engine oil temp sensor

[Greg Field]

How're those square wheels workin' out, Greg?

 

If you would only learn to truly think "outside the box," you'd see that square tires are the obvious answer. Scratch that. Once square becomes "the box," though, some clown will have to go outside of it and declare that only triangular tires are good enough. And so it goes . . .

[Dan M]

Thanks for the answer Dan. It is certainly not my intention to start a flame war on this, but I must state I disagree.

 

The reason is the following:

The sensor has a resistance span of some 100k over temp range of some 160°C (-40/125°C). Let us say this is being measured using a 10-bit ADC by measuring a voltage drop over the sensor. At 0-100k, 1 bit resolution would account for ~100ohm. The way I see it (correct me if I am wrong please) is that past 80°C the ADC would be unable to distinguish between 80° and 90°, 90° and 100°, 100° and 125°, etc. The resistance change would simply be to small to affect the readings even if the influence of noise (voltage fluctuations, radio emissions/sparking, etc.) is disregarded.

 

As for the question why would engineers use it in that range, I can state (mere speculation here, so everyone is free to go at it at will) that it was never intended to be used as a fine regulator but more like a on/off switch. Example, once the resistance drops bellow 100 ohm-> off, once it raises over 300 ohm -> on.

 

Does that make sense?

 

No, it does not. First off, I'm not trying to "flame" you here. I understand your reasoning but you are looking at the entire range of the sensor. The map focuses chiefly on running temps with adjustments made outside of that range (colder) being less precise. The reason they use thermistors rather than a more linear resistance temperature detector is thermistors are more accurate over a small range. The range in this purpose is normal operating temperature. In modern internal combustion engines that range is 90 to 110C. The whole thing is emissions and fuel control. They need to be accurate to control fuel properly. In the early 1980s when electronic fuel injection was becoming more widespread some manufacturers did use a coolant switch that just closed at a certain predetermined temperature. It was quickly found that more accuracy was needed and the move to thermistors was made.

When you monitor coolant temps with a scanner, you are looking at what the computer says it is seeing. During warm up temp reading is changing in chunks, sometimes 5 or more degrees at a time. Once the engine is up to operating temp you can watch the temp move degree by degree.

 

In other threads on this subject, there were claims of better fuel economy after adding conductive paste to the sensor holder. This clearly demonstrates that fuel trim in the operating range is altered by sensing more heat. It is not simply an on / off switch.

 

Vince Fischelli wrote an easy to understand article on the operation here: http://www.asashop.org/autoinc/may98/techtotech.htm

 

Another article, here: http://www.facstaff.bucknell.edu/mastascu/...sors/TempR.html shows a graph that illustrates where the sensor has accuracy and how the accuracy fades off as temperature cools down.

 

The fact that ohms increase in large, hard to determine chunks as temp cools, shows it is out of its calibrated range.

[Guzzi2Go]

No, it does not. First off, I'm not trying to "flame" you here.

I didn't say you do. I wrote the sentence as a precaution, since some people seem to take asking questions as some sort of a personal attack. This is clearly not a case here. Happy to see we can have a sensible discussion without worrying of hurting each others feelings.

I understand your reasoning but you are looking at the entire range of the sensor. The map focuses chiefly on running temps with adjustments made outside of that range (colder) being less precise. The reason they use thermistors rather than a more linear resistance temperature detector is thermistors are more accurate over a small range. The range in this purpose is normal operating temperature.

You are right about that. I am looking at the entire range. I've seen that the datasheet mentions 5% accuracy but says nothing about its whereabouts, which led me to believe that entire range is meant. Is there a convention about accuracy/certain range which make it redundant to be explicitly mentioned?

In modern internal combustion engines that range is 90 to 110C. The whole thing is emissions and fuel control. They need to be accurate to control fuel properly.

True. I believe you are aware of the fact that the same sensor type is used for air temperature measurements? Clearly this would be in a different range, 10°-40°C, rather then 90°-110°C. Any thoughts on that?

In the early 1980s when electronic fuel injection was becoming more widespread some manufacturers did use a coolant switch that just closed at a certain predetermined temperature. It was quickly found that more accuracy was needed and the move to thermistors was made.

When you monitor coolant temps with a scanner, you are looking at what the computer says it is seeing. During warm up temp reading is changing in chunks, sometimes 5 or more degrees at a time. Once the engine is up to operating temp you can watch the temp move degree by degree.

 

In other threads on this subject, there were claims of better fuel economy after adding conductive paste to the sensor holder. This clearly demonstrates that fuel trim in the operating range is altered by sensing more heat. It is not simply an on / off switch.

 

Vince Fischelli wrote an easy to understand article on the operation here: http://www.asashop.org/autoinc/may98/techtotech.htm

 

Another article, here: http://www.facstaff.bucknell.edu/mastascu/...sors/TempR.html shows a graph that illustrates where the sensor has accuracy and how the accuracy fades off as temperature cools down.

 

The fact that ohms increase in large, hard to determine chunks as temp cools, shows it is out of its calibrated range.

I think I understand what you are saying, and I could agree with it if we were talking of analogue electronics where stable behavior of the system would rely on careful composition of components with adequate characteristics. It is quite different with digital electronics where elegance and cleverness of a good design gave way to brute force of crunching numbers. And this is where I loose you. Looking at the capabilities of an average microcontroller equipped with a 10-bit A/D converter, I am inclined to think that in the "most interesting" temp range (>80°C), ECU would be unable to read out sensor's value accurately, no matter how sensor itself is accurate. As I wrote earlier, a change of resistance of 100 ohm would result in a change of a single bit in ADC. 100ohm at 90°C covers a span of >10°C, so ECU can only guesstimate the temperature in steps of 10°C.

 

This may be corrected using clever circuitry, but I don't see how would that work over extended range. Look at this:

A simple voltage divider + low pass filter. Would you expect to see something different here?

[Dan M]

I responded to your post by PM to save others some pain.

This thread should be laid to rest.

[Guest ratchethack]

I responded to your post by PM to save others some pain.

Dan, please continue on the Forum.

 

The truth will always be painful for those inherently afraid of it.

 

Others are actually here to seek it out.

This thread should be laid to rest.

But au contraire, mon ami.

 

It's just starting to get interesting!

 

Leave us now proceed with enthusiasm!

 

Crank up some more throttle, and engage a higher cog to boot!

[raz]

I responded to your post by PM to save others some pain.

This thread should be laid to rest.

I thought it was an interesting discussion. Hey, anyone not wanting to read it can skip this thread!

[Guest ratchethack]

UPDATE:

 

Mileage with thermo-paste, heat sink, and variable resistor installed vs. mileage with OE sensor/plastic holder with .015" air gap, no thermo-paste, no heat sink, no var. resistor:

 

42.86 MPG today vs. ~40 MPG (typical) previously

(5.48 liters/100 km vs. 5.88 liters/100 km)

 

Ambient temps ~75-80°F (~24-27°C), a truly STELLAR, MANDATORY day for a favorite ride.

 

NOTE: "Library" PC III map dynoed with and for OE sensor/plastic holder in both cases, latest mileage on "hard flog" mountain climb, using entire tread edge-to-edge of Metz Z6's, 50-80 mph sweepers amply punctuated with 2nd gear hairpins and everything in between up to 7,260 ft. (2,213 m) from ~500 ft. elevation, all 166.4 miles back road, no slab. BTW: remains of last snow on the ground at the top.

 

NOTE (Part II): Previous attempts to run with above map and OE sensor/plastic holder WITH thermo-paste but WITHOUT heat sink and var. resistor unrideable at full operating temp, at idle, off-idle, trailing throttle, and low RPMs: Over-lean symptoms of missing, balking, coughing, surging, hunting, and snuffing. ALL PRIOR SYMPTOMS ABSENT WITH thermo-paste, heat sink, and variable resistor installed. Today, smooth as a billiard table at all RPMs, all throttle openings, and at all operating temps -- even at the summit after a long, hard haul up the legendary East Grade of Mount Palomar.

 

NOTE (Part III): I understand how bass ackwards, wrongedy-wrong and absurd this is (at least for some). . .

 

And yet, there you have it. . .

[Greg Field]

Whatever works, works. Placebos work as often as not.

[Guest ratchethack]

Placebos work as often as not.

Placebos, eh, Greg?

 

I reckon I must've dreamed the whole ride today, and dreamed up my fuel consumption too.

[Dan M]

Placebos, eh, Greg?

 

 

 

Does this mean that you can pack the holder with sugar and have the same effect as copper paste?

 

 

 

Just when I thought I was out, they drag me back in.

[dlaing]

UPDATE:

 

Mileage with thermo-paste, heat sink, and variable resistor installed vs. mileage with OE sensor/plastic holder with .015" air gap, no thermo-paste, no heat sink, no var. resistor:

 

42.86 MPG today vs. ~40 MPG (typical) previously

(5.48 liters/100 km vs. 5.88 liters/100 km)

 

Ambient temps ~75-80°F (~24-27°C), a truly STELLAR, MANDATORY day for a favorite ride.

 

NOTE: "Library" PC III map dynoed with and for OE sensor/plastic holder in both cases, latest mileage on "hard flog" mountain climb, using entire tread edge-to-edge of Metz Z6's, 50-80 mph sweepers amply punctuated with 2nd gear hairpins and everything in between up to 7,260 ft. (2,213 m) from ~500 ft. elevation, all 166.4 miles back road, no slab. BTW: remains of last snow on the ground at the top.

 

NOTE (Part II): Previous attempts to run with above map and OE sensor/plastic holder WITH thermo-paste but WITHOUT heat sink and var. resistor unrideable at full operating temp, at idle and off-idle, and low RPMs: Over-lean symptoms of missing, balking, coughing, surging, hunting, and snuffing. ALL PRIOR SYMPTOMS ABSENT WITH thermo-paste, heat sink, and variable resistor installed. Today, smooth as a billiard table at all RPMs and all temps, and at all operating temps -- even at the summit after a long, hard haul up the famous East Grade of Mount Palomar.

 

NOTE (Part III): I understand how bass ackwards, wrongedy-wrong and absurd this is (at least for some). . .

 

And yet, there you have it. . .

 

Good stuff Ratchet!

You must have been going to fast for me to see you up on Mt. Palomar today.

I measured 37.5MPG today, based on one tank, which was maybe 1 MPG better than expected.

 

So, are you now using the brass adapter or the plastic?

How did you use the resistor? Was the resistor dialed to about 500 ohms the whole trip, or just when needed?

Got any photos of the heat sink mounted?

Is it simply mounted between adapter and sensor?

[dlaing]

Just another quick thought here and I'll shut up.

 

Looking at the spec'd sensor's values. It is ranged to be most sensitive in the 90C to 110C area. Interestingly, the exact operating temperature range of a modern liquid cooled motor. (thermostats typically open at 90 and cooling fans come on at about 110) The air cooled lump varies widely on either side of this range. Seems to lend some credit to someone's earlier theories on trying to mimic a coolant reading.

It looks like most of the variation is in the lower temps.

The early V11 map has more variation around 100C.

The later V11 and especially the MGS01 do not need great accuracy at about 100C

[dlaing]

SNIP

 

If I had a line on a different sensor or sensor/holder altogether that might be more suitable than the above, I’d have tested it. I don’t know of any, so I’ve worked with the best of what I know about, as tested.

 

SNIP

Temperature Sensor Output

 

This data table on the NTC thermistor was shamelessly lifted from Cliff’s link here:

 

http://www.cajinnovations.com/MyECU/temperature.htm

 

Temperature °C vs. Resistance ohms

 

As noted in prior posts, this is the only relevant data to consider when adding a variable resistor to enrich A/F at operating temps. It maps the output of the thermistor under the only temp sensor feed to the ECU that is read at operating temperatures after startup. It’s the same data in Cliff’s previously posted TempR line. At 125°C, dialing up an additional 1K Ω “fools” the ECU into believing the motor is running at ~50°C, richening the A/F considerably. At 125°C, and dialing up an additional 100 Ω, the ECU is “fooled” into believing the motor is running at ~100°C, richening A/F relatively slightly.

 

-40 100950

-30 53100

-20 29120

-10 16600

0 9750

10 5970

20 3750

25 3000

30 2420

40 1600

50 1080

60 750

70 525

80 380

90 275

100 205

110 155

125 100

Weber Marelli makes a WTS05 and WTS09

I think ours is the 05 and the 09 has a shorter probe.

I don't know why you would want the shorter probe unless you got a shorter holder, or maybe went with NO holder

I can email someone the PDF if they want to see it.

It has physical dimensions.

Thread is M12 x 1.5

The Resistance per Temp numbers are essentially identical to Cliff's numbers.

They give the tightening torque spec as 24Nm max! But whatever you do don't use that spec with the plastic adapter ROTFLMAO!

Accuracy is claimed 5% (W/°C) @ -40>+125C

[Bruce Reader]

What type of insulator material could be used to sleeve or wrap around the brass temp sensor holder and withstand the heat involved ?

 

Cheers

 

Bruce

[Guest ratchethack]

So, are you now using the brass adapter or the plastic?

Plastic holder, filled with thermo-paste, with heat sink and variable resistor.

How did you use the resistor? Was the resistor dialed to about 500 ohms the whole trip, or just when needed?

Per previous posts, it's wired in series with the sensor. I cut into one wire of the 2-wire "extension" that runs between the AMP connector at the sensor and runs up the right-side of the spine to somewhere up near or on the coil packs, and soldered the connections. I keep it at "0Ω" added resistance and only use it when needed, typically when I anticipate, or at the first hint of lean-burn symptoms, as in after a long hard pull up a steep grade or high-speed flog, and then abruptly haul down to an extended stop at idle, or suddenly have to wait for a rubbernecker to pull off the road on a scenic turnout (as happened yesterday) -- or whenever I know the motor is really hot and isn't getting good air flow, as in stop-n-go traffic. This is when I figure the sensor body is up to maximum heat content, dumping unwanted excess heat back into the thermistor tip, and fouling a correct read of lower combustion temps at idle by the ECU. Under these conditions I dial up +~300-400Ω, and the lean-burn symptoms that would otherwise appear with thermo-paste but without heat sink and var. resistor never materialize. I flick it back to "0Ω" again as soon as I get underway with good airflow, and leave it there. Until the motor first achieves full operating temp there's no need to use it at all. For warm startup, +~500Ω lights it off instantly. Lately, I've been using +~300Ω for cold startup, which seems to fire it up with maybe one less crank rev, "just 'cause it's there".

Got any photos of the heat sink mounted?

Is it simply mounted between adapter and sensor?

I tried some shots of it in situ, but my camera's apparently not capable of handling the high contrast between the dark recesses under the tank and the brightness of the tank and rocker cover. They didn't turn out.

 

Per prev. post, the heat sink is fit betwixt the sensor body and holder. I was obligated to put a 45° chamfer in the center mounting hole to match the odd conical washer permanently fit to the sensor. I carefully matched the depth of the cut on the drill press so as not to compromise the OE .015" gap betwixt sensor tip and holder base. I put thermo-paste over and under the conical washer to ensure optimum heat flow.

 

I reckon ~43 MPG hauling Mt. Palomar has gotta be pretty hard to beat with a V11, regardless of map or engine mods.

 

But without much question, on this one, somebody's M is always gonna V.