engine oil temp sensor

[Guest ratchethack]

I won't buy the theory that Guzzi actually made that 1/10" air gap on purpose. No way

Me neither. They bought a job lot of sensors designed to be stuck in a water jacket or radiator because it was cheaper than doing it properly.

 

Pete

By my measure with dial caliper, the gap's more'n double that with the brass holder, .25", or 6.35 mm. That's one great wallopping miss if it was spec'd to seat with full contact, as it does (very nearly to dead-nuts) with the plastic holder, which has a FLAT surface for the FLAT end of the sensor to seat against. The bore in the brass holder has a conical, drill-point bottom, obviously NOT designed for the sensor to seat against. It might've been a mistake or a FUBAR'd cost-cutting measure by the bean counters, but correcting it on the shop floor would've been such a simple machining job that I could do it myself on my Craftsman drill press. For wotever reason, I reckon it got signed off somewhere, which would've made it "deliberate".

 

But o'course, that's just me.

[Greg Field]

I've set up dozens of V11s with those sensor holders and conductive paste. They all ran great. I don't believe it's because I'm in chilly Seattle, either. Mine ran great in 100-plus-degree heat in California this summer.

[Dan M]

Me neither. They bought a job lot of sensors designed to be stuck in a water jacket or radiator because it was cheaper than doing it properly.

 

Pete

 

I agree. Once a design gets to production they pinch pennies at every turn. Sometimes changes are made post production but MG used this combo of plastic holder and an air gap for a number of years. It does look to me like every coolant temp sensor I've ever seen. I think the plastic holder was a stop-gap fix. If I recall there is no way the sensor can make metal to metal contact with the original plastic holder. It seems to me the factory mapping was done with the plastic holder in the mix. Any changes that will cause different readings (accurate or not) will alter the fueling. The plastic holder and air gap will not only insulate the sensor from showing actual temp but it will have much slower response to changes.

Like Pete said that style sensor is usually in coolant. Liquid cooled engines change temp much slower and keep a much more even temp than air cooled. I'm thinking the insulating plastic is used to mimic that and slow readings.

 

Like I said in an earlier post, after I packed mine with paste to take up the gap, I experienced some lean misfires on hot days. (the bike fueled perfectly before that) I don't know if there was a correlation but it would follow that if the temp sensor was seeing hotter temps than before it would be leaner. This spring I will certainly try to run it the way it came from the factory.

Just throwing stuff out here.

 

Edit: Greg, when setting up V11s were you altering mapping at the same time or just adding the brass & paste.

[dlaing]

Guzzi call it "oil temp sensor", not cylinder head temp sensor. That goes for both Sporti and V11. With our primitive EFI systems I think air temp is much more critical than oil temp for getting the mixture right. Oil temp is mostly needed for some boost while the engine is cold.

 

Then again you may have OEM temperature maps or experiences that contradict this. I have no idea why. It's a Guzzi

 

OTOH, if they really meant it to be just an oil temp sensor... why oh why did they not just mount a fool proof oil temp sensor in the sump instead of trying to morph it with a CHT sensor?

When I pulled mine there was no oil on it.

As for the maps, I don't think anything can be determined about air gap, but we do see that the MGS01 (that has no emission requirements) does no leaning after 50C while the V11s continue to lean it out. Could this be for emission testing??? I think so.

I am convinced the 99-01 V11 is too rich when cool and too lean when hot.

Is it because of air gaps or plastic vs. Brass? Maybe it is both, but I think the best solution is mapping, but yah, not everyone can afford Tuneboy, Directlink, or MY15M.

Even with mapping, the ultimate fix may involve insulation of the sensor, conduction at the tip (or air gap???), and shielding from weather.

[raz]

When I pulled mine there was no oil on it.

That was my point: They took a coolant temperature sensor, mounted it as a cylinder head temp sensor and dubbed it an oil temp sensor. You just gotta love them!

[Dan M]

That was my point: They took a coolant temperature sensor, mounted it as a cylinder head temp sensor and dubbed it an oil temp sensor. You just gotta love them!

 

That's the genius of it Raz. At some point in the late 1990s at a cafe on the shores of Como after an afternoon of linguine, several Peronis and a few grappas to top it off. It was discovered while doing some figuring on a Campari cocktail napkin that if you take a coolant sensor, mount it in a plastic holder and locate it on the inside surface of a V's cylinder head, viola! you get oil temperature.

[Guest ratchethack]

Back off you blaggards!! I simply must hasten to the aid of the defenseless Luigi's here.

 

I do b'lieve you Gents are indulging in heartless cruelty of the most dastardly behind-the-back kind!

 

Yes, they've evidently used a commonly available auto industry sensor designed for temp monitoring liquid, and yes, the Guzzi manual refers to it in English by the term likely most commonly used in industry for the thing, "oil temp sensor", even though in its application on the Guzzi, there's no oil involved. Would there have been a better sensor/holder design with which to accomplish ECU control of the FI? Undoubtedly. Would it have cost more? Undoubtedly (Part II).

 

But d'you really want to hold this against our Pals, who must by all rational analysis remain blameless here under such duress as they were no doubt powerless to control? In any case, somewhere between the revolving door ownership and the resulting perpetually negative budget pressure, the Luigi's spec'd in and approved wot we got to work with here. This is just me, but I don't find anything particularly malicious about this. And I'm not yet convinced that it's unworkable either, with a little more knowledge and understanding, only part of wot I b'lieve is yet known and fully understood hereabouts. I have yet to see anyone here (or anywhere else) recommend a superior retrofittable alternative to the OE setup.

 

Now this part's just me, but as far as I can tell, the plastic holder is a PRACTICAL IMPROVEMENT over the older design, which was brass. I say PRACTICAL IMPROVEMENT, because I've begun to build wot I b'lieve might eventually shape up into a pretty good case that despite its inability to take a wrench from someone enthusiastically cranking on it expecting it to be made of steel, the plastic ones actually function BETTER in terms of ECU FI control than their brass predecessors -- at least by my experience comparing both back-to-back, multiple times.

 

NOW HOLD ON JUST ONE MINUTE! EVERYONE POSTING ABOUT THE PLASTIC HOLDER SAYS, "IT'S CRAP"!!

 

Not quite everyone, Grasshopper. I note that the "It's crap!" posts come from those who invariably formed thier opinions after they broke theirs, got all worked up over it trying to get the remains out, and evidently lashed out irrationally, looking for the most convenient target other than themselves to blame -- most not evidently having been observant enough beforehand to note that the freakin' thing was made of fragile plastic, and therefore needed all the consideration and gentle handling one would rightfully expect to have to engage to remove it without shattering it -- which, when observed, works just fine by my experience!

 

NOW THEN. We might reasonably enough assume that the V11's were mapped both from the factory and in the case of aftermarket maps, with plastic sensor holders, presumably on a well-warmed motor, presumably making the usual up & down runs on a brake dyno, the air cooled motor being cooled by wotever kind of fan(s) happened to be handy that day, said fans set wherever the dyno operator figured it (they) should be set so as not to allow overheating of the motor -- and perhaps himself as well. . . D'you see anything potentially inconsistent in all of this when it comes to effects of air cooled motor heat as read thru an inconsistent sensor/holder when developing a map?!

 

Wot we got here with the plastic holder, Gents, is wot I believe to be an inconsistently functional sensor APPLICATION (per Pete's Axone reads and Greg's and many other's multiple replacement track records) of a perfectly functional sensor that evidently CAN be made to function more consistently -- at the very least, by making a CONSISTENT direct thermal contact between the sensor tip and the base of the holder.

 

That much is all old ground here. But what's evidently new here, at least in my own case, is that direct thermal contact with the brass holder is SO FAR OUT O' WHACK with the map I'm using that it simply won't run at operating temps at low to idle RPM's.

 

At least with my setup, there's evidently SOMETHING about the heat flow characteristics of the plastic holder that allows a far more accurate and consistent sensor read at the ECU and far better low RPM operation -- even without additional direct thermal contact via thermal conductive material between the sensor tip and holder base. Again -- In my case, that clearance in the plastic holder is very close to, if not dead-nuts on ZIP (as in full contact).

 

Now back off on the Luigi abuse, Gents. Don't you think they've suffered enough?

 

More testing results as time and weather permit.

 

Will advise (Part V).

[Bruce Reader]

I b'lieve this fairly cries out for a rousin' revue o' th' famous Dead Parrot skit:

 

 

"Lovely plumage, innit?"

 

"It's plumage is entirely beside the point! It's bleedin' demised!"

 

 

Yes ! Wonderful black plumage. Unfortunately it's dead.

 

Cheers

 

Bruce

[Dan M]

Back off you blaggards!! I simply must hasten to the aid of the defenseless Luigi's here.

 

I do b'lieve you Gents are indulging in heartless cruelty of the most dastardly behind-the-back kind!

 

At least with my setup, there's evidently SOMETHING about the heat flow characteristics of the plastic holder that allows a far more accurate and consistent sensor read at the ECU and far better low RPM operation -- even without additional direct thermal contact via thermal conductive material between the sensor tip and holder base. Again -- In my case, that clearance in the plastic holder is very close to, of not dead-nuts on ZIP (as in full contact).

 

Now back off on the Luigi abuse, Gents. Don't you think they've suffered enough?

 

More testing results as time and weather permit.

 

Will advise (Part V).

 

 

Sorry, but I awoke to yet another snowfall this morning, I have not been able to ride anything two wheeled since late November and perhaps I harbor some resentment toward the Luigis who stayed behind and didn't migrate to the land of opportunity as my grandparents did. Because if my ancestors stayed behind, I'd likely be waking in San Benedetto on the Adriatic today which seems like a better place to be right now. And besides in my view the Luigis have not suffered at all. Like I said, spending the average midday hours sitting in a cafe musing about Italian motorcycle design is not what I consider a life of suffering. So excuse my lingering ill will but it seems like an appropriate focus.

 

All joking aside, if they did engineer these things like Hondas what would we talk about?

 

Seems you & I are in agreement about the plastic thing Ratch. I believe it slows response and makes fuel mapping easier especially for the WW2 era ecu we use. Sometimes in the effort to improve things we get away from the hows and whys things were designed to operate and we create problems.

[Greg Field]

Well, it was probably John Wittner who spec'd it. I'll ask him about it.

[Greg Field]

Well, it was probably John Wittner who spec'd it. I'll ask him about it.

[Dan M]

Well, it was probably John Wittner who spec'd it. I'll ask him about it.

 

I was hoping somebody had a connection to some real answers. Let us know if the truth is out there.

I'm dissapointed his name doesn't contain more vowels though....

[Guest ratchethack]

Well, it was probably John Wittner who spec'd it. I'll ask him about it.

Well, it was probably John Wittner who spec'd it. I'll ask him about it.

OUTSTANDING, Greg.

 

Might be worth calling him twice, at that!

 

Please advise.

[Guest ratchethack]

All joking aside, if they did engineer these things like Hondas what would we talk about?

As Rumpole of the Old Bailey would certainly have observed:

 

Heaven Forfend!

 

Seems you & I are in agreement about the plastic thing Ratch. I believe it slows response and makes fuel mapping easier especially for the WW2 era ecu we use. Sometimes in the effort to improve things we get away from the hows and whys things were designed to operate and we create problems.

Speaking of "creating problems" where none previously existed. . . (It's Winter, as I'm sure you're still far more aware than I?)

 

UPDATE:

 

I've road tested all combinations with the brass holder that I'm going to try without doing a re-map first. Filled solid with lead, with 2 mm air gap, 4 mm air gap, and no lead (6+ mm air gap). All had the same unacceptable hot running symptoms (noted above), none tolerable.

 

There IS an OE air gap between the plastic holder and sensor, at least in my case. I get ~.015" by gauging the thickness of the zinc-based silicone heat sink compound left on the sensor tip after testing. The symptoms on the road with the thermo compound after warm-up were every bit as unacceptable as with the brass sensor.

 

I've begun to road test the plastic holder with significantly larger air gaps (no thermo-goop) by shimming up the sensor with washers.

 

To date:

 

With a small-diameter washer providing a ~.075" air gap: Same as fully seated OE config. This is certainly acceptable, and a far cry from the brass holder.

 

With ~.075" air gap using large, 1.5" OD fender washer bored to fit the sensor, acting as additional thermal finning: BEST YET, with limited testing time to date at full operating temp.

 

I'm starting to come around to the idea that the "ideal" head-temp sensor/holder config is highly dependent upon the specific bike, and in particular, the specific map it's using, and it certainly would be dependent upon what sensor/holder config was used to generate a custom map (if any). With any semi-wonky air cooled sensor/holder setup, I reckon operating conditions at time of a dyno tune would of course tend to throw yet another set of variables into the mix.

 

NOTE: Just for reference, I'm using a "library" PC III map.

 

Will advise (Part VI), with an attempt to firm up the superior symptoms of using the fender washer ASAP, weather permitting.

 

Hey Greg -- any response from Wittner yet?

 

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

[fotoguzzi]

could you just put a variable resistor in line and w/an Ohm meter follow readings to find out what the optimum reading "should" be.? Then correct the the sensor with a small resistance? I'm not afraid to ask dumb questions!