DRW -
Quote:
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Originally Posted by DRW
I don't know how a scangage works, but this quote seems accurate.
I've watched the injector pulsewidth and O2 volts on my dataloggers under various conditions. During normal cruise I can see the O2 volts cycle above+below stoich like they should. This is the ecu trying to keep the A/F ratio at 14.7:1. The ecu can add/subtract fuel accurately enough to consistently cycle the O2 volts around .15 to .75v. At the same time the injector pulsewidth shown on the logger remained the same at around 1.79ms for example. The ecu uses a two byte variable to control fuel, while the logger only sees the hi byte. I can also see the airflow reading from the MAF vary slightly at the same time, so I know the ecu is tracking the airflow and adjusting fuel to match it.
My car is OBD1. I can't imagine OBDII having LESS accuracy.
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I think the ScanGauge is great because it takes advantage of the OBDx specifications, but all our engines and ECUs are different, so the SG can't be considered a perfect measure across all car platforms. It is a jack-of-all-trades because of the specification, but it is up to the car manufacturers to implement the specifications. The SG is on the outside of the black box of the ECUs, so it is vulnerable to the tolerances/deviations in the manufacturer's implementation of the OBDx protocols.
And now there will soon be a CAN protocol, isn't that right?
That's my two bytes,
CarloSW2
smartzuuk 
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