Anyone worked with the 16196397 yet?

[RobertISaar]

so, I'm blind. these images looked in-focus through the viewfinder of the SLR, turns out I really, REALLY need to go have my lens prescription updated. autofocus doesn't appear to like many-faceted reflective surfaces, so I had to go about it manually. combine that with a 1.8 aperture and things can get messy at times. these are the best of the groups that I shot.

all of the images should be in the same orientation as the mspaint outline, at least the chip-sides are. on the reverse side of the board, obviously there is going to be a horizontal flip, but it shouldn't be too difficult to figure out.

[RobertISaar]

i can't figure out how to reasonably format the text in the posts either, so here is the .txt version. should be a little easier to read considering how many Tabs I put into my documents.

[Xnke]

Back in the workshop tonight.

Since the heads needed a valve job anyway, I set the flow bench up in %Flow and started working on the intake port. I still don't have my calibrated venturis made, so I can only measure gains against the fixed orifice plate. I have what the stock heads flowed on a different bench on a different day, but using a clean valve and clean stock port, on the factory valve job, I set a baseline, then worked the port to produce a fair increase in flow while only removing 2.1CC's of material. Low-lift flow didn't suffer any, flow at 0.250" lift picked up 14%, and flow at 0.500" lift picked up 16%. Port is a little howly at 0.500" lift. At 0.550" lift it is louder, same pitch, and flow only picks up about 4% over stock. At least it didn't loose any! Stock, the port was quiet at all lifts. I did not open the gasket face of the port up any at all, MCSA is unchanged from stock. Mostly reduced and re-shaped the valve guide boss, the rest of the port just needed a little cleaning up of casting flaws around the valve seat. Port hasn't been cartridge-rolled yet, so it's right off the carbide. I didn't nick up the stock seats, so this is all on a stock valve job so far. The combustion chamber needs some attention, lots of sharp edges left over from the factory seat cutter, basically a sharp ring all the way round the valve on the intake. Exhaust valve has a nice smooth cut though, on most of the chambers. I will clean off the sharp edge and that's it for the chamber.







Found out that Comp Cams PN 26986 springs will fit the stock seats/seals/retainers, which is nice. They seem to be a universal spring with a 1" ID and 1.45" OD at the base, and with the 0.650" ID at the top, LS1-style retainers work too. PAC-1286 is the same spring, Scorpion Racing SRP-1286 is the same spring. I am calling PSI springs tomorrow to see what they got. The Comp springs are slightly over budget at this point, but something will have to happen, as the stock springs checked out all over the place for spring rate...out of 12 springs, the deviation from mean was 22%.

I asked about the resistors as I am trying to work out how they're arranged...is it a series 10K with a 1K pulldown on the 68HC11 side or a 1K pulldown on the outside-world side?

[RobertISaar]

going off of memory, it's going to be something like:

sensor signal wire->pulldown resistor->isolation resistor->A/D pin

most of the a/d channels have a cap after the isolation resistor to form a RC low-pass filter, but I don't believe that I found one with the A28 circuit, but I did with the A4.

[Xnke]

Do the existing O2 sensor lines have that low pass filter circuit?

I just checked my A28, it doesn't appear to have a cap in place either. Only need one of these to be suitable, I know an Innovate LC1/LC2 can source enough to drive most A/D inputs, just have to work out what the logged values would be. In this case, A28 will likely need that 1K pullup removed and reconfigured for a 10k/10k voltage divider, good medium impedance input but still a 1:1 ratio-simple 0-255 range over which to work a 0-5V logged voltage. Wideband O2 fueling control isn't really needed if it's being logged.

You seem to have A28 listed as connected to E-side 68HC11 channel 4, as well as T-side mux channel 5. Is that correct?

[RobertISaar]

i would be surprised if it were setup any differently than how it is on every other GM ECM:



since O2LO is tied to ground, the cap running from O2HI to O2LO after a 100 ohm resistor is a RC low-pass circuit. without knowing the value of the cap, hard to say what it allows though.

A28 should be a pulldown, not a pullup? it's possible I stuck my probe onto a 5V reference pad and saw no resistance, but I'm fairly certain I just used the gigantic ground planes to be certain. as-is, a 1K pulldown with a 0-5V signal will draw up to 5mA, I would think that would already be well within the wideband controller's capabilities? a 10K would obviously bring it down to .5mA peak.

with the pulldown being where it is in relation to the isolation resistor, it isn't going to form a voltage divider, if that's what you're thinking.

I do remember A28 being a weird setup.... as if the factory intended to use it for something but dropped it for production vehicles. the code never references using that channel on either PROM, so what exactly was going to be done with it, I don't know. considering that there was barely enough space left on the T-side to perform an A/D conversion, I get the feeling that there was either a 64KB PROM on at least the T-side at one point(I never check to see if the PROM's pin 3 trace was broken out or not), or it was being used as an engineering-specific extra a/d channel... no idea what they would have used it for though.

something I'm remembering at the moment is that for GM MAP sensors, there is supposed to be a 50 or 51K pulldown for the A/D channel, though I couldn't say why(a guess would be due to the MAP sensor itself being fairly high impedance), it's just something I'm remembering seeing on the datasheet for one of them. something to keep in mind should a baro sensor route be taken.

[Xnke]

It's funny you mention the PROM size, as both my 4347 and 6397 have 256K chips fitted to the board. What's limiting the program size?

Yes, the widebands I am familiar with will drive a 5mA load, but I generally try not to ask much of the sensors I can't control-with so many wideband controllers out there, some of them may not drive a 5mA sink.

I'll do a little more digging around on the board before I close up the 6397 case, make sure things are working the way I'd need them to and confirm with you that A28 is a viable input for a wideband logging input.

EDIT: It looks like on the 6397, at least in a main-power-off state, that a 0-5V input results in a 0.9 to 1.5v change on pin AD4 on the E-side MCU. That's good enough for me, I believe that logging and reporting the voltage on that pin could be used to monitor AFR. Is there enough room left in the program to log 0 to 255ADC count as a linear 10.0 to 20.0 AFR? That would work out as a simple 0-5V wideband input, usable by most brands of WB02 controller out there.