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Rolf Halvorsen

Temperatur sensor resistance

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A friend came by today complaining that his bike (Quota) seems to be running too rich when warm.

After a little discussion - and since I had a new sensor, we decided to switch sensors. But before we did this - we measured the resistance of the new sensor to be around 2.3 KOhm (cold). After switching - the bike seem to run better, and my friend is happy. (who and where can you find a new sensor when you need one?)

The old sensor measured about 3.8 KOhm (cold).

Can anyone tell me what the resistance values of good sensor should be? (I intend to buy a new and perform measurements on it.)

Rolf

 

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Rolf, Is this the Engine (head) Temperature Sensor or the Air Temperature Sensor?

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The temperature sensors are usually NTC thermistors mounted in a housing. NTC (negative temperature coefficient) means that as the thermistor temperature rises, it's electrical resistance drops. The measurements you made need to account for temperature of the sensor, for example is it in your warm hand or outside in the cold.

If you are talking about the air sensor in the air box, it is usually trouble free, unless your friend is in the "pod filter" brigade. Then he needs to mount the air sensor somewhere where it measures only intake air. https://www.v11lemans.com/forums/index.php?/topic/19831-air-temp-mod-for-no-air-box/

Since a thermistor circuit is usually low current to avoid self heating, the circuit is sensitive to extra resistance from a bad connection. Unplugging and replugging connectors can help, especially if you clean and treat the connectors with something like DC4 or DeoxIT.

I bought packs of 20 thermistors from Aliexpress for about $2 a pack. Let me know if you want a selection sent to you,  I know I will never use them all. Note that the rating for thermistors is measured at 25 degC. 

The illustration below is for the V11 air intake sensor, but the V11 oil temp sensor has the same rating thermistor in a different housing.

Air Intake Sensor.jpg

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Thank you Marty for your responce. It is the engine head sensor (mounted in a plastic house on the right cylinder head.

Do you hav any specific data for this? I had if on a bench (not touching) . About 20 degrees Celsius.

Rolf

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1 hour ago, Rolf Halvorsen said:

Thank you Marty for your responce. It is the engine head sensor (mounted in a plastic house on the right cylinder head.

Do you hav any specific data for this? I had if on a bench (not touching) . About 20 degrees Celsius.

Rolf

Here is some extracts from the V11 workshop manual, and information about the brass sensor support I fitted to my bike.

Oil Temp Sensor.jpg

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Marty: PERFECT, thanks.

 

Here is an interesting article from Murray (Down under) posted May 22, 2007

After just playing with one to find out its not the problem The "engine oil temp sensor" which is acutally the head temp sensor and has little to !@#$ all to do with the oil temp. What makes me say that I have a bike that has an additional temp sensor in the oil cooler and the reading out of that are radically different to the head temp sensor. Is a NTC (negative temperture coefficent) themocouple with a range of -40 to 170 ish degrees celcius. NTC means as the temp goes up the resitance goes down resitance at 10 degrees is around 3.7K ohm and at 80 degrees is 0.37kohm. Buy rights you should be able to bung a 10cent resitor in there and run home on that if it fails. The sensor does not earth through the cases oil preasure switch style but has a return line to the ECU. Hope this helps NB all temps are celcius/metric.

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As I can measure - there is an air gap inside between the sensor and the holder. There has never been a heat leading paste inside the ones I have worked with. And why is the original made of partly plastic? 

Plastic insulate better than brass in a housing. Would a brass house leak heat away?

Rolf

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Since this sensor should act as an oil temperature sensor - the oil inside the head should transfere the temperature to the surrounding aluminium (in the head). Let us consider this to be ok. 

Then the aluminium (head) (after being cooled by air) should transfere its temperature to the copper metal base of the sensor bracket. This should also be ok.

Then the temperature of the copper base should transfere the temperature to the brass sensor - with an air gap?

The best insulator in the world is - nothing (vacuum).

Then comes air (dry).

Next is any fluid material. (Water can evaporate - so you cannot use that.) Any fluid oil should work, but a very thick oil substance (grease) would be better. I think any grease will work fine since the distance  is around 1mm level. Specific thermal grease - or whatever you call it - should not be needed, even if it technically is better.

Any comment?

Rolf

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Having used both the OEM plastic and the all-brass "upgrade", I can say my 2000 Sport runs better with the plastic one.

Theory is, that the brass retains heat too long and makes the ECU adjustments lag slightly behind actual conditions, leading to poor running.

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46 minutes ago, JBBenson said:

Having used both the OEM plastic and the all-brass "upgrade", I can say my 2000 Sport runs better with the plastic one.

Theory is, that the brass retains heat too long and makes the ECU adjustments lag slightly behind actual conditions, leading to poor running.

This is my experience, also. Mind you, we have very high ambient temperatures in the US south and my Sport has never liked this with low speed traffic, parking, restarting.

Dan M did some interesting data collection on the higher mass sensors becoming a heat sink with resultant diminished responsiveness.

 

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Maybe we all have the wrong focus.

The transition resistance between the sensor-pins and the cable  - might be where we should focus.

The ECU measures the resistance only. from about 4.0 KOhm (cold) down to 0.4 KOhm (warm). 100% contact = 0 Ohms.

To measure resistance you will require a relative low voltage to be sent. 

A low voltage combined with corroded pins - might give you a higher resistance NUMBER than it should be. Telling the ECU to think the engine is colder than reality - and feeding more fuel than necessary.

Am I into something here?

Rolf

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Main purpose of this sensor is to control start-up and warm-up enrichment. Its influence on the drivability is overestimated.

My maps are set to zero above 50°C (enough) and below -10°C (failsafe)

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1 hour ago, Rolf Halvorsen said:

Maybe we all have the wrong focus.

The transition resistance between the sensor-pins and the cable  - might be where we should focus.

The ECU measures the resistance only. from about 4.0 KOhm (cold) down to 0.4 KOhm (warm). 100% contact = 0 Ohms.

To measure resistance you will require a relative low voltage to be sent. 

A low voltage combined with corroded pins - might give you a higher resistance NUMBER than it should be. Telling the ECU to think the engine is colder than reality - and feeding more fuel than necessary.

Am I into something here?

Rolf

Indeed. I found that conditioning the connectors in my harnesses contributed to better running overall. Nothing specific. 

Caig DeOxit® ! :thumbsup:

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21 hours ago, Rolf Halvorsen said:

As I can measure - there is an air gap inside between the sensor and the holder. There has never been a heat leading paste inside the ones I have worked with. And why is the original made of partly plastic? 

Plastic insulate better than brass in a housing. Would a brass house leak heat away?

Rolf

Yes, you're right that the brass housing would radiate heat, just in a slightly poorer way than the adjacent aluminium fins. However, it would still be at cylinder head temperature all the time. I think that the plastic housing would be cheaper than brass. My original plastic housing didn't have any heat conductive paste in it either, but after I broke it, I made sure that the replacement housing had some.

18 hours ago, Rolf Halvorsen said:

Since this sensor should act as an oil temperature sensor - the oil inside the head should transfere the temperature to the surrounding aluminium (in the head). Let us consider this to be ok. 

Then the aluminium (head) (after being cooled by air) should transfere its temperature to the copper metal base of the sensor bracket. This should also be ok.

Then the temperature of the copper base should transfere the temperature to the brass sensor - with an air gap?

The best insulator in the world is - nothing (vacuum).

Then comes air (dry).

Next is any fluid material. (Water can evaporate - so you cannot use that.) Any fluid oil should work, but a very thick oil substance (grease) would be better. I think any grease will work fine since the distance  is around 1mm level. Specific thermal grease - or whatever you call it - should not be needed, even if it technically is better.

Any comment?

Rolf

I think that a temperature sensor should be thermally coupled to the part that you want to measure.  If the engine does not run well like that, then there is an opportunity to tune the engine so it does run well. Having an air gap seems to add the chance of ambient air (temp and speed) corrupting the sensor output.

18 hours ago, JBBenson said:

Having used both the OEM plastic and the all-brass "upgrade", I can say my 2000 Sport runs better with the plastic one.

Theory is, that the brass retains heat too long and makes the ECU adjustments lag slightly behind actual conditions, leading to poor running.

I can't see how the brass retains heat. It is thermally coupled to the cylinder head, so is always within a fraction of a degree of the same temp as the head. If you are meaning the sensor is slow to respond to cylinder head temp changes due to the internal air gap, then I agree. I added thermal paste to remove that possibility on my bike, thinking that Luigi was being economical with the thermal paste, just like the lack of lubrication in the steering head bearings.

I am really happy with how my bike starts and runs, with good relays (credit Docc), great electrical function & grounds (credit KiwiRoy), awesome engine performance (credit Meinolf), and nice shifting (credit Chuck, Scud & Lucky Phil). :notworthy:

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