[Trainrex]

Well all I can compare it to is how my temps behave, and believe me the fans don't come on that often. In fact I have seen my normal operating temps drop to 80*C when going down a hill or when driving with not much load on the engine... Thus my assertion the most of the temp control was happening with the T-Stat and the radiator... My normal operating temps float between 85*C and 88*C 99% of the time doesn't really matter how I drive. Thus the fans on my car rarely come on... Now there is a few things that I have done but the system is still 100% stock...

Try unplugging them. You'll find out how much they come on. They come on all the time when you're driving, you just don't hear them.

 

[mangostick]

the only reason a car has a thermostat in the first place is to allow it to warm up quickly. After it opens it pretty much stays open until the car is shut off and the coolant starts dropping blow the "full open" temp rating of the t-stat. The radiator and fans control over all engine temp.

The only time you'll see a t-stat actually modulate engine temps is in extremely cold weather applications.

why run a cooler t-stat anyway? all you're going to accomplish is poor atomization (less power) and piss poor fuel mileage as the ecu reads a low temp and starts dumping fuel in to compensate.

 

[MainFrame]

the only reason a car has a thermostat in the first place is to allow it to warm up quickly. After it opens it pretty much stays open until the car is shut off and the coolant starts dropping blow the "full open" temp rating of the t-stat. The radiator and fans control over all engine temp.

That's pretty much my understanding.

 

[Trainrex]

the only reason a car has a thermostat in the first place is to allow it to warm up quickly. After it opens it pretty much stays open until the car is shut off and the coolant starts dropping blow the "full open" temp rating of the t-stat. The radiator and fans control over all engine temp.

The only time you'll see a t-stat actually modulate engine temps is in extremely cold weather applications.

why run a cooler t-stat anyway? all you're going to accomplish is poor atomization (less power) and piss poor fuel mileage as the ecu reads a low temp and starts dumping fuel in to compensate.

I want to have your babies, well put.

 

[mangostick]

uhh.. woah... lol

Well I come from a lengthy mess of playing with turbo fords (sohc 2.3T) .. they tend to run hot, and if not kept up they tend to over heat routinely so everybody wants to run a low temp t-stat or literally take them out all together..

then they ***** about not having heat or that the car never warms up and the fuel mileage is ****ty (not to mention running rich enough to wash the cyl bores and thats just really bad news) ..

the real problem in the older ford turbo cars (and many others) is the condition of the radiator. They're a poor cheap design to begin with and they're likely plugged up with gunk.. the older the car the more gunk .. usually. Good clean coolant makes a huge difference too.

I was making 417hp, using a radiator about 2/3 the physical size of the factory one with a fmic out in front of it.. difference was the rad design/material and fan application (factory is copper w single fan, I went alum with double fans). I still ran a factory spec 192* t-stat and never ever had a problem over heating. Even beating on it mercilessly @ 26psi the car never ran over 208* in the heat of fl summer. And I had heat QUICK when it was cold out while running it after moving to Va.

cooling systems can be complicated but the principles are pretty simple. Even more complicated cars have a very simple thermostat and various fan operating modes. If the fans didn't do much.. why go to all the trouble of programming the ecu to vary the fan speed? .. That tells me the t-stat just opens up once warm and the rest is fan n rad.

 

[wrxdrvr]

OK, I just can't leave this alone... So I went for a test drive and wrote all the numbers down... :tongue:

15 mile drive around town 86*C to 88*C all the time, about 3 red lights I had to stop for, the rest normal/good flow city driving...

3 mile long 7% grade hill 89*C up 84*C down,

parked and idled for 15 Minutes after the drive,
0 min 88*C
1 min 90*C
2 min 89*C
3 min 91*C
4 min 87*C
5 min 86*C
6 min 88*C
7 min 86*C
8 min 88*C
9 min 86*C
10 min 89*C
11 min 86*C
12 min 90*C
13 min 87*C
14 min 91*C
15 min 86*C

That's all I could stand to sit around for, so that is how my STi cooling system works... The fan NEVER came on... It's just how it is... As can be seen the temps go up, the T-Stat opens and the temps go down... over and over. IAT 30*C at MAF sensor. I still agree, when the radiator can't keep up and the fans come on, THEN the fan controls peak temps...

 

[Trainrex]

OK, I just can't leave this alone... So I went for a test drive and wrote all the numbers down... :tongue:

15 mile drive around town 86*C to 88*C all the time, about 3 red lights I had to stop for, the rest normal/good flow city driving...

3 mile long 7% grade hill 89*C up 84*C down,

parked and idled for 15 Minutes after the drive,
0 min 88*C
1 min 90*C
2 min 89*C
3 min 91*C
4 min 87*C
5 min 86*C
6 min 88*C
7 min 86*C
8 min 88*C
9 min 86*C
10 min 89*C
11 min 86*C
12 min 90*C
13 min 87*C
14 min 91*C
15 min 86*C

That's all I could stand to sit around for, so that is how my STi cooling system works... The fan NEVER came on... It's just how it is... As can be seen the temps go up, the T-Stat opens and the temps go down... over and over. IAT 30*C at MAF sensor. I still agree, when the radiator can't keep up and the fans come on, THEN the fan controls peak temps...

Unplug the fans and try it again.

 

[wrxdrvr]

Yes, I will do this again, in the summer, and see/document the actual temps and how long between fans turning on when parked and idling for 15 minutes... I fully expect the fans to come on when it's warmer, but I also expect the temps to be just as stable while driving, but the temps should certainly go up more than it did this time, while parked and running... It IS winter right now so I'm sure this test doesn't stand up. As for when parked and running, I can 100% guarantee the fans DIDN'T come on for the 15 min of idling, as I was right there, listening and watching them and they didn't move for sure for the 15 minutes parked and running. While I was driving I can't say for sure but the temps were lower while moving then while parked so I "assume" they didn't come on... I "might" actually do the test again tomorrow with the fans unplugged, but we'll see...

 

[mangostick]

More important.. at what location are you measuring the temperature and with what device?

 

[wrxdrvr]

I was reading the coolant temp from the ECU with a ScanGauge, but tomorrow I will do a data log with the AP...

 

[Donkey]

Yes, I will do this again, in the summer, and see/document the actual temps and how long between fans turning on when parked and idling for 15 minutes... I fully expect the fans to come on when it's warmer, but I also expect the temps to be just as stable while driving, but the temps should certainly go up more than it did this time, while parked and running... It IS winter right now so I'm sure this test doesn't stand up. As for when parked and running, I can 100% guarantee the fans DIDN'T come on for the 15 min of idling, as I was right there, listening and watching them and they didn't move for sure for the 15 minutes parked and running. While I was driving I can't say for sure but the temps were lower while moving then while parked so I "assume" they didn't come on... I "might" actually do the test again tomorrow with the fans unplugged, but we'll see...

I can tell you in 35°F weather my fans come on after 5-10 minutes of idling. This is with an all aluminum radiator and 160° thermostat.

 

[mangostick]

that should be pretty accurate. Where is the coolant temp sensor located? You want the temp right at the t-stat housing to prove/disprove the statements being tossed around regarding t-stat function.

Now it could be very possible that the system is efficient enough that the rad keeps the Idle temps at bay all on its own. This would be very pleasing to me since if the rad is at a thermal disadvantage at Idle with low outside ambient temps its definitely not going to be comfortably efficient under load during warm weather. Turbo cars develop crazy thermal loads.. and need healthy cooling systems to stay on top of things. Especially if the center section of the turbo is also water cooled.

The problem with the logic that the thermostat modulates engine temp after reaching full open temp is that they open and close pretty slowly, especially if the temp change is minimal. Most that I've tested aren't even accurate to the temperature stamped on them. Some up to 10* off. OEM ones seem to be much better than aftermarket but still.. its not exactly a precise piece of machinery.

What have your local ambient temperatures been? Its been pretty cold here in Va Beach lately and I have noticed that my fans dont kick on much if at all with easy driving. I'd be really happy to know that the factory radiator is as efficient as your data looks.

 

[Donkey]

OK, I just can't leave this alone... So I went for a test drive and wrote all the numbers down... :tongue:

15 mile drive around town 86*C to 88*C all the time, about 3 red lights I had to stop for, the rest normal/good flow city driving...

3 mile long 7% grade hill 89*C up 84*C down,

parked and idled for 15 Minutes after the drive,
0 min 88*C
1 min 90*C
2 min 89*C
3 min 91*C
4 min 87*C
5 min 86*C
6 min 88*C
7 min 86*C
8 min 88*C
9 min 86*C
10 min 89*C
11 min 86*C
12 min 90*C
13 min 87*C
14 min 91*C
15 min 86*C

That's all I could stand to sit around for, so that is how my STi cooling system works... The fan NEVER came on... It's just how it is... As can be seen the temps go up, the T-Stat opens and the temps go down... over and over. IAT 30*C at MAF sensor. I still agree, when the radiator can't keep up and the fans come on, THEN the fan controls peak temps...

The fans kick on around 204°F

 

[wrxdrvr]

that should be pretty accurate. Where is the coolant temp sensor located? You want the temp right at the t-stat housing to prove/disprove the statements being tossed around regarding t-stat function.

Now it could be very possible that the system is efficient enough that the rad keeps the Idle temps at bay all on its own. This would be very pleasing to me since if the rad is at a thermal disadvantage at Idle with low outside ambient temps its definitely not going to be comfortably efficient under load during warm weather. Turbo cars develop crazy thermal loads.. and need healthy cooling systems to stay on top of things. Especially if the center section of the turbo is also water cooled.

The problem with the logic that the thermostat modulates engine temp after reaching full open temp is that they open and close pretty slowly, especially if the temp change is minimal. Most that I've tested aren't even accurate to the temperature stamped on them. Some up to 10* off. OEM ones seem to be much better than aftermarket but still.. its not exactly a precise piece of machinery.

What have your local ambient temperatures been? Its been pretty cold here in Va Beach lately and I have noticed that my fans dont kick on much if at all with easy driving. I'd be really happy to know that the factory radiator is as efficient as your data looks.

The temp sensor is at/near the top of the engine, the T-Stat at the bottom . Thus the different temp (lower) T-Stat is designed in to make up the difference for what the temps are at the top ...

Well what else but the T-Stat would be controlling the engine temps when the fans never came on, and you can see the temps going up and down as the car was idling while parked?

I agree, I no longer am saying the T-Stat controls the engine temps all the time... engine temps will rise despite the T-Stat being fully open once the radiator is heat-soaked and won't come down until the fans lower the coolant temps in the rad or you are moving fast enough for airflow from the front to cool the radiator down.

Local temps during test was 37*F I'm quite sure if it was 90*F the fans would be on often. Thus my agreeing about the T-Stat not controlling the engine temps once peak temps are reached, then it's the fan and when it comes on that determines what the engine temps get up to...

 

[mangostick]

Cooling systems are kinda fun to play with for a few reasons.
1 the whole system works together.. no one single part serves its own purpose.. they all play in concert.
2 fluid dynamics/material and ambient outside temperature are huge factors in the efficiency of the exchanger (radiator)

You had asked what would control temp aside of the T-stat.. well, if at the t-stat the temp is enough to be full open.. then the radiator efficiency at given outside temp will determine how well the coolant temp is regulated. At Idle with your outside temp you found the balance right around 88*c average. The better the exchanger sheds heat the better it will cool the liquid inside. This is why proper sizing of the exchanger is vital. Constant level temps are prefered .. Too large a exchanger and it will over cool and cause the t-stat to constantly open/close.. creating a fluctuation in engine temps if not a complete over cooling scenario. Too small and it cannot shed enough heat to get the job done.

IF the engine isn't making enough heat to actually heat soak the exchanger then it will self regulate with unrestricted flow.

The fans dont kick on when the radiator is heat soaked that would be bad, they kick on well before that to keep over all temp regulated as long as you're still within the operating limits of the exchanger. Heat soaked means that the exchanger cannot shed heat as fast as it gains and will continue to build in temperature. Its imperative this doesn't happen.. this is why we have fans. Otherwise the exchanger or radiator would have to be absolutely massive. Since most often when under load the car is moving and there is good airflow over the exchanger, its efficiency is increased. While stopped after a period of load though.. the fans keep that airflow going and allow the system to maintain steady temps regardless of vehicle speed or load.

 

[wrxdrvr]

I did the test over today, and dataloged everything and tried to be much more thorough... This is what I got. Oh and I didn't disconnect the fans as I thought about it and realized there is not really too many places to pull over, as there is about 8' of snowbanks on the edge of the roads around here. 38*F ambient.

First part of the trip, Left the driveway at about 150*F and the fans never came on...
Second part of the trip started going up and down the 3 mile long 7% hill, the fans came on 1 time...
Third part of the trip going home from the bottom of the hill fans came on 1 time...
Fourth part sitting in the driveway for 13 min engine idling, fans came on 4 times...

I'm beginning to suspect my theory "works" or is close at these lower ambient temps but at say 70*F+ you guys theory would be more correct/closer... I can't seem to figure out how to post the logs for everyone's perusal...

On my car the fans turned on at about 90*C/195*F thus my lower temps I guess...

 

[mangostick]

does the wrx/sti have a variable speed fan setup? I've not really dug into this car much since I really haven't planned on any extensive mods.

If it does.. even though its on it may only be at slow speeds. If not that line of thought is completely irrelevant lol.. but anyway.

Yeah man I think the only odd variable is the cold outside temp.. in which your t-stat SHOULD be at least resticting flow through the rad as its not needed as much to keep a constant temp.

Neat **** here I like this thread. lol

 

[Trainrex]

Neat **** here I like this thread. lol

Me too.

He just found out that without the fans, even in the frigid weather, the temp would take off like a runaway freight train. Especially under heavy load.

Back to the original subject, if you want your car to run cooler, run a cooler thermo-fan switch coupled with a cooler thermostat. Possibly just the thermo-fan switch.

 

[wrxdrvr]

Me too.

He just found out that without the fans, even in the frigid weather, the temp would take off like a runaway freight train. Especially under heavy load.

Back to the original subject, if you want your car to run cooler, run a cooler thermo-fan switch coupled with a cooler thermostat. Possibly just the thermo-fan switch.

Now now, play nice... :nono: I NEVER said you don't need the fans to help control the engine coolant temps. The fans coming on 1 time for 10 seconds climbing a 3 mile long 7% hill isn't a runaway situation... What I did say was you only need them for controlling the peak coolant temps. Tho it turns out that ambient temps do make a difference as to how often those peak events happen. Yesterday the temps were 32*F and the fans never once came on, doing the same trip that I did today where they ended up coming on... 6 times on a 37*F ambient day, so... I surmise that below 32*F ambient normal driving the fans do only help deal with peek coolant temps, and my theory is "right". Above 32*F I surmise that the peak coolant temps happen more and more as the ambient temps get hotter thus in the end you are "right"... When peaks happen all the time one right after another they are no longer peaks it becomes the norm thus the fans actually do end up controlling the coolant/engine temps probably because the radiator is too small and the efficiency isn't too good especially with an AC condenser in front of it. BLa Bla Bla...

 

[Trainrex]

The minute the fans don't come on the runaway situation starts. The hotter it gets, the less it can control it.