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Thread: DIY LTCC or similar system for LT1s

  1. #751
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by kur4o View Post
    I did one start with some idling till warmed up.
    Are you meaning with engine running from all 8 cop coils, or some other testing configuration?

    Quote Originally Posted by kur4o View Post
    Started within 1 second of cranking.
    This is not what I would call a good description of an LT-1 starting. I've had one somewhat "sketchy" start since moving to the 0.9.40 release. Otherwise it's been great, but with maybe 90 degrees more crank rotation. I actually logged it and can see the EST line arming / going high and then firing before the first cylinder would have fired (but wasn't because no dwell). I might do a pass-through thing for this to get fire sooner because the issue is going to be flooding the engine before any spark is delivered. But I think you have some other issues. A full second of cranking is very long for a healthy LT-1.

    Quote Originally Posted by kur4o View Post
    Will do more tests of random cranking.
    My suggestion would be not to worry a bunch right now about trying to make it break during startup with random "trickery". Unless your perception of 1 second (1000 milliseconds) is a lot different than mine, you have some other start related issue that's obviously happening with your stock ignition system also. You said it here "Started on the second try which is not unusual on my setup".

    I may be completely out to lunch here, but I think your injector flow constant is way off in left field. I would like to say you can trust me but I can't. What I can say is that after about a year of trying to extrapolate my IFC by way of trim numbers and then settling on where I'm at now, it hasn't started this well since I put my Multec injectors in the storage tote.

    Quote Originally Posted by kur4o View Post
    On light throttle change I feel very little hesitation, On hard throttle change no hesitation at all.
    Let's revisit this after you answer my first question.

  2. #752
    Fuel Injected!
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    All 8 coils hooked up for the test.
    There were total of 12 led events before it fired off and I got a led on second or third crank TDC which is pretty good.

    It only takes some time to fire up only on first start, after it have been sitting for some time[First cold start]. I suspect fueling since I was seeing coil firing on the leds. After the first start it fires off almost immediately[0.3s range]. After it get soaked on the first short try. It fires off immediately on the second try. I might play with FIC constant or first prime pulse.

  3. #753
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by kur4o View Post
    It only takes some time to fire up only on first start, after it have been sitting for some time[First cold start]. I suspect fueling since I was seeing coil firing...
    I personally think you have a badly leaking injector, fuel pressure regulator, or bad check valve in your fuel pump. But it could be anything. Unfortunately without having known perfect fuel injector data, it's going to be very difficult to surmise where the problem is.

    Whatever the case, for the benefit of everyone else watching this thread, kur4o sent me a PM of a video of his start attempt. Out of respect for his privacy I'm not going to share it. But I do plan to go over it frame by frame. My initial impression is that I have no reason to doubt it. So I think we have a winner!

    kur4o let me know via PM how I can get the prize to you and in what form you would like it (if other than 100 USD).

    More importantly let me know how it goes when you try to re-start it after cool-down, etc.

    I think I'm going to go start mine if only for amusement purposes. My neighbor already refers to it as "the engine" so what harm could come of some more punishment of their aural senses?

  4. #754
    Fuel Injected! spfautsch's Avatar
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    Here's another release.

    Code:
    0.9.41 - 9/22/2020
    
    Removed all references to arduino digitalRead() and digitalWrite()
    
    Added EST passthrough in EST rising edge interrupt handler for faster first dwell
    
    Increased MAP vs RPM multipliers slightly in cruising range
    I've driven this about 275 miles without major incident. Mileage on the last fill-up was 24.3 mpg, which was somewhat surprising since I haven't exactly been babying the go pedal. Cold starts have been a little slobbery, but the ambient temp has been dramatically lower in the mornings the past week or two. Then this morning it set a DTC43 when starting, which cleared on it's own after a few seconds of runtime.

    I was somewhat concerned with this DTC when I hooked up my laptop to see what it was, because eehack has a description of "ESC Failure" for it. But EagleMark's original thread [here] describes it as a "Knock Sensor (KS) Circuit". So not sure what to make of this. I haven't seen the CEL light with the engine running in around 2 years. I didn't even think the '95s were equipped to sense a disconnected knock sensor circuit??? Would love to have a better description of what this DTC trigger conditions are but haven't been able to locate where these live in the 2000+ pages of the FSM. Whatever the case I'll report back if it reoccurs.

    Still haven't heard anything further from kur4o - hoping everything's well. I'd like to get you your prize money and hopefully try to see if we can further investigate the light acceleration stumble you mentioned. That is, if your rig is still in running order...
    Attached Files Attached Files

  5. #755
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    Quote Originally Posted by spfautsch View Post
    Here's another release.

    Code:
    0.9.41 - 9/22/2020
    
    Removed all references to arduino digitalRead() and digitalWrite()
    
    Added EST passthrough in EST rising edge interrupt handler for faster first dwell
    
    Increased MAP vs RPM multipliers slightly in cruising range
    I've driven this about 275 miles without major incident. Mileage on the last fill-up was 24.3 mpg, which was somewhat surprising since I haven't exactly been babying the go pedal. Cold starts have been a little slobbery, but the ambient temp has been dramatically lower in the mornings the past week or two. Then this morning it set a DTC43 when starting, which cleared on it's own after a few seconds of runtime.

    I was somewhat concerned with this DTC when I hooked up my laptop to see what it was, because eehack has a description of "ESC Failure" for it. But EagleMark's original thread [here] describes it as a "Knock Sensor (KS) Circuit". So not sure what to make of this. I haven't seen the CEL light with the engine running in around 2 years. I didn't even think the '95s were equipped to sense a disconnected knock sensor circuit??? Would love to have a better description of what this DTC trigger conditions are but haven't been able to locate where these live in the 2000+ pages of the FSM. Whatever the case I'll report back if it reoccurs.

    Still haven't heard anything further from kur4o - hoping everything's well. I'd like to get you your prize money and hopefully try to see if we can further investigate the light acceleration stumble you mentioned. That is, if your rig is still in running order...
    As someone who owns a '95 and had that CEL himself, yes, they're wired the same way as all the older C4s (which is why the knock sensor part number is shared until 1996). The knock sensor on our cars has a resistor inside the sensor that the PCM uses to detect whether the sensor is physically present. When this resistor inevitably breaks or fails to be in the correct range, it triggers DTC 43. But this doesn't mean the sensor failed--it just means the resistor is no longer in spec. You can fix it by replacing the sensor, but I just disabled the DTC in my BIN since I could see in EEHack that the sensors were still working perfectly fine.
    1994 Corvette (Automatic)
    1995 Corvette (Manual)

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