Quote:
Originally Posted by mrcrunch
Do you know this for sure? MAP based EFI on cars use the O2 sensor to tune the A/F mixture. You can increase breath-ability all day long with no upgrades to the electronics or fuel injectors. Except at WOT in closed loop mode.
Does the ninja FI system not used an open loop mode with the O2?
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You're not quite right here. Most factory EFI systems (cars and motorcycles) use one or more narrow-band O2 sensors, but these sensors aren't used in the manner you've described. These sensors are there mainly to confirm that the EFI system is functioning as it was designed to by the engineers. And on cars most of their concern is centered around emissions control.
In a factory EFI system the narrow-band O2 sensors are mainly there to
confirm that the fueling is occuring correctly. If the system gets slightly off and the narrow-band O2 sensor reports crossing its 14.7 to 1 air/fuel ratio sweetspot at the wrong time the system is programmed to compensate a bit.
But if the narrow-band O2 sensor continually reports instances of "crossing 14.7" at weird or unexpected times compared to what the ECU is factory programmed for, as it would if you'd changed or modified the intake and exhaust, the EFI system will "throw a code" for maintenance and might even go into a "limp-home" mode.
You might have been thinking about a wide-band O2 sensor system, which is much more complex and expensive. An aftermarket EFI system like the Microsquirt ECU that I use on my EFI project bike is purposefully set up for use with a wide-band O2 system so it can carry out "self tuning" operations on a do-it-yourself fuel injection system. A wide-band O2 system (the wide-band sensor plus a wide-band controller and a wide-band capable ECU) can read the whole spectrum of air/fuel ratios that an engine might experience during operation (while a narrow-band can only report when the air/fuel ratio crosses 14.7 to 1 air/fuel ratio).
You don't find wide-band O2 sensors on production vehicles because they cost quite a bit, they don't last nearly as long as narrow-band, and vehicle engineers don't need them anyway because they develop the car or motorcycle in a laboratory type environment in which they account for the engine's entire operating envelope ahead of time during testing.
They don't need or want to build in adaptability to allow people to change exhausts or intakes, where's the profit in that? There isn't any profit in that, which is why there's so many warnings about actions like that "voiding warranty". Messing with or changing the equipment, as installed at the factory, is bad for reliability which is the goal of a vehicle producer.
Having said all that, there's always an exception to every rule. There are aftermarket EFI systems that can do a pretty good amount of "auto tuning" activity. There's some tricky programming that can allow the ECU to predict and react to the small amount of information that a narrow-band sensor provides. The Ecotrons system does this.