Is The 280Z Fuel Injection a "Good" System?

sblake01 · January 4, 2012

I was pretty sure the FI systems could be chipped if not programmed. In fact, I thought they changed the rules a couple years ago to allow that in ITS, and that's what they're doing to get the kind of power John mentioned.

You'd have to define 'chipped' but they definately can't be programmed. There is no software/instructions/memory/storage etc. in them and therefore, nothing to communicate with and change/adjust etc. Chipping is what some some people are referfing to when they place resistors in the system at different points to 'fool' or 'trick' it, thereby changing a particular signal so as to effect performance. Edited January 4, 2012 by sblake01

John Coffey · January 4, 2012

The 280Z system has an Electronic Control Unit with a number of integrated circuits. Those can be replaced with programmable units and resistors. JWT and Jet both offered these upgrades at some point in the past. The units have to be sent to the shops and turn around time was about a week. There is (was?) a kit that let you install the 280ZX ECU in place of the 280Z ECU and that ZX ECU was easier to program/modify.

240260280z · January 4, 2012

I looked at a 280z ECU many years ago and all I recall are transistors being the only silicon stuff.

The circuit is basically a waveform shaper whose input is a timing "pulse". It generates a waveform of PWM square wave that is basically the duty cycle of the fuel injector... a longer "on time"/Puslewidth causes a longer squirt of the injector.

There are additional inputs to a voltage to pulse-width summing circuit that add to the base width of a pulse to compensate for engine temp, air temp, WOT/Idle at TVS etc. There is also a logic circuit for fuel cut off when coasting with foot off the pedal.... I'll try to dig up some more details....maybe even a circuit diagram. Here is an intro to the system I wrote many moons ago:

http://atlanticz.ca/zclub/techtips/efisystem/overview.html

240260280z · January 4, 2012

kjohnson2444 · January 5, 2012

Wow, what a thread! You've got to love the people in this club.

jimbob_racing · January 5, 2012

I just parted out a '75 280Z and the ECU had a sticker on it that said that it was a performance version done by an aftermarket company. It's now buried in my garage so I can't find it to take a picture and I never did plug it into my good '75 280Z to see if it made a difference. Maybe in the spring.

240260280z · January 5, 2012

I can't find a schematic but here is a crude diagram

and some geeky probing here:http://www.205gti.com/bosch/mods.htm

240260280z · January 5, 2012

CHECK OUT THE PDF BELOW

NTB94-097 (Nissan ECU Guide).pdf

Captain Obvious · January 5, 2012

Excellent! That's some great stuff! I haven't dug through all of it, but it's clear that it is in fact analog.

Dig those metal can transistors with the flying saucer heat sinks. Very 70's. :laugh:

I don't see any trimpots or other adjustments for calibration. They must have been pretty consistent. I would have expected some factory adjustability.

I can't find a schematic but here is a crude diagram
and some geeky probing here:http://www.205gti.com/bosch/mods.htm

The pictures of the L-jet on that geeky probing site are very different than the ones you posted. I'm guessing that there were different variations of the L-Jet over the years but the basic block diagram is probably similar for all of them.

Captain Obvious · January 5, 2012

Another question... The system is batch fired and all six injectors open at the same time once per engine revolution. The timing on this is accomplished by picking off a signal from the ignition coil. The ECU pulses the injectors once for every three spark events.

The question is... Which three spark events?

The injectors could seemingly open on sparking 1+4, or 2+5, or 3+6 depending on how the engine ended up when it shut off last time? Luck of the draw on which pair?

Probably doesn't matter, but just unusual by today's standards that the ECU wouldn't have an absolute timing mark in addition to the relative one.

240260280z · January 5, 2012

In theory, individually synchronized injector events seems to be the ideal but from what I recall reading online, it does not seem to matter much...especially at high rpms.

Here is the most detailed circuit info I have (from 75 280z manual's EF section)....sorry no board artwork or detailed schematics seem to be in the public domain.