Long time member, new job with DIYAutotune.com

[Captain Obvious]

Why not just give then a call to see if he is there, or just ask for some information?

Tomohawk, I think you're getting your users a little confused...

User "billyjarrell" is the guy who started this thread. He started this thread to announce that he had just gotten a new job working at a company that develops, builds, and sells the MegaSquirt brand of engine management systems. That company is called DiyAutotune.com. I don't know if he is still working at that same company, but if he is, he could probably be reached there.

User "superlen" is a different guy who popped up about a third of the way down the thread announcing that he had been working on a digital based drop-in replacement for the original ECU. He (superlen) is the guy that seems to have evaporated. I suspect life got in the way and this project has stalled again on the bench.

I've got a million of those projects...

[EuroDat]

User "superlen" is a different guy who popped up about a third of the way down the thread announcing that he had been working on a digital based drop-in replacement for the original ECU. He (superlen) is the guy that seems to have evaporated. I suspect life got in the way and this project has stalled again on the bench.

I've got a million of those projects...

Thats a darn shame. It sounded promising. Sounds like most my projects.

I really like the idea of digitalising the ECU to make it tunable, but thats on hold like so many other "good idea while I am at it" projects.

Now working on one thing at a time, being the complete brake system resto.

Chas

[TomoHawk]

I think most people don't really want the replacement to be totally like the "digital" stuff. It's just that to make it work kinda like the vintage analog stuff, you will probably need some digital parts with programming to fill in the gaps. But some tuning would be welcome.

[FastWoman]

Tomo, I have to disagree. There's no reason, IMO, that a replacement ECU has to be digital, and there's no reason you can't tune an analog ECU. I see this as being a two-stage process, just off the cuff:

The first stage is to create a base pulse from the AFM reading. You'd use an op amp to follow the AFM output voltage and then ramp the voltage of a capacitor by applying that voltage. Then you'd run that to a comparator. I suppose you could have a variable resistance charging the capacitor, giving you a primary adjustment for the base pulse width.

The second stage is to generate reference voltages for the other input of the comparator. There would be a base voltage, set by a potentiometer, leading to an op amp follower, which inputs via a fixed resistor into an additive op amp circuit whose output feeds to the comparator. Additional inputs to the additive op amp would be for the CTS (send current through fixed resistor and through CTS, amplify/offset voltage, with 2 adjustments); for the ATS (same treatment as CTS), for the TPS (adjustable fixed voltages applied for idle and WOT enrichment); for the O2 sensor -- probably a low-pass treatment of the O2 sensor signal by charging/discharging a capacitor. (I think it would be a very good idea to upgrade the system with the O2 sensor, but this sensor could be omitted from an installation if desired.)

There would be a counter circuit to reset the ramp on the capacitor the AFM signal charges with every 3rd spark. When the ramp is reset, fuel is sprayed until the AFM circuit's voltage exceeds the additive circuit's voltage. Then fuel flow is cut off.

The cold start is not controlled by the ECU, so it can stay as currently wired.

I was wrong before to say that a multiplier circuit would be required. I think the whole thing could be handled with conventional, ubiquitous op amps. The hardest part is coming up with the time to do it! While it's easy to envision the building blocks of the system, prototyping and debugging the whole thing can be a bear, especially since some of it has to be done "in the field."

[Captain Obvious]

Haha! Sounds like an integrating A/D where you're tweaking the de-integration reference voltage a little based on temperature and then opening the injectors during the de-integration phase.

I'd be a lot more comfortable just digitizing the inputs and performing the calculations in a micro. Tell you what... Let's both start right now and design and build our different proposals and see who's is "working" first.

And yes, neither of us ever finishing our respective projects is a completely realistic outcome. Probable even! :laugh:

[EuroDat]

Tell you what... Let's both start right now and design and build our different proposals and see who's is "working" first.

And the winner gets to sell one to me:D. That is if I live that long!

Save me the trouble of starting a project Illnever finish.

Edited January 27, 2013 by EuroDat

[TomoHawk]

Sarah,

I wasn't suggesting that a replacement be (completely) digital, but with a combination of things, I think it could be nostalgic, yet better than the original.

Don't forget to include a way to control the AAR.

[FastWoman]

Captain, you're on! You, with your fancy, new-fangled digital wizardry, and me with my old-school analog design that you can adjust with a screwdriver as Gawd intended!

Tomo, the stock AAR doesn't need controlling. It simply receives +12 from the IGN circuit and slowly closes as it heats up. Of course an electromechanical AAR would be a nice upgrade. A multivibrator circuit could be used to drive the simple electromagnetic type, based on RPM. A stepper AAR would of course require evil digital circuitry.

I have to say that an analog ECU, designed of op amps and adjusted with sealed 20-turn pots, would probably be quite stable. Moreover, if the ICs are socketed, they can all be pulled and replaced to refresh the circuitry every 30 years or so. ;-)

I have to say, though, that anybody but me should probably prefer a digital design. However, since I have quite a background with analog circuits, and since that's appropriate to the era of the car, there's just something romantic (to me) about an op amp design. If the car were much older, I would probably enjoy trying to design a fuel injection system running on vacuum tubes. (While the EFI would be an anachronism, I think it would be more of a "creative" anachronism.) Of course you would have to warm up the ECU before even THINKING about turning the key!

[TomoHawk]

Yes, the factory AAR should be replaced with something, even a solenoid-operated valve.

BTW- I've got a small box of 324s and 741s in the drawer still, but I haven't breadboarded anything since college.

[Captain Obvious]

Bring it! I've already gotten started. I grabbed a mechanical pencil and sharpened it!

You with your 20 turn pots and your capacitors... Yeah, they'll be stable. Stable until the temperature changes that is.

If the car were much older, I would probably enjoy trying to design a fuel injection system running on vacuum tubes. Of course you would have to warm up the ECU before even THINKING about turning the key!

Haha!!

[FastWoman]

Yes, the factory AAR should be replaced with something, even a solenoid-operated valve.

Perhaps for future availability/affordability of parts. However, I've not found the electromechanical AARs much more reliable than the type we have on our Z's. They tend to get stuck and need to be cleaned -- at least the stepper motor variety.

BTW- I've got a small box of 324s and 741s in the drawer still, but I haven't breadboarded anything since college.

I haven't made anything since the mid 90's, aside from a circuit I built to turn an airbag light on and off. Much of my test bench equipment is gone -- sold, given away, etc. However, I still have the basics.

The single op amps are annoying. I much prefer the quads. My favorite was TI's TL084. Its JFET inputs are very tame, and it works well for narrow voltage ranges, outputting effortlessly to almost 0.5V from the rail voltages. It's still in use, apparently -- now in surface mount. The nice thing about quad op amps is that they all (?) have the same pinout.

Captain, I'm ready for ya'! I'll see your fancy mechanical pencil and raise you a slide rule! Ha!

[TomoHawk]

One question :

Would it be possible to include an OBD interface to this homebrew controller, or is it a totally different can of worms? I get the feeling that such a thing is a part of a totally digital controller.