Temperature Reality

[Norton47]

Temperature reality time. I decided to buy a 16 inch fan from JEGS and while waiting for it, took out the old radiator and the fan temp switch and the temp sender unit.
I decided to break in my wife's brand new range just delivered on the 22nd, and set up a small pan of water with the sender unit and a type K thermocouple suspended in the water. I hooked the temp sender to a Fluke multimeter and the thermocouple to a Fluke thermocouple meter. I also suspended the fan switch and hooked it to a separate Fluke multimeter.
I took temp readings at each 5 ohms of resistance change. I will publish them all in a chart format soon. For now I found that 160 degrees is = to 145 ohms, 180 degrees is = to 105 ohms and 200 degrees is = to 75 ohms.
The fan switch closed at 177 degrees.

I then connected a variable 1K resistor to the lead from the car temperature meter and ground and adjusted it to have the car meter needle read on the 1st, 2nd and 3rd marks.
The first needle mark took 107 ohms, the 2nd or middle mark took 70 ohms and the 3rd or 3/4 mark took 45.9 ohms.
I connected a battery charger at a 2 amp charge to keep the battery voltage more or less stable at 13 volts.

With my sender unit this would appear to make the first mark = to a temperature of approximately 178 degree, the 2nd or middle mark = to 202 degrees and the 3rd or 3/4 mark = to somewhere in excess of 210 degrees. My highest water temp was 219 degrees with a resistance of 56.5 ohms.

This would seem to indicate when I have been driving my car at freeway speeds or around town without many stops the car has been at a temperature of around 202 degrees and in stop and go traffic when stopped it is going up to over 218 degrees. This is with a 180 degree thermostat.

Does this seem right? I worry now that it is on the hot side!

Where do most of your cars indicate on the temperature gauge at constantly moving speeds, 1st or 2nd mark? What is the highest you see them go when stopped on average? This top one can really be affected by the daily temp, but using 70 to 80 as normal daily range what do they seem to indicate?

 

[TR6oldtimer]

Put in a lower temperature thermostat, say 160, and your temperature should come down.

 

[Norton47]

Here's a photo of the stove test setup.

 

[philman]

hey that looks like one of my experiments!! even down to the drop in stove and meter!? I decided on a 160 thermostat.

 

[tdskip]

I think I know the problem - the Rockstar Energy drink is effecting you cars metabolism. Too much caffeine.

Stop using that as an additive and I bet you'll be OK.....

<grin>

 

[Dave Russell]

------ This would seem to indicate when I have been driving my car at freeway speeds or around town without many stops the car has been at a temperature of around 202 degrees and in stop and go traffic when stopped it is going up to over 218 degrees. This is with a 180 degree thermostat.

Does this seem right? I worry now that it is on the hot side!

I think you left out an important bit of information. If you put the thermostat in the same water, what are it's start & fully open temps? Once it is open it will not cause further increases of engine temperature. The average 180 thermostat can have widely varying opening temperatures depending on the brand & even within the same brand.
D

 

[Norton47]

Dave
Yeah I thought about that later. To much Rockstar. However it was new and if it does fully open and it still gets to warm then I am concerned about radiator efficiency. This is the original radiator (has a Coventry marking on it anyway)which I had boiled out and rodded and checked by a radiator shop.
But I think it's worth putting in the 160 thermostat and giving it some head room to work with.

 

[Tim Tucker]

Norton47,
Our numbers agree very well.
degrees F ohms
82 558
100 495
135 233
160 147.5
180 105
200 69.4

I found this guy's write-up interesting:
https://home.mindspring.com/~purlawson/files/SmithsVoltageStabilizer.pdf

I believe the voltage stabilizers in our cars are designed to regulate around 10VDC. When I bought my TR (1yr,6days ago) I found the temp transmitter to be an open. I replaced with one from Moss. My temp guage then read just below hot with a 180F thermostat installed. I pulled the sender and set up a hot plate (at the car) so I could use the car's components to test where the fault was. At 180F (using a quality Fluke meter) my temp guage shows just under hot. FWIW, my fuel guage is spot on. I have reached the conclusion that the temp sender is the culprit.

I hope to adjust the temp guage to match the sender by placing a small screwdriver in the 2 adjusting slots on the back of the gauge and turn to move the needle to the centre at 180F. Feedback is always welcome.
Tim

 

[Tim Tucker]

You may also find this helpful:
https://www.tr6web.com/Documents/tr6/gaugetesting.html
Tim

 

[TR3driver]

I believe the voltage stabilizers in our cars are designed to regulate around 10VDC.

Well, "regulate" isn't quite the word. Instead of a constant voltage, the output swings between zero and full battery voltage, such that the _average_ is 10v.<div class="ubbcode-block"><div class="ubbcode-header">Quote:]
I hope to adjust the temp guage to match the sender by placing a small screwdriver in the 2 adjusting slots on the back of the gauge and turn to move the needle to the centre at 180F. Feedback is always welcome. [/QUOTE]Should be doable; but some things to note :
1) The adjusting slots don't really 'turn', rather they move side-to-side in the window. I found it pretty much impossible to make small changes with a screwdriver, so I wound up making a tool that would fit in the window and apply side force to the slot.

2) The adjustment near the cold end of the scale affects pretty much the entire range; while the adjustment near the hot end affects the hot side of the range more than the cold side. So it's best to pick two readings to calibrate at, one near the cold side and one near the hot side. But since the 'hot' adjustment does have some effect at the cold end, you'll need to work back and forth to get them just right.

3) The movement is very slow, so allow plenty of time for it to settle after applying power, or changing resistance. But you don't need to wait after making an adjustment, the adjustments take effect immediately.

4) A little fingernail polish or similar might be a good idea when you're done, to keep the adjustment from moving later. I found some that were loose.

 

[TheSearcherMan]

My TR6 always runs once warmed up, within say, one eighth of an inch from the center marking, doesn't seem to make much difference how hot or cold the ambient temperature is. This is with the original radiator. I use an infra red temperature sensor to check the actual temperature of the coolant, you can actually see when the T stat opens like this. This would seem to indicate the stock cooling system is capable of cooling the car. If you install electric fans, I don't see where the HP increase comes from, except when the electric fan is not running, which in the summer, mite not be much. Now when you are running down the interstate, and your electric fan is not running, on the stock set up, there would not be much load on the fan as you are suppling air to it, and it doesn't have to pull it thru the radiator, and under this condition, it doesn't take much to turn the fan anyhow. The right set up, would be with a newer car type thermal fan clutch, which only uses the horsepower needed, depending on temperature load, however some new cars do use electric fans, and their electrical system was designed for the increased load. With electric fans, you just transfer the HP loss to turning the alternator, increased load makes it harder to turn, you don't get something for nothing, which mite not be a great idea. Now, with electric fans, you would most likely get a faster warm up, which would save fuel. I think you decrease reliability with electric fans, it would be harder to get the car home, if you had an electrical failure, due to the increased load on the battery. And you have another electric motor and sensor that could fail. Electric fans are probably ok for racing, but, then again, I don't see NASCAR using them. I run a 180 T stat all year round, the needle stays just shy of the center point, except on the 90 + degree days, then it goes a little to the right of center, if idling for very long periods of time. Electric fans are great for people who make money selling them, and owners who like to tinker. Remember, todays electric motors are most likely made "off shore", and I would question their quality.

 

[swift6]

Searcher, above about 30mph, you don't need a fan at all. Mechanical or electric. The airflow of the car moving down the road forces more air through the radiator than your fan ever could by itself. The horspower gain comes from not having the fan beat the air needlessly at high rpm where it robs horspower through air resistance. In all it might only be a couple of hp so you probably won't feel a difference othe butt dyno. May only be slightly visible on a chassis dyno. The real gain is in increased efficiency. NASCAR doesn't use any fans as far as I can tell.

 

[swift6]

a 160 degree thermostat will only open earlier. If the cooling system is still allowing temps over 200 degrees with a 180, it will do it with a 160 as well.

 

[TheSearcherMan]

I touched on that. When air is being forced thru the radiator, ie, being supplied to the fan, as in going down the highway, there is very little load on the fan as it does not do anywork pulling air thru the radiator, as it is already being forced thru the radiator, so where is the increased efficiency? Now, its also possible, that the electric fan windmilling, may decrease efficiency, it most likely being a larger fan, and blocking air flow when going down the highway. That is why they "feather" props on multi engine airplanes, to decrease the drag caused by a windmilling prop. Also, the same cooling system was used on the 150 HP cars. Now, I do not know the temperature design specs, however, they knew most of the cars were coming overhere, so a stock USA spec car, with 100 HP, should have alot of extra capacity in the cooling system. The only dyno results I have seen in forums, except RP's car, are below 150 BHP, which should be about 128 rear wheel. If someones cooling system is not doing the job, then, it's broke, not designed wrong.

 

[TheSearcherMan]

Also, I would think, to switch to 180 in the winter, would be to make the car heat better, as the heaters are somewhat weak. I see no advantage to switching to 160 in the summer, as you say, the car would most likely run higher temps anyhow. Once again, its all about the cabbage.

 

[swift6]

I agree about the 'broke, not designed wrong' comment.

Otherwise, the efficiency comes with the electric fan freewheeling. It doesn't rob any power and it doesn't interfere with the airstream. Its also lighter than the original setup with the fan extension and 13 blade fan on later 6's. If the the stock TR6 fans did use a fan clutch that would allow freewheeling I would nearly consider it a draw. Since they don't, they beat the air equal to the engine crank speed. Air is a fluid, moving through it causes friction. Its a small inefficiency granted, but a mechanical fan is still less efficient. It is nearly foolproof though from a reliability standpoint.

Also, an electric fan is more efficient at cooling when it is needed. Since a mechanical fan turns at engine crank speed, it turns slower while idling. An electric fan turns at full speed, drawing more air through the radiator regardless of engine speed. So, when a fan is needed, below 30 mph, the electric fan moves more air than the stock fan. And unless you have the wipers going, headlights on, heater motor spinning and stereo blasting. The amp draw on the alternator vs the extra hp needed to spin the alternator under load is pretty small. So know, its not a free gain, but it is pretty inexpensive on the hp front.

The most common cooling problem on these cars seem to be old radiators anymore. Just because its been cleaned out and it passes a pressure test, doesn't mean that it is still as efficient as it should be, even designed to be. They are old and they do get less efficient over time. A new radiator core will go a long way on fixing cooling issues.