How do modern cars regulate temperature so well?

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couple comments=

My stock 73 318 will stay at 165 all day in all conditions in super hot and humid FL city/mixed driving.
Sunpro gauge and IR agree.

Turn on the AC, though.......

I have a "Scangauge II" unit that will read degrees frm the sensor on an OBD II car. This can be used to determine "normal" and other points on the factory gauge. It also reads and clears trouble codes, and calculates MPG.
 
I put a reman engine in a corvette. During run-up it started creeping up past 220, and fans wouldnt run. After some research, 230 is the cut in temp.

have done lots with various conventional vehicles, watching temp rise with scan tool and when fans come on. Thing is, its like its almost too late when fans engage. 215-220 seems normal.
 
So......
Looks like I have enough radiator and fan.....gauge is pretty accurate too.
Modern cars are probably BS'ing me.....
Might improve with EFI controlling AF and timing.....

Stop worrying about it for now?
210 is absolutely fine and safe...220 no good?!!!

Jeff
 
So......
Looks like I have enough radiator and fan.....gauge is pretty accurate too.
Modern cars are probably BS'ing me.....
Might improve with EFI controlling AF and timing.....

Stop worrying about it for now?
210 is absolutely fine and safe...220 no good?!!!

Jeff
I don't like my older cars to reach 200* That's just me......
 
Another reason I believe the newer cars gages are not moving with the engine a few degrees one way or the other, is the electric fans will click on at a certain temp, but the gage doesn't move up to that range. Gage stays the same but the fans will click on in a drive through.... Hmmmmm......
 
I agree......but the concensus here seems to be otherwise? ??
To each their own, I guess. I usually run a 160* or 180 t-stat and my cars never hit 200 - ever. We took my wife's '77 Ramcharger from Illinois to the Grand Canyon in '18, and it never came close to 200* We turned it about 2500 rpm's all day long in the heat.
 
To each their own, I guess. I usually run a 160* or 180 t-stat and my cars never hit 200 - ever. We took my wife's '77 Ramcharger from Illinois to the Grand Canyon in '18, and it never came close to 200* We turned it about 2500 rpm's all day long in the heat.

Ramchargers have a big *** rad. tho ! Most dont make any serious h.p. either !
 
Ramchargers have a big *** rad. tho ! Most dont make any serious h.p. either !
just an over the counter rad from an autoparts store. 2 core I believe. Looks like a 1/2 ton pickup D100 rad. I don't know if his 318 makes more power than the 360 4bbl. I do know the full time 4x4 and almost 5000 lbs works it going down the road, and the 13 mpg proved it ... LOL Doesn't matter, though. We've traveled in cars as well. He can solve the heating issue....
 
The key word on the newer cars is cooling SYSTEM.. This includes the coolant flow within the engine, also.
The main reason the oems don't put numbers on the temp gauges, is they don't want to scare the uninformed driver. I have seen a few vehicles, that have 195 t stats but don't turn on the cooling fans untill about 240 degrees.

Right. It also includes the stuff you never see anyone talk about here when they have cooling issues, but I HAMMER on it constantly. The grille opening, any spaces and voids behind the front bumper. Openings in the K frame forward of the main cross member. On these cars with really high horse power builds, "all that area" needs to be closed off, like on a new car. All those plastic shields under new cars? It ain't there for looks! It's all part of the cooling system to help direct more air through the grill opening. Just like front air dams on most newer cars. There's "something" under the front bumper (cover) or the cover itself is engineered to help push air trying to go under the vehicle back up and through the grill opening. I've preached it till I'm blue in the face that these mods will help out older cars as well, but am usually ignored.
 
Two things----- First have you checked the temp of the inlet and outlet on the radiator, there should be a 20 degree drop. If not then you don't have enough airflow (fans) or a restriction. I bought an inexpensive laser temp gun to check my car. Second-----does it overheat sitting at a light or on the highway at constant speed, this makes a big difference??
 
From what I can see in this discussion is no one addressed the fact that the older cars aren't actually "regulating" anything. Regulation requires some "smarts" being built into the system. Older cars "attempt" to do it with what they had. Water hits a certain temp, fan starts in order to stop the rise, or bring it down etc, meanwhile the temp is rising because, that ramp up has already begun and it's not easy to stop, eventually, it will happen, but then the water might cool too much and the cycle starts over. The problem with this is of course, the timing of it all. It's like a diabetic who take insulin right before eating instead of 15 minutes before. You have to try to match the curves and the older stuff just isn't up to the task.

Nowadays, temperature control is often done with a PID loop. The system uses a controller, which "knows" based on the current temps, and rates of change measured by the differneces in the current and last few measurements, how to predict when to start and stop the fan. Doing this, you get a far greater accuracy than a simple on/off that's activated on a general temp.
 
It runs 190 most of the time, but when it's hot outside it climbs over 200 - 205....
That's without AC which I am definitely going to add AND a mild 318 build....couldn't imagine what it would do with AC and more hp (stroker planned in future)
Some days when the outside temperature is mild, 190 around town and 180 on the freeway. ...
It's all over the place.

All seals in place and good condition.

Jeff

I don't like my older cars to reach 200* That's just me......

200°F is not hot. Neither is 205°F. My Contour electric fans are set to keep my Duster between 200°F and 210°F, and really that's lower than it needs to be.

Remember what the stock thermostat on these cars was? It's a 195° F. You think they ran everywhere at 200°F? They did not. And most of the factory gauges do not have actual temperatures on them, so they're no better than a new car. Probably less accurate too.

Even with only a 7 psi cap boiling should be around 230°F. With a 16psi cap like newer radiators run it's more like 250°F. So I wouldn't stress anything lower than 220°F. Some of that is about tuning, I'm not saying you'll run your best 1/4 mile at 220°F. But on the street? Not a problem if it stays there.

From what I can see in this discussion is no one addressed the fact that the older cars aren't actually "regulating" anything. Regulation requires some "smarts" being built into the system. Older cars "attempt" to do it with what they had. Water hits a certain temp, fan starts in order to stop the rise, or bring it down etc, meanwhile the temp is rising because, that ramp up has already begun and it's not easy to stop, eventually, it will happen, but then the water might cool too much and the cycle starts over. The problem with this is of course, the timing of it all. It's like a diabetic who take insulin right before eating instead of 15 minutes before. You have to try to match the curves and the older stuff just isn't up to the task.

Nowadays, temperature control is often done with a PID loop. The system uses a controller, which "knows" based on the current temps, and rates of change measured by the differneces in the current and last few measurements, how to predict when to start and stop the fan. Doing this, you get a far greater accuracy than a simple on/off that's activated on a general temp.

Exactly. And, they're all electric fans. No worrying about what CFM the fan is putting out at a given engine RPM, the fan spins at the RPM it's rated for which means even at idle electric fan can pump out its max rated CFM. With a mechanical fan the lowest CFM it moves is at idle, which is usually when the engine is hottest because there's no air flow but the fan. And when the engine rpms are up and your fan is pushing a ton of cfm and stealing all kinds of power- you don't need the fan at all because the air flow through the front of the car is plenty.

Still...............I want mine to run like modern.
Do I not have enough radiator? Fan?
Better controller?

All of the above?

Jeff

More fan.

I looked up your fans, they're rated for 2,700-2,799 cfm. Which is enough, but, not much extra. The Contour fans I run are rated for ~3,000 cfm on low speed, and will move ~5,000 cfm on the high speed. The vast majority of the time the low speed is all I need, but I have had the high speed kick on a few times when I was stuck in traffic with outside temps over 105°F. But my 340 is .060" over and 9.8:1 with ported iron heads and a Lunati 60404. Not crazy by any means not not exactly mild either.

And your controller, well I'm not too sure about it. I looked it up, but it wasn't super clear about how exactly you get to actually control the fans. How do you set the temperatures?

I use a Dakota Digital controller. I can program the on and off temperatures for both the high and low fan speeds. If I remember right the "on" temps can be set in 1° increments and the "off" temp in 2° increments. It also has a 0-5 min run time on shut down that can be programmed, so just like a new car the fans will keep running after you shut the car down. It has a low voltage protection on that as well so it'll shut the fans down before it kills the battery if that's an issue. I've been using the one I have for over 6 years now without any issues, it runs the fans off of a pair of relays.

A better controller makes it easier to maintain the temperatures you want as long as you have the fan to do it. Based on your current temperatures you're fine, so a better controller might improve that some. Add a bunch of power and you might also want more fan though.
 
Because back in those days, the car companies gave you what you got... They weren't trying too hard to give us the best that they could do...

It wasn't until the Japs came in and started taking over the market, that the OEM's started trying harder to give us better products...

The foreign car companies came in and started doing it better, so the OEM's had to step up their game or loose their business...
I agree with everything except that you misspelled LOSE.
 
I don't see where anyone's mentioned the new antifreeze/coolant formulations.

What do they have now, four different ones?
 
No one has considered the air flow under the hood either. There are modern automobiles that dont have a large grille to pull air through. There is so much shrouding under the car that air has to pass around the engine, then down the firewall.
Then there's the lack of temp range. They all come with a 195 degree thermostat. Water temp goes up to that and is controlled from 195 to 210. Difficult to notice such a small and brief change at the gauge. I see a slight needle movement right before the electric fan starts in my 96 Camry but that's because it has a bottle of Barsleak head gasket fix in it. I watch the heck out of that temp gauge. And BTW, that stuff really works in some cases. The worry never goes away.
 
200°F is not hot. Neither is 205°F. My Contour electric fans are set to keep my Duster between 200°F and 210°F, and really that's lower than it needs to be.

Remember what the stock thermostat on these cars was? It's a 195° F. You think they ran everywhere at 200°F? They did not. And most of the factory gauges do not have actual temperatures on them, so they're no better than a new car. Probably less accurate too.
I won't argue about it. You can hit the disagree all you want, but when I sit in a drive through on a hot summer day, my temp gage doesn't move but the electric fans will kick on at a certain temp. That tells me the engine temp raised but the gage did not. It's true in the newer Dodge mini vans, my 'stang, etc. Also, I don't care where others chose to run their cars for temp. Mid 70's Shop Manual states 190* stat is standard equipment, and that is to ensure you have a Happy Heater in the Winter and emissions, not because it's where the car is the happiest. Again, I couldn't care less what anyone runs their temp at, I'll run mine on the cool side.
 
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I won't argue about it. You can hit the disagree all you want, but when I sit in a drive through on a hot summer day, my temp gage doesn't move but the electric fans will kick on at a certain temp. That tells me the engine temp raised but the gage did not. It's true in the newer Dodge mini vans, my 'stang, etc. Also, I don't care where others chose to run their cars for temp. Mid 70's Shop Manual states 190* stat is standard equipment, and that is to ensure you have a Happy Heater in the Winter and emissions, not because it's where the car is the happiest. Again, I couldn't care less what anyone runs their temp at, I'll run mine on the cool side.

Hey, do what you want. Running an engine cold causes more wear on the components, but whatever. 200°F is a perfectly normal operating temperature. My 340 is much happier at 200°F than it is at 160° or even at 180°, which is why I bumped up the temperature on my fan controller. Factory gauges are calibrated so 195°F is pretty much dead center in the middle of the gauge. Why do that if that's not the temperature it's supposed to be? Gauge doesn't show it being hot, and if that's the only gauge you'd think it was perfectly normal.

My factory gauge, autometer gauge and fan controller. The factory gauge has a factory sender, the autometer has it's own and the controller runs off the autometer sender. The autometer gauge itself reads a little hot, but that's just the cheap gauge.
IMG_9217.jpeg
 
I think everyone would agree that the OLD factory gauges read real temp. But newer cars definitely have a 'dead zone' built into them. That, and they react super slow which helps the gauge cover normal fluctuations. This keeps 'Karen' out of the dealership while the warranty is intact. Almost all gauges have some sort of non-linear response but I'm convinced newer model cars have it engineered specifically to cause non-alarming gauge needle behavior until the engine has departed the engineered operating parameters.

I too will echo the sentiment that ALL the openings from the grille to past the fan, and likely to the K frame should be as closed as possible to help create a 'wind tunnel' to help with air flow - and also that quality electric fans will beat mechanical every time. The only drawback of an electric fan is going cheap and having them stop operating. This is what makes the contour fans attractive: OEM level of engineering put into them (and if the knock off is at least half as good, it's twice as good as those parts store fans).
 
But newer cars definitely have a 'dead zone' built into them. That, and they react super slow which helps the gauge cover normal fluctuations. This keeps 'Karen' out of the dealership while the warranty is intact.
What I quoted is well spoken!!
 
It's a. 030 over 318 (321) with home ported iron heads, Whiplash cam, stock 8.1:1 compression, Mopar stock iron intake and Edelbrock 4 barrel. Champion aluminum radiator, dual electric fans and an Autocoolguy controller. Dougs D453 headers.
The hardest test for a cooling system is Idling,stopped in traffic, on a hot tarmac, with the hood closed. If your system cannot keep your engine cool enough to satisfy your opinion of what "normal" should be, then it needs tweaking, to satisfy your opinion. Or you gotta change your opinion.
If your temp creeps up in this situation with the fans running full time, your system needs work.
Your engine is the first part of the equation
And in that, you gotta think about what is going on in the combustion chamber at idle. I'll guess you have this cam.

HUG SMC1326AL
SMC1326AL.jpg

This appears to be a small at .050 cam,
claiming 213/226/109+5 But Hughes doesn't tell you that the advertised is probably close to 264/276/109.
Now, what you gotta see is that, in at 104 , the compression degrees are just 124, with an Ica of 56*.
The power duration is just 108*. and
The overlap is quite generous at 52*.
Lets stack 'em up
264/124/108/276/52overlap; and the factory 318
240/133/121/248/22
So what is that showing us?
Well, check out your compression degrees of 124 versus the stock 133, So your cranking compression is expected to be 128psi (720ft elevation) compared to 137psi for the nominal factory 8/1 engine. What this translates to is a Dcr of 6.8 for you compared to 7.1 for the stocker. Not too big a deal by itself.
But check out your power degrees of 108 versus the factory 121. This shows us two things; 1) you get lousy fuel mileage, because the pressure in the combustion chamber is released very early at just 108* ATDC, compared to the factory at 121, or 13* later; and so that pressure could have been used to turn the driveshaft. Instead it is running out your headers, heating them up. But on there way out, they cook the water in the heads, surrounding the ports.
And now, the overlap. This is the time in the cycle, during which BOTH intake and exhaust valves are open. The piston is at TDC or within a few degrees. The headers if working right,are tugging on the chamber to pull the last of the exhaust out. But, since both valves are open, that tug goes right across the chamber to the intake plenum and gets that started towards the chamber too! In your case your Whiplash has 52* of time for this to take place , which is a lot of time. It is 42% of your compression duration and 48% of your power duration, so that's a lot. So what's going on here at idle?
The header is gonna pull some of that intake charge straight out into the exhaust system. Where, it could catch fire when it gets to the merge, because of the still burning residues from other cylinders.
So, taken all together; at idle; This is a terribly inefficient running mode, with a lot of the energy being wasted as .............. heat , external to the combustion chamber. If you couple that with retarded ignition timing, which causes the mixture to still be burning with the piston on it's way down in the cylinder, and so heating up the water jackets; You got a lot of heats to deal with; namely; Water jackets, exhaust ports, headers, and even the exhaust pipes.
Please, tell me your carb is sucking air NOT from under the hood. That would be like feeding a runaway nuclear reactor.
Remember, we are still idling in traffic.
Where is all this heat going?
The only way out, is under the car; and stopped, your fans are gonna have to push it out, cuz hot air rises, and continuously heated air rises continuously. So your heads are being triple-cooked; once from the water,once from the hot exhaust,and once from the underhood hot-air. And your induction system gets a double dose, and your engine oil is not liking it either.
So, before you condemn your cooling system, consider what it is trying to deal with.

You might think that retarded timing does not apply to you. But I can tell you that for sure your idle-timing is retarded. Go warm up your engine. Check the timing. Now loosen the D and crank in a bunch more timing, until the rpm no longer rises; now read the timing again. This is the idle-timing your engine wants, at whatever rpm it climbed to. Don't be surprised to see high 30s* and more. Ok now retard it back to whatever she earlier had. I'll guess you were at or near 50%.

So what's the solution?
Well you know where I'm going, but before I say it, prove me wrong.
How?
Warm your engine up; crank the rpm to 1600, then advance the timing, to peak the rpm. Continue until she hits about 1800 rpm; then turn the fans on full time, leaving the hood open. Finally, twiddle the mixture screws for best lean rpm.
Grab a beer and your IR gun, and watch the temperature. This set-up, eliminates most of the sources of waste heat, and allows what is being created, to escape, and gives your carb half a chance at finding cooler than 350* air.
Wait 3 minutes and record the hottest spot around your stat housing. Mark the spot. Wait 4 more minutes and check again. Continue this way until you get two consecutive same/similar readings, or if the temp exceeds 220.
At the end of the test, idle the engine down, retard the timing back to the start. and give her a break.

What's it mean?
What we have done, is take the worst case situation, and made the best of it. This is the potential your current system has. If it cannot maintain a sub 220 temp, you are gonna have to make some changes.

Obviously you cannot drive with your hood open. This was an effort to give your carb cool air, and to give your fans an alternate place to send the air. You could repeat the test with the hood down, but I don't see a way to IR shoot the stat-house for an apples to apples test. Perhaps if you have a fast-acting water gauge and had recorded the temps previously, comparing them to the IR gun. If that shows the same temps, then you can try the test again with retarded timing, or retarded timing and open hood ,etc; until you find the worst contributor ...... and then you will have an idea of what to do.

In a later post I'll tell you what I exactly know to have cured my over-heat problems to the point that my system runs within a couple of degrees no matter what the circumstances.
 
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408, aluminum heads, solid roller cam, stock pulley ratios, dual electric fans, aluminum radiator, 180 thermostat, AC, sequential port EFI. It will maintain 180 when cruising but climbs to about 195 when in traffic, but drop right back down once I get moving. FYI. I live in south Louisiana. I just had it out over the weekend. It was 95 degrees out and I didn't have any problems. Contrary to what another comment was about sequential not being worth the trouble, while the difference may be minuscule, the car does idle better with sequential EFI. It wasn't designed for high RPM as he stated. It was designed originally for low RPM emissions.
Do you have stock ratio pulleys? Do you have a 6 blade or 8 blade water pump? I'm not a fan of the aftermarket pulleys since they slow down the water pump so much. They may work in the northern states, but not down here.
 
And your controller, well I'm not too sure about it. I looked it up, but it wasn't super clear about how exactly you get to actually control the fans. How do you set the temperatures?
THE AUTO COOL GUY's web site is bad...he really needs someone to redo it and rewrite everything. his PWM controllers are interesting if that's the style of controller you want. HERE'S the instruction pages. setting the "ON" temp basically involves using a heat gun and setting the on temp, measured at the radiator outlet, ~ 10' below what your thermostat opening temp is. that sets the "ON" temp, and the controller ramps the fan speed up and down using that for a base line
 
The new cars are designed to control heat. They were designed that way! End of story.
 
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