space-junk

iTrader: (1)

thanks!...

/thread jack...

Hypoid

Hey man, very cool.

I did a project where I built an isolator board from the ECU lines to a DAQ and watched what was going on with TI Labview. We had TPS, Injector duty cycle/RPM, and the VSS. We watched it with a laptop and could see instantaneous/averaged fuel economy etc.

I've kinda been meaning to do a whole gauge cluster in a long LCD display across the top of the dash, but we'll see if that ever happens.

What isolation, if any are you doing between the ECU and the microcontroller?



Good luck!

leebee

subscribing to this and will be interested in purchasing one as well.

lee

ahickman

Hypoid, for most of the voltages I am using a unity gain op-amp. For things like Vss (battery), I have added a voltage divider to the op-amp to knock it down to the 0-5 V range of the ADC.

MtGoat, thanks for the insight as to needing the wide band O2 sensor. Don't know anything about the wide band sensor. How exactly does it differ? Is the sensor voltage a direct measurement of A/F ratio? Or are there other variables involved in determining A/F?

mt_goat

Hell if I know

space-junk

iTrader: (1)

IIRC, the wideband o2 sensor is what the newer vehicles use to decide the
A/F ratios in order to always be at the perfect 14.7... i dont think that the narrow band o2 sensors do that...

here:
"A variation on the zirconia sensor, called the 'wideband' sensor, was introduced by Robert Bosch in 1994 but is (as of 2006) used in only a few vehicles. It is based on a planar zirconia element, but also incorporates an electrochemical gas pump. An electronic circuit containing a feedback loop controls the gas pump current to keep the output of the electrochemical cell constant, so that the pump current directly indicates the oxygen content of the exhaust gas. This sensor eliminates the lean-rich cycling inherent in narrow-band sensors, allowing the control unit to adjust the fuel delivery and ignition timing of the engine much more rapidly. In the automotive industry this sensor is also called a UEGO (for Universal Exhaust Gas Oxygen) sensor. UEGO sensors are also commonly used in aftermarket dyno tuning and high-performance driver air-fuel display equipment. The wideband zirconia sensor is used in stratified fuel injection systems, and can now also be used in diesel engines to satisfy the forthcoming EURO and ULEV emission limits."

more info at: http://en.wikipedia.org/wiki/Oxygen_sensor

scope103

Think of a "regular" O2 sensor as a "high gain" sensor. It drives from rail to rail on either side of some tiny amount of O2 in the exhaust. (Ideally, there is no O2 in the exhaust, but it has to switch somewhere.) As a result, the ECU is constantly moving the mixture up and down to confirm that the O2 sensor swings to the other rail. If the O2 sensor doesn't swing, it keeps adjusting the mixture until it does.

As a result, the regular O2 sensor does not tell you "how much" O2 is in the exhaust. A wide-band sensor (in theory) can, as it can change its voltage more slowly as the O2 concentration keeps going up. So it has "lower gain," giving a smaller voltage change for a given O2 concentration change.

abecedarian

here's a little bit about how the O2 sensor is used by the ecu on a 22re:
specifically the Vf signal in the diagnostic connector...
http://www.well.com/user/mosk/Vfsignal.htm

bigtrucknwheels

nice link Abe

LADave

Late to the party here, but fuel trims are important for keeping tabs on O2 sensor(s). As they wear out they get increasingly reluctant to produce voltage. High voltage indicates a rich condition, so fuel trim creeps up. That plus slower cycling means it's time to change the (upstream) sensor(s).