theoretical engine tune control o2 sensors
been scanning and working on computer control cars since CCC and OBDI first came out in the early 1980's
and later OBDII came out 1990's
never thought much of it, it was easier for me to get more power with a carburetor.
OBD systems were just a necessary evil, because they became embedded in the vehicle by the 1990's,
and could not be completely disconnected and disabled. in the old days we could just bolt on a carburetor.
and disable the entire OBD system, not anymore. not that easy.
so I got to thinking, in open loop on the V12 the computer puts in its own 450mv signal,
and keeps the o2 sensors output signal shut off,until the coolant temp sensor reaches operating temp
then it turns over mixture control to the o2 sensor inputs, which vary based on what they sense in exhaust,
from 50 to 900 mv. low value being a lean mixture sensed more oxygen, high value being a rich mixture sensed less oxygen. fuel being primarily hydrocarbons HC, there's less o2 in the exhaust stream when HC levels are high. one displaces the other.
well it occurred to me, if the computer can put in its own 450 mv signal in open loop,
why can't I put in my own signal too ?
what if I injected a signal of let's say, 600 mv into the harness connector,
and pulled the wire off the o2 sensor.
would the computer be tricked and vary fuel injection to that new value.
open loop using 450 mv is too rich for daily driving.
so a higher value of 500-700 mv would lean it out,
and make more power,
this would sort of be like changing jets in a carburetor, they're fixed values.
not varying. (although carbs had power valves and metering rods that did enrich at part throttle/full throttle, vacuum controlled)
typically a setup like this may be on the rich side at idle, in order to be dead nuts on at wide open throttle
if it's dead nuts on at idle, it will typically be lean at WOT
having said that...take it a step further. introduce a varying control using a potentiometer or resistance value,
whereby you can vary, from the drivers seat, the voltage the ECM "sees" and assumes is coming from the o2 sensor
now you can tune from the drivers seat, on the fly, and for track or street conditions, or for weather conditions.
the big question now is, what will the ECM do, when it sees a steady o2 value, rather than a varying one it is expecting ?? my previous 02 sensors did not vary, they were defective. the computer still did not put on the check engine light, or store any codes. yet when the car warmed up, it did go into closed loop anyway, and one oxygen sensor struggled to fluctuate from 40-400 mv. the other stayed steady 50 mv.
that's what made me go "...hmmmmm"...maybe I can manipulate this system for more HP, and wrest control of the mixture system away from the ECM programming.
to take it another step further, I believe most coolant temp sensors turn over control to o2 sensors and go into closed loop, by grounding the circuit at a certain temperature.
could you not just ground the circuit with a toggle switch, thereby putting it into open or closed loop at will ? sort of like a hand choke on a 1940 chevy on a carburetor, complete manual control. I have a mechanic friend who routinely grounds the coolant temp circuit on cars, to force it into closed loop, to check the system sensors. usually he did this to test and replace a defective coolant temp sensor, or o2 sensors, and wanted the system in closed loop like right now, not later.
there would be a market for such a device, imagine saying goodbye to all these computer control problems, by simply over-riding it with a dial and a switch, and putting in your own values with a knob. a digital output meter that could read and supply any chosen value to the o2 sensor circuit, or simple big knob with rich and lean on both sides of knob, like a volume knob on a stereo.
are the light bulbs going off out there ?
any input or ideas welcome. has anyone tried it ?? there are no right or wrong answers here, just ideas.
if someone sold such a device today, and it was EASY TO INSTALL, that's the crucial point, I'd buy it and put it on my car immediately. on any of my cars. I could always shut it off and return control to the OBD system if I wanted.
imagine the flexibility of such a system. I see guys tuning the ecm's to get a tighter fan on the o2 values, to vary from 650-950 mv, rather than 50-800 mv. but what I'd want to do, is be able to just not use the varying fan at all. just put one constant value in, and stay there. the only reason it varies is for emissions, nothing else. because it spends half its time too lean, which pollutes less. keep that in mind, OBDII is primarily an emissions system that has control of the car. think of it as a greedy stingy king or queen, that is saying "there's no bread, let 'em eat cake"...
it's saying "there's no fuel, let 'em eat air"