Thermostat Rating (Page 1/2)
FieroMark OCT 15, 11:06 AM
What is the group consensus for a "good" cooling system thermostat rating. I have used 180F and the temp gage reads nicely at just below mid-range. With a 190F thermostat, the gage reads about 2/3rds scale and nicer in winter since the heater discharge temp is hotter, or course. So, I'm thinking of just switching out to 190 in November then back to 180 in April since they are ridiculously simple to swap out.

What do other owners use?
Patrick OCT 15, 02:53 PM

In all my Fieros (2.5 and 2.8), I use what the engines were designed to be run with, year round... a 195°F thermostat.

By the way, don't put too much trust into what the factory temperature gauge is telling you.
olejoedad OCT 15, 04:06 PM
Patrick is correct.

Run the stock 195°F thermostat year round for best performance and gas mileage.
There is NO BENEFIT to running a cooler thermostat.
82-T/A [At Work] OCT 15, 05:08 PM
Ok... so... buckle up, because I'm going to get flamed for this.

The 195 degree thermostat is a requirement that was levied by the Federal government under what was called the "Clean Air Act of 1963" (as amended in 1968).

You can look this up under eCFR (Code of Federal Regulations), somewhere under 40 § 85.2122.


Basically... it's bull **** . And before everyone gets mad at me... I do care about the environment. But the higher thermostat requirement (which wasn't effectively implemented until about 1975) was used to try to improve the effectiveness of smog pumps which were starting to show up on cars to help eliminate smog in most big cities. Basically, an engine operates more efficiently (burns hotter) when it's operating at a higher temperature, and as such, a hotter thermostat promotes this. That much is obvious... but somewhere, people started saying that lower temperature thermostats were bad, and then it became a thing that everyone repeated without question ... without actually understanding the science behind it. There are very reputable people who literally "parrot" that changing a thermostat does nothing, and you're hurting your engine. They even say that going to a lower thermostat means your car will overheat more quickly, which is also totally ridiculous. Before 1968, for example... cars were designed to operate at 160 degrees... and earlier than that (1930s, etc.), cooling systems weren't even pressurized... which meant that they largely operated in the low 100 range.

Now, I'm not saying you should switch to a 160 degree thermostat. But if you live in places like Florida, Arizona, etc... you absolutely can use a 180 degree thermostat and YES... your car WILL run cooler. It completely ignores science to suggest that a lower thermostat somehow doesn't mean your car will run at a lower temperature. It's like saying the Earth is flat, but people continue to state this all the time like it's settled. I respect everyone here... so not trying to make enemies. But if you live in the deep south, you absolutely can benefit from running a 180 degree thermostat during the summer months.

Remember that the temperature that the thermostat is rated for is the temperature at which your car BEGINS cooling. So it'll never, ever get cooler than that at any given time. If you're sitting in stop and go traffic in the city in the dead of summer... I'd want that floor to be lower SO THAT when I do get the opportunity to accelerate, I'm able to cool the engine more quickly. Basically, I don't want my operating floor to essentially be 200 degrees in the dead of summer.

All of that said, 180 degrees is the absolute lowest I'd want to go in a stock car... that's because your ECM programming is designed to operate with the assumption of 195 degrees (same with your fans). A 180 degree thermostat isn't such a huge change that it's going to affect your fuel map though. So 180 degree thermostat for the summer is good, and 195 degrees for winter is also good. But you can also improve the cooling your engine (at 195 degrees) by using better coolant, and even additives that promote better heat transfer (the one I like to use is Redline Water-Wetter). Heat destroys a lot of things, including hoses, oil, etc... and while all of these things are designed to work with 195 degrees, less heat in the engine bay is better, and 180 degree thermostat is a decent way to accomplish this during the summer.


I just want to emphasize this point. Government regulation is not always the miracle we think it is. It's made up of humans, and they are sometimes wrong. When they mandated catalytic converters in 1974, they made a bad decision which was based heavily on influence from a corporation that stood to make a lot of money. There were two kinds of catalytic converters available at the time... the charcoal pellet style (which our earlier year Fieros came with), and the honey-comb style catalytic converters. They were effectively the same cost, but the pellet style robbed considerable horsepower from the engine, and while it did improve emissions, it resulted in dramatically less efficient engines, which means fuel economy dropped and people used more fuel to drive the same distances they had previously. Manufacturers didn't start switching to the honeycomb style until the Federal regulations were updated at some point in 1986 to allow it. I forget the exact update (I can look it up if people need me to), but it also repealed the 85mph mandatory speed limit cluster, and a whole host of other things.


Anyway, yes... a 180 degree thermostat is OK for summer.

[This message has been edited by 82-T/A [At Work] (edited 10-15-2024).]

Patrick OCT 15, 05:24 PM

quote
Originally posted by 82-T/A [At Work]:

Before 1968, for example... cars were designed to operate at 160 degrees... and earlier than that (1930s, etc.), cooling systems weren't even pressurized... which meant that they largely operated in the low 100 range.



Let's go back to leaded gas!
pmbrunelle OCT 15, 06:37 PM
I have tried 160°F, 180°F, 195°F on my V6.

In the end, I liked 195°F the best, and that's what I use all the time (summer/spring/fall, car is not really driven in the winter). My Fiero sees 0°C - 30°C ambient temps.

Below about 180°F, the fuel evaporates less readily from the intake port walls. From the tuner's perspective, I see that more acceleration enrichment fuel is required (the engine computer's maps are configured to do just this). From the driver's perspective, I see that the throttle response is a little bit less snappy.


quote
Originally posted by 82-T/A [At Work]:

Ok... so... buckle up, because I'm going to get flamed for this.

The 195 degree thermostat is a requirement that was levied by the Federal government under what was called the "Clean Air Act of 1963" (as amended in 1968).

You can look this up under eCFR (Code of Federal Regulations), somewhere under 40 § 85.2122.


Basically... it's bull **** . And before everyone gets mad at me... I do care about the environment. But the higher thermostat requirement (which wasn't effectively implemented until about 1975) was used to try to improve the effectiveness of smog pumps which were starting to show up on cars to help eliminate smog in most big cities. Basically, an engine operates more efficiently (burns hotter) when it's operating at a higher temperature, and as such, a hotter thermostat promotes this. That much is obvious... but somewhere, people started saying that lower temperature thermostats were bad, and then it became a thing that everyone repeated without question ... without actually understanding the science behind it. There are very reputable people who literally "parrot" that changing a thermostat does nothing, and you're hurting your engine. They even say that going to a lower thermostat means your car will overheat more quickly, which is also totally ridiculous. Before 1968, for example... cars were designed to operate at 160 degrees... and earlier than that (1930s, etc.), cooling systems weren't even pressurized... which meant that they largely operated in the low 100 range.

Now, I'm not saying you should switch to a 160 degree thermostat. But if you live in places like Florida, Arizona, etc... you absolutely can use a 180 degree thermostat and YES... your car WILL run cooler. It completely ignores science to suggest that a lower thermostat somehow doesn't mean your car will run at a lower temperature. It's like saying the Earth is flat, but people continue to state this all the time like it's settled. I respect everyone here... so not trying to make enemies. But if you live in the deep south, you absolutely can benefit from running a 180 degree thermostat during the summer months.

Remember that the temperature that the thermostat is rated for is the temperature at which your car BEGINS cooling. So it'll never, ever get cooler than that at any given time. If you're sitting in stop and go traffic in the city in the dead of summer... I'd want that floor to be lower SO THAT when I do get the opportunity to accelerate, I'm able to cool the engine more quickly. Basically, I don't want my operating floor to essentially be 200 degrees in the dead of summer.

All of that said, 180 degrees is the absolute lowest I'd want to go in a stock car... that's because your ECM programming is designed to operate with the assumption of 195 degrees (same with your fans). A 180 degree thermostat isn't such a huge change that it's going to affect your fuel map though. So 180 degree thermostat for the summer is good, and 195 degrees for winter is also good. But you can also improve the cooling your engine (at 195 degrees) by using better coolant, and even additives that promote better heat transfer (the one I like to use is Redline Water-Wetter). Heat destroys a lot of things, including hoses, oil, etc... and while all of these things are designed to work with 195 degrees, less heat in the engine bay is better, and 180 degree thermostat is a decent way to accomplish this during the summer.


I just want to emphasize this point. Government regulation is not always the miracle we think it is. It's made up of humans, and they are sometimes wrong. When they mandated catalytic converters in 1974, they made a bad decision which was based heavily on influence from a corporation that stood to make a lot of money. There were two kinds of catalytic converters available at the time... the charcoal pellet style (which our earlier year Fieros came with), and the honey-comb style catalytic converters. They were effectively the same cost, but the pellet style robbed considerable horsepower from the engine, and while it did improve emissions, it resulted in dramatically less efficient engines, which means fuel economy dropped and people used more fuel to drive the same distances they had previously. Manufacturers didn't start switching to the honeycomb style until the Federal regulations were updated at some point in 1986 to allow it. I forget the exact update (I can look it up if people need me to), but it also repealed the 85mph mandatory speed limit cluster, and a whole host of other things.


Anyway, yes... a 180 degree thermostat is OK for summer.




I think that we should not discuss the government regulation aspect. This adds confusion/noise to the topic. Benefits of hotter/colder should be discussed on their technical merits.

The hotter the coolant temp, the more efficient the engine is (less heat transferred from the combustion chamber to the cooling system).
The hotter the coolant temp, the more the radiator is effective at rejecting heat to the environment, so a smaller/lighter/cheaper radiator is needed.

I have seen some information on the internet showing increased cylinder wear with lower operating temperatures. Why is this? Is this due to the piston-to-bore clearance being greater at lower temperatures, hence there is more rocking and rubbing? If an engine is designed to run at 160°F, should the piston-to-bore clearance (at room temperature) be smaller than for a 195°F engine, knowing that the aluminium piston will expand less at operating temp?

Should your proposition to run a lower-temperature thermostat be accompanied with a tighter piston-to-bore clearance spec, and a larger radiator to ensure that the engine never heats enough for the piston to seize?

[This message has been edited by pmbrunelle (edited 10-15-2024).]

82-T/A [At Work] OCT 15, 07:05 PM

quote
Originally posted by pmbrunelle:

I have tried 160°F, 180°F, 195°F on my V6.

In the end, I liked 195°F the best, and that's what I use all the time (summer/spring/fall, car is not really driven in the winter). My Fiero sees 0°C - 30°C ambient temps.

Below about 180°F, the fuel evaporates less readily from the intake port walls. From the tuner's perspective, I see that more acceleration enrichment fuel is required (the engine computer's maps are configured to do just this). From the driver's perspective, I see that the throttle response is a little bit less snappy.

I think that we should not discuss the government regulation aspect. This adds confusion/noise to the topic. Benefits of hotter/colder should be discussed on their technical merits.

The hotter the coolant temp, the more efficient the engine is (less heat transferred from the combustion chamber to the cooling system).
The hotter the coolant temp, the more the radiator is effective at rejecting heat to the environment, so a smaller/lighter/cheaper radiator is needed.

I have seen some information on the internet showing increased cylinder wear with lower operating temperatures. Why is this? Is this due to the piston-to-bore clearance being greater at lower temperatures, hence there is more rocking and rubbing? If an engine is designed to run at 160°F, should the piston-to-bore clearance (at room temperature) be smaller than for a 195°F engine, knowing that the aluminium piston will expand less at operating temp?

Should your proposition to run a lower-temperature thermostat be accompanied with a tighter piston-to-bore clearance spec, and a larger radiator to ensure that the engine never heats enough for the piston to seize?




Government regulation is entirely appropriate for this, because it was done for improved emissions, at the expense of reliability and longevity. Heat soak became a major problem in the 70s (carburetors boiling over, etc.) and it is detrimental to the long-term reliability of the parts as a whole. The difference in piston clearance from 15 degrees is negligible, and well within the scope of what's appropriate. Prior to the Federal mandate, most car companies ran 180 degrees with engines they then ran at 195 degrees just a year later with no change. Emissions are improved substantially in other areas, and the only reason why this was implemented was to improve the efficiency of the smog pump. I run a 195 nearly all the time, but if I'm daily driving a Fiero in the summer, in Florida where it's exceptionally humid and ~100 degrees ambient temperatures on asphalt... the lower temperature helps keep the car from extreme temperatures with no ill affects.

160 degrees is way too low, and I wasn't suggesting this.


We should argue about Archie V8 versus that other guy, or whether or not the Crane H272 Cam is better with the 1.52:1 roller rockers, or 1.6:1 roller rockers. Or better yet, we should argue about whether we should take social security at 57, or wait until 65. Haha...
sleek fiero OCT 15, 11:41 PM
HI Pmbrunelle; pistons are aluminum and need clearance because they expand much faster than cast iron cylinders. I have built engines commercially for 45 years and I can say cooler is better for engine life. Proper engine clearances are important but too much heat destroys engines because heat creates friction and causes excess wear. Yes too cool will not help you pass emissions but it will make your engine last longer. sleek
Vintage-Nut OCT 15, 11:57 PM
As a fact, the V6 ECM was designed efficiently with a 195-degree thermostat
Personally, I always maintained the factory thermostat as was designed on my 'stock' engine.

My coolant system is running properly however, I prefer Rodney's 210-dregee "On" / 200-dregee "Off" Radiator Fan Switch keep the coolant temperatures lower than the GM 235-degree "On" Switch.

And no, my radiator fan doesn't turn on often in normal driving and only if I'm stuck in slow traffic.......

When the 195-degree thermostat opens, the dash coolant temperature reads ~175-degrees

BTW - you can review this thread from last year:
180 or 195 Thermostat by MasterBaker
https://www.fiero.nl/forum/Forum2/HTML/147099.html


------------------
Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles

FieroMark OCT 22, 06:57 PM
Wow! What a great discourse. Love the thoughtful commentary.

Now for my next topic, I was thinking about discussing which is better...Coke or Pepsi ;-)