some pressure sensor observations (for Boscoe)

[fairdeal]

I bought a 6AW-8366B-00-00 cooling water pressure/pitot speed sensor
it was a used part - cheap - with no representation that it was in working order.

Turns out - it was not - apparently shorted internally -
connected with a 5 volt reference feed, "blue to black" read 4.83 volts.

Interestingly - with that "output" - the F225txrd ECU refused to recognize that it was connected.

But - I now knew that the oil pressure sending unit used the same connector

So, foiled in experimenting with 6AW-8366B-00, I proceeded using the oil pressure unit.
With some interesting results.

First - using the prepared regulated air pressure test setup -
I compared the "Command Link" (NMEA 2000) oil pressure output values
to a bourdon tube gauge:
just about dead nuts (its a new gauge, but certainly not "NIST traceable")





more to follow

[fairdeal]

next - I plugged the oil pressure sender into the Command Link "W" lead

with a "good" input - the ECU immediately output NMEA 2000 "Cooling water pressure" values



somewhat surprisingly - given the "wrong" sensor
the "interpreted" pressure values were very close to actual -
though consistently overstated by ~2 psi.

Interesting that the designed output curve of the water pressure sensor is very close to -
but not the same as -
the oil pressure sensor.

next - the speed sensor

[fairdeal]

so then I plugged the oil sensor to the Command Link "S" lead
and again, immediately got N2K "water speed" output

(took me a while in the Garmin menu to find it, and a place to display it)

so we earlier established that although we are using the "wrong" sensor -
the "blue to black" voltage output actually matched fairly closely
what the ECU is expecting for a particular pressure.

I conclude that likewise, the pressure used to generate these "speed" readings
was close to what the pitot tube would actually generate.

and in these photos I also captured the "blue to black" sensor output voltage at each pressure
(the voltage at "zero" pressure was 0.497 volts)

[fairdeal]

one final observation

plotting the data points where I measured sensor output voltage gives this:



given the crudity of the experiment, a decent linear regression.
Extrapolating, for the "Speed sensor" check that you shared recently:
2.5 volts is the equivalent of ~100
and 4.5 volts ~200 miles per hour

[boscoe99]

Interesting. Thanks for taking the time to do the test and post the results.

Surprising isn't it to see the amount of water pressure that is built up to indicate 45 mph.

Equally as surprising to me is the MFD displaying speed thru water to the second decimal. 4.61 mph. Even to one decimal is a bit silly IMO.

I can hear in my mind a guy complaining to Yamaha "yesterday my WOT speed was 45.4 mph but today it is only 45.3 mph. Something is wrong with the motor. I want it fixed under warranty".

[99yam40]

Why does the 45.4 MPH /26 PSI cause a
neg 1.451 VDC reading

[fairdeal]

Why does the 45.4 MPH /26 PSI cause a
neg 1.451 VDC reading

sharp eye!

its not really different polarity than the others -

you can see that has a different gauge -

when I changed the setup I accidentally reversed the meter leads

[99yam40]

Just jacking with you.
seems I have found in some instances reversing polarity can give slightly different readings with some meters.

Just an observation from different situations

[fairdeal]

oh BTW - I don't recall ever seeing it mentioned -

the thread on the Yamaha sending unit is 1/8" "British Standard Pipe Parallel" with 28 TPI

close to - but not quite - 1/8" NPS - which is 27 TPI

[99yam40]

where do you find taps and dies for that?

or what kind of parts can you find the will have that thread so you can rig up testing?

[fairdeal]

of course now with the internet you can get just about anything,

and for peanuts if you can wait the month or so for the mail from China


but BSP to NPT adapters are common at the local auto parts store

[99yam40]

I guess I never looked for them so had no idea they are available local

[boscoe99]

of course now with the internet you can get just about anything,

and for peanuts if you can wait the month or so for the mail from China


but BSP to NPT adapters are common at the local auto parts store

I just used Amazon to buy some cheap analog volt and ammeter panel instruments. Yep, came all the way from China. Shipping was free. Or actually embedded in the ridiculously cheap price.