'06 does not have atmospheric pressure sensor

[Constant Mesh]

The '05 and earlier FJR's included this sensor as part of their fuel injection system. The revised '06 system is similar to that of the Honda ST1300. Probably at key 'on' before the engine is started the pressure reading from the intake air pressure sensor is saved in the ECU memory. This is the atmospheric pressure for that time and location. At the next key 'on' (before cranking) a new value is read and saved. This might affect the operation of the engine when large changes in elevation occur between restarts.

 

[mindtrip]

Good to know when going through the mountains--like a windows machine, if you start having problems the first step is to reboot...

 

[Fred H.]

If the system has intake air pressure why would it also need to know ambient air pressure as well? If the ambient air pressure changes, wouldn't intake air pressure also change by the same amount?

 

[worldbound4now]

True Fred, but if the ECU only prompts to measure the pressure at start-up and not over a given interval during engine run time, then I can see problems occuring. OTOH, this motorcycle is modern enough that I'd have a hard time putting it past the Yamaha engineers to not consider the need for real-time environment and exhaust monitoring to provide continuous fuel mixture adjustments.

Just my guess. Not an educated one.

 

[Fred H.]

I would be real suprised if only one reading was taken at key on. That would defeat the whole purpose of putting the sensor in the intake airflow stream. The sensor is designed to measure changes in the airflow density of the incoming air into the engine, much like a heated element mass airflow sensor does. If you go to the trouble to put it in the airstream, then you obviuosly aren't going to take just one reading at key on before the engine is even running.

I'll bet that readings from the sensor are taken continously.

I suspect what Honda did on the ST1300, was read the ambient pressure at key on so it could meter the proper amount of fuel for cold engine start based on altitude. Once the engine is running, you can get all the air density info you need from the intake air pressure sensor, as that is all that really matters to the engine anyway (density of incoming air).