Rethinking the Analog EFI

[rossiz]

... I take advantage of the multiplicative properties of my ramp circuit to apply corrections proportionately to the air intake, as metered by the AFM.  Unfortunately I don't know how much voodoo is built into the AFM...

 

ok, i defy anyone reading this thread to bust out their best Hikaru Sulu voice and repeat this sentence in the mirror... priceless!!

you guys (and gals) rock 

[FastWoman]

^^^  That really did have me doing this ---> 

 

Ahhhhhh.....  Thanks!  I needed that!

[Captain Obvious]

Unfortunately I don't know how much voodoo is built into the AFM, Captain.

 

 

[hr369]

Perhaps you are looking at this problem of "crumbling ecu's" from the wrong direction.  Wouldn't it make more sense to be just replace those

old capacitors with a more modern non-electrolytic.  There are several types of modern capacitors, such as polyester film, polypropylene film, metalized polyester, and so on. New capacitors—even the cheapest ones—vastly exceed the originals in performance and reliability.

 

The L-Jet gives was designed to give you a dead flat AFR across the rev range if you keep the TPS installed and working correctly.

The only advantage of adding an oxygen sensor would be for max emmisions efficienty not power right?  Great for smog inspections

if you're cursed with failed smog checks. But a properly running L-jet should pass even in california by a wide margin. I know i've done it.

HC's were half the calif limit.

 

I suggest someone maps out which caps and other ailing components that should be replaced and make a packaged kit for the DIY people.

Or a nice business opportunity for those that are good at soldering.

 

[Captain Obvious]

There are no electrolytic caps in any of the ECU's I've ever seen open. They are already film.

 

While I wouldn't be surprised to find that the values have drifted some over the past 40 years, I don't think the caps are a big problem.

[FastWoman]

Personally I think it's failure of the semiconductors -- most likely the mysterious black-box linear chips in the little "spider" cans.  Given enough heat, usage, and time, semiconductors do go sour.  Here's a little article about it that's a bit over my pay grade:

 

http://spectrum.ieee.org/semiconductors/processors/transistor-aging/0

 

The most common failure mode for Hitachi ECUs ('77/'78) seems to be a shortening of the injector pulse, hence a leaning of the mixture.  It would be difficult to trace down how/why this happens, because we know nothing of the proprietary circuits inside the mysterious little black boxes.

Edited July 11, 2015 by FastWoman

[Chickenman]

Oh, and you want insanity?  If I had the time and the right automobile -- a 1950's something or another -- I'd enjoy working out some sort of EFI using vacuum tubes, with the ECU glowing in all its glory, displayed proudly in the cabin like a "flux capacitor."  But alas I have neither.

Reminds me of a line from a favorite song of mine: " Lady... you crazy "    .... but in a good way.

 

Now for bonus points, name the Group and Title of that song...

[hr369]

Do you have a wideband to measure your AFR's ?

 

The most common failure mode for Hitachi ECUs ('77/'78) seems to be a shortening of the injector pulse, hence a leaning of the mixture.  It would be difficult to trace down how/why this happens, because we know nothing of the proprietary circuits inside the mysterious little black boxes.

 

Do you have a wideband to verify this?

[FastWoman]

No, I don't have a wideband at this time, but it's on my wish list.     

 

Several of us have arrived at the same conclusion.  We've gotten there by systematically straightening out everything in the engine -- vacuum leaks, electrical, all of the EFI components checked per the bible, AFM, fuel pressure, injectors refurbed/flowed or new, timing, distributor advance, valve lash and timing (per the 1-2-3 hole positions).  And then we still come up short of fuel.  We richen the mixture, and then we're fine, give or take.

 

-------------------------

 

Thank you Chickenman!    (But no, I don't know the song...  And google wasn't much help...)

 

But tell me a few magic eye tubes wouldn't be part of an awesome vacuum tube ECU -- over the transmission tunnel, under the dash, in a plexiglass enclosure!

Edited July 12, 2015 by FastWoman

[hr369]

There are bigger variables in the system than the ecu aren't there?  such as afm spring being worn out, flaky oxidized wiring, flaky fpr's, correct voltage to

the fuel pump, worn fuel pump etc...

 

But having said that...  there are people that have NEWER ecu's than ours and the caps are failing. Toyota has the problem  http://www.driftmotion.com/1JZ-ECU-Cap-Service-p/dm1251.htm

Edited July 12, 2015 by hr369

[FastWoman]

As I say, there are a few of us who really straightened everything (and I mean EVERYTHING) out.  This is now a known issue with the ECU.  As for my own system:

 

AFM spring: calibrated to spec.  Wiper trace cleaned and inspected.  Output scoped -- very smooth, no gaps.

Flaky oxidized wiring:  replaced with crimp/solder/marine-heat-shrink connections, all new connectors with crimp/soldered contacts and even some new wire.  All now literally much better than new.

Flaky FPR: Not likely.  The FPR is a very robust part.  All that can fail is a diaphram or a spring.  My FPR is good and regulates exactly to spec.

Fuel pump:  Voltage is fine (much of the fuel pump circuit rewired).  Pump is actually brand new (old stock Bosch OEM)

ECU: Re-flowed solder joints

All components verified good at the ECU connector.

 

On the issue of fuel pressure, I could get my engine running almost at a rich enough mix by clamping off the return fuel line and running the fuel rail at about 50 psi.  It definitely wanted more fuel.

 

As Captain obvious points out, there are no electrolytics in our ECUs.  I've gone through the innards of mine, and no such creatures exist.  The electrolytic cap problem you cite is on digital ECUs, and those caps likely aren't used for precision timing circuits.  The problem occurs when their leakage corrodes the board.  I can't say why Bosch and Hitachi didn't use any electrolytics, but they didn't -- maybe because they realized the devices are prone to leakage and failure.

[Chickenman]

 

But tell me a few magic eye tubes wouldn't be part of an awesome vacuum tube ECU -- over the transmission tunnel, under the dash, in a plexiglass enclosure!

 

When I was a kid, my Dad used to have an old Marconi console radio. Had all kinds of weird bands including Short Wave.

 

It had what was called a " Magic Eye " for tuning in stations. It was an Evil looking thing It reminded me of the Martian creatures from HG Wells " War of the Worlds". That radio terrified me... Dad made it worse by off tuning SW stations and the Radio would make all sorts of strange " Outer Limits " sounds. Dad said he was talking to the " Martians ".

 

 

I eventually gave the radio to a friend of mine. It was in semi working condition. Needed a few Vacuum tubes and a couple of knobs. Wonder what a Vintage Marconi radio is worth these days.....

 

Edit: Crikey...looks like he had a 1938 Marconi Model 138

 

http://radiosfelix.weebly.com/console-radios---consoles.html

 

Sorry to get off topic. Back to your normal Radio station or Bat Channel...

Edited July 12, 2015 by Chickenman