Short Statement on "Cooler" Thermostat's Facts and Fiction

[Crossbow]

"I put a 170 or lower thermostat in my car, and now my ECT's are lower!"

Lower thermostats do NOT increase a vehicles cooling system's effectiveness. Once a thermostat is fully open, there is no difference between a 160, a 170, or a 190 degree thermostat in terms of cooling. You can actually increase your ECT's by running too low of a thermostat.

The thermostat's function is to keep coolant in the engine until a set temperature is reached. At this point the water circulates into the radiator, and the cooler water in the radiator into the engine. Of course thermostats start opening significantly earlier before their "full open spec", so some level of water is almost always flowing into the radiator and into the engine.

The thermostat will vary its amount of open/close based on the internal coolant temperature of the engine, and the spec of the thermostat. Once the thermostat is fully open, it will act like any other fully open thermostat at any spec rating. So if your engine coolant temp is 190, the 160, 170, 180, and 190 thermostats are all the same.


But I heard running a lower thermostat will lower my coolant temp and increase performance???

When current mazda's reach 200F coolant temp, the engine retards timing, generally (Depends on specific vehicle), the timing retard is around 8%. This timing retard continues again at 210F, and severely at 220F, sucking horsepower away from the vehicle. Thus many people want to try to keep their coolant temp below 200F as easily as possible, which is one of the reasons why thermostat discussions come up.

A lower thermostat will only lower coolant temps if the vehicles cooling system is capable of maintaining a lower coolant temperature. The thermostat only regulates coolant through the engine, it is not responsible for the temperature of the coolant itself...that is determined by the vehicles cooling system. The radiator, the coolant mix, the electric fans, the water pump, and of course the ambient air level. If the vehicles coolant system is bottle necked at one particular area, even removing the thermostat completely will not keep your coolant temps down.

In reality, in our engine, the only time you'll realistically see lower coolant temps in the engine block, is in winter, or in a situation where the cooling system is capable of maintaining that lower temperature. (Basically cold ambient air, and lots of airflow/upgraded cooling system through the radiator).


So what's bad about removing the thermostat all together?

Earlier I mentioned that it's possible to actually get higher ECT's from too low a thermostat. This is because the water needs to spend a certain amount of time in the radiator, much like air does in an intercooler, to have it's heat removed. I doubt this is a problem with our particular vehicle, but in some cars, removing the thermostat causes the water to rush through the radiator too quickly, and not have enough heat removed to properly cool the engine internals. Additionally, since the only real time a cooler thermostat will ever show any major difference is in cold climates (when the cooler ambient air increases the effectiveness of the entire system), you'll run into major issues with the engine warming up properly. It'll take longer for fluids to reach operating temp (could take the oil longer then 15 minutes in extreme cases), which can spell disaster for internal engine components.

Remember in this car that the coolant is not only responsible for cooling the turbo, oil, and engine, but it's also responsible for heating everything up. The coolant runs through the oil cooler/heater above the oil filter to try to get the oil up to it's temp spec as quickly as possible, before the user decides to slam on the accelerator, and spin up a turbine's heat level to volcanic proportions.


So how would I actually gain a benefit from a lower thermostat?

First you'd need to upgrade your vehicles cooling system. The cheapest way's of doing this are with ducting, and changing your vehicles coolant mix. Generally most car's are safe with a 60/40 mix (water/coolant), though those in heavy snow areas which see -20F or lower, might want to stick with 55/45 or the standard 50/50 mix. In warmer climates (such as CA or closer to the equator) a 70/30 mix will work nicely. Do note however, that deviating from the standard 50/50 mix will require you to be adamant with the maintenance of your cooling system, and require you to change and flush the coolant more often then is normal, such as every 30k, instead of every 50-100k.

Ducting would just be to ensure that all the incoming air goes through the radiator, and not around it. Ducting is one of the cheapest methods for increasing the efficiency of any air/fin based cooling system. Such as rotors, intercoolers, or radiators.

If you have additional money, you can look into actually replacing the radiator with an all aluminum model, which may have additional cores, and bigger end tanks. Adding an oil cooler will also reduce the load on the cooling system, but make sure to use a thermo based unit, so you don't over cool the oil. (Oil must run within a spec temp range for maximum lubrication)

Last but not least, replacing the water pump and/or electric fans is another alternative, as well as purchasing/creating a fan controller which allows you to engage the fans based on a specific coolant temp, instead of relying on the stock ecu.

Here is a useful link on calculating your coolant/distilled water mix, and a chart showing you the freeze point of coolant per mix levels.

http://www.challengers101.com/Coolan...nd Overheating

[bnoon]

It may be interesting to note that on most cars, lowering the stat open temp will only lower the operating temps at highway speeds, where you would need it least for performance applications. That is, unless you perform one or more of the mods you listed.

The fan temps are controlled by the ECU, so if any of the tuners see fit, they could enable lower temp settings for us to help with the around town temps where they could actually do some good. Who here is holding their breath on that one? Anyone?

[evidence]

Originally Posted by bnoon The fan temps are controlled by the ECU, so if any of the tuners see fit, they could enable lower temp settings for us to help with the around town temps where they could actually do some good. Who here is holding their breath on that one? Anyone?

slo4now actually threw his fan on a switch it seems, so that is another option also. Run it 100% of the time.

I live in AZ so going with a more aggressive water mix seems the way to go. Just need to locate some docs on draining the coolant.

[redrocketz]

Originally Posted by evidence slo4now actually threw his fan on a switch it seems, so that is another option also. Run it 100% of the time. I live in AZ so going with a more aggressive water mix seems the way to go. Just need to locate some docs on draining the coolant.

theres a drain on the bottom of the radiator to fully get it all out you can use a hose to push out all the old coolant.

a note with these cars is that the thermostat is the whole black housing. not a normal style one.

[evidence]

Originally Posted by redrocketz a note with these cars is that the thermostat is the whole black housing. not a normal style one.

Even if you don't replace the thermostat you should still see the benefit of the more efficient mix no? Water will take in and release the heat quicker than the anti-freeze meaning the water cooling in the radiator will be lower coming into the engine, and it will be able to obtain the heat from the engine at a faster pace. During mild AZ wheather my ECTs still sit in the low 190s, and when you start creeping up it usually because the unused mix has not had enough time to cooldown, or am I way off?

[slo4now]

I've been running the 170 thermostat for a little while now and my car
has not seen over 187deg yet.
That is with 60% distilled water and 40% coolant, fan is on a swith.
No extra ducting and i have a cpe fmic. Even though the summer here
in FL is almost over, so far so go.

[slo4now]

My freind runs 100% distilled water on his Buick T-type with 6 bottles
of water wetter and a 160deg thermostat, that damn car sits for 1/2
an hour in hot fucking traffic and it has never seen over 168 deg.
He does have a bigger radiator and a good as electic fan from a
Lincoln Continental.



Oh btw this is on a 700hp+ car

[TurboGhost]

For normal driving you want the engine to reach full operating temp. When then engine is less hot, more of the heat from the fuel you paid for gets sponged off by the cold heads, piston and cylinder thus less is pushing the piston down. You lose some fuel economy and the engine gets gunked up more bc contaminants are not boiled out of the engine oil. At the track it's a different story, different topic.

The cooler starting point is a little help for a few seconds of WOT, that's it. If you don't change the fan cut in, you won't even get that at low speeds or in rush hour traffic.

It's a little strange that people can read Crossbow's post and still want a colder stat for a daily driver.

[evidence]

In my case I easily get into 230+ sitting in traffic, if I don't let the car sit overnight its up at 180 by the time I get out of the driveway. While I'm not looking at changing the stat, since it will do me no good, I am wondering if a heavier water mix will be a quick/easy aid to help bring traffic/stoplight temps down a bit?

[ztuner]

you want efficient ? Run silkolene at 5 % with pure distilled water. Use what McLaren F1 uses.

Harry

[AutoXRacer]

An important factor missed here, is that with todays tighter tolerances in engine design, running a cooler thermostat could potentially lead to increased engine wear...this would be do to the expanding/contracting nature of the metals not reaching designed nominal temps.

Just something to ponder...