TheSamba.com :: View topic - Heater box paint color

Wed Mar 24, 2010 7:53 pm

Here's another blurb from a veteran VW mechanic..even he misses the key point about the decklid being closed, so the engine is in the dark anyway:

"The truth is, with regard to any part of your engine not in contact with hot oil, you may paint it . . . or chrome it . . . any color you wish. In the case of your shrouding, tin-ware and blower housing, the finish . . . paint, chrome or what-have-you . . . is there only to protect the metal. These metal parts are not a factor in the transfer of heat via radiation. The metal is there to contain the envelope of cooling air. I realize the metal will get hot through both conduction and radiation absorption but the quantity of that heat is minuscule when compared to that being radiated by those parts of the engine in contact with the oil. Indeed, this perception of heat is subjective. When the engine is running and the car is moving, the shrouding and tin-ware is usually only slightly warmer than the ambient air temperature. It is only when the vehicle is brought to a halt and the engine shut off that any significant quantity of heat can be absorbed by the tin-ware. The subjective part is the fact that you can not put your hand on the tin-ware when roaring down the highway at sixty mph... but you can when the vehicle has stopped... by which time the tin-ware feels hot to the touch. And Conventional Wisdom wins again."

Fri Mar 26, 2010 10:15 am

Quote:
1. When the deck lid is closed, the engine is in the "shade", so no colored light is being absorbed or reflected, therefore, there is, in effect, no color. Paint it green or blue or red or white and it doesn't matter. That's why so many custom Beetles have painted shrouds and run just fine for years. Now if you have an open engine bay, like a baja bug, THEN you might get some heating of the tin as it would be exposed to sunlight.

I agree with you about the heat absorption, but disagree that it's only related to sunlight. The questions is does flat black dissipate heat faster than other colors? You already agreed the answer is "Yes". (with your valve cover example). So if this is the case even engine tin, that direct air can benefit from the same principle. If the black engine tin dissipate heat to the air moving though the engine(or cooling fan)then that's more heat not inside the compartment. Less heat in the compartment means cooler incoming air get's heated less before hit has to cool the engine.
Quote: 2. Several ACVW variations had brown, green, yellow or camouflage paint (WWII) on the shroud and tin...in the heat of North Africa, no less, and they were noted for their durability, when other vehicles over-heated.
Sure sometimes it might be better to not get shot at than run the car cooler. During the war although fuel was in short supply, you will drove big tanks to the front lines. Can't really make a solid argument here.
Quote:
3. I've had colored shroud/tin in the past, including red and orange set-ups (hey, it was the '80's Wink ) and the temp gauges never read any differently. Those engines racked up a pile of mileage, too .
Sure who didn't. Hey I remember wearing patches on jeans and luminous green shoe laces.

Quote: 4. Regarding the video, what specific parts were chromed? If so, do we know if it was actually the "chrome" causing the problem, or the crappy aftermarket shroud design. At one time, you could get quality OEM-style chrome shrouds and they worked just fine...now you have Made in China crap.

It's possible that it was crappy tin that didn't do a good job cooling. I guess we would never know unless we test two side by side one OEM in black another OEM in chrome.

Quote: The above comments only refer to the fan shroud and cylinder tins, as valve covers are a different matter...
See first explanation.
_________________

Fri Mar 26, 2010 10:40 am

neil68 wrote: Beetle tin was painted black by VW because it was inexpensive and would contrast nicely with any body colour. When your decklid is closed there is no visible light reflection/absorption, so in the shade there really is no colour to affect temps...which it wouldn't for cooling tin anyway, since the purpose of tin is to direct the air, as pointed out above.

It's possible that exposed valve covers (eg. baja bug) might affect temps somewhat...

The thought is correct but the technical is wrong. Just for the record, black surfaces got hotter with any light striking them because black absorbs most visible light.....black surfaces also absorb infrared light. Even in pitch blackness.....any black non-reflective surface will absorb more heat. The vast majority of heat is infrared and is invisible.

Painting the heater boxes black will allow higher absorption of radiant infrared heat from the inside where the hot pipe is.....
But as zero posted....its really a negligable issue in teh case of teh heater box.
A large volume of high speed air moving through them pretty much insures that the extra heat volume the coloring might give.....is negligable. Ray

Fri Mar 26, 2010 10:57 am

neil68 wrote: Here's another blurb from a veteran VW mechanic..even he misses the key point about the decklid being closed, so the engine is in the dark anyway:

"The truth is, with regard to any part of your engine not in contact with hot oil, you may paint it . . . or chrome it . . . any color you wish. In the case of your shrouding, tin-ware and blower housing, the finish . . . paint, chrome or what-have-you . . . is there only to protect the metal. These metal parts are not a factor in the transfer of heat via radiation. The metal is there to contain the envelope of cooling air. I realize the metal will get hot through both conduction and radiation absorption but the quantity of that heat is minuscule when compared to that being radiated by those parts of the engine in contact with the oil. Indeed, this perception of heat is subjective. When the engine is running and the car is moving, the shrouding and tin-ware is usually only slightly warmer than the ambient air temperature. It is only when the vehicle is brought to a halt and the engine shut off that any significant quantity of heat can be absorbed by the tin-ware. The subjective part is the fact that you can not put your hand on the tin-ware when roaring down the highway at sixty mph... but you can when the vehicle has stopped... by which time the tin-ware feels hot to the touch. And Conventional Wisdom wins again."

All of that is 100% incorrect. I work with color and radiant heat for a living.

By definition...black is not a color. It is the total abscence of color. White light as the use of a prism will show you....is made up of every color and wavelength of light.....including invisble UV and infrared (heat) spectrums.
And any surface that APPEARS white to you eye....does so because it is able to reflect all of the colors of that white spectrum back to your eye.

Black....is black because it can reflect few if any of the colors of the entire spectrum. This also still...includes both heat energy (infrared light) and UV energy (high speed/high energy invisible spectrum above 280nm).

A gloss surface reflects enough spectral light AWAY from a surface to make a difference of up to 40% of the amount of light and heat energy absorbed.
Try these yourself kiddies:

Four identical pieces of 1/16" x 4" x 4" sheet metal. One painted flat white, one painted flat black, one painted gloss black, one painted gloss white.
Lay them out on a piece of ...whatever....in the sun. Using a non-contact laser thermoprobe...or a K-type thermocouple attached to your VOM you will generally find this level of variation.

(1) Gloss white will be the coolest. On a summer day with ambient of about 90*F, the gloss white part will be about 110F
(2) Flat white: same consitions and about 125-130F
(3)Gloss black: about 150F
(4) Flat black: about 165+F.

Check the same set around midnight with ambient about 80*

The white pieces both gloss and matt will both be right about ambient air temp. Both black pieces will usually be about 3-5 degress above ambient because they are absorbing infrared light radiating out of the surroundings.

Black surfaces that do not reflect (black matt) are also capable of absorbing radiant, convected, and reflected light. light is energy...all wavelengths. Heat is energy. All heat is light in the infrared wavelength...period.

Chrome is stupid for engines. Chrome reflects heat whether it is polished or not. The invisible side of chrome...the part that is against the metal it is plated to...also reflects heat. It does this because of the chrystalline structure it is comprised of . Even zinc and other crystallines reflect some heat.

Perception of heat is not subjective. Do the experiemnt I listed above. I have...many times and in many formats. The problem is that heat from say....a hot exhaust pipe...you might want to dissipate via air swirling around it when you drive.
Much of it will.....but higher energy infrared heat....RADIANT HEAT...is not subject to wind or air. In fact...radiant heat...and all light energy for that matter... readily travels across vacuum. How do you think sunlight gets here and is still hot after going through the cold vacuum of space. :roll: .
If radiant heat ....plays upon a dark matt surface that is too close to somewhere you do not want excessive heat.....that surface heats up and re-radiates that heat...some of which may be straight through the metal by conduction....into an area you do not need heat. Ray

Fri Mar 26, 2010 11:46 am

I agree with our observations Ray. So are you then saying if engine radiates heat and the tin is mat black, it should absorb that heat and then dissipate it to surrounding area better than say white gloss painted tin? (Let's just assume both side of the tin is painted the same color)

Fri Mar 26, 2010 1:04 pm

raygreenwood wrote: neil68 wrote: Here's another blurb from a veteran VW mechanic..even he misses the key point about the decklid being closed, so the engine is in the dark anyway:

"The truth is, with regard to any part of your engine not in contact with hot oil, you may paint it . . . or chrome it . . . any color you wish. In the case of your shrouding, tin-ware and blower housing, the finish . . . paint, chrome or what-have-you . . . is there only to protect the metal. These metal parts are not a factor in the transfer of heat via radiation. The metal is there to contain the envelope of cooling air. I realize the metal will get hot through both conduction and radiation absorption but the quantity of that heat is minuscule when compared to that being radiated by those parts of the engine in contact with the oil. Indeed, this perception of heat is subjective. When the engine is running and the car is moving, the shrouding and tin-ware is usually only slightly warmer than the ambient air temperature. It is only when the vehicle is brought to a halt and the engine shut off that any significant quantity of heat can be absorbed by the tin-ware. The subjective part is the fact that you can not put your hand on the tin-ware when roaring down the highway at sixty mph... but you can when the vehicle has stopped... by which time the tin-ware feels hot to the touch. And Conventional Wisdom wins again."

All of that is 100% incorrect. I work with color and radiant heat for a living.

By definition...black is not a color. It is the total abscence of color. White light as the use of a prism will show you....is made up of every color and wavelength of light.....including invisble UV and infrared (heat) spectrums.
And any surface that APPEARS white to you eye....does so because it is able to reflect all of the colors of that white spectrum back to your eye.

Black....is black because it can reflect few if any of the colors of the entire spectrum. This also still...includes both heat energy (infrared light) and UV energy (high speed/high energy invisible spectrum above 280nm).

A gloss surface reflects enough spectral light AWAY from a surface to make a difference of up to 40% of the amount of light and heat energy absorbed.
Try these yourself kiddies:

Four identical pieces of 1/16" x 4" x 4" sheet metal. One painted flat white, one painted flat black, one painted gloss black, one painted gloss white.
Lay them out on a piece of ...whatever....in the sun. Using a non-contact laser thermoprobe...or a K-type thermocouple attached to your VOM you will generally find this level of variation.

(1) Gloss white will be the coolest. On a summer day with ambient of about 90*F, the gloss white part will be about 110F
(2) Flat white: same consitions and about 125-130F
(3)Gloss black: about 150F
(4) Flat black: about 165+F.

Check the same set around midnight with ambient about 80*

The white pieces both gloss and matt will both be right about ambient air temp. Both black pieces will usually be about 3-5 degress above ambient because they are absorbing infrared light radiating out of the surroundings.

Black surfaces that do not reflect (black matt) are also capable of absorbing radiant, convected, and reflected light. light is energy...all wavelengths. Heat is energy. All heat is light in the infrared wavelength...period.

Chrome is stupid for engines. Chrome reflects heat whether it is polished or not. The invisible side of chrome...the part that is against the metal it is plated to...also reflects heat. It does this because of the chrystalline structure it is comprised of . Even zinc and other crystallines reflect some heat.

Perception of heat is not subjective. Do the experiemnt I listed above. I have...many times and in many formats. The problem is that heat from say....a hot exhaust pipe...you might want to dissipate via air swirling around it when you drive.
Much of it will.....but higher energy infrared heat....RADIANT HEAT...is not subject to wind or air. In fact...radiant heat...and all light energy for that matter... readily travels across vacuum. How do you think sunlight gets here and is still hot after going through the cold vacuum of space. :roll: .
If radiant heat ....plays upon a dark matt surface that is too close to somewhere you do not want excessive heat.....that surface heats up and re-radiates that heat...some of which may be straight through the metal by conduction....into an area you do not need heat. Ray

I agree with much of what you are saying, but again most of it does not apply to ENGINE TIN, which is what I was speaking to, in response to the quote about black tin being the best.

I agree that heater boxes or valve covers are another matter.

You talk about laying pieces of tin out in the sun...I've already agreed that an open engine bay like a Baja Bug would factor in to this discussion, but a closed decklid is not exposed to the sunlight, so your point is meaningless. I'm not going to pick apart each line that I disagree with, but I know from personal experience that fan shrouds and tin in a stock "closed decklid" Beetle are not affected by the paint colour or chrome. That is why "quality" chrome shrouds are still popular, they don't affect engine cooling, since their purpose is to direct air, not dissipate heat.

Now chrome valve covers, I would seriously question...as you've pointed out well, above.

PS: the quote that you quoted above, I posted just as an example of published info, since the other poster said that all the books he's read promoted black tin paint. My point was that it just depends on what you've read...

Fri Mar 26, 2010 1:59 pm

Yes! In the beginning I thought....how crazy is it to paint everything black when black absorbs so much heat. The issue we have found with heat reflection in all sorts of industrial situations...is that is you painted everything white or chromed it, or made it high gloss....you would have that radiant energy reflecting back all over the place.

Painting everything black absorbs stray heat. The thin gauge of the sheet metal means that there is not much mass with which to bank that heat. If the sheet metal has one side that has a temperature differential with the hot side...heat will flow to that cooler side....conduction.

Ray

Sat Mar 27, 2010 8:06 am

neil68 wrote: raygreenwood wrote: neil68 wrote: Here's another blurb from a veteran VW mechanic..even he misses the key point about the decklid being closed, so the engine is in the dark anyway:

"The truth is, with regard to any part of your engine not in contact with hot oil, you may paint it . . . or chrome it . . . any color you wish. In the case of your shrouding, tin-ware and blower housing, the finish . . . paint, chrome or what-have-you . . . is there only to protect the metal. These metal parts are not a factor in the transfer of heat via radiation. The metal is there to contain the envelope of cooling air. I realize the metal will get hot through both conduction and radiation absorption but the quantity of that heat is minuscule when compared to that being radiated by those parts of the engine in contact with the oil. Indeed, this perception of heat is subjective. When the engine is running and the car is moving, the shrouding and tin-ware is usually only slightly warmer than the ambient air temperature. It is only when the vehicle is brought to a halt and the engine shut off that any significant quantity of heat can be absorbed by the tin-ware. The subjective part is the fact that you can not put your hand on the tin-ware when roaring down the highway at sixty mph... but you can when the vehicle has stopped... by which time the tin-ware feels hot to the touch. And Conventional Wisdom wins again."

All of that is 100% incorrect. I work with color and radiant heat for a living.

By definition...black is not a color. It is the total abscence of color. White light as the use of a prism will show you....is made up of every color and wavelength of light.....including invisble UV and infrared (heat) spectrums.
And any surface that APPEARS white to you eye....does so because it is able to reflect all of the colors of that white spectrum back to your eye.

Black....is black because it can reflect few if any of the colors of the entire spectrum. This also still...includes both heat energy (infrared light) and UV energy (high speed/high energy invisible spectrum above 280nm).

A gloss surface reflects enough spectral light AWAY from a surface to make a difference of up to 40% of the amount of light and heat energy absorbed.
Try these yourself kiddies:

Four identical pieces of 1/16" x 4" x 4" sheet metal. One painted flat white, one painted flat black, one painted gloss black, one painted gloss white.
Lay them out on a piece of ...whatever....in the sun. Using a non-contact laser thermoprobe...or a K-type thermocouple attached to your VOM you will generally find this level of variation.

(1) Gloss white will be the coolest. On a summer day with ambient of about 90*F, the gloss white part will be about 110F
(2) Flat white: same consitions and about 125-130F
(3)Gloss black: about 150F
(4) Flat black: about 165+F.

Check the same set around midnight with ambient about 80*

The white pieces both gloss and matt will both be right about ambient air temp. Both black pieces will usually be about 3-5 degress above ambient because they are absorbing infrared light radiating out of the surroundings.

Black surfaces that do not reflect (black matt) are also capable of absorbing radiant, convected, and reflected light. light is energy...all wavelengths. Heat is energy. All heat is light in the infrared wavelength...period.

Chrome is stupid for engines. Chrome reflects heat whether it is polished or not. The invisible side of chrome...the part that is against the metal it is plated to...also reflects heat. It does this because of the chrystalline structure it is comprised of . Even zinc and other crystallines reflect some heat.

Perception of heat is not subjective. Do the experiemnt I listed above. I have...many times and in many formats. The problem is that heat from say....a hot exhaust pipe...you might want to dissipate via air swirling around it when you drive.
Much of it will.....but higher energy infrared heat....RADIANT HEAT...is not subject to wind or air. In fact...radiant heat...and all light energy for that matter... readily travels across vacuum. How do you think sunlight gets here and is still hot after going through the cold vacuum of space. :roll: .
If radiant heat ....plays upon a dark matt surface that is too close to somewhere you do not want excessive heat.....that surface heats up and re-radiates that heat...some of which may be straight through the metal by conduction....into an area you do not need heat. Ray

I agree with much of what you are saying, but again most of it does not apply to ENGINE TIN, which is what I was speaking to, in response to the quote about black tin being the best.

I agree that heater boxes or valve covers are another matter.

You talk about laying pieces of tin out in the sun...I've already agreed that an open engine bay like a Baja Bug would factor in to this discussion, but a closed decklid is not exposed to the sunlight, so your point is meaningless. I'm not going to pick apart each line that I disagree with, but I know from personal experience that fan shrouds and tin in a stock "closed decklid" Beetle are not affected by the paint colour or chrome. That is why "quality" chrome shrouds are still popular, they don't affect engine cooling, since their purpose is to direct air, not dissipate heat.

Now chrome valve covers, I would seriously question...as you've pointed out well, above.

PS: the quote that you quoted above, I posted just as an example of published info, since the other poster said that all the books he's read promoted black tin paint. My point was that it just depends on what you've read...

This last post simply shows that you have no idea what you are talking about from a scientific basis. Sorry to seem rude...just being honest.
The scientific reality of the test I suggested it that Ican repeat the exact results in a pitch black room.....using on IR light which is invisible.

Everything I pointede out has 100% to do with tinware..and any surface in this universe that gets hot. This IS how it works.

Heat is light....period. All TRANSMITTED heat is 100% infrared radiation. Where there is light ...there is heat...always.
In the dark...heat...is light. You simply can't see it. Once that heat is absorbed into a surface (like your tinware) it becomes CONDUCTED heat energy. That energy moving through metal.....is now electrons.
When it migrates to the surface and radiates...it once again becomes infrared radiation....unless there is enough energy to strip photons and become visible as a glow...or even sparks

I promote black tinware as well. It ARRESTS heat by actively collecting it. The problem is...going back to the original question...is that black surfaces do not dissipate heat faster...they COLLECT heat. They keep reflected heat energy from damaging heat sensitive areas.

Do not get hung up on the test I gave (the four squares of metal). The heat rise and loss of the two colors in flat and gloss...........is 100% indentical even in picthc blackness inside of the engine compartment with only engine heat as the INFRARED light source.

You can do the test with sunlight, lightbulbs, easybake oven, or in pitch blackness using only radiated heat. The result is the same.

This is how heat works. This is not up to opinion or perception. This has been known to be exact science for well over a century.
We can go round and round forever....but this is what I do for a living....light, color, heat.
Ray

Sat Mar 27, 2010 9:32 am

i love the samba... around here major cooling compents, like thermostats and air control vanes are deemed unnecessary quickly, but minor things like color of tinware can be argued forever or their benefit or detriment to cooling... Just a general observation, not directed at anyone... I do find humor in such things though... :lol:

Sat Mar 27, 2010 10:49 am

The fan shroud and cylinder tin (ie. the only items that I was commenting on, from a previous post) are there to direct air to the correct places...that is their sole purpose. They do not remove heat from the air, or else they would be finned or have other design features (as pointed out by someone else earlier). VW painted them brown, green and yellow back in pre-war and during WWII and black later on...it doesn't affect anything.

Ray, I have two B Sc degrees and have basic understanding of what you're saying, you don't need to re-hash things...I get it. However, you're talking mostly about items such as those connected to the engine system (valve covers, heater boxes, etc), not very thin "tin" that sits lightly on the engine. That's why you can touch the shroud or tin on a warmed up engine...it stays cool...

Sat Mar 27, 2010 12:01 pm

VW made them black at the factory.....I need no science beyond that!

Sat Mar 27, 2010 1:01 pm

http://www.thesamba.com/vw/archives/lit/74bug_sb/page8.jpg
In this photo the heater boxes were gray along with the muffler.

Sat Mar 27, 2010 3:49 pm

Black....gray.....whatever the factory did......this thread has too much discussion about chrome, white, light, dark, all kinds of crazy comments. The VW engineers had it figured out....they made the same damn car for 40 years!

Sat Mar 27, 2010 9:26 pm

[quote="rlutterb"] VW made them black at the factory.....I need no science beyond that!
quote]

As pointed out earlier there were two paint programs used by VW:

1. shroud & tin painted the same colour as the vehicle (eg. brown/green) '30's and '40's. Fairly easy, since everything on the vehicles was painted with the same colour...simple and inexpensive.

2. shroud & tin painted black (later assembly line) so that they contrasted with any body colour, late '40's onward (with a few exceptions). A single colour was cheaper when the mass production assembly lines took over.

Here's a '40's kdf refurb...don't think anyone will paint it black though:

http://www.thesamba.com/vw/classifieds/detail.php?id=903650

Sat Mar 27, 2010 10:21 pm

[quote=" I have two B Sc degrees [/quote]

I always call these degrees in B.S.

Sat Mar 27, 2010 10:32 pm

More than anyhing... there is blatant quote misuse/abuse goin on in this thread.
The point is... it doesn't make a bit of measurable difference in engine operation.
Where as people selling paint have stated otherwise.
If it did, the tins would be white or chrome to keep he heat where its supposed to be... otherwise the tins wouldn't be there.

Also... is conduction and convection transmitting light through solids?

Sun Mar 28, 2010 12:44 am

VW painted there motors black for the same reason Ford painted all the model T's black,, It is ezer to mas-per-douse... VW bugs were made to be cheep.