How the 4A-GE ECU works

[JMR_AW11]

Red Wrote:JMR-
I never said the Denso ECU's were primitive. In contrast, I said the ignition systems in these cars (and that means everything from the battery to the spark plug) were SEMI-primitive.
In the 1985 US AE88 we have a distributor cap and rotor, both mechanical parts that need routine replacement. That is, literally, SEMI (half) PRIMITIVE. If it also had mechanical points, I would call it totally primitive, because points+cap+rotor were the way cars were built 30 years earlier.
But by 1980, the US car makers had largely stopped using this system in favor of an all solid-state system (i.e. reluctor caps and magnetic sensors) so there were no mechanical tuneup parts to replace in the distributor cap. Toyota was still the more robust 2/3 of the obsoleted system, so I call it SEMI-PRIMITIVE since it was already OBSOLETE.
Thank god they at least got rid of the points, the worst part of it. I can set points to better than 1/2 degree of dwell, with just a feeler guage, but I'm happier not to need them at all.<G>

On using home builders? I'm fairly certain that Denso did in fact use them, I know that the Japanese auto industry used them for assembling startes and alterantors and this was reported in US business magazines which detailed the radical new "Just in Time" zero inventory system that the Japanese car makers were using, when it was "new" to US industry in the 70's or 80's. In the 70's Toyota was still pretty much a joke in the US, in the 80's these were still called "riceburners" because they just weren't up to par with the market standards, i.e. Honda had a massive class action suit over rust problems because they still hadn't learned to provide galvanic protection to metals.

The usual process would be for a company like Denso to build each of the ECU black modules themselves--just the black module with SMD's inside it--in a high tech facility. An then, at 7AM when a cottage worker came in to deliver the last night's work, they would be given ten or twenty more baskets, each basket with two black modules, to circuit boards, one ribbon cable--all the component parts to make up an ECU module. That "gross" assembly work would be done manually by 20-50-100 workers as it was needed to fill the next days orders. Literally, pieceworkers who were given NO WORK if there were no orders, and more work if there were orders. SMD assembly can also be done by the same process--you just need workers with different tools, better eyes, and a more valuable skill set. SMD "kits" of that kind are commercially sold in the US for various projects.

I do not know for a fact if Denso handled the ECU assemblies this way, I do know that style of work, in that industry, was happening at that time. And the way the ECU's are laid out, makes them a good candidate for that time of work.

When you consider the even the Apollo moon lander modules were all HAND ASSEMBLED, and the International Space Station today is still being HAND ASSEMBLED, it can still be the right way to build high technology products.<G>

Again, I didn't call the ECU's themselves primitive. Although, I would certainly like to know if they could be improved (for a stock NA engine like mine) and I'd really really like to know if there are specific differences in the ECUs or the maps from 1985 to the later models.

There are performance differences (significant gas mileage increase) in the last two years that none of us have found an explanantion for, in the US. The tire size change can't account for it, and I don't think the combustion chamber design or heads changed internally.

Sorry, my fault. I misread your earlier post.

The denso ECUs are certainly 'part' hand assembled as the final ops for fitting the power semiconductors require the fitting of some fiddly screws and washers/insulators. Some of the power semiconductors look like they may have been soldered by hand at the same time as the solder often has residues around the joints.

The big awkward components like ICs may well have been placed by hand as they often have some legs bent on the solder side to hold them in place prior to (flow?) soldering.

I would expect the main PCB soldering to have been done on a machine as it is so neat and even.

Those little black ICs are also filled with black sealant and they take a fair amount of work with a scalpel to get them open. The one in the image above is the main 5V filter/regulator IC for the ECU. It also generates the /RESET signal for the MCU chip and a few other things.

I've seen quite a few Denso ECUs and one thing they appear to do is have a manual inspection (pre solder?) rather than optical. The reason I say this is that the ICs in the ECU will usually have a little white pen streak on them.

It's as if someone checked all the ICs went in the right way round and marked them by hand with a white mark. Maybe I'm wrong about this as I'm really only guessing.

what a fun job that must have been... If labour was cheap they may well have had 20 workers (with a pen each) in a line. Each one checks their own specific IC orientation and marks it with a pen and the ECUs move down the line one step. This would be better than one person checking all 20 chips and going dizzy!