Guzzi2Go

March 1, 2009

In the range of 90C to 110C the variation is only 120 ohms. Pretty easy to pin point a temp.
By comparison, 0C to 20C it is 6000ohms. Far greater margin for error.

Make sense?

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?

February 28, 2009

...
Looking at the spec'd sensor's values. It is ranged to be most sensitive in the 90C to 110C area.

...

How do you come to that conclusion? Could you define "most sensitive" for us (or for me if I am the only one who does not understand) please?

February 27, 2009

Volume II - Influence of a heatsink on temperature sensor

- General Audiences

As promised, here is a short discourse on the effects of applying a heatsink to the temperature sensor.

Observe the following two tables:

First table shows how temperature measured varies depending on the heatsink efficiency (size) at constant power delivery. For the sake of the argumentation, assumed power input to the sensor is fixed to 10W. Convection (air flow) is disregarded, although it would contribute quite a lot (provide for even better sensor cooling) in a realistic situation. Another assumption is ideal thermal contact of the sensor (no air gap). So consider this to be a best case scenario. Heatsink values are in the range of 10°K/W (let us assume that this is the sensor's nut) and 0.1°K/W (a really big'un). A garden variety heatsink like the one shown in one of the previous posts would have a value of ~5°K/W.

First column (10K/W - no heatsink). Sensor is heating up quite nicely, and the readings would show the heat source's temperature. In an ideal case, sensor dissipates excessive heat through the object whose temperature it is measuring, namely, the cylinder head. In less than ideal case, some of the heat escapes through the sensor's nut.

Last column (big'un). Sensor temperature barely differs from the ambient temperature. One could practically stick the sensor in the air and save himself a trouble of drilling cylinder heads, constructing holders, "thermo pasting" them, etc.

Second table shows how temperature measured varies with power input and heatsink size at constant ambient temperature. This would be your 1-hour run through Mojave desert in summer, 7:00 AM. The purpose of this table is to verify the "10W input power" assumption. Observe "ridiculous" values (1025°C, 525°C) in the "100W row". One can conclude that either 100W is most likely to high value for input power, or that thermal resistance of the sensor's nut is significantly lower than 10K/W. However, looking at the nut and a proper heatsink, this is most likely not the case. Draw your own conclusions here.

Conclusion

Adding heatsink to the sensor is a bad idea. The bigger the heatsink, the closer one gets to measuring air temperature instead of motor temperature. Since your bike already has an air temp sensor it makes no sense to add another one. If you still chose to add a heatsink to the sensor, YMMV. A lot.

I am running out of space on this bumper sticker. Will post some info on the influence of the air gap on the measured temperature on another one.

February 27, 2009

Only for forums. In RL this would never work, there are just too many parties involved. I guess the ecu is continuosly polling the analog inputs, anything else would make problems only.

Hubert

Well, less frequent is still continuous. Anyway, the question was not what ECU does, but rather if the goal was to minimise impact of transients on temperature measurement, wouldn't there be other, simpler and more reliable methods then designing a special receptacle? An example of such a method would be infrequent sampling.

February 27, 2009

... It slows variation.

Wouldn't less frequent sampling have the same effect?

February 25, 2009

Phrase. Better?

February 25, 2009

Or one could just stick the temp sensor up his :moon: , keep it nice and warm and have even more predictable results.

And I bet that the phrase "riding feeling" would get a whole new meaning too.

Volume II (a short one, but nonetheless...), about influence of heat sink applied to the temp sensor is coming. Brace yourselves! :oldgit:

February 23, 2009

I think it would make more sense to not put the resistor in series, but have it as a complete bypass.
For example, once warmed up one could hit the bypass using maybe a 500 ohm resistor and the engine would always assume to be 70°C.

....

Yes, it probably would make more sense. It is certainly easier to live with, since the behavior of such a setup is more predictable.

Downside is that it would require "user input", whereas the resistor in series would work "automagically".

February 22, 2009

So, while ratchet is scheming on how to use effects of global warming to his advantage, let me try with more down to earth stuff. By far not so "scientific" as ratchet's interpretation of the laws of thermodynamics. Simple arithmetics (four basic operations) will do. English will be simpler too. Furthermore, and unlike ratchet, I am encouraging comments regardless of their "scientific" value or "sincerity". Smoke them if you got them. :rasta:

Let us try to see how adding a resistor in series to oil temp sensor may affect the fuel map. The objective of the exercise to is show what resistor values one may consider (is it 500k or less?). Observe the following table:

Explanation

Rn - nominal resistance of the WTS05 sensor straight out of the data sheet. Looking at the table under Temp(20°C) you can read that sensor outputs 3750 ohm

Davg - resistance amidst two adjacent temperature points. For the sake of argumentation, anything between 7860 and 4860 ohm would be treated as 10°C, 4860 to 3085 ohm as 20°C, and so on...

%err - these lines are there to confuse you. Ignore them. The only relevant figure there is the additional resistor value in the 0°C column. Three values are used in this example: 220, 470 and 1k ohm.

RGB colored lines are the relevant lines. The values in them represent total resistance = sensor + resistor

Green colored values tell you at which temperatures additional resistor has no effect on the temperature reading. For example, at 10°C your bike would be running stock map.

Yellow colored values tell you where temperature readings are affected by the additional resistor. Here your bike would be running richer.

Red colored values tell you where temperature stops affecting the map. The additional resistor takes over completely and the map is cut off. That would be similar to the map published on the Cliff's myECU page, which just stops adjusting anything beyond 40°C. By selecting proper resistor value you can decide where this point may be.

Examples:

With R=1k map would be cut off at 50°C, a tad rich between 30-50°C and stock bellow 30°C.

With R=470 ohm map would be cut off at 70°C, a tad rich between 50-70°C, and stock bellow 50°C

With R=220 ohm map would be cut off at 100°C, a tad rich between 60-90°C and stock bellow 60°C

Conclusion

Which resistor values make sense? I'd say anything up to whereabouts of 1kohm. 500k certainly not and that is because the sensor is rated 100k@-40°C. With 500k additional resistor one would venture into quite cold areas.

February 21, 2009

UPDATE:

With newly acquired linear 500K Ω variable resistor in hand today,...

500k?! How close to absolute zero are you trying to get?

February 21, 2009

Now if you have a Guzzi that runs BETTER with thermo paste in the plastic holder/sensor than without, regardless of whatever map you may be running, and particularly if you have cold startup problems, I suspect that the more RELEVANT LINES will indeed be the OilT and Crank lines, and that the TempR line will NOT be AS RELEVANT to you -- unless you have mileage problems. In this case, the TempR line will still -- and AGAIN -- be THE MOST RELEVANT LINE to you, because with the thermo paste in there, you are now likely to get better mileage due to a leaner A/F at operating temperatures as a direct result of adding the thermo-paste, as widely reported on this thread and others. Again, the ONLY RELEVANT LINE to you when considering mileage is the TempR line.

Please help yourself by understanding this^ and the following before you address a post to me on this again:

Well Ratchet, I must say you are a touchy sod. And I have an impression it is you who does not have understanding of what you wrote here.

Comprehensive writing

On the TempR line, I'm focused on wot's happening between 40°C to 125°C, which is a progressive drop in resistance over half again greater than an order of magnitude. This appears to be the only relevant data to consider here once the motor is warmed up to operating temp and running. It's at the high temp end of this range where I've consistently observed the undesirable low-RPM driveability anomalies (apparent over-lean condition) caused by adding thermal paste for a direct thermal connection between holder base and sensor tip using the plastic holder.

If that is meant to say: "Mixture is a function of temperature", then I do not comprehend two things:

1. What is the point of stating the obvious? We all know that it is.

2. Why using so many words?

Private Baldrick: No, the thing is: The way I see it, these days there's a war on, right? and, ages ago, there wasn't a war on, right? So, there must have been a moment when there not being a war on went away, right? and there being a war on came along. So, what I want to know is: How did we get from the one case of affairs to the other case of affairs?
Captain Blackadder: Do you mean "How did the war start?"

Reading comprehension

Two maps have been posted here. Cliff's where OilT/AirT are not influenced when the engine is warmed up, and WM's which is. raz/dlaing provided the RELEVANT maps for a stock Guzzi which is the one I am running, and is the only one worth discussing in a GENERAL discussion. From these maps it is clear that the engine will continue to lean out throughout the sensor's temperature range. The data in WM map contradicts your statement:

Regardless of Weber-Marelli map or a custom map, I b'lieve the answers to these questions are the same
...

Essentially, the OilT "choking boost" line says...there's NO BOOST to the A/F above [40°C].

There is a "boost", or better, lack of it at the high end of the temperature range for WM ECU.

As far as your "experiment" is concerned...

Evidently (Part II), a map that could deal with the error under a wide range of operating conditions could not be created with a direct connection. So they introduced an AIR GAP, which tended to spread and/or delay the error, providing more acceptable operation over a wider range of road conditions. However, this still leaves potential for SIGNIFICANT ERROR in both directions: In the creation of the map (any map), AND AGAIN in attempting to compensate for the error that gets built into the map after the fact.

Per previous posts, I had discovered that using a 1.5" OD fender washer between the plastic holder and the sensor as a heat sink made a noticeable improvement in the otherwise unacceptable idle and low-RPM behavior with the thermo-paste installed. Today, I figured better take the heat sink thing the next step forward, and do it properly and test it properly before surgery on the harness. So I chamfered a 45 degree bevel in the center hole of a vertically-finned, axial heat sink similar to this with their maps.

In order to get a clean baseline for tuning one has to sort out thermal contact AND shield the sensor from ambient influence. Hence, I don't understand the "intentionally spreading/delaying error" bit. What you are doing by adding a heathsink to the sensor is to aggravate an already bad situation by making an excessively ambient temperature dependent setup even more so, and then compensate by "adding resistance on the fly", although you have PCIII and with it (in)direct access to your maps. How's that for a snake-oil treatment?

February 21, 2009

And then there's this, which trumps the above in spades, and speaks volumes about this mentality. But hey -- at least it's consistent. . .
If we spend the money and don't survive, I can live with that.

Irony is like goldie or bronzie, only made of iron. :whistle:

February 18, 2009

Raz is talking about OilT and AirT lines, not TempR. The RELEVANT lines.

I used Cliff's map, since this is the one I found. Weber-Marelli is obviously different, and goes throughout the entire temperature range and that actually causes the engine to run leaner as it heats up. Cliff's just ignores events past 50°C, however, chance is that this is not the "latest and greatest", and that Cliff has fiddled quite a lot with it since he posted it.

Not sure how environmental homologation process looks like, but @TüV they measure emissions at idle and higher (like 3500) RPMs and motor temperature between 60-80°C. So there is no "ecological need" to adjust mixture past 80°C.

February 18, 2009

70's hairdos

February 18, 2009

February 16, 2009

Well, there you go. That's the answer.

February 16, 2009

Well ratchet, I still don't understand your fascination with the TempR line. Can you elaborate on that?

I am not arguing that I am not seeing the same effects as you do, I am finding it hard to undertsand your arguments.

The TempR line is a constant. It just shows how NTC's resistance changes under influence of heat. You can read this line out of the sensor's datasheet. Google for WTS05, and you'll find the TempR line in the Technical data section.

According to Cliff, there are only two lines that are influenced by the NTC. The OilT and AirT.

# OilT is the permanent choking boost
#Temp C   -30    -20     -10        0    10    20    25    30    40    50    60    70    80    90   100   110   125
OilT%    +64.1 +53.1 +43.8 +35.2 +29.7 +18.8 +10.2  +9.4  +5.5  +0.0

# AirT is the barometric adjustment for air temp(based on ideal gas law)
#Temp C   -30   -20   -10     0    10    20    25    30    40    50    60    70    80    90   100   110   125
AirT%   +24.7 +19.8 +15.2 +11.0  +7.1  +3.4  +1.7  +0.0  -3.2  -6.2

They both stop at 50°C. So in order for the air gap "feature" to work, the function of the air gap should be to keep the sensor within "tunable" range, meaning bellow 50°C. However, air gap or not, a prolonged ride on a hot sommer day in heavy traffic would push the sensor far past it. There will be no difference whether thermal paste is in there or not.

I say that "air gap" or better "elongated receptacle" is there to protect the sensors plastic parts from being excessively "heath-cycled" at temperatures exceeding it's operating range. Can head temperature go beyond 150°C? I'd say yes, but have no measurement to confirm. Anyone? Brake-rotor-temp-measurers? Could you point one of your rays towards the cylinder head after a ride? WTS05 is a water temperature sensor with operating range up to 125°C. I can imagine that Luigi tried to protect the sensor by placing it as far from the hot cyl head as possible. And being Luigi, he used even more temp. sensitive plastic than the sensor itself is built of. Hence the breakage + customer delight.

On the other hand, looking at the OilT and AirT lines, could it be that Luigi just plugged the sensors in wrong way around?

February 15, 2009

...
Essentially, the OilT line says that as long as the part of the EXTERIOR of the head where the holder is seated (REMINDER: this is not the INTERIOR OF THE HEAD) is below body temp, the sensor will be boosting the pulsewidth and A/F by bumping up the map, and there's NO BOOST to the A/F above that.

So once the EXTERIOR of the head is above body temp, and it's running, this says we may ignore both the OilT and Crank lines and focus exclusively on the TempR line.

On the TempR line, I'm focused on wot's happening between 40°C to 125°C, which is a drop in resistance of half again greater than an order of magnitude. This appears to be the only relevant data to consider here once the motor is warmed up to operating temp and running. It's exactly where I've consistently observed the undesirable driveability anomalies (apparent over-lean condition) caused by adding thermal paste/lead for a direct thermal connection between holder base and sensor tip using the plastic holder.

...

Not sure if I understand all this correctly, it is too much of English at once for me.

The ONLY RELEVANT line here is the OilT line, unless there are other lines not made available to general public. What is written in this line contradicts three statements made in this discussion:

1) Oil temp sensor is used for fine tuning fuel/air ratio throughout the entire working temperature range. It does not, as it shuts off after 40°C. That is a hot summer day for people that deal with Fahrenheits. In other words not much.

2) Mixture gets richer if engine gets too hot for the purpose of cooling. Same here, since there is no evidence of "movement" in either direction beyond 40°C.

3) If thermal paste is used, engine will run leaner. It can't! All that thermal paste will do is to allow the sensor to heat up quicker and stay like that. Again, 40°C is not much, even for the head surface temp.

So why does the engine appear to be running lean when the paste is added? It sure does, at least I have the same impression. Does it consume more fuel and runs rich on a cold winter day if the paste is not there? It sure does. But why? Is Weber-Marelli unit's map that different?

Furthermore, TempR line is simply characteristics of the WTS05 sensor. One can read it out of the datasheet, or do as Cliff did - measure it. It is used as input to the ECU, whereas OilT line is a function of that input which is together with a few more values, used towards the ECU's output stage.

February 15, 2009

The sensor holder is plastic, insulating all but the tip from the heat.
...

Ok then, what did I jizz into? :huh:

Any thoughts on "it will run to lean if thermal paste is added"?

Mind you, local woodoo priest says it does, scientist apprentice says it should not.

February 14, 2009

Sensor is all metal. It is electrical connector part which is plastic.

Plastic washer + some other form of temp. insulation for the thread is a step in right direction. But this will make ECU believe the engine is hotter then it really is

February 14, 2009

....
I say let rachet's snowmen melt and replace them with the snowwoman that showed up on the Hooters thread a short while ago!!

Finally someone who understands what global warming is all about....

(AND THAT IT IS A GOOD THING!) :lol:

February 14, 2009

Well, I haven't talked to Wittner yet but will. In the meantime, let me argue the case that you all have it backasswards. Here goes:

Break open your stock sensor. What is the small metal bit made of? It looks like copper to me. What does copper do really well? It transfers heat really, really well. It's also expensive. It would never be speced unless the spec-er wnated maximum heat transfer, for cost reasons. Then, after spec-ing expensive copper, what do they make the rest of the holder out of? Plastic. What does plastic do pretty well? Many things, but among them is that it is a poor conductor of heat. So, they encase a great conductor of heat, which is screwed directly into the heat source and then encase the conductor in an insulator. Why would someone do that? Let's see if your mental faculties are firing tonight . . .

I'd just like to add... :oldgit:

The spec-er drilled a hole in cylinder, filled it with air, took the coppery part, burried its tip 20mm bellow surface, and fastened everything with a nice, massive 19-wrench screw the the topmost cooler fin. What this thing actually measures is temperature of the cylinder head surface, not cylinder head (or oil temp, as per manual) itself. Never trust a spec-er (engineer)!

However, I agree with ratchet's statement here that the engine is tuned to honor this setup. On the other hand, the setup is far more ambient temperature dependent than it should be. If its colder, the engine will be running rich, hotter, probably does not matter (? - see bellow for explanation). If there is such thing as poor engineering on a Guzzi, than this is a blatant example of it. One way to address the issue of poor setup baseline without remapping (with all side effects that usually come from fumbling with vehicle electrics) could be to add a potentiometer in series to the NTC and to offset the entire map in the "direction of colder" (higher resistance) AND to fill the hole with thermal paste.

Reasoning

The sensor has a very non-linear (logarithmic) characteristics, and it's accuracy is not something to write home about (5%). To me that sound that at higher temperatures it is not used at all, and its primary (and most likely only) (am I now being parenthetical, or just pathetic-al? ) purpose is to serve as a choke button - cold - on/hot - off. To corroborate my claims I am quoting Jefferies My ECU tables being posted here: http://www.cajinnovations.com/MyECU/technical_site_map.html

There it says:

# TempR gives the value in ohms of the NTC temperature sensor
#Temp C   -30   -20   -10     0    10    20    25    30    40    50    60    70    80    90   100   110   125
TempR   51466 28618 16571  9712  5956  3742  2991  2408  1597  1077   746   524   375   274   203   152   102
# Crank is the % boost of the map injection times right after start
# this boost decays to 0 over about 20s
#Temp C   -30   -20   -10     0    10    20    25    30    40    50    60    70    80    90   100   110   125
Crank      80    70    65    60    60    60    55    50    35    25    20    15    15    15    15     0
# OilT is the permanent choking boost
#Temp C   -30   -20   -10     0    10    20    25    30    40    50    60    70    80    90   100   110   125
OilT%   +64.1 +53.1 +43.8 +35.2 +29.7 +18.8 +10.2  +9.4  +5.5  +0.0

TempR line maps temperature to the NTC's resistance. Observe the difference between 20-30°C and the one between 110-125°C. Not the sharpest tool at >100°C

Crank line is for cranking/choke. This one is valid for 20s. Observe that it is mapped up to 110°C in case someone wants to claim that head temp will never go over 70°C

OilT line is the interesting one. It says that if the measured temperature is >40°C, there is no influence whatsoever on the map.

Usual disclaimer: I reserve the right to be wrong on any or all accounts here listed, and would be glad to read an educated explanation on where did I go wrong in my line of thinking.

February 2, 2009

Uhh....nobody ever picked those as "best".

I'd argue about "nobody"...

...but I will not.

February 2, 2009

"That's just nuts" +1

:lol:

No, nuts remained intact! :oldgit:

It's the other thing...

February 2, 2009

PS. Beer sales are up 1% even in the depression

Is this a cause or a consequence of "the" depression? :bier:

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