Dear Ralph: You heard anything about this? The new Yamaha Apex models have a barometer display on the speedo cluster along with the speedo,...

Dear Ralph:
You heard anything about this? The new Yamaha Apex models have a barometer display on the speedo cluster along with the speedo, odometer, and trip meters. Problem is the baro reads way low, like in the 25-something most all the time. My friend’s reads exactly the same.
Our dealership said the Yamaha tech folks told them that it was only used by the computer for calibration. That doesn’t make sense in a few ways, mainly that it doesn’t change with the engine running or not. Any ideas? Why didn’t they just put a thermometer in there?
Gary Stoutenburg
Bishop, Ca.

Being the Apex models are fitted with a highly advanced electronic fuel injection system, it uses a atmospheric (barometric) pressure sensor to determine the proper amount fuel flow for the engine. It is displaying the “absolute” barometric pressure, not the “altitude compensated” barometric pressure reading you are likely comparing it to. For example, my two Apex models both displayed 27.98 inHg, while the altitude compensated barometer showed more like 30.20 inHg. Only at sea-level are absolute and corrected barometer readings the same. Meteorologists need to know what the local barometric pressure would be if the entire world were at sea level, so they calculate out the effect of altitude and call it corrected barometric pressure.
For our purposes, air density is a function of absolute pressure, not corrected pressure. This is more accurate than simply using temperature, as it also takes into consideration operating elevation and changes in weather. So yes, it is more for the EFI computer to determine the fuel delivery rates than it is for you and I to view. Whether the engine is running or not shouldn’t make any difference in the air pressure that is present.
The real question is why is this display even available if it is meaningless to the consumer? About all it does for you and me is verify the sensor is functioning properly, and yes, I agree that displaying ambient temperature would sure be nice. Problem is, the temp sensor is intake air temperature, not ambient temperature, so displaying that sensor data isn’t going to help much, either.

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