Heat soak - vented hood options that are not "louvered"

Chuck33079 · 11-10-2013, 04:57 PM

Quote:

Originally Posted by dmhenderson

Zspeed nismo undershroud would probably do that - it's vented but I'd be sacrificing downforce.

It makes no noticeable difference in temps. The vent is under the oil pan. You could cut a vent further up.

synolimit · 11-10-2013, 05:01 PM

Quote:

Originally Posted by Chuck33079

The fender vents aren't going to address the main issue, which is getting the hot air passing out of the intercooler/radiator out of the engine bay. The only thing the fender vent does is give the air exiting your oil cooler a place to go.

The scoop may also make things worse. If you're pressurizing the engine bay through the scoop, you may stall the air coming through the radiator.

Correct.

Wait the fender thing is the vents installed in front of the tires? Then a modded fender in the back? Yeah that's going to do nothing for engine bay heat even with a hood vent/scoop.

Chuck33079 · 11-10-2013, 05:04 PM

The scoop is pretty much a non-starter. The potential for messing up airflow is too high without a ton of research. OEMs that use scoops have wind tunnels to use. Since we don't, were stuck with vents. Even if the vent isn't 100% dead on in the right place, it will still make a positive difference as long as its placed as far forward as you can get it.

synolimit · 11-10-2013, 05:07 PM

Quote:

Originally Posted by Chuck33079

The gentler the change of direction, the better the flow.

True. But like you said, it's really all we have to work with, with the little room we have. I haven't done scientific testing but the yarn seems to flow how I want and I haven't been able to exceed 218 degrees on the oil with hard driving for like an hour straight on fast twisty country roads in the middle of summer . Next summer when the tracks open we'll see whats what. But I'm hoping Mitsubishi and Chevy did the work for us and hell the evo doesn't have much room either...

synolimit · 11-10-2013, 05:11 PM

Quote:

Originally Posted by Chuck33079

The scoop is pretty much a non-starter. The potential for messing up airflow is too high without a ton of research. OEMs that use scoops have wind tunnels to use. Since we don't, were stuck with vents. Even if the vent isn't 100% dead on in the right place, it will still make a positive difference as long as its placed as far forward as you can get it.

That and when stopped the heat pours out like a volcano!!! Its insane how fast and how much comes out. So in traffic you'll be much cooler.

Chuck33079 · 11-10-2013, 05:12 PM

My guess would be a vent in front of the motor and upgraded radiator and fans are going to be about all you can do.

dmhenderson · 11-10-2013, 05:48 PM

I think I'd go look for bigger radiator fans before I try to upgrade the radiator itself. Space comes at a premium under there these days.

Chuck33079 · 11-10-2013, 05:51 PM

I did the radiator, and before next summer ill swap out the fans. At least in TX it seems like you need to do both. If that's not enough its time to start cutting into the hood.

ANMVQ · 11-10-2013, 05:54 PM

I know my hood displaces a ton of heat during the summer.

dmhenderson · 11-10-2013, 05:56 PM

I'm sure they do but I don't like those louvered vents on the Z.

dmhenderson · 11-10-2013, 05:57 PM

Never fails that when I start one of these threads, I end up with more questions than I had when I started.

Alstann · 11-10-2013, 06:09 PM

My 2c here:

I think that hood venting is the way to go for serious heat soak issues. It's a uphill battle trying to fight the motor by adding a larger radiator and higher CFM fan if the air is still getting trapped in the engine bay. I'd say that if you can live with the look of a louvered or vented hood, it's easily the best way to improve cooling efficiency of the car.

From a theoretical and practical standpoint, there are limits to using a combination of radiator and fan to cool a motor. One is the size aspect - larger radiator and larger fan is less space in the bay, and there is a limit to how large we can fit of both. Also, CFM doesn't necessarily mean cooler temps.

At my university, we build a small Formula-style car a competition hosted by SAE, called Formula SAE, and I'm part of the engine design team. It's a competition where universities build the car from the ground up - chassis, intake, exhaust, suspension, etc. For reference, the engine we use is a GSX-R 600cc. Google has lots of pictures of different cars - you'll get the idea if you search it. ^^

Something quite astounding that I've discovered while doing design on the cooling system is that the car (moving at an average of 30-45 mph on the track) is actually moving too FAST through the air, for achieving maximum cooling efficiency across the radiator. The solution to this problem is to design a sidepod (like the ones you see in Formula 1) that goes from small to big, back to small. This is to slow down the air. Of course, our motor is directly to the atmosphere, mounted in the rear.

The reason for this efficiency loss is as the air moves too quickly through the radiator, it builds up pressure behind and in front of the radiator, creating a boundary layer that lowers the true amount of air moving through the radiator. One might say: Why not use a higher flow fan to create a vacuum and move the air better? There are two reasons on a car: the first being that you want the air to spend a certain amount of time "inside" the radiator (not too slow where it's stopped, and not too fast that it creates the boundary layer), and second being that in most car engine bays, the bay is sealed enough that pressure builds up regardless. These speed values are different for every car, radiator design, hood design, grille design, etc.

But, of course I concede that a larger radiator and higher CFM fan usually increases cooling efficiency. I just know for a fact that venting the engine bay will, unless you are on the surface of the sun, always increase the cooling efficiency by letting nature do its work by letting heat escape. Also, with a larger radiator and larger fan, you also add weight to the car, and you change the dynamic of the water flow through the radiator, since the water pump is still stock. The reason we shoot for maximum efficiency, while still maintaining a reasonable safety factor, is literally, because racecar.

Any amount of extra weight that isn't necessary in design, is making the car slower.

Also another thing to think about is that turbulent air and turbulent water through the radiator actually increases cooling efficiency.

Chuck33079 · 11-10-2013, 06:34 PM

Quote:

Originally Posted by Alstann

My 2c here:

I think that hood venting is the way to go for serious heat soak issues. It's a uphill battle trying to fight the motor by adding a larger radiator and higher CFM fan if the air is still getting trapped in the engine bay. I'd say that if you can live with the look of a louvered or vented hood, it's easily the best way to improve cooling efficiency of the car.

From a theoretical and practical standpoint, there are limits to using a combination of radiator and fan to cool a motor. One is the size aspect - larger radiator and larger fan is less space in the bay, and there is a limit to how large we can fit of both. Also, CFM doesn't necessarily mean cooler temps.

At my university, we build a small Formula-style car a competition hosted by SAE, called Formula SAE, and I'm part of the engine design team. It's a competition where universities build the car from the ground up - chassis, intake, exhaust, suspension, etc. For reference, the engine we use is a GSX-R 600cc. Google has lots of pictures of different cars - you'll get the idea if you search it. ^^

Something quite astounding that I've discovered while doing design on the cooling system is that the car (moving at an average of 30-45 mph on the track) is actually moving too FAST through the air, for achieving maximum cooling efficiency across the radiator. The solution to this problem is to design a sidepod (like the ones you see in Formula 1) that goes from small to big, back to small. This is to slow down the air. Of course, our motor is directly to the atmosphere, mounted in the rear.

The reason for this efficiency loss is as the air moves too quickly through the radiator, it builds up pressure behind and in front of the radiator, creating a boundary layer that lowers the true amount of air moving through the radiator. One might say: Why not use a higher flow fan to create a vacuum and move the air better? There are two reasons on a car: the first being that you want the air to spend a certain amount of time "inside" the radiator (not too slow where it's stopped, and not too fast that it creates the boundary layer), and second being that in most car engine bays, the bay is sealed enough that pressure builds up regardless. These speed values are different for every car, radiator design, hood design, grille design, etc.

But, of course I concede that a larger radiator and higher CFM fan usually increases cooling efficiency. I just know for a fact that venting the engine bay will, unless you are on the surface of the sun, always increase the cooling efficiency by letting nature do its work by letting heat escape. Also, with a larger radiator and larger fan, you also add weight to the car, and you change the dynamic of the water flow through the radiator, since the water pump is still stock. The reason we shoot for maximum efficiency, while still maintaining a reasonable safety factor, is literally, because racecar.

Any amount of extra weight that isn't necessary in design, is making the car slower.

Also another thing to think about is that turbulent air and turbulent water through the radiator actually increases cooling efficiency.

You're failing to factor in the intercooler into that. With the additional flow restriction from the intercooler, not to mention the fact that now you're feeding hot air to the radiator, a larger radiator and a more powerful fan may just be getting you back stock efficiency.

Jayhovah · 11-10-2013, 06:53 PM

Do those fancy vented fenders I see all over the body/exterior section help at all?

Chuck33079 · 11-10-2013, 06:54 PM

Not one bit for underhood temps.

11-10-2013, 05:04 PM	#33 (permalink)
Chuck33079 A True Z Fanatic Join Date: Nov 2011 Location: Houston Posts: 12,265 Drives: 2011 370ztt Rep Power: 29538	The scoop is pretty much a non-starter. The potential for messing up airflow is too high without a ton of research. OEMs that use scoops have wind tunnels to use. Since we don't, were stuck with vents. Even if the vent isn't 100% dead on in the right place, it will still make a positive difference as long as its placed as far forward as you can get it. __________________ 2011 MB Touring-Sport-6sp-Nav/GTM TT/FI TT TDX/JTran/Kosmic/Eibach/Hotchkis/SPC/CSF/RPS/SoThatsWhereAllMyMoneyWent

11-10-2013, 05:12 PM	#36 (permalink)
Chuck33079 A True Z Fanatic Join Date: Nov 2011 Location: Houston Posts: 12,265 Drives: 2011 370ztt Rep Power: 29538	My guess would be a vent in front of the motor and upgraded radiator and fans are going to be about all you can do. __________________ 2011 MB Touring-Sport-6sp-Nav/GTM TT/FI TT TDX/JTran/Kosmic/Eibach/Hotchkis/SPC/CSF/RPS/SoThatsWhereAllMyMoneyWent

11-10-2013, 05:48 PM	#37 (permalink)
dmhenderson A True Z Fanatic Join Date: Feb 2011 Location: Maryland Posts: 5,930 Drives: AWD TT 370z Rep Power: 26	I think I'd go look for bigger radiator fans before I try to upgrade the radiator itself. Space comes at a premium under there these days. __________________

11-10-2013, 05:51 PM	#38 (permalink)
Chuck33079 A True Z Fanatic Join Date: Nov 2011 Location: Houston Posts: 12,265 Drives: 2011 370ztt Rep Power: 29538	I did the radiator, and before next summer ill swap out the fans. At least in TX it seems like you need to do both. If that's not enough its time to start cutting into the hood. __________________ 2011 MB Touring-Sport-6sp-Nav/GTM TT/FI TT TDX/JTran/Kosmic/Eibach/Hotchkis/SPC/CSF/RPS/SoThatsWhereAllMyMoneyWent

11-10-2013, 05:56 PM	#40 (permalink)
dmhenderson A True Z Fanatic Join Date: Feb 2011 Location: Maryland Posts: 5,930 Drives: AWD TT 370z Rep Power: 26	I'm sure they do but I don't like those louvered vents on the Z. __________________

11-10-2013, 05:57 PM	#41 (permalink)
dmhenderson A True Z Fanatic Join Date: Feb 2011 Location: Maryland Posts: 5,930 Drives: AWD TT 370z Rep Power: 26	Never fails that when I start one of these threads, I end up with more questions than I had when I started. SouthArk370Z and luigi90210 like this. __________________

11-10-2013, 06:09 PM	#42 (permalink)
Alstann Track Member Join Date: Oct 2011 Location: South Florida Posts: 882 Drives: 12 PW 370z 6MT Sport Rep Power: 14	My 2c here: I think that hood venting is the way to go for serious heat soak issues. It's a uphill battle trying to fight the motor by adding a larger radiator and higher CFM fan if the air is still getting trapped in the engine bay. I'd say that if you can live with the look of a louvered or vented hood, it's easily the best way to improve cooling efficiency of the car. From a theoretical and practical standpoint, there are limits to using a combination of radiator and fan to cool a motor. One is the size aspect - larger radiator and larger fan is less space in the bay, and there is a limit to how large we can fit of both. Also, CFM doesn't necessarily mean cooler temps. At my university, we build a small Formula-style car a competition hosted by SAE, called Formula SAE, and I'm part of the engine design team. It's a competition where universities build the car from the ground up - chassis, intake, exhaust, suspension, etc. For reference, the engine we use is a GSX-R 600cc. Google has lots of pictures of different cars - you'll get the idea if you search it. ^^ Something quite astounding that I've discovered while doing design on the cooling system is that the car (moving at an average of 30-45 mph on the track) is actually moving too FAST through the air, for achieving maximum cooling efficiency across the radiator. The solution to this problem is to design a sidepod (like the ones you see in Formula 1) that goes from small to big, back to small. This is to slow down the air. Of course, our motor is directly to the atmosphere, mounted in the rear. The reason for this efficiency loss is as the air moves too quickly through the radiator, it builds up pressure behind and in front of the radiator, creating a boundary layer that lowers the true amount of air moving through the radiator. One might say: Why not use a higher flow fan to create a vacuum and move the air better? There are two reasons on a car: the first being that you want the air to spend a certain amount of time "inside" the radiator (not too slow where it's stopped, and not too fast that it creates the boundary layer), and second being that in most car engine bays, the bay is sealed enough that pressure builds up regardless. These speed values are different for every car, radiator design, hood design, grille design, etc. But, of course I concede that a larger radiator and higher CFM fan usually increases cooling efficiency. I just know for a fact that venting the engine bay will, unless you are on the surface of the sun, always increase the cooling efficiency by letting nature do its work by letting heat escape. Also, with a larger radiator and larger fan, you also add weight to the car, and you change the dynamic of the water flow through the radiator, since the water pump is still stock. The reason we shoot for maximum efficiency, while still maintaining a reasonable safety factor, is literally, because racecar. Any amount of extra weight that isn't necessary in design, is making the car slower. Also another thing to think about is that turbulent air and turbulent water through the radiator actually increases cooling efficiency. __________________ 2012 Pearl White 370Z GReddy Twin Turbo Last edited by Alstann; 11-10-2013 at 06:13 PM.

11-10-2013, 06:53 PM	#44 (permalink)
Jayhovah Premium Member Join Date: May 2013 Location: St. Pete, FL Posts: 3,848 Drives: 520whp Fire Breather Rep Power: 86950	Do those fancy vented fenders I see all over the body/exterior section help at all?

11-10-2013, 06:54 PM	#45 (permalink)
Chuck33079 A True Z Fanatic Join Date: Nov 2011 Location: Houston Posts: 12,265 Drives: 2011 370ztt Rep Power: 29538	Not one bit for underhood temps. __________________ 2011 MB Touring-Sport-6sp-Nav/GTM TT/FI TT TDX/JTran/Kosmic/Eibach/Hotchkis/SPC/CSF/RPS/SoThatsWhereAllMyMoneyWent

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