2
    pic3
    pic4

    Getting to this milestone, I have to ask kur4o if he might be able to pick apart the portions of the $ee program pertinent to how MAP effects dwell and explain it in laymen's terms. I'm sure anything I come up with for this will be better than no dwell compensation, but I'd like to utilize this additional input's data in the most efficient way possible.

    I'm jonesing for an email from Lloyd telling me my heads are on their way back. In the mean time I'll try to finish the schematic and see what options there are for pcb design. I found this on Monday, but haven't gotten as far as building it or trying it out.

  12. #357
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    So are you adding second map sensor or using the stock one with shared wire. First check for interference between PCM and arduino. Maybe some isolation will be needed.
    What I remember it uses some delta map value to find out when the engine was accel and decel mode. The dwell was added only in accel mode. I will dig through it more thoroughly and write back shortly.

  13. #358
    Fuel Injected! spfautsch's Avatar
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    The intention was shared wire to the factory map sensor. The ADC inputs on the arduino are fairly high impedance (100M ohm) and using the internal reference voltage will give 0-5v range so no voltage divider will be needed. I don't anticipate a problem doing this, but I will test by disconnecting the map wire from the controller while running and observing if the PCM is reporting a change.

    By delta are you saying it stores the most recent map value in a variable and then compares the next reading to the stored one? That sounds simple enough. I'll probably want a deadband around the stored delta value or use some hysteresis logic to prevent oscillation.

  14. #359
    Fuel Injected! spfautsch's Avatar
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    After pulling most of what little hair I have left out, I'm happy to report it's finally running again.

    Spent the last two weeks beating my head against a wall trying to figure out why I was getting noise on the low res input. Since everything important has changed - new opti pickup, major wiring harness revision, prototype controller board - there were plenty of variables to weed out. I'm still not sure, but I think the optical sensor had the biggest effect. In the end I found that some of the input capture code I used for the timer that measures rpm via the low res signal had some problems that were disabling the noise canceling section of the timer. One line of code was the difference between starting and stalling immediately, and running.

    The map sense line appears to work without affecting the PCM's analog input. Also the major code revision removing all the voltage and rpm conversions to human readable values (thus eliminating the floating point math burden from the mcu) seems to work fine. I hope to test another version tomorrow that gives 4us instead of 16us timer ticks for rpm tracking which should give better resolution there. Also hoping to get a test drive in to see if there are any signs of hesitation like the initial test drive.

    There's still a bunch of code cleanup and optimization to do, and I still haven't had a chance to finish the schematic or put any effort into designing a pcb. Even worse, I have to reverse some of the changes I made to the prototype board trying to eliminate possible sources of noise so I can verify the entire circuit works as designed.

  15. #360
    Fuel Injected! vilefly's Avatar
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    I am constructing a test bench setup, now that I have my coils, so that I might be able to post some waveforms as I try to follow along. Debating whether or not to dig up a distributor to spool up using a drill/motor or use a signal generator to get my input signals for the system. I suspect I should use the distributor approach to keep reality in the game. Haven't had much time as of late to do anything.

    I take it that the MAP sensor input is a prequel to setting up a spark table of some kind in the future. I wonder if there should be some optional code for a 2-bar map sensor. Just divide a regular map sensor reading by 2. This, of course, is not a priority.

    I hope to catch up, and provide some help on the matter soon.

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