Nice work on deciphering the abbreviations.
Nice work on deciphering the abbreviations.
Actually... it wasn't me doing the figuring out... a retired Delco engineer contacted me after reading my post and provided the information. So I'm pretty confident about its reliability.Originally Posted by sailorbob
Going back to this chart: https://i.postimg.cc/vH0WjsGV/Memcal-ESC-info.jpg it's clear that there are many ESC circuits (MASK SET=7KR, SUBSTRATE=2) that differ only in the laser trimming of the resistors and possibly the capacitors. If anyone has such an unused (or even blown-up) MEMCAL that they would be willing to donate to the cause, it might help me decipher which resistors are responsible for the various parameters in the table. The goal being a new ESC board that can be populated to reproduce any of these knock circuits. I will start tracing my ESC board tonight. BTW.... Does anyone know what engine used PROM code BAKJ... That's the MEMCAL I'm starting with.
Last edited by JeffS; 4 Weeks Ago at 06:00 PM.
BAKJ was used on a Buick V6 3.3L 'LG7' engine in the 01228706 ECU.
I haven't been able to locate a schematic for the 1228708 ECU. I know the 1228707 is basically the same in an "indoor" version with different connectors, but I haven't been able to find that schematic either. What would anyone suggest as an available schematic to start with in order to trace out the 1228708. In other words what available schematic is most similar to the 1228708 to give me a starting point?
Nice work! I am happy to donate a memcal or two for research if it helps.
Delcohacking.net is hosting copies of Ludis Langens' old ECM pages. These are the only sources I am aware of for schematics. We were told years ago that 1227749 is closest to the 8707/8708. There is additional circuitry in the 8707/8708 used to detect the presence of a 1X signal from the ignition module and if you are interested I believe I can track down posts from gearhead-efi that have more information.
The requirement for the additional 1X signal can be disabled in software.
There is at least one US calibration for 1228708 which does not use the 1X signal.
I've made some progress with my copy of the ESC circuit. The hardest part was carefully removing the snotty passivation goop covering the circuit. After that I traced the conductors with an ohm meter and measured all the resistor values. The input circuit is a bandpass filter using a multiple feedback op-amp topology. Guessing that the input capacitors were 1nF and plugging in the resistor values I measured results in a center frequency of 4.16KHz, a gain of 0.32, and a Q of 1.55. The gain and Q come pretty close to matching the 3.3L Buick parameters in the P4 Style ESC chart I referred to in post #18. My particular ESC has a small number "2" near one corner, and the number "05" laser etched in a box along the long edge. Could the "2" indicate substrate type "2" and the "05" refer to the number in the "Cal Code" column in the chart (for the Buick 3.3L engine)? If anyone has a spare memcal on hand for a known application, could you look for the laser etched number on the long edge and see if it matches the "Cal Code" entry for that engine in the "P4 Stye ESC" chart? http://www.gearhead-efi.com/Fuel-Inj...ges/attach/jpg
Last edited by JeffS; 2 Weeks Ago at 11:42 PM.
Well... the proof is in the measurement. On the network analyzer the center frequency is exactly 6.00Khz, the Q is 1.50 and the gain is 0.32 so my initial guess of 1nF caps was way off. But using 680pF for the caps gives a perfect match between the derived circuit, the measurements on the bench, and the parameters listed on the "P4 Style ESC" chart. Still a long way to go, but the input stage is now well understood.
Last edited by JeffS; 1 Week Ago at 05:32 PM.
Is that '1052' shown in the CalCode.jpg part of a 7 digit code? If so, I think the '05' is the Cal Code. The first digit is the board revision number and the remaining 4 digits are a date code.
SailorBob: That guess for the number in the big blue box is as good as any. Unfortunately, I left that memcal at work so I won't be able to view the remaining digits until Monday. But everyone out there with a memcal in hand could do a simple check to see if the laser etched number I've pointed out, or the seven digit printed code in the middle of the board match the Cal Code from the "P4 Style ESC" chart for their application.
1010270 - Esprit SE, 1181224 - Esprit GT3.
And those two memcals correspond to cal codes 01 and 18? How about the small box along the edge? Are they etched with 01 and 18?
I've seen several photos of other memcals on this forum, and they all seem to adhere to your numbering scheme for the first two or three digits. https://www.gearhead-efi.com/Fuel-In...0&d=1604228370 I can't make sense of any kind of date code.... standard date codes on electronic components are usually 4 digits with the first two being the week and the second two being the year... (e.g. 3491 would be 34th week of 1991).
Last edited by JeffS; 1 Week Ago at 04:04 AM.
The Esprit Cal Codes are from notes I have so I cannot check for any other numbers on the ESC filter.
Did a little more investigating today and figured out that the "Ignore Time" of 3 milliseconds and "Add On Time" of 4 milliseconds are done with RC time constants and comparators... so a simple and purely analog solution. The ignore and add times also correspond exactly to the times specified in the "P4 Style ESC" chart for Cal Type "05"
Last edited by JeffS; 1 Week Ago at 07:11 AM.
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