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Thread: DIY LTCC or similar system for LT1s

  1. #451
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    beta 1 - the obvious subtext here is the need for testers.
    I would be interested, just starting tuning but familiar with arduino and Electronics. Master Electrician and have 3 93 Camaro Z28's, a 95 LT1 I am putting in an 80 Camaro and 3 LT1 engines in boxes.

  2. #452
    Fuel Injected! spfautsch's Avatar
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    I'll shoot you a PM after tomorrow assuming I don't die in a fireball. Fair warning - the letters "DIY" in the title are literal. I'll do what I can to help but what I have is an assemble-yourself PCB sans case, a few text files with wiring pinouts and a handful of connectors that might make it easier to install. You'll need to use some creativity but if you're comfortable hacking on wiring harnesses and have a mule you don't mind being out of service for a week or so it should be relatively straightforward.

    I've put a little more than 50 miles on it today including some highway cruising. That's the same amount of mileage accumulated throughout all of 2018, so I consider that a victory already. I'm about 80% confident what the butt dyno is feeling around 1700 rpm is lean misfire from removing spark advance in these low-load ranges where the cam overlap generates lots of EGR. My new tuning guru tells me I need to add spark advance in this region right before the cam starts to breathe. I've been doing a little tuning on that today and it's responding nicely. I've even regained the use of 6th gear below 65mph, which is probably partly due to the longer rods and bigger displacement.

    I've got my fire extinguisher, the phone # of a towing company on speed dial, and my lucky 4 leaf clover ready for my commute tomorrow. I hope none of them are called on.

  3. #453
    Fuel Injected! spfautsch's Avatar
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    Put roughly ~130 miles on it today directly to and from work with no breaks. Mild weather day so no extreme temps, but nothing went wrong. Ran like a champ - cruising on i-70 in 6th the rev counter was right on 1700 and much of the two lane driving had it hovering around 2000. Ran pretty much like I remember it before I gutted the opti except a lot more available power when my right foot developed a mind of it's own. The added power is due to an increase of displacement, not the ignition controller btw.

    To the extent I've been able to test - where the primary instrument has been the venerable butt dyno, I'm happy with the current state of the 0.9.17 firmware. I'd love to see someone confirm or debunk my results, preferably on a bone stock LT-1 that runs well. If it weren't for my wife directly threatening to kill me if I buy another car, I'd go shopping for a test mule this weekend. But funds are thin and I've got a lot of tuning to do.

    I have two unclaimed PCB kits that I can have programmed with the 0.9.17 firmware and ready to hit the mail early next week. I also have some water resistant connectors (see post 407) for anyone with a suitable crimper. You'll need 8 coils, 8 connectors for said coils, a way to mount the PCB that will keep it out of the weather, and enough grit to chop up a perfectly good wiring harness.

    I'll entertain PMs for the remaining PCB kits, but please don't waste my time. If this is as far as this project goes I'm happy with what it is.

  4. #454
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    Put another 60+ miles on it over the weekend collecting tuning data. Running open loop and in the process of determining base fueling, thus running really rich, I experienced zero problems I could remotely attribute to the ignition controller. Not even one "hiccup".

  5. #455
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    Do you suspect you are running into a lean-cruise vs cam situation? It would make it harder to jump the gap during a lean condition, for sure. Seen it with other vehicles that had vacuum leaks from their plastic manifolds. I wonder if messing with the lean-cruise setup would help. Per usual, I have spoken before I did my research. I am not even sure it can be tinkered with or not.

  6. #456
    Fuel Injected! spfautsch's Avatar
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    There's no lean cruise strategy in $EE as far as I know, it's 100% reversion from the cam. As I mentioned, running in open loop there were no problems. In fact when I was tuning on it Sunday afternoon the thought that the ignition system had been modified so extensively never once crossed my mind.

    For the most part, I'm considering my work here as being done. I would like to have a more complete "product" with a case and partial harness, but that isn't something I anticipate having time for because I'm moving on to bigger and better things like learning the ins and outs of the wideband O2, figuring out how to objectively find the flow constant of my mystery fuel injectors, and perfecting my tune.

    There are still two PCB kits available. $25 shipped to the lower 48, $30 to non-customs regions, and $35 to any place requiring it go through customs. PM me with your intentions and I'll dole them out to the best test candidates. F-Body wanted both but one of his projects is a transplant and the others sound like they're built and thus aren't what I would consider ideal for verifying the functionality of the ignition controller. I will still send you one if you'd like though.

    It's time the rest of you do your part to make the project be fruitful and multiply. Or not. I really don't care one way or another. I have about 500 miles on it thus far and quite happy with where it's at so probably won't report back unless a problem is encountered or I make changes to the source.

  7. #457
    Fuel Injected! vilefly's Avatar
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    I guess it is time for a project summary, then.
    For those who weren't with us when it started, one merely needs to click the "Arduino based coil per cylinder controller for LT1s" link at the bottom of Spfautsch's posts.
    This will take you to the GitHub page for the project files and details, including schematics.

    The code has user changeable parts in it for things such as what type of coil you are using and what the target dwell time should be. The Ion Sense portion of it is for me to tinker with, so I might be able to use it to create a spark advance table on the fly or something else entirely.

    The code also tells you to select Arduino Uno as your board so that you can flash program it using the Arduino software. Remember folks, this is open source, so have fun altering what you like, but keep us informed of any breakthroughs.

    The next step in this project, for me, is to add another arduino to read/process Ion Sense data, so spark advance can be controlled in a closed loop fashion, with a dedicated memory array for adaptive learning/engine mapping feature. The great part about Ion Sensing, is individual cylinder knock sensing, which should result in a more robust timing table. Anyways, I need to stop rambling on, and get to work on installing my coils and system.

    A hearty round of applause for SpFautsch, if you please, who championed the project when it had begun to falter, and saved it from becoming a pipe dream.

  8. #458
    Fuel Injected! spfautsch's Avatar
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    Thanks for the summary - I also wanted to drop a link here to the post #387 with some PCB assembly pointers.

    Attachment 'diy-ltcc-rev1-bom.txt' contains the bill of materials to help with identifying the component values.

    'pcb-connections.txt' identifies what the different input and output designators on the board are, and includes some notes about how I tapped into my harness, fuse requirements, and some useful usb->rs232 info.

    'wiring-pinouts.txt' mainly identifies the pinouts for the waterproof connectors I used - this probably wont' be useful to anyone but the wire colors might be helpful. It also lists the connector and pin #s of the different circuits that need to be tapped if you want to connect near the PCM.

    I'll try to make time to package these up in a zip with the assembly notes from that post sometime soon. Will upload to github or possibly move it all to my personal webserver.

    F-Body you should be seeing your kit sometime in the next day or two.

    Edit: I still have one board kit that's not spoken for
    Attached Files Attached Files

  9. #459
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    Quote Originally Posted by spfautsch View Post
    I still have one board kit that's not spoken for
    Hey there! I'm currently on a binge reading through all the threads from start to finish on $EEhack, $EEX and DIY-LTCC since I just acquired a '94 Corvette. I usually work on JDM vehicles, and have been dealing with serial data interfaces and hardware modifications for about a decade now on things like Subarus, Nissans and Hondas. I even have a G-sensor based around an ATmega328 controller running a GT-R's AWD system, so when I saw that your DIY-LTCC used the same controller I was pretty impressed!

    The Opti in my C4 is running for now, but as with all Optis I'm sure it's a matter of time, and my very first thought was to swap to COP. I'd love to give your solution a shot, and should be able to give any necessary feedback or troubleshooting assistance with development. I will however say that when it comes to fine-tuning ignition timing in hardware I'm inexperienced, so I'm afraid that I can't immediately offer any suggestions on improvements or changes to the Arduino code you have up already. Is this last board kit still available? If so, I would love to try it out. Either way, best of luck to you on the project! I'll keep an eye out!

    P.S. Looks like you're pretty popular, your PM box is full. ;)

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  11. #461
    Fuel Injected! steveo's Avatar
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    if anyone is desperate i have a kit too and i doubt i'll ever use it due to lack of time and other proects...prove it'll be used for a good cause and for productive testing and i'll send 'er to you for postage.

  12. #462
    Fuel Injected! spfautsch's Avatar
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    Hey steveo why don't you hang on to that for someone in Canada. Or, just use it as a paperweight - as I said I wanted to express my appreciation in some way. The cost and hassle of getting it back through customs would be shamefully wasteful.

    I do have one more unassembled kit I was hoarding for an emergency, and I will make it available if the right person comes along. I also have an assembled spare for myself so it's not going to cause me any difficulties.

    Once these are all gone I will make some revisions and get another batch of boards made. In addition to wanting to add an ICP header, the coil indicator leds need to be omitted because I believe they're overtaxing the AVR's power capabilities. I've yet to confirm this scientifically, but one of my chronic problems has been running extremely rich. I believe this has developed over time due to the AVR's internal current shunt burning out causing the output voltage to drop which I suspect results in very weak spark. When I got this running at first it was running phenomenally, but the more I ran it the worse it got now to the point it won't idle b/c the iac is pegged open. I'm waiting for pushrods to get my engine back together before I can confirm. Once I can I'll post a revised assembly guide to address this.

    EDIT: By the way - for anyone intending to test I thought it would be a good idea to mention that you try and locate the board / case in the coolest location possible. There's a post somewhere that demonstrates where mine is mounted below the battery. Inside the passenger compartment couldn't hurt either but may be overkill. Whatever the case, I wouldn't advise mounting it where the ICM was - right behind the radiator's airstream. The 328P (microcontroller) is rated for a maximum operating temp of 125C. Some of the other components aren't quite as robust.

  13. #463
    Fuel Injected! steveo's Avatar
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    i appreciate it for sure, the effort you've put into this is pretty insane.

    honestly i do plan to build one but it might take a few years since i don't have a vehicle to use it on, and it probably wont be an LT1 so i'll have to redesign large chunks of it, but most it will be workable.

  14. #464
    Fuel Injected! spfautsch's Avatar
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    Anyone with a kit who's intending to use it, particularly NomakeWan and F-Body you guys will want to drag your heels a bit on your plans with that. If you haven't noticed my other thread, I'm having driveability problems since summer and the accompanying humidity have arrived, and a lot of my problems seem to point to consistently weak spark. See discussion thread here.

    In the process of trying to track down the problems I discovered the coils I have are not the higher energy truck / corvette coils that only require ~4ms, but in fact normal 6ms coils. The firmware on all the AVRs I've shipped is using the 4.5ms dwell target. This is easy to fix by simply un-commenting the dwell targets you want and re-flashing the AVR.

    Last night I had a chance to do some testing with a scope and was able to confirm that the dwell time is correct - commanded 5.8ms at idle is giving exactly that according to my antique test equipment.

    What I'm concerned with is the current draw the coil's igniter circuit is drawing. As I mentioned previously the coil indicators LEDs may be causing problems as well, but I didn't get a chance to measure their current draw. Measurements indicated the coils are only drawing 0.000425 amps (425 microamps). This seems low compared to what I've seen others mention. But it could also be nothing if the igniters have very sensitive FET inputs. I'm going to be experimenting with smaller resistors in the circuit to see what happens. If I can find enough 100 ohm resistors I hope to report back this weekend. Otherwise I'll have to wait for the parts from DigiKey.

    Sorry for any problems this might cause those of you who are actually planning / working on installing.

  15. #465
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    Thank you for the update! I wasn't planning on starting the project until this month anyway, so if I just hold off a little longer that's fine. I'll wait to see what your experiments with current draw find, then get to trying to adapt it to my car. That way if I have to build a driver circuit or something I can do it all at the same time.

    Best of luck, as always!

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