Using the EFI Correction Box

[TomoHawk]

OK, so I've built the corrector box (refer to the attached schematic) and when you plug it in series with the Coolant sensor, it works as you'd expect. You can even tell that the engine runs (or sounds) differently as you fool with the switch and potentiometer.

Be mindful that this device is intended to be used to see how much your ECU electronics may have drifted over the years.

So should you be using a sniffer to find out if, and how much drift there is, or how you otherwise determine that? I suppose you could use the old seat-of-the-pants method, but since that is so imprecise, any adjustments you'd make would probably be hit-or-miss.

"Disclaimer"

Also, please be aware that this is what you'd call a "very advanced" technique, which is not for anyone that is fully knowledgeable about the Bosch L-Jetronic Fuel Injection system used on the L28E engine.

Discussions?

[Wade Nelson]

I'd like to point out that this is how a lot of the "go fast" boxes work. You know, you hear about guys "chipping" their trucks or motorcycles.

The systems can work in one of several ways, but "sensor offset" is the leading mechanism for "fooling" the EFI system into running an engine richer or leaner.

A lot of times guys install these, it briefly runs rich (more power), then the long-term adaption of the EFI system nulls it out and 30 days later they're back where you started --- provided you didn't melt your catalytic converter with all that extra fuel...

Here's a great article if you'd like to learn more: Written about Harley Davidson EFI & such but the principles are the same

Dr. Dyno explains 02 sensors and closed-loop systems

[siteunseen]

How about posting a picture of that fancy box, I'm curious to see the difference from what I did here. Except I ran mine into the cabin and mounted the knob where the radio volume knob should be.

http://atlanticz.ca/zclub/techtips/tempsensorpot/index.html

[Zed Head]

It's the same as the common potentiometer installation (isn't a two terminal connection more properly called a rheostat?).

Seat of the pants or an air-fuel ratio (AFR) gauge or nose are the ways to measure effect. It changes the response curve across the complete range of conditions, I believe.

If you want to change the idle AFR only, it would be be better to use the idle air screw on the side of the AFM. That's the one where a "sniffer" is recommended, by the FSM instructions.

[TomoHawk]

A lot of times guys install these, it briefly runs rich (more power), then the long-term adaption of the EFI system nulls it out and 30 days later they're back where you started --- provided you didn't melt your catalytic converter with all that extra fuel...

The L-Jet EFI isn't a digital EFI system,without any "chip" or "programming," so none of that will happen. Any resistance you add to the sensor circuit is permanent unless you remove it. Also, it's not intended as as a 'go fast" device. It's simply a way to correct the aging electronics so the engine gets the amount of fuel it's supposed to.

My box is just a simple Altoids box with a short pair of wires coming out of the side. You plug it in and leave it on top of the intake manifold, though you could extend the wires to the driver's area.

[TomoHawk]

A photo..

[Wade Nelson]

The L-Jet EFI isn't a digital EFI system, without any "chip" or "programming,"

Really?

[Walter Moore]

Really?

Yes, the early EFI systems are basically just calibrated analog timing circuits that fire the injectors on a pulse and hold them on for a variable length of time. Remember, the first patent for a microprocessor was issued in 1973. Digital computers fast enough to control a FI system, and rugged enough to survive in an automobile didn't exist outside of the military until well into the 1980's.

Edited May 20, 2013 by Walter Moore
Forgot the word "analog".

[TomoHawk]

Perhaps Wade knows how you can re-program the L-Jetronic system, or where the memory chips are, and how you can alter what's on those too?

[FastWoman]

To expand on what Walter and Tomo have written, the analog L-Jet ECU is an open-loop system with no lambda feedback (O2 sensor) or any other sort of feedback. It does not adapt and correct the way modern systems do.

Also, unless you have a California Z, you have no catalytic converter. My end-of-the-line, Kentucky version 1978 280Z has a spledidly analog ECU, no oxygen sensor, and no catalytic converter. It does have "chips," but those chips are analog and packaged in oil cans -- probably not the sorts of chips you're thinking about. But yes, they came from silicon wafers (just like discrete transistors did/do).

[Wade Nelson]

Perhaps Wade knows how you can re-program the L-Jetronic system, or where the memory chips are, and how you can alter what's on those too?

Or perhaps he's an electrical engineer with a long history of working on fuel injection systems (going back to Robert Bosch's ORIGINAL digital EFI based on the Motorola 6805 MCU...which he helped program) and you misread his original post.... really? REALLY!

[TomoHawk]

Didn't Herr Dr. Bosch pass away in 1942? That's 32 years before the 6805 was invented.

If you have a wealth of useful information on how to improve the L-Jetronic Fuel Injection system, please share it.

Edited May 21, 2013 by TomoHawk