Why change coolant fan temps?

[sdhager]

In almost all of the aftermarket tunes that I have seen, and that has been very few, the coolant fan temps have all been lowered. I can understand this if the thermostat has been lowered to maybe 180' F. But what if you have a stock 195'F thermostat?

Why do you want the engine to run cooler by installing a 180'F thermostat?

Why would you not want to leave the fan settings the same as factory?

I am working on a 98 Firebird that has the stock thermostat. Why not stay with factory fan settings? Why should I overwork the fan? I have seen settings that made the fan come on trying to keep engine temp below thermostat temp, forcing the fans to run continuously.

Anybody have any good theory on this?

[joecar]

If you have the stock thermostat, you want the fan settings to be close to stock.

The idea behind a lower temp thermostat is that a drag car can make more torque|power by virtue of the combustion chamber temperature being lower meaning the air/fuel charge density is higher...

while this may be true, there are several other considerations:
- lower combustion chamber temperature helps in reducing ignition knock,
- thermodynamic efficiency is higher as temperature increases (this is tricky, not necessarily having to do with MPG, but with the amount of fuel required to produce a specific amount of torque or power, which then also determines MPG) allowing more power|torque to be made regardless of ECT effects on air/fuel denisty,
- lower coolant temperature keeps the auto trans fluid cooler (stock in-radiator atf cooler),
- ditto on power steering cooler (on F-body, PS cooler is inline with the [hot] upper radiator hose),
- sufficient crankcase temperature (be careful, oil temp is not the same as coolant temp, but may be influenced by it to some extent) is required for the oil to function as it was designed, to correctly lube the cam and cylinder walls, and to sufficently evaporate water and gasoline from the oil,
- insufficient crancase/oil temperture may cause the cam to wear abnormally,
- the thermostat influences the temperature of HVAC hot air (think about this if you drive in a cold climate),

There is an abundance of debate on this topic.

A 160F thermostat might be ok for a drag racing only car (altho drag racers are starting to look at this from a scientific/engineering POV -> thermodynamic efficiency), but it may be too low for a street car.

A 180F thermostat is fine for an auto trans street car, the auto trans will be happy, the engine oil/cam will be happy... with appropriate fan settings, the ECT will be about 195F-205F, an may help to reduce some spark knock as found in the later F-body model years.

A 195F thermostat with approriate fan settings, the ECT will be about 210F-225F (this is also heating the atf via the stock in-radiator atf cooler... atf likes something like 180F-200F).

(Remember, the boling point of 50/50 water/coolant at about 20 psi is something like 265F --> i.e. with no pressure leaks in the cooling system).

At low speeds/idle, the fans determine the aiflow thru the radiator and directly control the ECT downto thermostat closing temperature; at higher speeds there is sufficient airflow thru the radiator to allow the thermostat to directly control the ECT.

The fan off temp should be above the thermostat's all-the-way-open temp which is generally about 10F above the TS's stated opening temp, otherwise the fans will run a lot which wears not only the fans but also stresses the alternator and battery.

The fan low on temp should be say 10-15F above the low off setting.

The high off/on temps should be above the low off/on temps, and typically the high off temp is same as or close to the low on temp.

[TFZ_Z06]

In almost all of the aftermarket tunes that I have seen, and that has been very few, the coolant fan temps have all been lowered. I can understand this if the thermostat has been lowered to maybe 180' F. But what if you have a stock 195'F thermostat?

Why do you want the engine to run cooler by installing a 180'F thermostat?

Why would you not want to leave the fan settings the same as factory?

I am working on a 98 Firebird that has the stock thermostat. Why not stay with factory fan settings? Why should I overwork the fan? I have seen settings that made the fan come on trying to keep engine temp below thermostat temp, forcing the fans to run continuously.

Anybody have any good theory on this?

My car as is runs 194F with a stock fan, 11:1+ compression.
For whats its worth, I like to set my high fan to 195F when at the drags. This helps fight against hot days, idling in staging lanes, etc.

I haven't worked much with the 160 thermos, but when I tested a 160F thermostat in my car (on dyno ran 180F constantly with it), I lost power.

I'm thinking the way to go is a better radiator with a stock thermo.

[mr.prick]

for some reason some people think that low ECT no matter what is the thing to do.
for me i have found that ECT 195F-205F and IAT 70-80 is the sweet spot.
keeping ECT that high with an EWP is very hard especially this time of year.

[sdhager]

So, would stock settings on a 195'F stat be a good thing for a street car then?

[joecar]

The stock settings are:
Fan low off/on = 219/226
Fan high off/on = 227/234

The 195F TS is fully open at about 205F-209F...
the following settings would allow an operating ECT just above that, (so you won't get excessive fan running):
Fan low off/on = 210/217
Fan high off/on = 218/225

At slow speed (traffic, idle) you would be running about 10F cooler than stock (but still be sufficiently warm for good engine/oil operation)...
at higher speeds (freeway) you would see the same as stock (about 205F).

Try it and see... log the STATE pid that shows when the fans run (fan1=low speed, fan2+fan3=high speed).

[TFZ_Z06]

for some reason some people think that low ECT no matter what is the thing to do.
for me i have found that ECT 195F-205F and IAT 70-80 is the sweet spot.
keeping ECT that high with an EWP is very hard especially this time of year.

Interesting point. Are you suggesting that since the EWP is running constantly even at slow rpms, you get too much cooling? Is the EWP always on, or does it respond by ECT temps via pcm programming? IE, fan wiring??

[mr.prick]

mine (meziere) is always on,
therefore i need to drill 1/6" holes to keep from
overworking the pump and burning it up.
so at 50+ MPH ECT is around 170F.

i have heard some nonsense that the stock pump "outflows"
the meziere at RPM.
but the fact is the meziere flows more than stock and is always on
where as the stock pump would need to be spun quite high.

i guess i could rewire/add a thermocouple or something,
i personally would not waste the money on one again.
i will say the meziere pump is a solid pump for almost
5 years/40,000 miles it has lasted and still going strong.

[WeathermanShawn]

Yes, I also spent a lot of time reading on the 'cooler ECT' is better theory for quite a while. I 're-worked' my stock thermostat to open at about 186F, and running ECT temperatures stabilize at ~198F. I only kick in my Low fan speed if it ECT's gets above 210F, and High-fan if above 218F. I figure getting oil temps above 212F on occasion is a good thing.

My ECT sweet-spot is almost exactly where Mr. Prick's is. I also have found summer IAT is the real 'killer'. Sometimes just turning that fan on with high IAT's will spike that IAT even higher.

Are you sticking with your stock 195F for now?

[sdhager]

Yes, I also spent a lot of time reading on the 'cooler ECT' is better theory for quite a while.

I really like Joecar's discussion. I 're-worked' my stock thermostat to open at about 186F, and running ECT temperatures stabilize at ~198F.

I only kick in my Low fan speed if it ECT's gets above 210F, and High-fan if above 218F. I figure getting oil temps above 212F on occasion is a good thing.

My ECT sweet-spot is almost exactly where Mr. Prick's is. I also have found summer IAT is the real 'killer'. Sometimes just turning that fan on with high IAT's, will spikes that IAT even higher.

Mr. Prick will testify to high IAT's/Density Altitude living in Prescott, AZ.

So, sdhager, are you sticking with your stock 195F for now?

..WeathermanShawn..


Yes. I'm staying with the current thermostat. Thanks for your input.

[eboggs_jkvl]

My "tuner", when I had the LS6 installed, set the fans down and dropped in a 160 t-stat (I asked for a stock one but he didn't listen). I have a fan switch installed and can manually run the cooling fans on low and high or "stock". A perk of the fan switch is the fact that I installed LEDs on it and they light when the fans run. I found that while I was driving down the highway, my cooling fans were running even though the temp gauge was down below 180. Hell, my cooling fans were running all the time. That is not good so I replaced the 160 with a stock t-stat and put the fans back to stock. Car runs fine, never overheats, and I live in Florida. The fan doesn't run now at highway speeds regardless of the IAT reading.


Elmer

[Aint Skeered]

Is it true that an aluminum motor is better with a stock ts where as an iron block would do better with a 180? I was thinking of changing the one in my Avalanch out for a 180.

I took my modded tune and put stock timing back in it to see how it did and my gas milage went down 2mpg. I also noticed while towing my camper with it that going up a steep bridge I got 2deg knock retard with the timing not stock.

I am putting my other tune back in as stock timing is not working out, just have to go in on the log I took and pull a little timing where the knock occurred in the heat.

[Highlander]

In my experience, the way I see it, a cooler block helps fighting detonation.. THAT IS IT. Most often times a hotter car will not get the "advance" that normally gets the power output.

If the head gets too hot it will ping. Installing a thermostat will help with this as you can cool the car efficiently w/o overworking the fans.

Now.. these engines (ls1s) make most power @ 190F. You could (and I am considering it on my personal car) to use a 180F thermostat in order to achieve a 186-190F temps. I have done the test on my dyno, running @ 160F and I can loose up to 8rwhp than at 190F. After that it gets tough to fight detonation and make a "consistent" vehicle.

I like a vehicle that I can hit and it will not ping. If it's too hot it will ping consistently, you will have to lower the timing and thus have a lower HP output.

Thermodynamically, the hotter the engine the more power it makes, because you do not loose combustion energy in the form of heat (because its already there) and thus you get more expansion power. But given some balances in temps... Well you get a lil more consistent power by having the engine a tad cooler. A cooler engine is also a bit safer on the head gaskets :).

So in the end... it will not "yield" more power but it will make the car a little bit more consistent.

[joecar]

+1, the trade off in combustion chamber temperature is thermodynamic efficiency vs detonation.

[gmh308]

In my experience, the way I see it, a cooler block helps fighting detonation.. THAT IS IT. Most often times a hotter car will not get the "advance" that normally gets the power output.

If the head gets too hot it will ping. Installing a thermostat will help with this as you can cool the car efficiently w/o overworking the fans.

Now.. these engines (ls1s) make most power @ 190F. You could (and I am considering it on my personal car) to use a 180F thermostat in order to achieve a 186-190F temps. I have done the test on my dyno, running @ 160F and I can loose up to 8rwhp than at 190F. After that it gets tough to fight detonation and make a "consistent" vehicle.

I like a vehicle that I can hit and it will not ping. If it's too hot it will ping consistently, you will have to lower the timing and thus have a lower HP output.

Thermodynamically, the hotter the engine the more power it makes, because you do not loose combustion energy in the form of heat (because its already there) and thus you get more expansion power. But given some balances in temps... Well you get a lil more consistent power by having the engine a tad cooler. A cooler engine is also a bit safer on the head gaskets :).

So in the end... it will not "yield" more power but it will make the car a little bit more consistent.

Hey Highlander. Good info there on the 190F on the dyno and max power. The whole coolant temp discussion is an interesting one and has been for as long as I can remember.

With higher temps and the onset of detonation, did you get a chance to look at reducing spark/revising fueling to get away from detonation and seeing if the power level still dropped/stayed same/increased with more elevated temps than 190F?

Is this an engine dyno or a chassis dyno?

:cheers:

"There can be only one....!" :grin:

[Highlander]

Always... but there is no more power.. you start loosing power because of heat that is causing detonation and often times is not dependent on timing and others, fuel is just too hot inside the cylinders and preignites. The only way to "control" it is with cooling and/or reduce timing and reducing power. The other problem is that the car becomes way too inconsistent.

I have been tempted to test the Evans NPG to see if I can run a hotter vehicle with more timing and thus get more power.

[gmh308]

Always... but there is no more power.. you start loosing power because of heat that is causing detonation and often times is not dependent on timing and others, fuel is just too hot inside the cylinders and preignites. The only way to "control" it is with cooling and/or reduce timing and reducing power. The other problem is that the car becomes way too inconsistent.

I have been tempted to test the Evans NPG to see if I can run a hotter vehicle with more timing and thus get more power.

Evans NPG?

The iron SBC's would produce a little more power up to about 220. But no cooling system margin at all at those temps. Not worth the extra few ponies. Alloy block/heads/EFI/current chamber design makes a whole different ball game.

Cheers.