CentralCoaster

In lieu of all the thermostat questions... it deserves a new name.

I'm renaming it as the "Engine heating valve". It's a valve to keep the engine warm, above it's rated temperature, 160, 180, 195, whatever it happens to be. IT DOES ABSOLUTELY NOTHING ELSE!

It's like what your house thermostat does when you only have a heater. When it's too cold, it closes, warms you up, then sits there patiently in case the house cools off again.

Now the folks with the a/c in their house, that's like having a cooling fan switch. When it gets too hot, it turns on to cool it down.

So this "engine heating valve" controls the minimum temperature, and the electric cooling fan controls maximum temperature. Each of these components has hysteresis. They start working at one temperature, and go off at another. The fan for example, goes on at 228, and off at 210, or something like that.

Now, the operating range in between the "heating valve" and cooling fan is known as the "dead-band" where the engine is happy and cozy and neither component is doing anything. A dead band is always necessary. If your "heating valve" hysteresis and cooling fan hysteresis overlap, then you have no deadband, and the systems are working at the same time and fighting each other. The thermostat will be trying to heat the engine while the fan tries to cool it. If the thermostat is winning the fight, the fan will never ever shut off.


So you can see here that drilling holes in your engine heating valve makes about as much sense as drilling holes in your wetsuit. Either way you'll freeze your *** off when its cold.

bogus

Got ya.

I agree 100%.

aboatguy

redfast

central..nothing to do with your post but i agree.. I see you did a zf-6 conversion on your vette. What you have to do..Thanks im very interested

C4Crazy787

"Engine heating valve".

Powerdrive

Man thats alot better than the new phrase I coined

Internal Combustion Engine Temperature Regulation Control Device

I was hoping it would catch on, but now I have my doubts

hippy

I think you should call it...



"THE REGURGITATOR."

Jerris

Central I agree with your reasoning entirely. Well thought out piece.
I love it when someone has a theory and is familiar enough with the topic to properly articulate their hypothesis.
I vote for engine temperature regulator
Jerris

jfb

You have described 90% of the thermostat and cooling system, the other 10% requires courses in math and physics up to and including differential equations, heat transfer,and feedback control systems. (good lord please don't ever make me have to take those courses again !!!! )
Any future posts on 160 stats, if you don't beat me to it, I am going to post a copy of your explanation!

Aggravated4life

Excellent write up and fun to read.

CFI-EFI

Well done.

I have been citing those facts in responses to posts, but I never went into all the details as to why. A lot of people have posted, "My car runs too hot, I'm gong to install a cooler thermostat." I have simply responded that the thermostat doesn't control how hot the car can run, only how cool it can run. I have also preached about fans that would never shut off, but I haven't talked about the "dead band".

Good job.

RACE ON!!!

CentralCoaster

Hopefully people regurgitate this. Now I'm off to see the wizard and spew some more articulate mistruths.

bogus

Don't forget to clean up after yourself.

DG'sVette

In lieu of all the thermostat questions... it deserves a new name.

I'm renaming it as the "Engine heating valve". It's a valve to keep the engine warm, above it's rated temperature, 160, 180, 195, whatever it happens to be. IT DOES ABSOLUTELY NOTHING ELSE!



We might as well take it one step further. How about calling it the EHV?

skybolt31

Ok, just to be a disagreeable type, the max temp isn't always controlled by the fan. At least in this part of the country! If you are moving and it is cold out, the fan will never come on and the dead band gets very small. So the minimum and maximum would become essentially the same and you could lower the operating temp by putting in a lower temp thermostat, opps I mean engine heating valve!

Anyway, thanks for the very analytical look at the cooling system!

CoffeeDrip

Back a little over 20 years ago. I asked the guy that told me it was a thermostat(he was explaining how cooling systmes work). I said "why do they call it a thermostat? It doesnt measure anything, it just opens at a set temp right? So how is it a thermostat?" He just gave a blank stare. I think he was wonding how a 9 year old could figure out within minutes that a "thermostat" is anything but.

He never gave me an awnser.

vinnies87

ditto and more

CentralCoaster

Boo... Hiss! I would reword that in saying that it's very cold so the engine is bouncing off the heating valve continuously, and never makes it to the cooling setpoint (fan). It'd be like in your house in the extreme cold, when the heater stays on almost continuously trying to keep the temp up. The a/c would of course never kick on.

The deadband is not determined by where your engine operates on any given day, it's determined by the heating and cooling setpoints. I think the above explanation is still 100% legitimate, and more importantly, makes the concept much simpler to understand.

bump.

CentralCoaster

Thermostat, as far as I know, means simply that it is an adjustable termperature controller, and only has to be able to get feedback from the temperature in order to control the temperature. The fact that a house thermostat also displays the temperature, is just a convenience feature.

Old convection heaters use thermostatic valves to turn on the heat, and the valves are adjustable with a pneumatic control. Even older ones use a manual valve with no thermostat.

The car thermostat, technically speaking, is more of a reverse-acting temperature switching valve.

CoffeeDrip

Thermostat, as far as I know, means simply that it is an adjustable termperature controller...
my point exactly. The thermostat in a vehicle ISN'T adjustable. So how can it be a thermostat. Coolant valve, or just about any thing is more accurate than "thermostat'

Like you said.. it IS reverse-acting temperature switching valve.