1976 530i ECU internal circuit boards view
Posted: Thu Feb 20, 2020 5:24 pm
Everyone,
I wanted to fork off this post from my "Eleanor" rebuild project so it would be easier for search queries to find (should anyone find the internals of an ECU interesting).
I've been reading Robert Bondi's excellent write-up on adding Lambda control to our L-Jetronic vehicles http://firstfives.org/faq/ljet/lambda530i.html and was curious if my ECU as-is had the pinouts to include an oxygen sensor to the wiring harness.
If you look at http://firstfives.org/faq/ljet/ecu_pinout.html, you'll see that pins 23 and 24 are meant for O2 connection. My ECU does have these pins intact as shown below:
Here's my ECU, follow the pinout in the link above to see the corresponding pinouts. You'll note that 23 and 24 are present on my ECU.
Disassembly is very easy. On the back are two flathead screws. Remove them.
And slide the aluminum housing backwards. The circuit boards will be exposed then.
One side of the ECU.
The other side of the ECU.
And an image of both circuit boards removed from the holding bracket. Note there are ZERO microchips! Yes, all of the air/fuel mixture "calculations" are done with clever usage of capacitors, resistors, diodes, and other circuitry that we nowadays relegate to microchips.
A closer look at one side...
And the other side.
I am amazed that the "complex" air/fuel ratios are controlled by these two circuit boards. But remember, this sort of technology also got a man to the moon...so while this is simplistic in comparison to modern DME's, it shows that clever usage of various electrical components can do these complex jobs.
(And yes, I am aware that microchips are effectively super-small versions of what we see here, but to see that in 1976, Bosch chose not to design a silicon microprocessor in lieu of this design, is kind of like seeing how the "sausage" was made.)
Mike
I wanted to fork off this post from my "Eleanor" rebuild project so it would be easier for search queries to find (should anyone find the internals of an ECU interesting).
I've been reading Robert Bondi's excellent write-up on adding Lambda control to our L-Jetronic vehicles http://firstfives.org/faq/ljet/lambda530i.html and was curious if my ECU as-is had the pinouts to include an oxygen sensor to the wiring harness.
If you look at http://firstfives.org/faq/ljet/ecu_pinout.html, you'll see that pins 23 and 24 are meant for O2 connection. My ECU does have these pins intact as shown below:
Here's my ECU, follow the pinout in the link above to see the corresponding pinouts. You'll note that 23 and 24 are present on my ECU.
Disassembly is very easy. On the back are two flathead screws. Remove them.
And slide the aluminum housing backwards. The circuit boards will be exposed then.
One side of the ECU.
The other side of the ECU.
And an image of both circuit boards removed from the holding bracket. Note there are ZERO microchips! Yes, all of the air/fuel mixture "calculations" are done with clever usage of capacitors, resistors, diodes, and other circuitry that we nowadays relegate to microchips.
A closer look at one side...
And the other side.
I am amazed that the "complex" air/fuel ratios are controlled by these two circuit boards. But remember, this sort of technology also got a man to the moon...so while this is simplistic in comparison to modern DME's, it shows that clever usage of various electrical components can do these complex jobs.
(And yes, I am aware that microchips are effectively super-small versions of what we see here, but to see that in 1976, Bosch chose not to design a silicon microprocessor in lieu of this design, is kind of like seeing how the "sausage" was made.)
Mike