My Guzzi is drinking stupid amounts of petrol

[Skeeve]

Of course the temperature sensor's function to the ECU is to enable determination of fuel/air mixture ratio but what I'm saying is the plastic housing must be of the correct material for the job to conduct heat to the temperature sensor because if it needed a brass housing to make the bike run correctly then surely that's what the oem part would have been and not the plastic one fitted if the plastic material is not capable of conducting the heat to the sensor itself. I realise that its like everything else that costs need to be cut in some places to enable healthy profit margins and value but if this part is critical to the overall well being and running of the bike then surely they would have used a brass part instead of the plastic one that is fitted?

 

Plastics [for the most part] are mostly poor conductors [of electricity, & therefore by roundabout physics, likewise heat.] They are, however, very cheap to use in quantity production. Think how happy the Aprilia bean counters were to replace the original brass part which must have cost at least $.50/ea with a plastic substitute that ran at most one-tenth the price?

 

Note: accountants are very rarely qualified to make engineering decisions. That doesn't stop them from doing so frequently on the basis of "corporate solvency."

 

IF you ride your Guzzi long enough, the air in the gap btw the sensor and the aluminum in the head, and the plastic housing, will all eventually come up to temp and the sensor will begin transmitting the correct (or close enough) value to the ECU. Take your Guzzi on an all-day trip, burning thru several tankfuls in succession. Keep track of your mileage [don't forget the odo reads in km, even on an mph speedo; there's a thread around here somewhere dealing w/ that odd disparity] each tankful, and watch it magically rise as the engine eventually heat soaks and everything starts working like it should.

 

But since you say you already filled the gap w/ thermal paste & it had no f/x, I'm thinking your problem lies elsewhere. Did you check the continuity of the wires to/from the ecu to the sensor? What about the duff sensor issue? Your situation seems odd, since this issue has been adequately resolved in the past by the course of action already recommended, so if this hasn't worked for you, we need to look for another source for the problem...

[dlaing]

Of course the temperature sensor's function to the ECU is to enable determination of fuel/air mixture ratio but what I'm saying is the plastic housing must be of the correct material for the job to conduct heat to the temperature sensor because if it needed a brass housing to make the bike run correctly then surely that's what the oem part would have been and not the plastic one fitted if the plastic material is not capable of conducting the heat to the sensor itself. I realise that its like everything else that costs need to be cut in some places to enable healthy profit margins and value but if this part is critical to the overall well being and running of the bike then surely they would have used a brass part instead of the plastic one that is fitted? If the temp sensor is broken itself then that's a different issue surely? I'm just theorising here and not challenging anyone view or opinion that has been kind enough to lend me some advice as my knowledge of the Guzzi engine isn't substantial enough in order for me to come to logical sound conclusions on these matters.

I find it hard to believe that ALL of the below are TRUE:

A: Guzzi chose a cheap piece of crap plastic and brass bit to save money.

B: They did not foresee reliability problems with such crap as a tiny tweak of torque will break it.

C: It provides inferior thermal properties to the brass unit that was used for years before they switched to the plastic and brass unit.

 

Regarding A, if someone could show me a Fiat cross ref, I'd be convinced.

Regarding B, Luigi ain't perfect, but somebody must have questioned such wisdom, especially after the tenth one broke on the assembly line!!!!

Regarding C, The thermal sensor is likely designed for water cooled engines, not air cooled engines. If they wanted the sensor to get hot, they would have threaded the cylinder to match the sensor, not make or bulk buy some stupid adapter to space it away from the heat. Even the brass unit had cooling fins on it. Following the bean counter theory, no adapter would have saved more money than a brass/plastic/brass adapter. Also, the plastic helps reduce the affects of weather on the engine temperature reading.

 

Still, I'll agree that there is a slow warm up condition that results in the engine running too rich as it warms, and that more direct conduction of heat from engine to sensor tip could be a good thing.

I'd like to see a stronger insulated housing with a conductor going not to the housing the way the brass unit does, but to the sensor tip.

 

But that is just my opinion and all are welcome to disagree.

[dlaing]

This loose connector might be the wiring for the electric petcock. Your 2001 originally had an electric petcock but it appears that the previous owner swapped it for a manual one (good thing!). At least your petcock looks different from my electric one. If so, then that connector doesn't have anything to connect to anymore and isn't a problem. My money is still on the temp sensor.

Yep, that is the connector to the electric petcock that was replaced with the manual one shown.

[Skeeve]

I find it hard to believe that ALL of the below are TRUE:

A: Guzzi chose a cheap piece of crap plastic and brass bit to save money.

B: They did not foresee reliability problems with such crap as a tiny tweak of torque will break it.

C: It provides inferior thermal properties to the brass unit that was used for years before they switched to the plastic and brass unit.

 

Regarding point A:

 

Didn't the change to plastic adapter occur after Aprilia took over Guzzi? It's purely conjecture on my part, but my thinking goes along the lines of: Guzzi has the new & improved replacement for the 1100 Spot/Sporti mostly sorted & ready for market, Aprilia buys out the company & puts everything in motion to produce what can be produced & get turnover/cashflow/any other tasty-good financial terms happening. As Aprilia's finances tighten due to spending too much on MotoGP, they start looking for cost savings anywhere & everywhere and switch to the plastic housing.

 

point B:

 

No reason to foresee breakage problems of the part: the plastic was almost certainly plenty strong during assembly before it went thru myriad heat cycles. By the time reports from the field started coming in that it was an unsatisfactory switch, Aprilia was already going into receivership and the new 4 valve was in the works anyway... why bother changing it now?

 

C:

 

Why do you find it hard to believe that the plastic doesn't work as well as the original brass part? If for no reason other than longevity, I'd rather it was a cheap galvanized steel part than plastic; it would still conduct heat better, and at least you wouldn't need to worry about it crumbling on you if you ever needed to remove it... [NB: I'd still rather have brass, or hey, how about this? Aluminum.... aaaahh, now there's a radical idea! ]

[il_cacciatore]

With the update, took it to the dealership about two weeks back and was told that its been remapped for optimal performance and not fuel efficiency by a magnetti marelli specialist. Just going to leave it be cause there is no running problems and no noticible flat spot either.

[raz]

With the update, took it to the dealership about two weeks back and was told that its been remapped for optimal performance and not fuel efficiency by a magnetti marelli specialist. Just going to leave it be cause there is no running problems and no noticible flat spot either.

I can see that jetting a carb for optimal performance may have to mean bad mileage, but EFI means you don't really have to compromise. Then again, optimizing for both will take more time = more money, and it's best done on a real brake dyno (as opposed to a WOT roller toy).

[dlaing]

Why do you find it hard to believe that the plastic doesn't work as well as the original brass part? If for no reason other than longevity, I'd rather it was a cheap galvanized steel part than plastic; it would still conduct heat better, and at least you wouldn't need to worry about it crumbling on you if you ever needed to remove it... [NB: I'd still rather have brass, or hey, how about this? Aluminum.... aaaahh, now there's a radical idea! ]

Longevity is the only negative of the plastic.

Once packed with something to conduct the heat to the sensor tip the plastic's insulating capabilities make it superior.

The key is to conduct to the sensor's tip and not the body, and not to cool down the conduction the way the brass unit with cooling fins does.

You want to measure the internal temperature of the engine, not an external temperature that better aproximates the variable temperature of the cooling fins, as they endure different weather.

The brass fitting, unless you wrap it with insulation, gives a closer indication of the temperature of the cooling fins than the core of engine.

The plastic AND brass unit results in a cooler running sensor, and if there is direct conduction to the tip of the sensor it gives a truer indication of the core of the engine.

Copper and Ceramic might be a better solution.

Or as I have said before, the bean counters simply could have ordered the engines tapped to fit the sensor directly, assuming heat is not a problem, as some claim, but I think it is too hot.