JOnway YY250-T Temp Guage Calibration By calmissile (Read 1,137 times)

[calmissile]

In the process of troubleshooting a thermal problem on my scooter, I decided to check the calibration of the temp guage so that I could equate what the guage displays vs what the coolant temperature really is. It was done with the temp thermistor removed and the calibration (resistance) read while immersed in a controlled oil bath. The guage calibration was characterized by using a precison resistance decade and recording the guage readings vs resistance (simulating the thermistor). The data was plotted on the graph attached. As you will note, the thermistor is very non-linear. The results turned out a little better than I expected because the markings on the guage are not linear and compensate somewhat. Note that in spite of the non-linearity, the span between each 25% mark on the guage is between 23-28Deg F. which is not bad. The results can be summarized for each of the markings.
0% = 128 Deg F.
25% = 155 Deg F.
50% = 180 Deg F.
75% = 203 Deg F.
100% = 230 Deg F.

Some variations may exist between different thermistors due to manufacturing tolerances, but this should be close enough for a feel of the guage calibration.

Doug

[imnts2]

I have no idea what you are trying to do and what your question is. Is there a question?

Cheers
lefty2

[calmissile]

There is no question! It is technical data for members that may find it helpful.

[JR]

Great chart and graph and it lines up with some of the scooter specs too. For instance the thermoswitch in the radaitor that cuts the fan on. Here is the switch temp ranges;

Starts to close (continuity)....... 208-216 deg F
Starts to open (no continuity).. 196-210 deg F

At just a touch over the 50% mark of 180F the fan switch closes and the fan comes on. I don't know at what point on the YY250T gauge the fan cuts on but on my linhai it is consistant with the graph and the gauge always reads a little above the half way mark beore the fan kicks in.

Nice job!

JR

[speedracer]

My gauge may off some then. My fan could go on right at the half way point and other times just above the half way point. One thing it never waits to the gauge hits 3/4.

[yoster]

This totally confirms my suspicions that my fan is coming on WAY too early. My fan always kicks on before it even gets to the 25% mark. It could be 40 degrees outside and I can't do a run without the fan being on almost the entire time.. despite the fact that the temp gauge is reading no more than 1/4 lol.

Great data - thanks for posting!

[cruiser]

My fan is performing similar to yours, Matt. Comes on at about the 1/4 mark, but it did cycle on an off during my Spring inaugural ride of about one hour. Temp hovered right around the 1/4 mark for the ride. Outside temp was about 73 degrees.

[timk225]

My Jonway YY250T (Viva MP250RO), has the same problem, the fan comes on WAY too early and never lets up. It comes on before the gauge gets to the 1/4 mark. I installed a switch on the handlebars to break the circuit so the fan cannot turn on unless I allow it to.

I was hoping that ram air blowing through the vents behind the front wheel would be enough, but no, the radiator doesn't get enough air forced through it like that. Even on cool days the temp will slowly climb over several miles, and I'll have to turn the fan on to cool it off.

What is the normal operating temperature for the 244cc engine? If the gauge really does read 1/2 way at 180 degrees, I'm comfortable with that, I have extensive automotive experience and 180-200 is a normal temperature for high performance engines. Yes, this is a Chink scooter I'm dealing with, but I don't know why they wouldn't aim for 180 or so on it to be a normal temperature.

I also have a charging system problem, and I felt that the fan being constantly on was taking power from the battery. But that's another story.