Functional hood vents finally done!
#31
09-20-2012, 04:22 PM
My post from a related topic thread:
"Here are some tid bits to chew on. Food for though.
A vehicle with its hood removed will run hotter than with the hood in place.
Operating Temp of a water cooled vehicle is controlled by thermostat.
The air used to heat exchange at the radiator is drawn in from outside the underhood enclosure."
Trying to nicely say, net temp is determined by the effectiveness of the radiator coupled with the thermostat, air temp at the IN side of the radiator can impact water temp, air temp downstream does not.
"Here are some tid bits to chew on. Food for though.
A vehicle with its hood removed will run hotter than with the hood in place.
Operating Temp of a water cooled vehicle is controlled by thermostat.
The air used to heat exchange at the radiator is drawn in from outside the underhood enclosure."
Trying to nicely say, net temp is determined by the effectiveness of the radiator coupled with the thermostat, air temp at the IN side of the radiator can impact water temp, air temp downstream does not.
#32
09-21-2012, 09:59 AM
I've replaced my zmag hood vent for a Realwheels version for couple reasons:
1. Realwheels is thinner and lighter cut out of 1 piece of aluminum. The hood wouldn't stay open with the zmag version.
2. The vents are more slanted on the Realwheels version about 30 dregees so it alows less water to fall in.
3. Because the Realwheels is thinner it looks more flush with the hood.
1. Realwheels is thinner and lighter cut out of 1 piece of aluminum. The hood wouldn't stay open with the zmag version.
2. The vents are more slanted on the Realwheels version about 30 dregees so it alows less water to fall in.
3. Because the Realwheels is thinner it looks more flush with the hood.
#33
09-21-2012, 10:19 AM
If "heat" is referring to the water temp as it exits the block within the cooling system, hood vents aren't going to let that heat escape anywhere.
If the vent(s) were configured in such a way to increase air flow throw the radiator by allowing air to more freely move out of the underhood enclosure after it exits the radiator, that could theoretically improve cooling efficiency, but .......... where the air can exit and how fast changes with vehicle speed (ie. a certain vent location may work better at 30MPH than at 65MPH or vice versa). At no or very low speed (under say 10-15MPH) the fan is moving all the air, not vehicle speed, and the fan can only pull so much air regardless of vents or not. At a certain speed ??MPH, that vehicle speed begins to push air IN the radiator as fast, or faster than the fan as speed increases. The greater the velocity of the IN air, the further to the back of the hood a vent(s) would have to be located to avoid a venturi effect, which may not be a bad thing, but will not increase the IN air flow to the radiator. The bulk of air flow in through the radiator has been engineered to exit at the bottom rear of the engine compartment, not the top, so vent(s) may actually do nothing or even reduce efficiency with any turbulence created depending upon where they are located.
Way back at the start of this thread where I posted "functional for what", ........well you see what I mean. The idea may seem good, but the reality of application may lead to a different conclusion.
None of the above impacts any of the cool factor of the OP's vent, if it works for him, KUDOS!
#34
09-21-2012, 10:43 AM
While the louvers may help to reduce underhood temps, the running temp of a stock OEM engine won't be effected much from lower underhood temps unless you are running it for extended periods standing completely still.
Keep in mind, the fan itself drawing high volumes of air through the radiator via the shroud will force hot out of the engine bay regardless whether or not you give it a small opening up top. It is not a closed box. The entire bottom half of the engine bay is open. Heat is constantly forced out by the air movement of the fan regardless of whether it is forced out up or down.
In addition, when the vehicle is moving at virtually any speed at all, the vaccum effect of cool air passing under the vehicle will also draw hot air out of the engine bay.
#35
09-21-2012, 11:34 AM
Ok I wrote a huge reply then crashed my comp, I agree with a lot of that but my comments were, in short:
Everything is theoretical, I'll give you that. But the heat problems are to be more prevalent at idle. Therefore, for a minute, lets skip over the highway driving issue. With our 3's skidplated up the air actually has to go down and around. from a process prospective less downstream resistance = more flow, more flow=better cooling. So your theory is it won't help, mine is it can't hurt.
Water in the engine bay? I guess be careful? There are thousands of models that came or come stock with scoops, louvers or cowls, are they all taking unnecessary risks?
Highway driving - less fan drag is more horsepower, better mileage and cooler temps. also louvers opening the dam that is the engine compartment also is better performance and mileage and the air over the windshield is more downforce on the front tires ie ZL1. Many performance vehicles that spent time in a wind tunnel and on the nurburgring during development have louvers, cowls etc, for this reason.
OP said his new louvers are at a tighter angle and I think that is the way to go. Get the air out without increasing hood drag. Awesome.
Everything is theoretical, I'll give you that. But the heat problems are to be more prevalent at idle. Therefore, for a minute, lets skip over the highway driving issue. With our 3's skidplated up the air actually has to go down and around. from a process prospective less downstream resistance = more flow, more flow=better cooling. So your theory is it won't help, mine is it can't hurt.
Water in the engine bay? I guess be careful? There are thousands of models that came or come stock with scoops, louvers or cowls, are they all taking unnecessary risks?
Highway driving - less fan drag is more horsepower, better mileage and cooler temps. also louvers opening the dam that is the engine compartment also is better performance and mileage and the air over the windshield is more downforce on the front tires ie ZL1. Many performance vehicles that spent time in a wind tunnel and on the nurburgring during development have louvers, cowls etc, for this reason.
OP said his new louvers are at a tighter angle and I think that is the way to go. Get the air out without increasing hood drag. Awesome.
#37
09-21-2012, 02:25 PM
Ok I wrote a huge reply then crashed my comp, I agree with a lot of that but my comments were, in short:
Everything is theoretical, I'll give you that. But the heat problems are to be more prevalent at idle. Therefore, for a minute, lets skip over the highway driving issue. With our 3's skidplated up the air actually has to go down and around. from a process prospective less downstream resistance = more flow, more flow=better cooling. So your theory is it won't help, mine is it can't hurt.
Water in the engine bay? I guess be careful? There are thousands of models that came or come stock with scoops, louvers or cowls, are they all taking unnecessary risks?
Highway driving - less fan drag is more horsepower, better mileage and cooler temps. also louvers opening the dam that is the engine compartment also is better performance and mileage and the air over the windshield is more downforce on the front tires ie ZL1. Many performance vehicles that spent time in a wind tunnel and on the nurburgring during development have louvers, cowls etc, for this reason.
OP said his new louvers are at a tighter angle and I think that is the way to go. Get the air out without increasing hood drag. Awesome.
Everything is theoretical, I'll give you that. But the heat problems are to be more prevalent at idle. Therefore, for a minute, lets skip over the highway driving issue. With our 3's skidplated up the air actually has to go down and around. from a process prospective less downstream resistance = more flow, more flow=better cooling. So your theory is it won't help, mine is it can't hurt.
Water in the engine bay? I guess be careful? There are thousands of models that came or come stock with scoops, louvers or cowls, are they all taking unnecessary risks?
Highway driving - less fan drag is more horsepower, better mileage and cooler temps. also louvers opening the dam that is the engine compartment also is better performance and mileage and the air over the windshield is more downforce on the front tires ie ZL1. Many performance vehicles that spent time in a wind tunnel and on the nurburgring during development have louvers, cowls etc, for this reason.
OP said his new louvers are at a tighter angle and I think that is the way to go. Get the air out without increasing hood drag. Awesome.
When at idle or very low speed (rock crawling) your fan pulls the IN air through the radiator, that volume and velocity is fixed by the fan capacity, vents or no vents. Therefore the IN radiator air volume and velocity will not be increased by vents in the hood when at idle. The only way to raise or lower the coolant temp is to raise or lower the air temp and/or volume going IN to the radiator. Letting out hot air behind it, wherever it exits, in and of itself, would have zero impact on coolant temp.
#38
09-21-2012, 02:28 PM
What Doc is trying to convey is that the temp of the engine bay is not a primary controlling factor in the operating temp of a water cooled engine. It is cooled by the coolant itself which is managed by outside air.
While the louvers may help to reduce underhood temps, the running temp of a stock OEM engine won't be effected much from lower underhood temps unless you are running it for extended periods standing completely still.
Keep in mind, the fan itself drawing high volumes of air through the radiator via the shroud will force hot out of the engine bay regardless whether or not you give it a small opening up top. It is not a closed box. The entire bottom half of the engine bay is open. Heat is constantly forced out by the air movement of the fan regardless of whether it is forced out up or down.
In addition, when the vehicle is moving at virtually any speed at all, the vaccum effect of cool air passing under the vehicle will also draw hot air out of the engine bay.
While the louvers may help to reduce underhood temps, the running temp of a stock OEM engine won't be effected much from lower underhood temps unless you are running it for extended periods standing completely still.
Keep in mind, the fan itself drawing high volumes of air through the radiator via the shroud will force hot out of the engine bay regardless whether or not you give it a small opening up top. It is not a closed box. The entire bottom half of the engine bay is open. Heat is constantly forced out by the air movement of the fan regardless of whether it is forced out up or down.
In addition, when the vehicle is moving at virtually any speed at all, the vaccum effect of cool air passing under the vehicle will also draw hot air out of the engine bay.
Good stuff too!
#40
09-21-2012, 02:38 PM
Yes, but this is a Hummer forum, and the H3 is not about aerodynamics and those 1000s of models you speak of.
When at idle or very low speed (rock crawling) your fan pulls the IN air through the radiator, that volume and velocity is fixed by the fan capacity, vents or no vents. Therefore the IN radiator air volume and velocity will not be increased by vents in the hood when at idle. The only way to raise or lower the coolant temp is to raise or lower the air temp and/or volume going IN to the radiator. Letting out hot air behind it, wherever it exits, in and of itself, would have zero impact on coolant temp.
When at idle or very low speed (rock crawling) your fan pulls the IN air through the radiator, that volume and velocity is fixed by the fan capacity, vents or no vents. Therefore the IN radiator air volume and velocity will not be increased by vents in the hood when at idle. The only way to raise or lower the coolant temp is to raise or lower the air temp and/or volume going IN to the radiator. Letting out hot air behind it, wherever it exits, in and of itself, would have zero impact on coolant temp.