The thermostat flap hinge on my Giardi is coming undone, fixing it properly looks like an engine-out job, which got me thinking.
Air cooled bikes have much more efficient finning, and don't have or need a thermostat.
When the weather's cold is when I open the cabin heat flap, thermically this must be the equivalent of an open thermostat flap (when you'd imagine it closed).
As for the engine warm-up period, if a big-finned bike engine can cope with it, wouldn't the Fiat small-finned engine warm up even faster, thermostat or no thermostat ?
So doesn't it make sense to just lock the flap open, or I am missing some subtle point whereby the thermostat is not a bit of heat management overkill ?

Perhaps you could use an infrared thermometer to take temperature readings to compare how quickly the engine heats up with the flap operating normally, or fixed fully open?

The thermostat flap on my 500F takes a long time to open with the engine ticking over on the driveway, but after a run is fully. I've not had any overheating problems. I suppose the cooling system was designed for lots of different climates from sub zero to +40c. I live in Devon, a couple of miles from the coast, and seldom have any frost's. I'm sure my car would run ok with the thermostat wired open but it's not something that I would choose to do without checking the effects on engine warm up time.

Ah!
I never had a flap on my D, so I guess it was always open.
Maybe this extended the time taken to reach warm operating temp but surely not by much
Bearing in mind it lived in a warm climate

I fully agree with your remarks about warm-up rate, if your cold starting routine includes checking that the cabin heat flap is shut.
Damn it, I used to think wedged-open thermostat flaps reflected poorly on their drivers' character, now I'm fixing to join them

Depends where you live. In southern Italy, a lot of cars don’t have the flap or the cabin heat duct connected.

Rob

It is misguided to think that the thermostat is a superfluous feature whether or not you live in a hot or a cold country. It is also incorrect to simply think of it as a cooling feature.

The thermostat is not an ON/OFF mechanism but has an infinitely variable response to the temperature of the air which has already passed over the finned parts of the engine.

I have noticed that once opened, it responds extremely quickly to the lack of air movement when the engine stops running. Consequently, when firing-up again after a brief stop it is possible that a wide-open thermostat-flap has already close-up again.

Since the external temperature of the engine is expected to be very high when in operation, even in hot weather (yes we do occasionally get that here at 57 degrees north), it can take quite some time for the temperature of the forced air to become sufficiently high that it activates the thermostat. In our temperate (cold) climate the exit-flap is rarely wide open.

The perils of allowing your engine to run cool for much of the time seem to be overlooked on this Forum whilst the damage that might be caused by overheating seem to be well understood.

Given that FIAT went to the effort of devising a simple system which provides a feedback loop with regards to keeping a consistent and near-ideal engine temperature, it seems a bit regressive to remove this very simple system and assume that an absence of temperature regulation will provide a more reliable and consistent output from the engine.:bang:

Very sensible observations, and I made it clear in the OP that the motivation for disabling the thermostat was lazyness, not wanting to pull the engine and dismantle the cowling just to fix the flap hinge just now (this is UNDER the engine on the Giardi).
I find it idiotic to presume to know better than the engineers who designed any system. However...
It remains that the vast majority of air-cooled engines live long, happy lives without a thermostat.
And unless I'm mistaken, the delicate regulation of the cooling stream you describe is utterly defeated by simply leaving the cabin heat flap open, it's a thermostat bypass.
Ultimately you're right, and I will live with your cruelty in pointing it out and the guilt of what I'm about to do for the duration

giardini said:

Very sensible observations, and I made it clear in the OP that the motivation for disabling the thermostat was lazyness, not wanting to pull the engine and dismantle the cowling just to fix the flap hinge just now (this is UNDER the engine on the Giardi).
I find it idiotic to presume to know better than the engineers who designed any system. However...
It remains that the vast majority of air-cooled engines live long, happy lives without a thermostat.
And unless I'm mistaken, the delicate regulation of the cooling stream you describe is utterly defeated by simply leaving the cabin heat flap open, it's a thermostat bypass.
Ultimately you're right, and I will live with your cruelty in pointing it out and the guilt of what I'm about to do for the duration

Click to expand...

[emoji3][emoji16][emoji23]
A very good reply to a rather preachily-toned posting.[emoji4]
I've often wondered if the fact that I use the heater so frequently might help with cooling; but it certainly increases engine warmup times as you've pointed out.

giardini said:

And unless I'm mistaken, the delicate regulation of the cooling stream you describe is utterly defeated by simply leaving the cabin heat flap open, it's a thermostat bypass.

Click to expand...

....not really. If engine speed, heat output and flap opening remain constant and then hot air is directed to the cabin, the exiting airstream will expand and slow down because of the increased area of the exit passage and each cubic unit of air will therefore retain a smaller amount of the heat...the air will be cooler. So the thermostat will respond by closing the flap a little. If the heater is used before the engine reaches operating temperature this will impede a more rapid warmup but the thermostat will be sensitive to the fact that heat has been diverted and will take longer to open than would otherwise be the case. I worked this out the other day in reverse when my engine was getting rather hot. I used the heater to help with cooling: the thermostat fairly quickly started to reduce the opening of the flap Without a thermostat the heater would be pretty feeble.

fiat500 said:

....not really. If engine speed, heat output and flap opening remain constant and then hot air is directed to the cabin, the exiting airstream will expand and slow down because of the increased area of the exit passage and each cubic unit of air will therefore retain a smaller amount of the heat...the air will be cooler. So the thermostat will respond by closing the flap a little. If the heater is used before the engine reaches operating temperature this will impede a more rapid warmup but the thermostat will be sensitive to the fact that heat has been diverted and will take longer to open than would otherwise be the case. I worked this out the other day in reverse when my engine was getting rather hot. I used the heater to help with cooling: the thermostat fairly quickly started to reduce the opening of the flap Without a thermostat the heater would be pretty feeble.

Click to expand...

Absolutely. Paradigm shift ! I think the guys at Fiat weren't worried about engine cooling, but more about squeezing in more creature comforts through ingenuity while keeping costs down.
My mistake, not "heat management overkill" at all, but a smart and inexpensive way to insure good heating and demisting throughout the engine temperature range. Thanks for that, Peter !
Incidentally, I see in my docs that a "superheater" version was available, I wonder if a specific market got it, or if anyone has actually seen it ?

I feel sorry for you in hotter countries; you can't very often get the benefit of this fantastic Fiat feature of a toasty heater.
But I watched a TV programme this week where tourists visited Athens in winter and although compared with Scotland it was lovely weather, I think a good car heater would have been very useful. [emoji16]

I have owned 500s,in a variety of versions, during and since I was an apprentice, over### years ago, and one thing I have never suffered, is being cold in one (except upon initial start, but that is common with practically all cars). During my the last year of my apprenticeship (in a M/Benz, R/R, Bentley, Jensen and Aston Martin dealership) I was one of the 2 breakdown men; and I can assure you, my little Fiat was a darn site warmer then the Land-Rover (complete with crane on the back---remember them?) I had to use for breakdown duties. The Land-Rover heater was so poor that 2 candles in close formation would have produced more heat! For a device so simple, the Fiat's heater is extremely effective.

I completely agree with you both, 10°c is open-top & windows-down weather in the 500 for me, thanks to the heat wave coming from below.
It also keeps the smell of oil down to a pleasant whiff