Blowing max hot air into cabin to cool engine
10-19-2017, 11:43 AM
#1
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Thread Starter
Blowing max hot air into cabin to cool engine
Am I silly for thinking that dragsters can gain a few milliseconds off their ET by turning the heat all he way up and blowing max air?
I mean, the heating we get in our cabins comes from the combustion process, right? Its simple physics. If we allow our cabin to become a heat sink via the HVAC system then aren't we reducing the engine temp? It has to be zero sum.
Now whether this is actually significant is another debate. But I remember my grandpa telling me that they turned the heat fully on and windows open to tow heavy stuff in their old diesel trucks. It was the difference between stalling and getting your load going.
I mean, the heating we get in our cabins comes from the combustion process, right? Its simple physics. If we allow our cabin to become a heat sink via the HVAC system then aren't we reducing the engine temp? It has to be zero sum.
Now whether this is actually significant is another debate. But I remember my grandpa telling me that they turned the heat fully on and windows open to tow heavy stuff in their old diesel trucks. It was the difference between stalling and getting your load going.
10-19-2017, 12:10 PM
#2
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Am I silly for thinking that dragsters can gain a few milliseconds off their ET by turning the heat all he way up and blowing max air?
I mean, the heating we get in our cabins comes from the combustion process, right? Its simple physics. If we allow our cabin to become a heat sink via the HVAC system then aren't we reducing the engine temp? It has to be zero sum.
Now whether this is actually significant is another debate. But I remember my grandpa telling me that they turned the heat fully on and windows open to tow heavy stuff in their old diesel trucks. It was the difference between stalling and getting your load going.
I mean, the heating we get in our cabins comes from the combustion process, right? Its simple physics. If we allow our cabin to become a heat sink via the HVAC system then aren't we reducing the engine temp? It has to be zero sum.
Now whether this is actually significant is another debate. But I remember my grandpa telling me that they turned the heat fully on and windows open to tow heavy stuff in their old diesel trucks. It was the difference between stalling and getting your load going.
10-19-2017, 12:13 PM
#3
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It pulls the heat from the coolant and unfortunately the control unit will adjust the radiator fans to compensate generally you'll see next to no different on a modern vehicle
10-19-2017, 12:16 PM
#5
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Dont take what I am about to say as scientific in any way but....
I have this old Dodge Caravan (2005) that I use for work. Long story short, I was on a long drive (about 1 1/2 each way) in it and as it turns out the radiator had a small leak. This leak was old so the radiator was already running low, and it basically was running out by that day.
So, on my way back temps start rising quickly, I am stuck in LA traffic on the freeways and the next exit is a little far away. Unfortunately its already about 100 degrees outside so its a hot day. Regardless, I started turning on the heat full blast for as long as I could take it then give myself a break. And the temp needle basically kept going up, then started dropping when I had the heat on, then up again when I turn it off, then down again when heat was on full blast.
So I can speak from personal experience that it helps and I think it still helps with our cars as well.
IIRC Blkrokt races with his heat on full blast.
I have this old Dodge Caravan (2005) that I use for work. Long story short, I was on a long drive (about 1 1/2 each way) in it and as it turns out the radiator had a small leak. This leak was old so the radiator was already running low, and it basically was running out by that day.
So, on my way back temps start rising quickly, I am stuck in LA traffic on the freeways and the next exit is a little far away. Unfortunately its already about 100 degrees outside so its a hot day. Regardless, I started turning on the heat full blast for as long as I could take it then give myself a break. And the temp needle basically kept going up, then started dropping when I had the heat on, then up again when I turn it off, then down again when heat was on full blast.
So I can speak from personal experience that it helps and I think it still helps with our cars as well.
IIRC Blkrokt races with his heat on full blast.
10-19-2017, 01:53 PM
#7
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My old Honda Civic used to run hot all the time, particularly during hot SoCal drives. I used to blast the heater periodically and it definitely lowered he coolant temp. This was decades ago, so I can’t speak as to whether it would work on a more modern car, as deadlyvt mentioned.
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10-19-2017, 03:38 PM
#8
Super Member
The short answer is .....NO, it will not.
the reason that it used to work was due to the fact that your heater control in your dash either had a choke cable or vacuum hose that physically connected to an underhood valve in the heater hose which would modulate coolant flow to the heater core depending on how far towards hot or cold you had the temp control set. Newer vehicles typically dont do this anymore. Instead of an actual valve in the coolant flow the temp is now controlled by blend doors in the hvac plenum which modulates air flow across the heater core to pick up as much or as little heat as the electronic control was requesting. with this being said, whereas the heater core USE to only have flow when heat was called for by the valve now the heater core has CONSTANT flow from the time the water pump starts spinning until you shut the vehicle down.
Now in theory, the plenum airflow across the core SHOULD pick up some of the heat from the core and deliver to the vents thus reducing the heater core outlet temp but that drop in temp would prolly be in the ballpark of maybe 1-2deg but then by the time that reduced temp coolant made it back into the system the radiant heat from the engine compartment will have added those 1-2deg back.
the reason that it used to work was due to the fact that your heater control in your dash either had a choke cable or vacuum hose that physically connected to an underhood valve in the heater hose which would modulate coolant flow to the heater core depending on how far towards hot or cold you had the temp control set. Newer vehicles typically dont do this anymore. Instead of an actual valve in the coolant flow the temp is now controlled by blend doors in the hvac plenum which modulates air flow across the heater core to pick up as much or as little heat as the electronic control was requesting. with this being said, whereas the heater core USE to only have flow when heat was called for by the valve now the heater core has CONSTANT flow from the time the water pump starts spinning until you shut the vehicle down.
Now in theory, the plenum airflow across the core SHOULD pick up some of the heat from the core and deliver to the vents thus reducing the heater core outlet temp but that drop in temp would prolly be in the ballpark of maybe 1-2deg but then by the time that reduced temp coolant made it back into the system the radiant heat from the engine compartment will have added those 1-2deg back.
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NotABaller (10-19-2017)
10-19-2017, 03:44 PM
#9
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Thread Starter
The short answer is .....NO, it will not.
the reason that it used to work was due to the fact that your heater control in your dash either had a choke cable or vacuum hose that physically connected to an underhood valve in the heater hose which would modulate coolant flow to the heater core depending on how far towards hot or cold you had the temp control set. Newer vehicles typically dont do this anymore. Instead of an actual valve in the coolant flow the temp is now controlled by blend doors in the hvac plenum which modulates air flow across the heater core to pick up as much or as little heat as the electronic control was requesting. with this being said, whereas the heater core USE to only have flow when heat was called for by the valve now the heater core has CONSTANT flow from the time the water pump starts spinning until you shut the vehicle down.
Now in theory, the plenum airflow across the core SHOULD pick up some of the heat from the core and deliver to the vents thus reducing the heater core outlet temp but that drop in temp would prolly be in the ballpark of maybe 1-2deg but then by the time that reduced temp coolant made it back into the system the radiant heat from the engine compartment will have added those 1-2deg back.
the reason that it used to work was due to the fact that your heater control in your dash either had a choke cable or vacuum hose that physically connected to an underhood valve in the heater hose which would modulate coolant flow to the heater core depending on how far towards hot or cold you had the temp control set. Newer vehicles typically dont do this anymore. Instead of an actual valve in the coolant flow the temp is now controlled by blend doors in the hvac plenum which modulates air flow across the heater core to pick up as much or as little heat as the electronic control was requesting. with this being said, whereas the heater core USE to only have flow when heat was called for by the valve now the heater core has CONSTANT flow from the time the water pump starts spinning until you shut the vehicle down.
Now in theory, the plenum airflow across the core SHOULD pick up some of the heat from the core and deliver to the vents thus reducing the heater core outlet temp but that drop in temp would prolly be in the ballpark of maybe 1-2deg but then by the time that reduced temp coolant made it back into the system the radiant heat from the engine compartment will have added those 1-2deg back.
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pjw1967 (10-19-2017)
10-19-2017, 03:50 PM
#10
Super Member
i feel the same same way....and like I said, this use to work like a charm to get you a noticeable drop in temp. Just goes to show you that through changes in how systems operate what ONCE worked in a given set of circumstances may no longer provide the same result..
.....unless we are talking about Proton Packs, then the same original rule applies (someone help me out with the answer please....)
10-19-2017, 03:50 PM
#11
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That is correct. Habit from the 90’s when it worked to keep temps down on DSMs - turn the heat on full blast as soon as you’re done with the 1/4-mile.
Don’t do it as much when it’s hot out, but yeah I’ll blast the heat and point the vents out the open windows at the track sometimes. Every little bit helps.
A little OT, but the new Dodge Demon redirects the AC into the intake to cool the air (I oversimplified it but hats basically right).
Don’t do it as much when it’s hot out, but yeah I’ll blast the heat and point the vents out the open windows at the track sometimes. Every little bit helps.
A little OT, but the new Dodge Demon redirects the AC into the intake to cool the air (I oversimplified it but hats basically right).
10-19-2017, 03:53 PM
#12
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10-19-2017, 11:14 PM
#13
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Ya it has that nasty little thing called a thermostat in the system which controls the engine temp which in turn regulates the fluid temp in the heater coil. Cabin heat is controlled by dampers asjusting the the amount of air going over the core not the coolant low so in theory it should help but if one expects there to be a huge difference I suspect once the system readjusts and equilibrium is re-established not sure there is much to be gained.
10-19-2017, 11:17 PM
#14
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The short answer is .....NO, it will not.
the reason that it used to work was due to the fact that your heater control in your dash either had a choke cable or vacuum hose that physically connected to an underhood valve in the heater hose which would modulate coolant flow to the heater core depending on how far towards hot or cold you had the temp control set. Newer vehicles typically dont do this anymore. Instead of an actual valve in the coolant flow the temp is now controlled by blend doors in the hvac plenum which modulates air flow across the heater core to pick up as much or as little heat as the electronic control was requesting. with this being said, whereas the heater core USE to only have flow when heat was called for by the valve now the heater core has CONSTANT flow from the time the water pump starts spinning until you shut the vehicle down.
Now in theory, the plenum airflow across the core SHOULD pick up some of the heat from the core and deliver to the vents thus reducing the heater core outlet temp but that drop in temp would prolly be in the ballpark of maybe 1-2deg but then by the time that reduced temp coolant made it back into the system the radiant heat from the engine compartment will have added those 1-2deg back.
the reason that it used to work was due to the fact that your heater control in your dash either had a choke cable or vacuum hose that physically connected to an underhood valve in the heater hose which would modulate coolant flow to the heater core depending on how far towards hot or cold you had the temp control set. Newer vehicles typically dont do this anymore. Instead of an actual valve in the coolant flow the temp is now controlled by blend doors in the hvac plenum which modulates air flow across the heater core to pick up as much or as little heat as the electronic control was requesting. with this being said, whereas the heater core USE to only have flow when heat was called for by the valve now the heater core has CONSTANT flow from the time the water pump starts spinning until you shut the vehicle down.
Now in theory, the plenum airflow across the core SHOULD pick up some of the heat from the core and deliver to the vents thus reducing the heater core outlet temp but that drop in temp would prolly be in the ballpark of maybe 1-2deg but then by the time that reduced temp coolant made it back into the system the radiant heat from the engine compartment will have added those 1-2deg back.
To reinforce your point, Ford is no longer making HVAC control modules nor it seems is the after market so a lot of folks with 2008 versions of their F150 trucks (and I expect others as well) have no recourse when the modules fail because there are no parts unless you can find one at a wrecker. Not cool!
10-19-2017, 11:56 PM
#15
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The short answer is .....NO, it will not.
the reason that it used to work was due to the fact that your heater control in your dash either had a choke cable or vacuum hose that physically connected to an underhood valve in the heater hose which would modulate coolant flow to the heater core depending on how far towards hot or cold you had the temp control set. Newer vehicles typically dont do this anymore. Instead of an actual valve in the coolant flow the temp is now controlled by blend doors in the hvac plenum which modulates air flow across the heater core to pick up as much or as little heat as the electronic control was requesting. with this being said, whereas the heater core USE to only have flow when heat was called for by the valve now the heater core has CONSTANT flow from the time the water pump starts spinning until you shut the vehicle down.
Now in theory, the plenum airflow across the core SHOULD pick up some of the heat from the core and deliver to the vents thus reducing the heater core outlet temp but that drop in temp would prolly be in the ballpark of maybe 1-2deg but then by the time that reduced temp coolant made it back into the system the radiant heat from the engine compartment will have added those 1-2deg back.
the reason that it used to work was due to the fact that your heater control in your dash either had a choke cable or vacuum hose that physically connected to an underhood valve in the heater hose which would modulate coolant flow to the heater core depending on how far towards hot or cold you had the temp control set. Newer vehicles typically dont do this anymore. Instead of an actual valve in the coolant flow the temp is now controlled by blend doors in the hvac plenum which modulates air flow across the heater core to pick up as much or as little heat as the electronic control was requesting. with this being said, whereas the heater core USE to only have flow when heat was called for by the valve now the heater core has CONSTANT flow from the time the water pump starts spinning until you shut the vehicle down.
Now in theory, the plenum airflow across the core SHOULD pick up some of the heat from the core and deliver to the vents thus reducing the heater core outlet temp but that drop in temp would prolly be in the ballpark of maybe 1-2deg but then by the time that reduced temp coolant made it back into the system the radiant heat from the engine compartment will have added those 1-2deg back.
Yes, some of them have done away with heater control valves, but most benzes still have them, they are just electronic now.
It's easier on the a/c system to not have hot coolant in the evap box at all times, especially now as the systems get smaller and more "efficient" to save costs. Stopping the constant flow of hot coolant into the cabin unless it's needed reduces the thermal load on the a/c system and in turn, takes less energy to cool the cabin to the desired temp. Going electric on the valve also means, with the electric auxiliary coolant pumps on most new Benz cars, you can have heater functions for 30 min+ after turning the engine off, because it can still cycle the coolant around without the engines water pump running.
