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Coolant Temp Question
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Old 11-16-18, 05:30 AM   #31
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Default Re: Coolant Temp Question

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Originally Posted by mheyman View Post
Uh, so SOA designed a gauge as only as good as a light? Whatever . . .
I was exaggerating a bit, but I never said it didn't have a use. It's use is to tell you that you are inside or outside of the "normal" operating temperatures. It does not, however, give you a more granular level of detail such as actual temperature which is read from the AP. That is all I meant.

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Dont remember reading of anything wildly fluctuating here, but you can be sure that a coolant temperature gauge that fluctuates wildly is malfunctioning one way or another, because coolant temps cant heat and cool in a wildly fluctuating manner. That requires energy gain and loss, and that requires time.
Again, I was exaggerating a bit, but that quote has to do with gauge accuracy not temperature fluctuation. A 30-degree dead band is not something I would call "accurate" however I understand its purpose, and it does that just fine.

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So if aren't experience an overheating condition where there is no coolant at the sensor a little movement is no big deal - and to be expected when you get on it, speed up or slow down or run air. Neither your thermostat, or your coolant system are perfect, and the conditions the operate in are always varying.
Agree.
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Last edited by BlueScooby; 11-16-18 at 05:34 AM.
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Old 11-16-18, 05:47 AM   #32
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Default Re: Coolant Temp Question

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Originally Posted by brapp View Post
Once the car's up to temp... it shouldn't move. It has a huge dead zone built into it -- from 185-215 degrees the stock gauge won't move.
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Originally Posted by mheyman View Post
Uh, so SOA designed a gauge as only as good as a light?
Quote:
Originally Posted by BlueScooby View Post
I was exaggerating a bit, but I never said it didn't have a use. It's use is to tell you that you are inside or outside of the "normal" operating temperatures. .
No, I did, and you explained that I was correct in calling it only as good as a light very well!
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Old 11-16-18, 05:50 AM   #33
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Default Re: Coolant Temp Question

oh ok. I thought you were disagreeing...
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Old 11-16-18, 07:44 AM   #34
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Default Re: Coolant Temp Question

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Originally Posted by mheyman View Post
Uh, so SOA designed a gauge as only as good as a light? Whatever . . .

No... they designed a gauge that's good for telling if the car is operating normally or not.

When my thermostat started going out this summer, I would watch the AP as well as the stock temp gauge *very* closely. Any temperature between 185-215 would read at the exact same normal point on the temp gauge.

As soon as the car hit 215, the needle would start to rise. At that point, a degree or two would be enough to make for significant movement. I never got it as hot as the 2nd tick so I'm not sure what temperature that represents.

It makes sense really... the gauge helps you know when the car is warming up and how close it is to being fully at operating temp. Then as long as the gauge stays still, you know the car is operating within normal range. If the gauge starts moving up above that... it's getting hot. Maybe not overheating... but it's getting hot.

Now I personally, like many others here, would prefer it was more linear and exact throughout the range... but I can definitely understand why they made it that way.
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Old 11-16-18, 10:19 AM   #35
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Default Re: Coolant Temp Question

yeah - to make a valuable tool exactly like . . . yesss . . . exactly what they are called . . . idiot lights!!

I DD drive an 05 and I never noticed my gauge was so poor. I does move though it doesn't have numbers in it . . . . Yes I have an AP permanently mounted to know , and I use it for warm up every cold start.
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Old 11-16-18, 07:00 PM   #36
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Default Re: Coolant Temp Question

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Originally Posted by mheyman View Post
yeah - to make a valuable tool exactly like . . . yesss . . . exactly what they are called . . . idiot lights!!

I DD drive an 05 and I never noticed my gauge was so poor. I does move though it doesn't have numbers in it . . . . Yes I have an AP permanently mounted to know , and I use it for warm up every cold start.
I keep going back and forth myself on an actual water temp gauge.

I like knowing exactly where temps are at myself. In the end I keep coming back to that it does do it's job and let me know if it's getting hot... even though it doesn't do so as precisely as I'd like.
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Old 11-17-18, 04:46 AM   #37
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Default Re: Coolant Temp Question

I agree It does its job. Mine moves small amounts all the time. There are no numbers to for me to complain about. Still, it could have had numbers for for the same cost.

Old fashioned meter design like yours and mine: The movement has a coil that is driven to full scale by a small current measured in mili-amps. Most often a shunt resistor is placed across it. The variable resistance sensor is connected. But thermistor sensors often used to measure temperature do not normally respond linearly, and often the dial is marked in a non-linear manner. More resistors can be added to the circuit to flatten the curve too. What I am saying is that the response of an old analog gauge will often not be linear and engineers work to make them more linear, not the other way round. Regardless of linearity, the gauge can be marked with numbers appropriately.

New cars use the same sensors, but are a while different ball game after that. The in circuit values, whatever they are, are measured accurately and can be compensated very well in code . . . Still linearization of the circuit is often done to maintain a minimum of resolution.
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IMHO, to justify its' price, the S209 needs to perform at least as well as my moderately powered 05 built beater, and even that might not convince me to buy one cause my next STI isn't likely to be moderately powered.

Last edited by mheyman; 11-18-18 at 04:29 AM.
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Old 04-19-19, 09:11 PM   #38
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Default Re: Coolant Temp Question

On my old 2005 STi bone stock, CSF Radiator, with 166k miles the car would cruise around 180-185f on a normal day. It would slowly creep to 204f when the coolant fans would kick in and bring the temps back down to 190f before turning off again. If the motor was heatsoaked in traffic, the coolant temps would slowly creep back up from 190f to 204f triggering the cooling fans as necessary. Once airflow was gained, the temps would settle around 180-185f again.

I monitor the temps using a bluetooth OBD2 adapter and the Torque Android app. Its much more accurate than trying to see if the needle moved 1mm. (Yes you can read the needle movement but its almost invisible and soo hard to establish a baseline unless you carefully sit upright in the same seating position each time when you stare at the temp needle to see if it moved 1mm.)

My "new" 2005 STi the car has a fresh built longblock and misimoto rad cruises around 174f. Everything about this engine seems to be 10 degrees cooler in operation than my old STi. It still climbs to 204f in traffic which triggers the cooling fan but it seems, in general, the engine runs 10 degrees cooler than my old car. I think its because the coolant channels and cylinder jackets are clean and haven't been contaminated with corrosion buildup and oily residue from having previously blown a headgasket so the coolant can more efficiently pull away heat from the metal walls.


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