Ya know, there is a reason they paint the top of the space shuttle white and the folding radiators in the cargo bay doors black......

It's done for a reason.....

That's why I'm painting the inside of the manifold black and the outside white and making all my engine tin out of Carbon Carbon so my engine compartment is always cool no matter how hot the engine gets.....

Ken

Lesson learned- never argue Physics w/ a German .


Attention Admins- :whiteflag: is now a needed Smilie.

Well, the truth is that light is the abscence of dark. So really, anything 'radiating heat' is really 'sucking dark.'

So if you want the coolest coating, you have to use a color that sucks dark the most, because as we all know, its very cold on the dark side of the moon. This will give you the most phonoffs (the anti-vibration of a phonon).

Or, you could try blocking the Bloch waves.

-Tony

i tought you can only find those when you throw pebbles in a gravity well ...
Andy

chit !

i swear half of these posts sound like alphy wrote them.

light is less absorbed by some "lighter colors". most visable light doesn't have any heat. only when the "light" excites a surface and cause the suface molucules to excite is it turned in to heat.

put a white pot and black pot in to a oven and as long as both coatings have the same properties except color they both will heat at the same rate.

now if you coated one with a coating of lets say the same stuff the is on the space shuttle [you now those BLACK tiles] that might not heat at the same rate.

'nuff i'm done.

let the nonsense continue.

Sorry if this is a repeat, but I couldn't finish reading all the posts before posting....





Heat can be observed through infrared radiation.

Using infrared visualization (a camera or other means), heat can be seen. In an infrared heater, the reflectors (which direct the infrared radiation) are shiny and bright. The reflectors loose efficiency when they become dirty and are no longer reflective.

Heat is energy and always will give off infrared radiation. Sometimes the heat can give off light waves that are in the visual spectrum that can be seen by the human eye, but more often it is in the infrared spectrum.

Just because you can't see it, does not mean that it is isn't there.

The Infrared spectrum of wave forms acts just as the visible spectrum. I.E. bright objects tend to reflect and dark objects tend to absorb.

You can believe what you want, but if you want to live in reality, you will accept facts.

Geez, I almost forgot.

For all practical purposes, it will not matter what color you decide to paint your intake runners.

Your car is doomed to live out eternity on jackstands.


(Besides, once all the engine compartment comes to equilibrium, the color will matter not.)

Black bodies will heat faster and dissipate heat faster (but only due to radiation).

"Just because you can't see it, it's there"? Hmmmmm ............................
Therefore, it's there because you can't see it? I LIKE that! Does it follow that if you CAN see it, it's NOT there? This is getting FUN! Glad I paid attention in things like Geometry and Philosophy ............ The Cap'n

I have no clue what you are talking about

So Andy, what would you like to argue about tomorrow, since our discussion seems to have generated so much interest ?

Andy likes to discuss cantilever slicks on 8" wheels

Exactly!

Why not simply repaint them to original specs? Dd the origional engineers really wan them to be that ugly? Doubt it. At light, semi flat, they are designed to neither absorb, nor dissipate heat (to any degree). So, why not put them in the condition the engineers deemed best?

I'll go out on a limb here & say that I ONCE had a set chromed! Huge, HUGE mistake - sucked up heat so badly that there was no way to tune the injection. Tried about a dozen times before I put them in the trash (Oh, they were gorgeous!). They were unusable, and unsalable - junk!

Guys - paint 'em the way the were meant to be.
Pat

Try this! I do not drive my car much but I use dry ice caplets inside copper tubing it lasts for days and is easy to refill! Cools my engine where ever I need cooling! Short trip/long trip it does not matter! Intake is the best!

I don't either, but this is almost more fun than I can handle .............. The Cap'n

If I paint my air cleaner white would I have cold air induction? I wonder if that would offset the black runners?

Pink intake sometimes raises my temperature...

Paul

based on this thread, I realise how much I did not pay attention in science class. However, you all did make is easy to decide on what color the intakes should be painted...........

Click to view attachment

Bingo!

What, no pink?

Fellas,

The Elephant in the Room that no-body is mentioning is that Air Cooled thing again... The Amount of heat transferred from engine tin or intake runners Radiated (because or inspite of pigment), is MAGNITUDES SMALLER than the heat transferred by the air flow.

You want COOL intake runners???... You already HAVE THEM.. they are ALUMINUM, and are in intimate contact with flowing engine room air, AND the air cooled heads. If you really want to enhance the cooling, machine the semicircular contour of the Intake Runner OD into some finned aluminum stock, and Solder/Weld on.

or.. Spray alcohol/water on the pipes....

or

Sewer Pipe from Front Right Headlight through the passenger bay and into the engine bay will make the biggest and most significant difference.

black intake runners will run hotter.

green yellow and black = Cool Runnings.

With all of this wondedrful quoting of theory how about some numbers. I have heard that Harley riders have noticed that engines painted black run cooler than similar engines painted other colors or even not painted at all. I suggest checking with your local Harley shop, or try out some biker message boards and see what their experiences say. You could probably even get a local bike shop to test this out with an infrared thermometer on some of their different bikes and see if there is an link between color and temp ranges. Remember, the bigger the sample size, the more likely the results represent a correlation or not.

What are we talking about?

a engine painted black will radiate more heat, thus running cooler.
Andy

what about painting the cylinders black with some motorcycle engine paint? what about the case for that matter?

the dominant heat source in an engine environment is best black. Oil coolers, radiators and such are black because black has the highest emittance value.

Cylinder head tin is black because it needs to shed heat as much as possible.


An object in direct proximity to these primary heat source should not be black unless you want them to absorb the heat being emitted.

Paint them a color that is less absorbtive.


Simple.


Harley engines are best black because the cylinders and heads are primary heat sources. The carbs are not black though.

Academic Masturbation...



Okay okay.. maybe it's not Academic... but I've always wanted to work that into a conversation somehow!!

Harley Engines are black because the fins are made of CAST IRON.

If you built a 914 engine using Nikasil Cylinders (aluminum fins), would you then INSULATE them by painting them with black paint?? (Or Black Anodize???)

Did Porsche MISS a huge cooling opportunity by NOT painting their crankcases and Aluminum Cylinder Fins BLACK on all their air cooled cars????

My assumption is that Porsche was/is known for being meticulous in their engineering.. YES you may radiate a couple more Watts to the Line-OF-Site HOT ASPHALT PAVEMENT.. but maybe it will backfire on you and ABSORB just as much heat or MORE!


Radiating to the sheetmetal serves little purpose as its only avenue to shed heat is via the high velocity air flowing over it, which is already in intimate contact with the cylinder fins.


IMAO (A for "Arrogant" as most engineers are labeled when spouting off)....Radiating heat is for Space Craft where there is no other means. It is a very crappy way of moving heat, but you have no choice there.

non oem intake gaskets for 1.7/1.8. pelican, 022 129 707F, $8.75.

k

non oem intake gaskets for 1.7/1.8. pelican, 022 129 707F, $8.75.

k

Umm, didn't Harley go to Porsche & have them redesign their engine because Porsche was good/experienced at converting air cooled engines to water cooled? I would think that would say enough about if they know how to cool something the right way or not.

if one wanted to go to the exspense of having the runners thermal barrier coated, i don't think it would hurt. about the same price as powdercoating.

k

Nobody is saying to paint your aluminum cylinders Brian.




A good designer considers every decision no matter how trivial.
But then again, maybe they picked black because its sophisticated and elegant.

Gray does look cool in that spot too.

Ya think maybe harley did it for asthetic reasons?

I think everyone is overthinking this. It won't make a measurable difference. The airflow and materials are more important.

Just paint the $*(#$% runners any *$%& color you want...

Just put some paint on there and let us know how it goes

you guys are ruining the fun by making it simple.

How about gold leaf like the F1 Hows that for not so simple?

Yes, if given unlimited freedom, $, and time. A good employer (i.e. somebody who is trying to make money ((Like Porsche)), will hold a gun to that designer's head with the instructions to get the most bang for the buck, and get on with it.

If the color of mechanical components contributed to a significant heat transfer such that efficiency was improved, they would have done it. If it had, we would all be running around with black cylinder heads as they are the achilles heal thermally to these engines.

Okay, I'm done, I'm puting it back into my pants and zipping up!

P.S. I do like the color "machine grey" for intake pipes. They can get dirty and it isn't as noticeable as it would be if it were a light.

Come on guys! Quit it with the IF IT WORKED it would be done stuff.

IF marketing didn't work, we would do things on what is best, not what is popular.

Just try different paints and see what the results say.

I am not an engineer, let alone one who understands thermal stuff,

But in a book I read about Dr. Porsche, he designed an air cooled diesel engine for a tank. He chose air cooled rather than water cooled because it suffered less power loss as it gained temperature and was more consistent in output, AND he could ENCLOSE it in armor. He said he could not do that with a liguid cooled engine for several reasons. I cannot remember them all but one had to do with the location of the water radiator which HAD to have airflow, and another was its variation in efficiency as it heated and cooled with a constantly cycling flow of water of a constantly cycling temperature.

In other words, and air cooled engine could be designed to operate in an enclosed box, or nearly enclosed box and it would somehow reach equilibrium and operate efficiently. He never did say the color of the paint on the tank had any effect.

Come on all of you thermal engineers, tell us we can paint our intake runners red if we want to....without any reason to worry.