Designing an Engine Oil Temperature Display Gauge Project

1

17-CB-002

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Thread starter
Csory (Hungary), may be you can help in this project.
After reading from your (Csory) idea on building display gauge, I pulled out some info together on the design of an Engine Oil Temperature gauge.
By tapping into the actual "EOT" circuit between the ECM and the EOT sensor, one can read the ACTUAL oil temperature in "volts".
The reading should be anywhere between 4.9v "Cold" and 0.01v "Hot".
When referring to the Toyota ECT Voltage/Temp conversion chart, one can logically deduct the actual Engine oil temp..
As per the Toyota ECT Theory file- The ECM feeds a constant 5 volt through 2 resistors (One fixed inside the ECM and the second variable NTC resistor inside the EOT). All are BOSCH design.
Negative Temp Coefficient (NTC)- when the sensor is cold, her resistance is high and vise versa when it reads hot, the resistance drop).
In theory, at room temperature, one should read 2.2 volts and around 0.02 volts with a normal hot engine

Note: If you are checking the EOT voltage, you will require a "High Impedance" meter or the meter will affect the reading).

Good Luck.

Handy information is contained in these links,

https://i.postimg.cc/SQnXpVtd/2-A0-ABFF7-7-BA4-43-DA-B5-F3-379-E9-EEF930-D.png
https://i.postimg.cc/j2nYkDc6/39-D706-BD-2-FD9-44-C7-B621-B794-C7-A75825.png
https://i.postimg.cc/JtwCwRYf/9-C4-C1-ECC-552-D-457-D-8-F00-DC9-AC38-FD0-E1.png
https://i.postimg.cc/pV3mV8wH/A6-B63664-4-B7-E-45-E8-A97-F-544-D169-CBA41.png
 
Alain: Thanks for the tip. Been toying with the idea but was a bit skeptical about tapping into the ECU's oil temp signal. First, I should be absolutely certain that one end of the voltage divider is connected to chassis ground (and not some sort of virtual ground provided by the ECU). The last drawing suggests this, but calling one half of the divider a "pullup" makes me a bit cautious. Another problem would be with the wiring/connectors: not sure if I could source a proper drop-in replacement, and just cutting/soldering in there is not something I'd expect anyone to do. Not even myself, at least not until the bike is under warranty :D Will take another look though.
 
Thread starter
Hi Csory, in my previous job at a Japanese automotive OEM and before the diagnostic scanners were available, we back probe the wire at either the ECM or sensor depending on ease of component access & location. We often leave it there for days during troubleshooting.
There is no need to worry about the "pull up" resistor if you are using a high impedance meter. The "pull up" resistor selection depends on the scale reading the engineers want to see inside the ECM.

You mention the "virtual" ground: Inside the ECM there are 3 types of ground. One for the "Input" sensors such EOT, Intake Air Temperature etc. then there is the "Output" device ground such as Injectors or the Idle speed control air valve, ignition timing etc. and the last ground is for the ECM internal circuitry. Then all these ground wires goes to the chassis.

Can you build a "look up table" that can read the EOT in voltage (between 0 & 5v) and display it in temperature C or F ?

Tomorrow, I will shoot a short video to demonstrate it using a Digital voltmeter on my bike.

Would it not be nice if we can read the real exact oil temperature especially if we are stuck in traffic!
 
Past experience on previous CBs in parked traffic (think Caribana in godforsaken Toronto in July/August) was not the engine oil, but the hydraulic clutch. It failed to the point of uselessness. Had to have it cool down over 30 minutes to be useful again.
 
Thanks in advance, Alain! (Lookup table, or even approximating with an n-level polynomial would not be a problem). Voltage measurement impedance on “my end” has the magnitude of megaohms - should not be a problem. The pullup worried me not for it’s existence, but for the particular word used. A bit of a layman’s term within a technical document - made me cautious about the credibility of the entire doc.

GoldOxide: was that steam bubbles forming in clutch liquid, or flex pipes softening up from the heat? Sounds rather ugly, being stranded for half an hour :(
 
Csory_imp said:
Thanks in advance, Alain! (Lookup table, or even approximating with an n-level polynomial would not be a problem). Voltage measurement impedance on “my end” has the magnitude of megaohms - should not be a problem. The pullup worried me not for it’s existence, but for the particular word used. A bit of a layman’s term within a technical document - made me cautious about the credibility of the entire doc.

GoldOxide: was that steam bubbles forming in clutch liquid, or flex pipes softening up from the heat? Sounds rather ugly, being stranded for half an hour :(
Click to expand...
Yes, I'm curious about the reason you lost the clutch because of the clutch fluid overheating?
Maybe stainless braided lines could improve matters?
A good job it wasn't the brakes... :(
Mind you, that will never be a situation that occurs here in England, UK!! :)
 
Bazbro_imp said:
Csory_imp said:
Thanks in advance, Alain! (Lookup table, or even approximating with an n-level polynomial would not be a problem). Voltage measurement impedance on “my end” has the magnitude of megaohms - should not be a problem. The pullup worried me not for it’s existence, but for the particular word used. A bit of a layman’s term within a technical document - made me cautious about the credibility of the entire doc.

GoldOxide: was that steam bubbles forming in clutch liquid, or flex pipes softening up from the heat? Sounds rather ugly, being stranded for half an hour :(
Click to expand...
Yes, I'm curious about the reason you lost the clutch because of the clutch fluid overheating?
Maybe stainless braided lines could improve matters?
A good job it wasn't the brakes... :(
Mind you, that will never be a situation that occurs here in England, UK!! :)
Click to expand...
Yes, I'm curious about the reason you lost the clutch because of the clutch fluid overheating?
Maybe stainless braided lines could improve matters?
A good job it wasn't the brakes... :(
Mind you, that will never be a situation that occurs here in England, UK!! :)
This was on a CB750SC. The clutch line was not braided and I seem to recall the line going to the crankcase, which was immensely hot. I couldn't determine in-the-moment if bubbles were forming, but that would not surprise me if it did. I did not see any "steam-like" gases anywhere. The net-net was lever pressure was like "98%" lost and clutch plate action was immediate and no modulation control was possible. At the time I thought I blew the line from the heat.

I expect today's CB1100 would not have that problem, but I have not been in that situation with an air-cooled engine for quite some time either.
 
GoldOxide_imp said:
Bazbro_imp said:
Csory_imp said:
Thanks in advance, Alain! (Lookup table, or even approximating with an n-level polynomial would not be a problem). Voltage measurement impedance on “my end” has the magnitude of megaohms - should not be a problem. The pullup worried me not for it’s existence, but for the particular word used. A bit of a layman’s term within a technical document - made me cautious about the credibility of the entire doc.

GoldOxide: was that steam bubbles forming in clutch liquid, or flex pipes softening up from the heat? Sounds rather ugly, being stranded for half an hour :(
Click to expand...
Yes, I'm curious about the reason you lost the clutch because of the clutch fluid overheating?
Maybe stainless braided lines could improve matters?
A good job it wasn't the brakes... :(
Mind you, that will never be a situation that occurs here in England, UK!! :)
Click to expand...
Yes, I'm curious about the reason you lost the clutch because of the clutch fluid overheating?
Maybe stainless braided lines could improve matters?
A good job it wasn't the brakes... :(
Mind you, that will never be a situation that occurs here in England, UK!! :)
This was on a CB750SC. The clutch line was not braided and I seem to recall the line going to the crankcase, which was immensely hot. I couldn't determine in-the-moment if bubbles were forming, but that would not surprise me if it did. I did not see any "steam-like" gases anywhere. The net-net was lever pressure was like "98%" lost and clutch plate action was immediate and no modulation control was possible. At the time I thought I blew the line from the heat.

I expect today's CB1100 would not have that problem, but I have not been in that situation with an air-cooled engine for quite some time either.
Click to expand...
I have been stuck in mid-summer traffic on the CB11 a few times at temps exceeding 115F (46C). Never had an issue with the clutch, although I was beginning to get worried about the engine oil temp.

I've found that overheating on an air cooled bike (my CB11 or CB750) isn't really a problem unless you're stuck motionless and idling in temps above 100F for half an hour or so. Even moving slowly (i.e 10 - 20 mph) provides enough airflow to cool the bike adequately.
 
Flynrider_imp said:
GoldOxide_imp said:
Bazbro_imp said:
Csory_imp said:
Thanks in advance, Alain! (Lookup table, or even approximating with an n-level polynomial would not be a problem). Voltage measurement impedance on “my end” has the magnitude of megaohms - should not be a problem. The pullup worried me not for it’s existence, but for the particular word used. A bit of a layman’s term within a technical document - made me cautious about the credibility of the entire doc.

GoldOxide: was that steam bubbles forming in clutch liquid, or flex pipes softening up from the heat? Sounds rather ugly, being stranded for half an hour :(
Click to expand...
Yes, I'm curious about the reason you lost the clutch because of the clutch fluid overheating?
Maybe stainless braided lines could improve matters?
A good job it wasn't the brakes... :(
Mind you, that will never be a situation that occurs here in England, UK!! :)
Click to expand...
Yes, I'm curious about the reason you lost the clutch because of the clutch fluid overheating?
Maybe stainless braided lines could improve matters?
A good job it wasn't the brakes... :(
Mind you, that will never be a situation that occurs here in England, UK!! :)
This was on a CB750SC. The clutch line was not braided and I seem to recall the line going to the crankcase, which was immensely hot. I couldn't determine in-the-moment if bubbles were forming, but that would not surprise me if it did. I did not see any "steam-like" gases anywhere. The net-net was lever pressure was like "98%" lost and clutch plate action was immediate and no modulation control was possible. At the time I thought I blew the line from the heat.

I expect today's CB1100 would not have that problem, but I have not been in that situation with an air-cooled engine for quite some time either.
Click to expand...
I have been stuck in mid-summer traffic on the CB11 a few times at temps exceeding 115F (46C). Never had an issue with the clutch, although I was beginning to get worried about the engine oil temp.

I've found that overheating on an air cooled bike (my CB11 or CB750) isn't really a problem unless you're stuck motionless and idling in temps above 100F for half an hour or so. Even moving slowly (i.e 10 - 20 mph) provides enough airflow to cool the bike adequately.
Click to expand...
I have been stuck in mid-summer traffic on the CB11 a few times at temps exceeding 115F (46C). Never had an issue with the clutch, although I was beginning to get worried about the engine oil temp.

I've found that overheating on an air cooled bike (my CB11 or CB750) isn't really a problem unless you're stuck motionless and idling in temps above 100F for half an hour or so. Even moving slowly (i.e 10 - 20 mph) provides enough airflow to cool the bike adequately.
The situation I experienced was a total trap:

* Parked on freeway.
* Off-ramps funneled to residential side roads parked.
* No natural air current.
* Super high summer humidity :@ .
* Hot summer day.
* Moved only 100 feet in 30 minutes.

Had to take to the sidewalk to bypass the situation. Ironically, a police car came out of a residential laneway and cut me off - rightfully so. However, they didn't care. They were more concerned about the vehicular traffic situation as nothing moved on the asphalt. An officer got out of the car and asked me to push the bike, not ride it. Then they went to evaluate the traffic situation. Nobody was moving except pedestrians.
 
As for the original idea, spent a few hours measuring the CB's (at least, my CB's...) built-in EOT sensor. The devil is in the details: if the same electronics are to be applied to bikes of different manufacturers, models or even model years, there has to be a guess made on which NTC thermistor is being used. Supply voltage might be different too - just too many variables I'd be comfortable to work with. There are some 50 or so standard NTC series, not sure if I could get a reasonable readout just by guessing. Of course it could be fine-tuned to any specific bike, but that would require some way to input points of the characteristic curve - basically, taking the EOT sensor out, dipping in a cup of hot water, and measuring temperature with resistance changes as the water cools down to room temp. Not something I'd expect to be a standard installation step :D
 
Csory_imp said:
As for the original idea, spent a few hours measuring the CB's (at least, my CB's...) built-in EOT sensor. The devil is in the details: if the same electronics are to be applied to bikes of different manufacturers, models or even model years, there has to be a guess made on which NTC thermistor is being used. Supply voltage might be different too - just too many variables I'd be comfortable to work with. There are some 50 or so standard NTC series, not sure if I could get a reasonable readout just by guessing. Of course it could be fine-tuned to any specific bike, but that would require some way to input points of the characteristic curve - basically, taking the EOT sensor out, dipping in a cup of hot water, and measuring temperature with resistance changes as the water cools down to room temp. Not something I'd expect to be a standard installation step :D
Click to expand...
Csory, just by following your project and reading your technical notes, I do not see any obstacles for you , knowledgable man in this field = you will do it :thumbsup:
 
Csory_imp said:
As for the original idea, spent a few hours measuring the CB's (at least, my CB's...) built-in EOT sensor. The devil is in the details: if the same electronics are to be applied to bikes of different manufacturers, models or even model years, there has to be a guess made on which NTC thermistor is being used. Supply voltage might be different too - just too many variables I'd be comfortable to work with. There are some 50 or so standard NTC series, not sure if I could get a reasonable readout just by guessing. Of course it could be fine-tuned to any specific bike, but that would require some way to input points of the characteristic curve - basically, taking the EOT sensor out, dipping in a cup of hot water, and measuring temperature with resistance changes as the water cools down to room temp. Not something I'd expect to be a standard installation step :D
Click to expand...
Not to complicate the plan, however, if things like these are a common challenge across bikes, one could consider creating a "common" module where generic I/O is wired to, as well as Vcc and ground. Add a low-cost bluetooth radio and broadcast the raw I/O digital values to a receiver module or phone app that will map the I/O to specific device profiles and display their real-world values - refreshing maybe every one or two seconds.

Since you are only reading the I/O and not controlling anything, this should be completely safe. This would be similar to an OBD device (but read-only), and wiring would be flexible to the end user's need.

- - -

You might be able to cobble together from off-the-shelf sources a low-cost common I/O module (4 port enough?), a bank of cheap ADCs, maybe a low-end MCU, integrate a BT radio and that will allow you to focus your energy on the your receiver module, or just a phone application.
 
Thread starter
Hi Csory,
For this CB1100 "EOT" I am confident that the resistance/voltage look-up table is accurate, so is the circuitry as described in my original posting.

Let's say that one wants to build a simple temp display with a 3 digit temperature reading and we know the following:
The constant supply voltage "VCC" is 5 volts.
The "EOT" reading is between 0.01 to 4.99 volts.
The "EOT" resistance (NTC) is 50 to 16 K Ohms.
We will temporarily back probe at the back of the "EOT" connector.
We may require a 12volt to 5 volt supply.

Note: The IAT (Intake Air temperature) is an identical circuit also.

Can you draw me the diagram & tell me what components are required?
If prototype is successful, we can get more CB1100 owners interested.

I will try to get the necessary components from my local electronic supplier to build one here in Canada.
Your assistance is appreciated.
Alain Lee
 
Alain: Attached please find a circuit diagram that would work with a 3-digit 3-segment LED display, and able to read 2 independent analog channels (EOT and IAT), both scaled between 0 and 5V. Impedance is megaohm/ish. Display decoding is done by the MAX7219, analog read and conversion (along with all the pretty stuff) is via the ATTINY85 microcontroller (programmable in plain C). This entire thingy is very similar to my original "gadget", except for ditching the DS18B20 temp sensors, light sensor, and adding a second analog voltage input. Hope this helps.

 
GoldOxide: I don't know either if this is a common "issue". Putting together an instrument you described should not be a big hassle, but tapping into the wiring could/would (and probably invalidate warranty). Also, there are not that many analog signals I can think of. IAT more-or-less equals to ambient air temp, EOT and ECT might be interesting - what else? Will have to finish the original project anyways - still fiddling with the display... :D
 
Csory_imp said:
GoldOxide: I don't know either if this is a common "issue". Putting together an instrument you described should not be a big hassle, but tapping into the wiring could/would (and probably invalidate warranty). Also, there are not that many analog signals I can think of. IAT more-or-less equals to ambient air temp, EOT and ECT might be interesting - what else? Will have to finish the original project anyways - still fiddling with the display... :D
Click to expand...
Sure, I assume warranty was not an issue since I think for most it would have expired by now. Tapping into wiring would be a hassle yes, but there are wiring "T-like crimp devices" that connect to the circuit without cutting or scraping the wiring sheath. I was just thinking if this was an approach, all the taps can be collated at a common I/O concentrator and converted to digital. A four port concentrator probably be enough with future expansion to spare. Generic, but sure, could be overkill. It depends on future ideas I suppose.
 
I am more than certain that all electric techs know about liquid insolation tape, which I used with a great success, mostly in difficult spots or cut insulation. I used proven good brand Wurth, and would advise to use good quality for the best results. Takes time and patience to apply a few coats but results are worth your effort.
'Here is just an example:
LIQUID ELECTRIC TAPE 118mL 893.198010
 
peterbaron_imp said:
I am more than certain that all electric techs know about liquid insolation tape, which I used with a great success, mostly in difficult spots or cut insulation. I used proven good brand Wurth, and would advise to use good quality for the best results. Takes time and patience to apply a few coats but results are worth your effort.
'Here is just an example:
LIQUID ELECTRIC TAPE 118mL 893.198010
Click to expand...
Would it be possible to retrofit a XR650L oil temp gauge filler cap to work on the CB1100 engine case?
 
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