Adding temperature sensor

[scootnewb]

Any updates?

[katt]

Yap i got all parts that's an update lol, will try tomorrow.

[katt]

Okay boiled the sensors a little bit and i find out that both thermal couples one goes over spark plug and one on electric fish tank temp gauge work in same way - when cold resistance is greater when hot resistance gets less.


Very crude values with my cheap multi meter

Spark plug sensor
55c - 2.1ohm
68c - 2.0ohm
73c - 1.8ohm
77c - 1.7ohm
81c - 1.6ohm
86c - 1.5ohm

Fish tank sensor
70c - 2210ohm
75c - 1940ohm
80c - 1370ohm
i bit got lazy here but you got the idea.

Basically the gauge that come with fish tank expects sensor to send larger resistance than we get from the spark plug sensor, pretty much only thing that needs to happen is convert
70c - 1.9ohm --> 2200ohm
75c - 1.7ohm --> 1940ohm

80c - 1.6ohm --> 1370ohm

etc.

in this approximate ratio.

How to do this i don't know yet and my head kind of slow today perhaps solder some kind of board or modify the lcd display board got to find out on the electric forum.

Conclusion my cheap man concept is working
Precision of thermal couple (Sensor) don't matter as we can find out what resistance reading it gives around 80-100C and map it to the digital display precise values. Display itself does not do any logic except show number on certain resistance value.

Here's similar problem described.

[scootnewb]

I sorta of understand.

"Display itself does not do any logic except show number on certain resistance value." <--- this i definitely understand.

I'm thinking I'll prolly have to pony up for trail mix kit unless you post a step by step

[katt]

Its probably better choice if you got money and no soldering skills (i solder crappy too).

[scootnewb]

I can solder but coverting the ohms is confusing me. It looks like the cheapest trail tech gauge that measures engine temp starts at $139 USD and it doesn't include the temp sensor or extension cable. I just wanted a simple set up where the sensor connected by the spark plug and a gauge that displayed it's temp.


Edit:

But I read this:

"The temperature displayed on such a device is just a consequence of the temperature on the OTHER side of that spark plug thread - in the combustion chamber. Any excessive temperatures in there will normally cause immediate knocking, pinging, power loss etc before the harmful reading (whatever value that would be) is available via the sensor discussed.

Long term it would be interesting to some extent, but for monitoring what is actually going on, combustion wise, there are better methods, IMHO."

So now IDEK but knocking, pinging, and power loss aren't happening so I got that going for me:XD  

[katt]

What i will do for sure is a oil temperature gauge will simply connect that sensor that comes with $5 dollar gauge to the dipstick and put some thermal heat shrink on it to keep together, then make a hole in the dipstick thread to put wire and fill with some sealant to avoid oil leaks.

I checked when engine works oil level in dipstick hole goes even higher than when engine off so should be getting a reading there.

Pretty sure oil is liquid and transfers heat pretty good as well.

[GrumpyUnk]

I think a pretty simple circuit could be devised to enable an automotive style 'knock sensor' to be used with a warning light such that pinging would turn on the light. If that's the goal, to know when pinging is occurring, that should suffice.
Pretty sure knock sensors 'listen' for specific frequencies of sound, carried from the combustion chamber by conduction through the cylinder head metal. Filled epoxy, such as by Devcon or 'liquid steel' types, JB Weld, etc, could be used to attach a sensor to the cylinder head. One wire to the sensor, and some transistor bias to turn on a light... I am not that good.
tom

[katt]

Okay i have finally made it happen also made more in depth review of resistance that $5 LCD expects from the sensor and will soon get some way to convert spark plug sensor resistance to range expected by LCD.

So far my highest reading was 85*C however i suspect in order to get exact reading i need to expose the entire sensor to the oil, in my boiling water test it would not go to 100c unless entire sensor was underwater.

[jstich]

Good job mounting the gauge. It looks stock.

[GrumpyUnk]

katt:" need to expose the entire sensor to the oil"

Remember that there will be hot oil being splashed around inside there whenever the engine is running. The sensor may be immersed in the oil with the engine at rest, but for sure should be covered with oil no matter where you place it/cord length, etc, when the engine is turning over. The crankshaft bearings are fed, and whatever oil they get, they'll sling around inside in addition to the crank throw whipping oil around. I think the connecting rod bearing is fed by the pump, along with the rockers, but the two 'end' bearings are lubed by splash, so you KNOW there's a lot of oil being flung around. Pretty much satisfied with an oil temp around 200F. Get to the middle 200's and you are getting too hot, I think.
tom

[katt]

Uh oh after almost non stop 3 miles ride in the city i looked at the sensor and it was 95 degrees C, i keep on going and then it reached 99.8 degrees for few seconds, thankfully it only went down from there, i have not felt any problems or loss of power at all.

After that it was staying in lower 80-90 degree. Doh perhaps i will pay more attention to the temp gauge from now on.

That's with the fancy fan installed.

Guess reason is i am running lean on high RPM so i need to jet up.

Grumpy perhaps height does not matter that much since it splashes the oil, but i did cut more rubber off to expose the sensor more, i think it will show better now.

[GrumpyUnk]

Welll.... 95C is still lower than the boiling point of water. Throw some water droplets on the fins, and they wouldn't even hiss or sizzle. To my mind, that is not hot. Hot being the point where there should be concern.
You are coming close with 99.8, but again, I think as long as you are under 220F regularly, you should have no problem. Get into the mid-200's and oil life will be affected, I think. Automatic transmission fluid regularly runs in the low 200's, and it lasts long enough for decent service.
Why don't you try my idea of draining the rocker arm oil into a copper tube that is exposed to airflow and let gravity run it back to the sump. Even just going through a bit of tubing exposed to ambient should dissipate some heat. Run the tube into rings just like the moonshine still condensers... A long run of tubing will effectively increase the lube volume while still keeping the level low in the crankcase. However much is flowing on its way back to the sump is the volume increase. Right now, that oil flows back to the sump via the chain chamber, trickling off the side of the head, and then down around the lower chain guide, more or less.
tom

[katt]

Okay i went to 100*C i think my gauge even though claims 110 it never showed more than 100c and its a boiling point.

Here's what i observed cruising on anything above 7000RPM will increase temperature closer to 8000 RPM faster temperature raise (up to 100*C).

Going just under 7000RPM temperature and temperature drops closer i go to 6000 RPM faster temperature drops (to slightly over 80*C).

7000 RPM seems to cause no changes in temperature.

Then this must be related to my carb problem or something else could be causing this?

[edwardtennant]

hey katt have you got a wiring diagram for how you wired up your temp sensor to your display?