Corvette Forum : DigitalCorvettes.com Corvette Forums banner

1 - 20 of 22 Posts

·
Registered
Joined
·
2,409 Posts
Discussion Starter #1
I called the insurance company this morning to reinstate my road coverage:cheers: and this afternoon took it out for a run.

I think, I say I think, I freed some HP with the electric Spal fans. One thing is for certain, when I let up on the gas to coast to a light, it takes longer to idle down than with the clutch fan dragging on it.

And now with the air cleaner grounded I can hear a decent radio too:D

Big concern is the coordination between the fans sensor and the T-Stat. I spent a lot of time experimenting.

I'd like to find a way to shut my Spal fans off after 3 minutes, and start again when the temperature is up. Right now the fans sensor and the t-stat are fighting each other on the low side.
I have a 185-200 sensor and a 180 t-stat. Both are new, replacing the first set which was 175-195 sensor and another 180 stat. The problem lies in the operating tolerances which are +/- 10 degrees in each, causing the fans to run continuously after the first climb to 200 and cool down to 180/185.

I know the fans shut off correctly,because I installed a 160 T-stat to see what happens. Then at cruise speeds the car runs at 160 which is too cool, and in town they shut off at about 180/185 from the 200 start like the sensor is set up.

I also drilled four holes in a 180 and that performed much like the 160. I now have a 180 with one hole drilled that didn't make much difference from a non drilled 180 t-stat.

Is there a timer I could wire in?
 

·
Registered
Joined
·
2,409 Posts
Discussion Starter #3
Re: Re: Drove the 72 today, lot to report

Speed Racer said:
What about skipping the timer and just install a fan switch?
The manual switch is a last resort. I'm anal I guess. It's supposed to work automatically. I just spent another $70 on sensors and t-stat's. I'm gonna make these system components work together properly one way or another.
 

·
Registered
Joined
·
129 Posts
That's why I went with the perma cool setup. They have a sensor that goes right into the radiator fins and is accurate to +/- 1 degree and its got adjustable turn on and turn off temps. Its great!!
 

·
Registered
Joined
·
3,027 Posts
When you say you want the fans to shut off after 3 minutes, are you talking about 3 minutes after it reaches 180 deg or 3 minutes after you shut the car off, like some of the newer cars do?
 

·
Banned
Joined
·
291 Posts
I'm running dual 12in Flex-a-lites on my stock 81 motor. They turn on with the ignition. The temp ussally sits around 190 plus or minus after she warms up. I had to bypass the temp switch becuase the stock switch is 238 on and 201 off.:surprised I may or may not put in a new switch.
 

·
Registered
Joined
·
84 Posts
Maby the problem is the location of the temp switch mine is a 195 on 185 off the instructions said to install in the head but I installed in the intake manifold both my fans are wired to the switch and it runs perferct they only run for about 3 min. on a hot day....
 

·
Mr. Casino
Joined
·
7,581 Posts
Remember
The thermostat is to control the engine temperature.
The fans are to control the radiator temperature.

Install the thermostat you need to control engine temp and setpoint for the radiator fans below the thermostat setting. The engine thermostat is expecting the returning coolant to be at a certain temperature (desired engine temp) to shutoff. If the fans are set higher than the thermostat the engine temp will rise to the fan settings if no other source of air flow is available.

The radiator also has to have the capacity to remove all of the excess heat and this is dependent upon ambient air temp and flow rates.

HTH

Henry
 

·
Registered
Joined
·
2,409 Posts
Discussion Starter #10
"If the fans are set higher than the thermostat the engine temp will rise to the fan settings if no other source of air flow is available."

That's exactly what I want. I want the fans to come on at about 200 and go off at 190. That way the 180 t-stat stays open.
 

·
Mr. Casino
Joined
·
7,581 Posts
f you take the thermostat out then the engine may go to the fan settings(air temp permitting) but the function of the thermostat is to cycle and maintain the engine temp not the coolant temp in the radiator.
To cool the engine the coolant supply from the radiator must be have a lower temp than the engine.

If the thermostat stays open you may not have enough fluid retention time within the radiator to provide cooling in hot weather or too much cooling in cold.

If you want a higher engine temp use a higher temp thermostat and keep the radiator below that setting so it can provide cooling when needed.
 

·
Registered
Joined
·
2,409 Posts
Discussion Starter #12
When I'm cruising at anything over 35 mph the engine temp has stayed down near 180. I can watch the gauge blip from 180 to about 183 and back to 180 as the t-stat is constantly openeing and closing. The system wants to run cooler than the t-stat let's it.

Now ....in traffic, using the temp senders available to me it's different.

Note: I have talked to Autometer and Painless about this. All their temp senders have a range tolerance of +/- 10 degrees. So a sender that is rated at 210 on and 190 off, could actually operate at 220 on and 180 off on one end and extreme case 200 on and 200 off:surprised . The actual range of the sender you get is a luck of the draw.

So, at the low end, and in traffic, the fans have been running at 180 and not shutting off. When I get on the highway from traffic, the fans stay on because the system is running cooler and the blooming sender and t-stat are fighting each other.

Hence the programable sender box.
 

·
Mr. Casino
Joined
·
7,581 Posts
I just replaced my temp sender again because the "new" replacement was reading 80 deg. high. Before I installed the new one I checked it by using a thermometer and a pot of boilng water. I ran the test twice just to make sure.

The sender/dash meter tracked the thermometer within 5 degrees as the water cooled. Now I can watch the thermostat open and close at the proper temp. The original 3 row radiator has been repaired and cleaned and still won't cool properly when then the ambient temp is above 90 degrees so I am interested in what you find to control the fans so they don't interfere with the thermostat. I plan to replace my radiator and stock fan very soon.

I intend to use the average radiator temp as the control point for the fans with a suitable deadband(if I can ever figure out what it should be)
 

·
Registered
Joined
·
2,409 Posts
Discussion Starter #14
elints said:
then the ambient temp is above 90 degrees so I am interested in what you find to control the fans so they don't interfere with the thermostat. I plan to replace my radiator and stock fan very soon.

I intend to use the average radiator temp as the control point for the fans with a suitable deadband(if I can ever figure out what it should be)
FYI, this last winter I replaced the OEM parts with a Dewitts aluminum radiator, Spal fans, and an Edelbrock aluminum water pump. So far it's much better than the OEM pieces.
 

·
Mr. Casino
Joined
·
7,581 Posts
biltogo said:
I just tool a look at the webpage with the fan controller.

The instruments in the dash are on switched power. When you turn the key off the temp guage will go to minimum and the fans will stop running. You will have to find another way to keep the fans running for the 3 additional minutes. This system still uses the engine temp for control of the radiator fans and this is not good control practice.

It also turns the fans on when the A/C clutch engages. This is ok if you are driving at slower speeds but there is no need to run the fans if there is plenty of air flow at highway speeds.

You will have fewer frustrations if you find a fan control system that has adjustable settings, close tolerances, and uses the actual radiator temp as the input. It should also be powered from a non-switched source.

FYI

http://www.atmel.com/dyn/resources/prod_documents/doc3ad4094256bbe.pdf
 

·
Registered
Joined
·
2,409 Posts
Discussion Starter #16
elints said:
I just tool a look at the webpage with the fan controller.

The instruments in the dash are on switched power. When you turn the key off the temp guage will go to minimum and the fans will stop running. You will have to find another way to keep the fans running for the 3 additional minutes. This system still uses the engine temp for control of the radiator fans and this is not good control practice.

So what's the difference between that and the OEM clutch fan stopping?

It also turns the fans on when the A/C clutch engages. This is ok if you are driving at slower speeds but there is no need to run the fans if there is plenty of air flow at highway speeds.

You will have fewer frustrations if you find a fan control system that has adjustable settings, close tolerances, and uses the actual radiator temp as the input. It should also be powered from a non-switched source.
This one has adjustable settings. Why the radiator temp? It's the engine temp we want to control, right?
FYI

http://www.atmel.com/dyn/resources/prod_documents/doc3ad4094256bbe.pdf
man those diagram's and write-up are way over my head. but thanks anyway
 

·
Mr. Casino
Joined
·
7,581 Posts
"Why the radiator temp? It's the engine temp we want to control, right?"

From an above post

"Remember
The thermostat is to control the engine temperature.
The fans are to control the radiator temperature."



If the radiator fan sensor is set higher than the thermostat then the thermostat will stay open and the engine temp will follow the radiator temp defeating the purpose of the thermostat. (Summer conditions)

Suppose the winter air temp is very low. The thermostat will cutoff coolant flow until the desired engine temp is reached. At this time the radiator is very cold and does not need any assistance. If the fans are dependent upon engine temp to turn on then they will even though they are not needed.

For both the engine control(thermostat(engine temp))
and the fan control(for radiator temp) to function as a team each must control what it is intended to control.

Let the fans control the radiator temp and the thermostat the engine temp. Set the radiator temp below that of the thermostat and as long as the radiator has cooling capacity and the water pump can supply worst case volume, the engine will maintain the desired temp.

Also the less you run the fans the longer service they will provide.($)
 

·
Registered
Joined
·
2,409 Posts
Discussion Starter #18
ok, lets say it like this.

On the highway, the radiator is getting blasted by oncoming air and cooling its contents.

The cooler fluid is entering the engine as long as the t-stat is open.

When the cooler fluid passes the t-tsat, the t-stat will close, and reopen when the heated fluid in the engine reaches the t-stat rating.

The cycle repeats itself over and over.

Now we get into traffic, and the car is idling at stop lights. The engine heats and the t-stat opens and cooler fluid again enters.

This repeats a couple of times until the radiator and engine fluids are the same high temperature.

The t-stat is wide open, and now the signal goes to the fans to kick on.

The fans cool the radiator fluid, and it passes to the engine.

As the cooler fluid cycles through the engine, the t-stat eventually recognizes it's lower closing limit and does just that, it closes.

Then everything repeats agian.

That's where my problem happens. The fans keep running because the temeprature signal for them to shut off is too close to the t-stat rating. Once that's established, they never stop.

It's best in traffic to keep the t-stat open a bit and have the fans shut down at let's say 10 degrees over the t-stat lower limit.
 

·
Mr. Casino
Joined
·
7,581 Posts
This is exactly the way you have it set up. The radiator sensors are higher than the thermostat. Install a radiator sensor and controller that can be set a significant amount lower than the thermostat. This will keep the radiator cooling available.

Honestly, the procedure I described does work quite well.

I don't know why the control and sensor suppliers don't provide such an "animal" but it may very well be because of profit.

After looking over the prices of the Tach circuit and the dash printed circuit boards, I guess they would have to sell for several hundred dollars in the automotive market.

The L88 hood also gives you the advantage of venting hot air out the top at slow or no forward speed. This has a positive effect of keeping the firewall cool and eliminating the "foot warmer"
I cut two underhood cowl vents in my stock hood and it sure made a big difference.
 

·
Registered
Joined
·
2,409 Posts
Discussion Starter #20
I think one of the reasons getting matched system parts is that most people want to operate at lower temperatures.

Just today I placed an order at Ecklers for a sender designed for a C4. It supposedly kicks on at 200 and off at 194. +/- 5 degrees. If it does perform this way, I expect to have the operating system I want.

I returned the Centech unit because it wasn't stable. After a few weeks use, I had to readjust it constantly. That's a PIA I don't need or want.
 
1 - 20 of 22 Posts
Top