How do modern cars regulate temperature so well?

Heating / Cooling / AC

  1. 72bluNblu

    72bluNblu FABO Gold Member FABO Gold Member

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    That seems like a terrible way to do it. So it's just a variable controller. Except electric fans aren't generally rated for variable speeds, they're rated at one speed. And the fan itself will be designed to be most efficient at that rated speed. That also means the fans are always on at some speed once you're within 10° of the thermostat open temperature? Again, there's no reason for that. The fans don't need to run at all once the car is moving at a reasonable speed, and the temperature won't necessarily drop low enough to shut them off even though you don't need them to be running.

    Not only that, but most electric motors tend to like a specific RPM range. Not all fans may like being hooked to a variable controller like that. Big pass on that one.
     
  2. Treblig

    Treblig Well-Known Member

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    I had two fans on my car, each had a variable start temperature. I had one set to come on at 180 and the other set to come on at 190. If the temp dropped below 190 one would automatically shut off, it the temp dropped below 180 both would be off. Worked pretty nice!!
     
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    • Mike69cuda

      Mike69cuda 64 is the new 17 FABO Gold Member

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      Pontiac firebirds have a couple of relays on the two electric fans. On London’s speed they ran in series, on high speed they ran in parallel. Pretty clever I thought.

      Edit: I love iPad spell checking. How did it get “London” out of “low“?
       
      Last edited: Sep 12, 2020
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      • famous bob

        famous bob mopar misfit

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        I aint gettin into the elec. fan vs mech. fans clutch fan thing , the newer cars engines are computer designed , and have way better coolant passages and bigger in the correct places too . Our dynosaurs dont have optimum anything , especially when the are h.p. monsters. w/o fake boost of some sort.
         
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        • kursplat

          kursplat FABO Gold Member FABO Gold Member

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          ya, the all fans end up being variable speed thing bothers me too. the site isn't very well put together so a call would be in order to answer a lot of these questions. i don't know why you wouldn't set the fan "on" point just above what ever max temp your willing to see, so they have a chance to turn off, once the car is in your happy zone. since this takes the temp at a very different location form where most people install the temp gauge, maybe that accounts for the thinking... i don't know...
           
        • 72bluNblu

          72bluNblu FABO Gold Member FABO Gold Member

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          I just don't understand why you wouldn't run a main stream controller. I think what you have there is a guy that knows enough electrical stuff to make a thing, but doesn't have the knowledge of the cooling system to actually optimize it. The fact that the controller runs the fans all the time is a huge mistake that compromises on of the biggest advantages to having an electric fan.
           
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          • kursplat

            kursplat FABO Gold Member FABO Gold Member

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            so looking into the PWM thing a little more, i (finaly) found a good explination of how it works.

            'So, the motor is being fed impulses of power. Imagine it the same way as if you were to turn the wheel with your hand. You can push the wheel every 5 seconds with the same amount of force, and you will keep the wheel spinning. You can also speed up the interval when you are pushing the wheel; let’s say you nudge it every 3 seconds..."

            "It is important to know that there is no voltage regulation involved here, and by using PWM regulation the motor is constantly being fed 12 volts."
            What is PWM and how does it work? - ekwb.com


            SPAL and DERALE both sell them too...
             
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            • Mike69cuda

              Mike69cuda 64 is the new 17 FABO Gold Member

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              The same principal is used for most modern variable speed controls. Variable speed drills and even house light dimmers operate this way. It basically turns the voltage off and on very fast, many times a second.

              Let’s say the voltage (12 V) is on half the of the time and off half of the time. That is roughly equivalent to running the motor on 6v, as you are running the motor on half the power. If you adjust the time the voltage is on longer (longer pulses) the motor goes faster (or the lights get brighter) because the the power is applied for a longer time.
               
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              • EdM

                EdM Well-Known Member

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                I run my 427 Windsor Mach 1 in 100 degree days in the Texas Hill Country with modern A/C on without issue. That said, a Be Cool drop-in aluminum radiator kit with twin puller fans just works. This confirmed via my Dakota Digital gauge. As mentioned above, engineering and money works.
                 
              • famous bob

                famous bob mopar misfit

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                My fuel inj. system will do that if I want it to.
                 
              • BillGrissom

                BillGrissom Well-Known Member

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                Sorry I didn't read all the posts, but I'll add a possiblity and a little engineering explanation. First, the thermostat (T-stat) in older cars (2015 and earlier?) is what engineers term a "proportional controller". It does not regulate to a precise setpoint, which we term "proportional droop". Carefully test one in a pot of hot water w/ a thermometer and you will see that it starts to crack at say 180 F and doesn't fully open until say 190 F. With a high thermal load (hot day and/or driving uphill fast), more coolant flow is required. That requires the T-stat to open more. That requires a higher temperature. Thus, you see the engine temperature rise slightly. One could decrease that operating band by making the T-stat touchier (more gain), but that risks "negative feedback oscillation".

                Most mechanics seem to think that the T-stat is constantly opening and closing. I doubt that. It should settle at a steady opening position (varying w/ thermal load). They must be basing their concept on how a home heater and AC works (on-off mode, termed "bang-bang control" in academic texts not kidding).

                BTW, if you want to know if your dash gage is accurate, note the average position the needle runs at and that should match your T-stat's temperature spec (if working perfectly), or measure with an IR gun at the sensor location.

                Many of the later cars now have an electronic T-stat to more precisely control the engine temperature, under all loads. I learned that in a recent RockAuto newsletter, so thank Tom Taylor.

                Before arguing with me, consider that you will be arguing with many engineering textbooks which millions of engineers in the world understand. Smarter to just google the terms I listed and learn.
                 
                Last edited: Sep 19, 2020
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                • BillGrissom

                  BillGrissom Well-Known Member

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                  I think all injectors, even in batch-mode pulse once per camshaft revolution. In TBI, it might be per crank revolution (no camshaft sensor). That makes the electronic controls simpler. Sequential just means that each injector's opening start is timed to its intake valve. The reason that sequential doesn't help at higher loads (and rpm) is that the fuel flow is high so the injector is spraying for sometimes most of the crank cycle, yet the intake valve is open for only ~25% of the time. Thus, the injector is spraying at a usually-closed intake valve under load. Sequential really only helps at idle, to reduce emissions and only slightly at that. As far as the details of the air flow and combustion, that still can't be well simulated. But, no need since they have engine tests stands and just play with the injector timing until they find the optimum settings.
                   
                • pishta

                  pishta I know I'm right....

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                  All true, but if someone is gonna pay $400 more for the new model 4 with SEFI instead of the model 3 that doesn't have it, expecting it to be better 'performance' wise...well there you go. Matter of fact the Pro-flow 4 for example may have SEFI, VVT actuator, boost control, trans CAN BUS, line lock, coffee maker, data logging, hand warmer.....but all that stuff isnt even present on a 340 in a 68 Dart. Just pointing out the features on a Pro-flow 2 may be all the person needs. I wouldn't recommend the Pro-flow 1 as it as not user programmable past +- 10% variance, unless you want to build a turn key stock internals 360 with only a Performer RPM camshaft and headers All other variables past this base tune need to be burned by Edelbrock and I'm not sure they even do that anymore. But it does come with a great intake, 28lb injectors and plumbed fuel rails. Great for a flexible MS2/3 conversion.
                   
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