engine oil temp sensor

[Guest ratchethack]

UPDATE:

 

With newly acquired linear 500K Ω variable resistor in hand today, there was just one more thing I wanted to try before taking the more reluctant step of tapping into the harness and wiring it in series with the sensor, as mentioned previously. I'm always hesitant to disturb the harness in any way, but that's just me.

 

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:

 

 

. . .so it would make solid contact with the sensor's odd conical washer, carefully went under and over the washer with the thermo-paste, and mounted it up, again with the plastic holder filled with thermo paste, and took off for an extended ride.

 

THE IMPROVEMENT WAS DRAMATIC over running exactly this way WITHOUT the heat sink (or fender washer), WITH the thermo-paste filling the OE ~.015" air gap, even after extended mixed-mode riding, long after up to full operating temp. This is just me, but I consider this a significant finding -- significant enough to at least temporarily stop me from wiring in the variable resistor, pending further testing and evaluation.

 

BUT THERE'S MORE!

 

Yes, indeed. Now very occasionally, my Guzzi has been known to exhibit what has been reported extensively on this Forum and discussed at length as the dreaded "V11 vapor lock syndrome". According to the posts I recall on this, the affliction has been variously treated with many kinds of insulation, reflective tape, re-locating fuel pumps, re-routing fuel lines, wrapping and stuffing everything in the fuel circuit under the tank with multiple kinds of heat-reflective materials, etc. as "cures" -- with success that can only be described (at least for the most part, as far as I can tell) as "hit-or-miss".

 

Please -- I'm begging you -- let's not hear again about the great success someone has achieved with insulation or re-routing fuel components, who's already whinged on about it here. (Or even if you haven't.) I'm not refuting or denying anything that anyone has said they've done, f'er cryin' out loud!

 

Despite the fact that I haven't taken any of the above precautions, only a few times in over 6 years has the dreaded VL been bad enough to render my own bike incapable of starting after a 20 minute heat soak, even in 120°F (50°C) heat in the desert, but it has happened. Much more often, after this period of time, it starts with some difficulty and stumbles for awhile, especially in hot weather, resuming normal operation almost immediately after getting underway. It hasn't ever risen to the category of a tiny concern.

 

That is, until today. With the "real" heat sink (see photo above) and thermo-paste installed in the plastic holder, I tried to make it "vapor lock". It would not begin to show the symptoms, even after heat-soaking the "ideal" time after getting it as warm as it will get in this weather. Without any heat sink, it would have. Significant finding, as far as I'm concerned, (Part II).

 

Seems to me that the relatively massive brass OE head temp sensor body is highly susceptible to "heat soak", therefore providing significant, extended over-lean low resistance signal to the ECU over time, and that a "real" heat sink offsets this tendency by more efficiently and more rapidly dumping heat off the sensor body.

 

Now before any of the latter day suspects begin leaping to conclusions in formation, whilst indulging in their recently trademarked group hissy fits without actually reading wot they're responding to carefully enough for anything resembling proper comprehension -- I'm NOT saying I've discovered the "long lost cure" for the dreaded V11 vapor lock! I'm simply experimenting here and as honestly as I am able, reporting wot I've observed.

 

. . .And as usual, I'm nearly as positive as I can be that somebody's M is surely gonna V. . .

[Greg Field]

It's long overdue for someone to testify about how much smoother is the ride after switching from round to square wheels.

[Guest ratchethack]

It's long overdue for someone to testify about how much smoother is the ride after switching from round to square wheels.

Say Greg

 

Wot's the favorite local Friday night single malt, IPA, "contraband" (or combination thereof) in Seattle?

 

Enquiring minds. . . (well, you know). . .

[Greg Field]

I prefer bourbon or Diamond Knot IPA. Haven't done anything harder in 20 years or so.

[Guest ratchethack]

Thanks for clarifying. Just had to ask. . .

[dlaing]

Today, with the "real" heat sink (see photo above) and thermo-paste installed in the plastic holder, I tried to make it "vapor lock". It would not begin to show the symptoms, even after heat-soaking the "ideal" time after getting it as warm as it will get in this weather. Significant finding, as far as I'm concerned, (Part II).

 

Seems to me that the relatively massive brass OE head temp sensor body is highly susceptible to "heat soak", therefore providing significant, extended over-lean low resistance signal to the ECU over time, and that a "real" heat sink offsets this tendency by more efficiently and more rapidly dumping excess heat off the sensor body.

 

FWIW I'll bet most of the people with vapor lock were running the plastic engine temperature sensor holder dry with no solder or other conductive.

Also FWIW, the weather in San Diego was cool today, and my bike ran very well today. Five degrees warmer and I would have been running lousy at low RPMs.

I do agree that the brass body is susceptible to heat soak, quite likely increasing the risk of restarting problems when hot.

Also FWIW, Unlike RH, I have never had the vapor lock issue and my fuel consumption is much worse, even when going back to the stock map.

It would be interesting to swap ECU's with RH, although the difference could be the break in method's that we used. RH used something like the MOTOman method and I babied mine, following the manual's RPM vs. mileage guidelines and making a conscientious effort to load the engine lightly (no lugging or heavy throttle) and varying the RPMs as much as possible as traffic permits.

And lastly FWIW, I appreciate RH's efforts here. While the results won't provide the ultimate solution, they provide a clue to what a better than stock solution can be.

[Greg Field]

All the V11s came with the plastic snesor holder. The only ones that vapor lock are the ones with the external pump. Y'all may draw your own conclusions. I already have. Back to square wheels. Who will admit to performing this amazing improvement on their bike?

[Guzzi2Go]

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?

[raz]

I miss the Leroy quote. Damn that was funny You know who you are.

[raz]

Okay, I sent my PCIII map to Jaap, so you guys can check it out when it's posted. But yes, the left side is getting way more fuel than the right. I'd be curious to know why there's an imbalance.

 

Anyway, here's a pic of my headers as well. The black is a high temp silicone spray that helps keep out the moisture and grime:

Thanks, I'll try wrapping. Unfortunately I've made some other things this winter so I wont be able to tell if the wrapping itself did any good. Anyway it's more for the looks, just like the pods.

 

Maybe I'm stating the obvious but it's fairly easy to swap the injectors left for right and see if the leaner condition moves with it.

[Guzzi2Go]

UPDATE:

 

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

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

[Guest ratchethack]

My, my. How the Winter of our discontent doth seem to be flushed out when it's cold outside.

 

Well, best get all the bad baggage out on the table so as to separate the wheat from the chaff, I suppose.

 

Though there still seems to be lots more chaff piling up as we go forward, I'm still finding significant value in this, and learning as I go, so I reckon I'll be at it for at least awhile longer. . .

 

For those who've made up their minds that this is all complete and utter balderdash, and that my understanding of what I'm observing here is entirely bass ackwards, I most enthusiastically welcome you to completely ignore everything you don't follow here. I've done the same with some of the above posts, and I reckon I'll be doing the same with many to follow.

 

As noted previously, my Guzzi with it's current PC III map runs more than acceptably well with considerable "slop" in the accuracy of the temperature read when there's no direct thermo connection between plastic holder base and sensor tip via thermo-paste. I've found it interesting lately to explore the other end of the accuracy spectrum by making that thermal connection as direct as possible, and observing the effects on driveability. So far, the only change I've made that allows me to even ride the bike with thermo-paste in there is the addition of the heat sink, as noted above.

 

For anyone sincerely interested, I've made some assumptions above about the operation of the sensor. Do with them what you will. All further assumptions below made on the basis of direct thermal contact (thermo paste installed) between plastic holder and sensor tip.

 

The thermistor presumably reads the temperature at the "probe" end, not at the sensor body. The probe end and sensor body can be, and often are, separated by different temperatures, depending on state of engine dynamics and operating mode, though the two are connected within the same relatively massive lump of brass. I b'lieve these are safe enough assumptions, but that's just me.

 

Now then. Being a relatively massive lump of brass, the sensor body acts as a heat reservoir. I think of the probe as a skinny "arm" of the sensor body, through which temperature flows as fuel flows from a fuel pump filler nozzle into a gas tank. With the plastic holder, no heat enters the sensor body except by way of the sensor tip. As the heads warm up in operation, the sensor body will draw heat off the probe until the body warms up to the same temp as the probe. Conversely, (this is where the fuel analogy isn't all that appropriate) the relatively massive sensor body will flow heat back into the probe when the probe cools. In this way, with heat constantly flowing back and forth, it makes sense to me that there's an unwanted "lag time" -- particularly when heat is flowing back into the probe tip from the relatively more massive sensor body, which would seem to be particularly problematic for an accurate read, often producing an unwanted over-lean hot running condition in my own case, creating a snowballing positive heat feedback loop, and evidently creating the reverse in others suffering from extended warmup problems. I b'lieve this understanding fits perfectly with my observations of over-lean running at idle and low RPM with the motor at full operating temp.

 

By introducing a heat sink to the sensor body, the heat is flowing much more in one direction only than it is in both directions, as it is rapidly drained from the heat reservoir on a constant basis, from the probe and into and away from the sensor body. I sincerely doubt that the temperature of the cylinder head sensed at the probe tip (where the drop in resistance is generated by the thermistor, as read by the ECU) can be significantly distorted by drawing heat off the sensor body through the heat sink, since the sensor body is not the part of the sensor where the thermistor reads the heat. When the motor is shut off at full operating temperature, the un-heatsinked sensor body can (and does) retain significant heat, keeping the probe end at a high temperature for an extended period of time. A heat sink on the sensor body would seem to thereby provide a more accurate match to the actual temp at the cylinder head under all conditions, both in operation and when not in operation -- but that's just me.

 

The evidence I have to support this is 1. the very significantly improved driveability at full operating temp with the heat sink installed vs. the unacceptably poor driveability without it, and 2. the lack of "heat soak", aka "vapor-lock" symptoms with the heat sink installed, vs. the presence of same symptoms without the heat sink, thermo-paste used in both scenarios.

 

Again, I'm not making any EUREKA! claims of discovery of hidden secrets here. I'm just experimenting by trial and error, as stated up front, and honestly posting my observations and my understanding thereof. With the weather clearing up nicely today, another longish ride with longer-term careful observations would seem to be in order.

 

And so it is!

 

Will advise (Part VII).

[tricatcent]

I am a new V11 Lemans owner and I have been brousing this forum often, and enjoying it very much.

 

One thing I don't understand about this thread is what does this sensor in the head control? I think there is also an air temperature sensor, isn't there?

 

Would it not be the case that the cylinder head temperature sender would control only the warm up. And the mixture control after a certain temperature had been reached would then be controled by the air temperature sender?

 

I notice that my bike idles fast until it has been warmed up for about two minutes. It is clearly running very rich during this time, it makes black smoke when you rev the engine. Once the bike is warmed up for a very short time the idle speed suddenly slows down. It is like a swich is being turned. I think this is the head temp sender causing this.

 

Obviously if this sender is not working, it will cause big problems, but does the exact temperature of it's operation really make all that much difference?

 

Nigel

[Skeeve]

I am a new V11 Lemans owner and I have been brousing this forum often, and enjoying it very much.

 

One thing I don't understand about this thread is what does this sensor in the head control? I think there is also an air temperature sensor, isn't there?

 

Would it not be the case that the cylinder head temperature sender would control only the warm up. And the mixture control after a certain temperature had been reached would then be controled by the air temperature sender?

 

I notice that my bike idles fast until it has been warmed up for about two minutes. It is clearly running very rich during this time, it makes black smoke when you rev the engine. Once the bike is warmed up for a very short time the idle speed suddenly slows down. It is like a swich is being turned. I think this is the head temp sender causing this.

 

Obviously if this sender is not working, it will cause big problems, but does the exact temperature of it's operation really make all that much difference?

 

Nigel

 

The head temp sensor has been shown on certain bikes [production variability rears its ugly head here] to take an abnormally long time to come up to temp and take the bike out of "cold start" mode. For some owners riding short commutes in cold climates, it may stay in the overly rich cold start mode all the way to work (& home again at the end of the day) with negative impacts on mileage and driveability. Moreover, if the rich condition prevents the engine from coming up to full temp, the water vapor buildup internally to the engine never gets the chance to convert to steam & blow off, turning one's oil to mayonnaise over the course of a winter...

 

The Bard of Bungendore some time in the past suggested short-circuiting the air gap between the end of the sensor and its place in the head as a means of curing these cold-weather/short ride ills, as having performed same experiment upon one of his customers' Guzzis (with their FK&C, of course!) had resolved the issue. All further disputation about the merits of doing so or not has taken place pretty much without any contribution by him to maintaining an even simmer, if not outright boil, of the conversation.

 

So, to sum up:

 

If you ride your V11 long enough at a stretch to get the heads up to full temp for a good 10 minutes before shutting off, and you're satisfied with your mileage, then you can safely ignore this thread & be on your merry way. If you habitually use your Guzzi solely for short hops [definition of "short" being temp dependent, ie: longer in colder local conditions] or have chronic poor mileage, then following along may not be such a bad idea.

 

I'm just a who can't resist the temptation of keeping track of all the tricks to my beloved Guzzi!

[badmotogoozer]

Motomonster - chuck thos eugly gear clamps on your pipe wrap and order some of the neat, tidy stainless straps from Summit Racing. Really cleans up the look. Cheers!