What is the best material to make a heat shield out of?
09-04-06, 01:32 PM
#1
What is the best material to make a heat shield out of?
I want to fab a heat shield between headers and intake manifold.
Also want to add heat shield under car between exhaust pipes and floor.
Is aluminum really a good heat shield since it radiates heat so much? Would it not just absorb heat from exhaust pipe and radiate that heat upward towards intake and floor?
Also want to add heat shield under car between exhaust pipes and floor.
Is aluminum really a good heat shield since it radiates heat so much? Would it not just absorb heat from exhaust pipe and radiate that heat upward towards intake and floor?
09-04-06, 03:18 PM
#2
Aluminum is probably the best low cost stuff. Its light weight and easy to work with. It dissipates heat well so any air going by will cool it down. Remember heat transfers three ways; conduction, convection and radiation. Aluminum controls the convection and radiation part well and if you are careful how you attach it the conduction element can be minimized.
You can go even further and add that heat resistant fabric to it. I want to say its still asbestos but I'm not sure.
You can go even further and add that heat resistant fabric to it. I want to say its still asbestos but I'm not sure.
09-05-06, 12:27 PM
#4
your cheapest bet would be what I use, and it works quite well. A sheet of aluminum with card board taped to it with homodepot foil tape around it. The foil reflects the heat and the cardboard acts as an insolater while the aluminum is the last ditched attempt to stop the heat. I guess as an exhaust heat shield you'd want something to reflect the heat rather than radiate it. Gold is the best, but I guess a highly polished steel would be a close second.
09-05-06, 04:21 PM
#6
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"Is aluminum really a good heat shield since it radiates heat so much? Would it not just absorb heat from exhaust pipe and radiate that heat upward towards intake and floor?"
Heat transfer by radiation is proportional to the Temp of the source raised to the 4th power, minus the temp of the receiver raised to the 4th power. This is not a linear function; it is a very steep exponential function.
Lets assume you have exhaust pipes at 1600 F = 2040 Rankine
assume heat shield is 400 deg F = 860 deg Rankine
assume intake manifold is 120 deg F = 580 deg Rankine
Exhaust to the 4th is 17,310,000,000,000
heat shield to the 4th is 547,000,000,000
Intake manf to the 4th is 113,000,000,000
Okay now, the radiant heat transfer is proportional to the differences of those 4th powers.
Difference between header and heat shield is 16763000000000.
The difference between heat shield and intake is 434000000000.
Sooo the radiant heat transfer from the header to the heat shield is 39 times more than the radiant heat transfer from the heat shield to the intake manifold (this is neglecting surface area and surface finish.)
This is why heat shields are so important - they re-radiate out much less heat than they take in. The heat they do absorb is transferred via convection into the air flow passing by.
Heat transfer by radiation is proportional to the Temp of the source raised to the 4th power, minus the temp of the receiver raised to the 4th power. This is not a linear function; it is a very steep exponential function.
Lets assume you have exhaust pipes at 1600 F = 2040 Rankine
assume heat shield is 400 deg F = 860 deg Rankine
assume intake manifold is 120 deg F = 580 deg Rankine
Exhaust to the 4th is 17,310,000,000,000
heat shield to the 4th is 547,000,000,000
Intake manf to the 4th is 113,000,000,000
Okay now, the radiant heat transfer is proportional to the differences of those 4th powers.
Difference between header and heat shield is 16763000000000.
The difference between heat shield and intake is 434000000000.
Sooo the radiant heat transfer from the header to the heat shield is 39 times more than the radiant heat transfer from the heat shield to the intake manifold (this is neglecting surface area and surface finish.)
This is why heat shields are so important - they re-radiate out much less heat than they take in. The heat they do absorb is transferred via convection into the air flow passing by.
Last edited by speedturn; 09-05-06 at 04:26 PM.
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09-07-06, 01:45 PM
#9
speedturn,
First off, thanks for the informative post. From reading that, it seems it would be best to use two layers of thin material as opposed to one layer of thicker material, is that correct? I'm thinking of shielding the exhaust pipe and shielding the object that you want to keep cool (intake manifold, starter, wires, A/C lines or whatever).
-s-
First off, thanks for the informative post. From reading that, it seems it would be best to use two layers of thin material as opposed to one layer of thicker material, is that correct? I'm thinking of shielding the exhaust pipe and shielding the object that you want to keep cool (intake manifold, starter, wires, A/C lines or whatever).
-s-
Last edited by scotty305; 09-07-06 at 01:49 PM.
09-07-06, 03:50 PM
#10
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Drivefast7: 1/8" thick mild steel is kind of heavy for a race car that should be on a diet.
Scotty, yes 2 layers with an air gap in between is better than one layer. What you use will all depend on ease of fabrication, weight, complexity, etc.
Scotty, yes 2 layers with an air gap in between is better than one layer. What you use will all depend on ease of fabrication, weight, complexity, etc.
09-07-06, 06:21 PM
#11
When you have the choice stainless steel works extremely well, it is strong enough that it wont fatigue crack and is a bit less conductive than steel, aluminum will usually crack at the mounts, a layer of heat resistant fabric (like exhaust wrap but in sheet form) also can help, a simple single layer shield alone will make a huge difference over none at all, stainless wont rust up either, this is what the trans am winning race shop recommended on one of my rides to protect the master cylinders from the headers
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09-07-06, 10:55 PM
#14
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okok what about taking soda cans and cutting them up into strips.
Then you could jb them together for high temp stuff or to a piece of thick cardboard for intake type stuff.
Then you could jb them together for high temp stuff or to a piece of thick cardboard for intake type stuff.
09-09-06, 01:34 AM
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what's your budget?
Realisticaly, the items you ae talking about really do not need 'shieldiing". Carbon fiber, gold and copper-- yeah right! Air is a good insultor.
For radiant heat- it does not take much- you need something light colored or shiny to reflect the heat.. Sheetmetal and tin are the most easy, and cheapest to work with. Look in the roofing section of home depot and buy the rolls of roofing tin to form your heatshield. As long as there is airspace between the heat source and the shield, this will work well. The shinier the better. For real heat resistance, put a layer of fiberglass (siliconized) fabric, or sheeting on top of the sheetmetal too, which will insulate it further.. Cheap and easy.
This is what i use on my headers.
Realisticaly, the items you ae talking about really do not need 'shieldiing". Carbon fiber, gold and copper-- yeah right! Air is a good insultor.
For radiant heat- it does not take much- you need something light colored or shiny to reflect the heat.. Sheetmetal and tin are the most easy, and cheapest to work with. Look in the roofing section of home depot and buy the rolls of roofing tin to form your heatshield. As long as there is airspace between the heat source and the shield, this will work well. The shinier the better. For real heat resistance, put a layer of fiberglass (siliconized) fabric, or sheeting on top of the sheetmetal too, which will insulate it further.. Cheap and easy.
This is what i use on my headers.
09-10-06, 07:39 PM
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Its called fiberglass fabric, a generic term for siliconized woven fabric. Usually will tolerate up to 1000F, will not burn. Same material as used on header wrap, welding balnkets. Fairly inexpensive, compared to other heat shielding material. Alone or lining the roofers tin, will provide shielding.
Buy it from McMaster Carr, or other sources. (Don't buy the stuff from an auto supply - will rip you off on price/yard).
Buy it from McMaster Carr, or other sources. (Don't buy the stuff from an auto supply - will rip you off on price/yard).
Originally Posted by DriveFast7
a roll of roofing tin. who woulda thought.
+ fiberglass it too? can the resin take the heat? it's flammible.
+ fiberglass it too? can the resin take the heat? it's flammible.
02-09-17, 07:24 AM
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No!!!
I want to fab a heat shield between headers and intake manifold.
Also want to add heat shield under car between exhaust pipes and floor.
Is aluminum really a good heat shield since it radiates heat so much? Would it not just absorb heat from exhaust pipe and radiate that heat upward towards intake and floor?
Also want to add heat shield under car between exhaust pipes and floor.
Is aluminum really a good heat shield since it radiates heat so much? Would it not just absorb heat from exhaust pipe and radiate that heat upward towards intake and floor?
02-10-17, 07:02 AM
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Any sheet metal should work. From HVAC duct work to old signs or scrape aluminium/steel. Make a template from cardboard and cut 2 metal signs up.
Bolt them together with a 1/4-1/2 inch airgap using washers/nuts.
Now bolt this between your Intake and Exhaust manifold. This will significantly drop your intake temps and should cost you nothing if you have some scrap metal and bolts in your garage.
If your bottom plate melts/burns out, you upgrade to a thicker steel/SS plate.
Our lemons FB ran aluminum sheet metal, the single plate melted at spots so we added another one with a small gap. Best mod ever!
Bolt them together with a 1/4-1/2 inch airgap using washers/nuts.
Now bolt this between your Intake and Exhaust manifold. This will significantly drop your intake temps and should cost you nothing if you have some scrap metal and bolts in your garage.
If your bottom plate melts/burns out, you upgrade to a thicker steel/SS plate.
Our lemons FB ran aluminum sheet metal, the single plate melted at spots so we added another one with a small gap. Best mod ever!
02-13-17, 10:47 AM
#24
Inconel would be the best solution but it can get pretty pricey. Stainless is nice but I have also seen old license plates perform the job as well...
TurboSource Inconel Heatshield Sheet
TurboSource Inconel Heatshield Sheet
02-13-17, 05:47 PM
#25
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