DIY LTCC or similar system for LT1s

[spfautsch]

I've googled both #s on the wheels and come up with nothing. I believe the one I have is an aftermarket maker - these distributors can be had complete on parts sites for < $100 and they're described as "completely new". But the remanned delco remys are $165 for just the base (no cap or rotor) with a core, and nearly $300 for a semi-complete one (also with a core).

What I'd really like to know is what MSD is putting in their super pricey unit.

I knew something was wrong when I noticed some inconsistency in when the high res signal would turn off in relation to the low res coming on.

I suppose I'll keep the old unit to use for testing the controller on a bench. I'll be happy to have the engine back in without finding any more skeletons. I also discovered today that my flywheel + clutch is toast.

[kur4o]

There is no need to rotate the wheel inside the opti. You can set base timing point here "12044 Spark Reference Angle".
You can measure the wheel with a protractor. If the low res lots are 90* apart it is good. I can`t see a problem with the wheel except the possibility of unequally spaced high resolution slots, but even in that case you can`t have more than 360 degrees in a circle. So if you sum all the deviations it should equal that.
if one cylinder is advanced one of the next cylinders should be retarded.

Mechanical play can explain some of the advance. Uneven stretched chain and uneven worn cam/crank sprockets tooths too. So you need to investigate further for some other issues before dumping the opti.
The one you have looks like crap but as long it is working it is good. The one I had apart has opti wheel spot welded and p/n was starting with 10. I forgot to take some internal pictures.

[spfautsch]

I asked about Spark Reference Angle early in 2017 when I was generating a base tune for first fire. What do I put here, -3.5? Nobody seemed to know and Steveo told me I should just skew my coolant temp adder table.

The timing set is a cloyes heavy duty roller with less than 5500 miles on it, so I highly doubt the problem is slop in the timing set. If it were that I would expect to see fluctuation in the TDC signal, especially when I turn the engine backwards. The only reasonable explanation is that the trigger wheel was poorly cut.

[kur4o]

I asked about Spark Reference Angle early in 2017 when I was generating a base tune for first fire. What do I put here, -3.5? Nobody seemed to know and Steveo told me I should just skew my coolant temp adder table.

The timing set is a cloyes heavy duty roller with less than 5500 miles on it, so I highly doubt the problem is slop in the timing set. If it were that I would expect to see fluctuation in the TDC signal, especially when I turn the engine backwards. The only reasonable explanation is that the trigger wheel was poorly cut.

You need to set it at 3.5 degrees but it needs a whole number so you choose between 3 or 4 degrees. This scalar is substracted from total advance the PCM calculates. So if the PCM commands 30 degrees and the cam is advanced 3.5 degrees you will get 33.5 total minus the scalar 3 degrees. You get 30.5 at the end.

The fluctuation you get might be normal play. The PCM also have built in error margin. It is +-2 degrees from mid point for high resolutions counter. I`ve monitor the counter it is called CYLID in the stream. The midpoints are 46,56,66,76 and 86 for different cylinders. i checked some logs and compare result. On steady throtle till 3-4000 rpm you get most of the time *6s, At higher rpm and rapid accelerations you go at *5s and very rare 4*. I checked your last log and there is excessive *5 at low rpm. So there is definitely something wrong. Opti wheel or excessive slope at hardware components. I will dig some old tunerpro logs with heavily stretch chain and worn crank sprocket to compare results.

So upto 1.5 degrees deviation might be normal. As you might have noticed half the cylinder got good signal 3,6,5,7 and the other half got high error number. That is one full crank revolution for 3,6,5,7 and one full crank revolution for 2,1,8,4. Maybe half of the opti wheel is bad or it is half of the cam sprocket or cam related. Does the results are similar with the opti wheel at stock position?

[spfautsch]

I should have a remanned distributor base sometime next week. Hopefully it will have the 10475417 trigger wheel. I'll report back when it arrives.

Thanks for the explanation on the 12044 constant. The description in the xdfs I have aren't very specific as to what it does, and since there's no external markings I would have had no way to confirm whether it was removing or adding timing.

I didn't test thoroughly with the wheel in the original location, but I did move it twice after I removed the distributor the other day and observed 4 degrees of skew between cyl 1 and cyl 8 each time. The fit between the center hole in the trigger wheel and the centering hub of the distributor isn't extremely tight, but I can't see it causing a consistent 4 degrees of skew.

[spfautsch]

The fluctuation you get might be normal play. The PCM also have built in error margin. It is +-2 degrees from mid point for high resolutions counter. I`ve monitor the counter it is called CYLID in the stream. The midpoints are 46,56,66,76 and 86 for different cylinders.

I wanted to reply to this the other day but was busy getting my hands dirty. The numbers your'e seeing there directly correlate to this function in the sequence detection.

int8_t detectSequence(uint8_t seqDegrees) {

  // note: returns the index of sequencer array, not cylNo
  if ((seqDegrees > 82) && (seqDegrees < 90)) {

    return -1;
    
  } else {
                       // 90 - 14 = 76 #4
    if ((seqDegrees > 72) && (seqDegrees < 80)) {

      // next cyl #4
      return 2;
                      //  90 - 24 = 66 #6
    } else if ((seqDegrees > 62) && (seqDegrees < 70)) {

      // next cyl #6
      return 4;
                      // 90 - 34 = 56 #7
    } else if ((seqDegrees > 52) && (seqDegrees < 60)) {

      // next cyl #7
      return 6;
                      // 90 - 44 = 46 #1
    } else if ((seqDegrees > 42) && (seqDegrees < 50)) {

      // next cyl #1
      return 0;
     
    }
  
  }
  return 0;
  
}

Where 86 are the four non-indexed low-res slots, four degrees wide (2, 3, 5 & 8).

i checked some logs and compare result. On steady throtle till 3-4000 rpm you get most of the time *6s, At higher rpm and rapid accelerations you go at *5s and very rare 4*. I checked your last log and there is excessive *5 at low rpm.

Can you give me timestamps of this? The number here directly correlates to the error statistic "E" that the controller is streaming. Essentially $EE is giving the degree count when the low res slot ends (falling edge) as "CYLID". Mine is giving the remainder of 90 minus however many high res degrees were counted since the last low res rising edge (TDC). If it isn't counting 90 between each TDC signal then an interrupt was missed or there was some oscillation of the cam or distributor shaft that caused the phototransistor to be switced on and off twice on one trigger edge. It's been a week or better since I looked over these logs, but I don't recall seeing consistent error counts at low RPMs in the plaintext logs. This makes me think the PCM might be missing interrupts more than the controller is. It's also possible on vented optis that a few thousands of clearance between the cam dowel pin and the index slot in the opti drive could be to blame.

Whatever the case, I wanted to thank you for describing how the PCM keeps time on the low res pulses for RPM. It got me thinking in the right context to optimize the RPM tracking. I was hung up on needing absolute / literal time intervals (i.e. microseconds) to work with, but I was able to find a timer prescaler that let me have 16us resolution (very adequate) while keeping the low res timer value / RPM lookup in a 16 bit space as well as eliminating a bunch of uneccessary code. I was also able to change the lookup table so it uses these same time intervals, which eliminated the need to perform any math beyond comparisons for RPM tracking. Ultimately I'll have the uart logging spit out this raw number as well, and then will use a script or something on the computer that's doing the logging to convert it to human readable RPMs.

The next thing I'd like to tackle is doing something similar with voltage detection. The way it currently works the controller is taking the raw ADC values and converting that to millivolts, then translating that to an index to the voltage table (1v / row). The millivolt conversion and subsequent dissection into human readable voltage is highly intensive floating point math. If I can figure out how to handle the table creation using the precompiler I hope to be able to do the same with voltage detection so it uses the raw ADC values for table lookups. This will speed things up immensely.

Edit: after dropping 8 bennys on a new clutch and flywheel yesterday I needed to do something a little lighter and less depressing, so I installed my freshly painted coil brackets. Notice, no wood grain!

Pic1
Pic2
Pic3

[kur4o]

The numbers I saw in your last log testing the arduino controller. The first part when you are idling is rich on *5s. I dig an old log I made with stretched chain and heavily worn crank sprocket and found that at idle it is full with *7s which is very interesting. I suspect very small deviations at the opti will lead to 1-2 degree error. The opti I have is the old design so it might not be directly comparable with the dowel pin design.

My last logs with new chain and almost new crank sprocket with the same opti bring very consistent *6s at idle with coolant temperatures ranging from freezing cold to really hot.Only a moderate drop to *5s is seen at heavy acceleration above 3000 rpm and single *4s at 6000 rpm.

So in comparison a stretched chain will increment the second digit by one in most cases.

Glad I helped to optimize the code. The voltage aquisition at the PCM is really simple. You got ADC channel hex value of 00-ff where 1 corresponds to 0.1 volts. So you got 255 steps or 0-25.5 volts resolution.
I don`t know how arduino converts the ADC channel in hex, so I suggest, to log some raw data in hex from the ADC channel and see how voltage changes with 1 increment in hex. Than you can figure some easy conversion.

[vilefly]

The 96 roadmaster optispark that came in earlier this week looked original. Mitsubitsi pickup and all. The optical wheel had 10475417 on it.

[spfautsch]

The first part when you are idling is rich on *5s.

It sure is - I keep forgetting about the "hacker" view settings. I'll have to add a user setting to eehack so that's the default view.

Strangely, I see very few count errors in the microcontroller's log data. Nothing remotely close to the number of 5s I'm seeing just skimming through the .eedata log.

My last logs with new chain and almost new crank sprocket with the same opti bring very consistent *6s at idle with coolant temperatures ranging from freezing cold to really hot.Only a moderate drop to *5s is seen at heavy acceleration above 3000 rpm and single *4s at 6000 rpm.

Is this with stock valvetrain or do you have mods? I don't know if my roller rockers could be contributing any, but I have ~170lbs seat pressure and ~380lbs open springs.

I don`t know how arduino converts the ADC channel in hex, so I suggest, to log some raw data in hex from the ADC channel and see how voltage changes with 1 increment in hex. Than you can figure some easy conversion.

I already have the conversions worked out - the only difficulty I will have is calculating the dwell skew for different voltage ranges. I'm going to try to work that out now. The ADC in the mcu returns 0-1023 (0x0-0x3ff), which is far more resolution than required. I'm also using a voltage divider network to keep the ADC input within a range of 0-5v.

The 96 roadmaster optispark that came in earlier this week looked original. Mitsubitsi pickup and all. The optical wheel had 10475417 on it.

Thanks - I'm relatively sure that's the Delco Remy part. Curious, is that a low mileage roadmaster? Ironically I saw a beige wagon with the wood "inlay" this morning on my way to work. My wife would shoot me, but I'd just love to have a b-body wagon.