[Q] EFI computers on different engines

[ARTHUR OKUN]

You wrote: 
>
>******************************************************************  
>* FIRSTLY A GENERAL QUESTION:                                    *
>* DOES ANYONE HAVE A WIRING DIAGRAM FOR A TOYOTA FITTED WITH A   *
>* 3T GTEU 1.8l Twincam turbo? I HAVE A COMPUTER (AGAIN ANALOG)   *
>* TO SUIT THIS ENGINE, AND AM WONDERING WHAT IT'S EXTERNAL       *
>* CONNECTIONS TO THE SENSORS ARE SO I CAN MAKE SOME MEASUREMENTS *
>******************************************************************
>
>Thanks for your reply Tom, interesting reading.      
>
>> > He wants me to make up a box that tweaks various inputs to get the
>> > fuelling correct.
>> 
>> [rest snipped just to save bandwidth]
>> 
>> Will this be an analog box to precondition the signals?
>
>That was the initial idea (a bit easier to fiddle with rather than
>having to 90% design a digital system before anything works).
>See below for what I intend to do now.. 
>
>> Have you thought about a uC box to replace the original? 
>> Have you done any uC work?
>
>I am about 1/3 of the way thru designing a microcontroller version 
(8051
>family-the 332 stuff is a bit too advanced for me :-)
>However, he wants a cheap and quick system up & going, hence trying to
>use an OEM box and tweak it's inputs to make it behave appropriately.
>Besides, the extra experience with oem boxes will help my 
understanding
>for doing my own from scratch.
>
>> [wants to remove air box vane meter... and replace it with
>> a map sensor]
>> 
>> The early Nippon Denso should be the BOSCH L jetronic analog
>> design. Contact switches for idle and full throttle should be on
>> the throttle body. 
>
>Yes, it's operation is virtually identical to an L jet. I got a 
generic
>EFI repair book (lots of manufacturers, condensed info of connections,
>voltages etc). Happily, it seems that these ecus are virtually
>identical, with the diagram in the book conveiniently matching what 
I've
>got on hand.
>
>I got my hands on this box last night, it's got 5 analog ICs (Custom..
>consecutive part numbers), several dozen C+R, a few transistors and a
>diode or two. There is about 10 resistors on PCB pins, which I thought
>was intriguing.. Then I realised these would almost certainly be the
>calibration resistors. Hmm.. (light globe above head comes on) I could
>make up a panel with a pot for each resistor, do a bit of reverse
>engineering and figure out what each one does - so I should be able to
>come up with something in a few weeks rather than #*&$ months/years!
>If anyone is interested I'll keep the group informed of any progress.
>
>OTOH, I've also got a digital ECU (from an 89 Mazda MX6 2.2l non 
turbo), so
>if the inputs to that could be tweaked it might self learn enough to
>work quite well.
>
>An importer of japanese engines here have piles of 2nd hand computers
>(at $US 15 each!! :-) and pumps, injectors etc. So, if I can get a 
workable
>solution with one particular type of computer that's in ready supply I 
could
>sell about 1/2 a dozen straight away (a few freinds are displaying 
keen
>interest in EFI). 
>
>> > My understanding of these trapdoor type systems is
>> > that almost all of the fuelling calculation is based on the 
trapdoor
>> > potentiometer, along with idle curcuit (switched by AFM or 
throttle
>> > position), 
>> 
>> Yes.  Ideal would be to "bench test" the donor computer, with all 
the
>> parts to get an idea of the functions of how much the air vane
>> position modifies the amount of fuel injected.
>
>Exactly what I plan on doing. I've already got a set of readings from 
an
>aftermarket computer tuned for the sort of engine I'm trying to run
>(Mazda 12A turbo rotary), so I've got a half decent start point.
>
>> > Questions:
>> > i/ If I have a MAP sensor and alter this signal ONLY and feed it 
into
>> > the trapdoor potentiometer input on the ECU (ie use a MAP instead 
of a trapdoor
>> > AFM), and leave all of the other sensors STOCK (unmodified), is 
this
>> > system likely to function successfully?
>> 
>> If possible, you may want to make a series of measurements to get an
>> approximate idea of the voltage vs. airflow from the air box from 
the
>> donor system.  Once you know that function, then it would be NICE to
>> have an actual system to compare manifold pressure vs. air vane 
voltage
>> readings.  This should give an idea of the function between the two.
>
>Hmm.. funny you should mention that ;-)
>I was planning to get a throttle body, trapdoor sensor on one side, 
MAP
>on the vacuum side, Vacuum cleaner/leaf blower to simulate the engine.
>Then I'll vary the throttle and the vacuum to simulate different 
engine
>conditions and take some readings from the AFM and from the MAP. If
>there is a straight line corellation then an opamp solution would be
>adequate, but if it's a curve then I think the LM3914 solution would
>offer a much better degree of tunability. (I HATE non linear analog
>electronics) 
>
>Regarding the pulsing in the manifold, I think that could be smoothed
>electronically or with a small damping chamber in the vacuum line.
>
>> There are those on this list who are much better qualified than I,
>> but thought I would at least toss out a few ideas to get the ball
>> rolling. 
>
>Hey, sometimes the 'grass roots' approach is easier to understand
>than the hi tech approach. Your input is very much appreciated.
>
>Cheers,
>Craig.
>
I THINK HYPERTEK USES A SIMILAR APPROACH ON FORDS TO IMPROVE 
PREFORMANCE    BY THAT A MEAN A  MICROPROCESSOR BASED DIGITAL SIGNAL
PROCESSOR BETWEEN THE  ECU   AND   ENGINE SENSORS AND  CONTROLS
IF I EVER BUILD ONE FOR MY 1988 2.8 L BUICK I WILL PROBABLY USE A
PIC 16 MICROPROCESSOR WITH AN ERASE WINDOW
THE BUICK USES A MASS AIRFLOW SENSOR OF BOSCHE DESIGN
AND A  MAP SENSOR    NEWER GM CAR WITH THE SAME ENGINE NOLONGER
USE THE MAF SENSOR.  IWONDER HOW WELL THEY WORK WITHOUT IT?
FROM WHAT I HAVE HEARD IT REQUIRES MORE COMPUTING POWER
TO CONTROL THE ENGINE  WITHOUT IT IE  CAN BE DONEWITH
SIMPLE ANALOG ELECTRONICS LIKE YOU DESCRIBE IN YOUR LETTERS