Hello,
I drive a 1994 Chevy Suburban 2500 4x4. The heat takes about 10 minutes at 40mph to really get hot. A friend of mine has a new Mercedes, and the heat comes on pretty much instantly. Once the air in the system is expelled, then the rest is hot. Same with A/C. You can go from hot to cold in 1 second. Not in the Suburban.
How do they get the air so hot, so quickly in a cold engine? And then is the A/C constantly on standby to freeze on command? How do these new systems work?
You are comparing apples to oranges. Your Suburban probably has a big V8 and large radiator and heater core. Lot of mass to get hot. The mercedes will have a much smaller heating system(hence a quicker response).
Pretty much ditto for the A/C.
Also has significantly less air space to heat/cool to reach a steady state, but that wasn't really what you were asking about.
If it is a diesel, they may have PTC strip heaters in the plenum.
And then
No, but a well designed system should not take very long to reach a "cold" state.
To make sure your truck is heating up as fast as possible, you can make sure the thermostat closes all the way, and opens at the proper temp, and is the proper temp for your truck.
That, and cardboard in front of the radiator in winter.
-Dave
Toyota has basically a hot water Thermos buried in its hybrids (Prius). The thing can keep water hot for 3 days with the idea that the hotter water supplied via a pump to the engine will reduce emissions as well as supply quicker cabin heat.
Or so I was told....
B~
Not really a fair comparison as far as heat goes (I'm presuming the Mercedes is a car)
The Merc probably has an electrically-driven radiator fan that comes on only when needed. The Chevy has a belt-driven radiator fan that is running all the time. Yes, I know, they have a clutch supposedly but they are still pulling air thru the radiator (cooling down a cold engine). These fans also contribute much to underhood noise.
Sounds like your 'burban has a thermostat that's stuck partly open. Getting heat soon isn't really an old car/new car thing at all. My 1966 Dodge will start blowing warm air within a minute of a stone-cold startup. Not "hot," but enough to start defrosting the windows and warming the interior.
Now *this* is the difference between a blend-door system and a water-valve system. If your 'burban is like my '66 Dodge mentioned above, the air flow is always across the AC coil and then the heater core in series. The heat level is regulated by a thermostatic valve that throttles hot water flow through the heater core, whether or not the A/C is on. If you decide to switch from heat to AC, it takes a minute or so to blow really cold because it has to cool off the mass of warm water in the heater core, even though no new warm water is coming in.
On the other hand a blend-door system doesn't send the air across both the AC coil and heater coil in sequence- air doors divert the air to the heater coil or away from it as needed. Switching from heat to cool instantly shuts off the hot air and stops all air flow over the heater core, so the fact that hot water is still circulating through it doesn't matter because its not even exposed to the air flow. The downfall of this type of system is that it can't dehumidify and then re-warm the air as efficiently as the water-valve regulated type system can under some conditions.
How would that cardboard be of any value? I woudl expect the thermostat to be closed and thus the heat from the engine to not yet be circulating through the radiator yet anyway.
That makes no sense. the heat would just be expelled in the radiator or heater core. Youd get one burst of heat upon turning on car but then the rest would be cold again.
Had to check the manual: Prius Owner's Manual - page 208 - "Coolant heat storage system" - Chapter "Information Before Driving Your Toyota" reads in part: "The coolant heat storage tank system stores hot coolant and feeds it via the electric water pump automatically to warm the engine as required."
Does seem to warm up rather quickly within a few blocks on cold mornings. Some may have to do with the car running off electric for most of the start/warm-up portion so the gas engine needs something to warm it up during it's idle period.
B~
Ahh thats interesting. I doubt it has anything to do with cold starts. Probably with keeping the engine up to temp while the car is running, as you suggested.
With a very small engine and a very cold day, this can help, not because it blocks air through the radiator, but because it cuts down airflow in engine compartment.
As we reduce the size of an engine, the ratio of surface area of the engine to capacity increases. The cooling is proportional to surface area of engine, the heat generated to the capacity. A smaller engine gets more cooling from airflow over the surface of the engine itself. In cold Minnesota winters small engines never get hot enough to open thermostats very far, and cardboard over radiator OPENING does help. Quicker warmup and warmer running. But, this is only in twenty below weather.
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