Get extra cooling on your bike with black paint.

[Guest]

So if I wear a black shirt and pants in the sun I wil stay cooler than wearing light clothing?

Rock, it depends on the direction. When wearing a tshirt, the sun will radiate towards you more than you radiate away from you. (environment hotter than the object). In an engine, the object is hotter than the environment.

Since black is a good absorber, bad on a hot day in the sun.

 

[quakeholio]

A couple of things, if someone has a lazer thermometer, some paint and some metal a test can be done. I would have three pieces of metal, one piece should be unpainted, the next should be painted black, and the final one should be painted something like white. Get the bits to room temp, then toss them in an oven for a few minutes, lets say 400F for 10 minutes (or what ever you want). If the hypothosis is acurate then the black metal should be hotter then the white, and hotter then the plain metal. If the plain metal is hotter then the paint is acting as an insolator, and not a conducter of engergy. This is only acurate if the objects are other wise the same, metal, shape, size and weight. A variation in any of these would affect the heating/cooling of the object. I also say look at the heating power instead of the cooling power because its simpler to get the temps all the same at room temp. I suppose you could use the freezer though.

The second part of this is would a oil cooler or larger cooler be effective in negating any temp increase in the engine?

 

[Jethro]

So with this theory my black exhaust should cool better than a chrome one?

 

[jm_foote]

Since this is still going:

If the metal was black. It would work.

But the metal is still shiney, therfore the heat will still reflect of the surface of the metal back towards the engine, preventing the heat from going to the paint, just as much as it would prevent the heat from going to the air. A barrier between metal and paint is still a barrier, just as a barrier between metal and air is. The paint and the metal are not the same, therefore you cannot treat them both the same (if the enginer reflects 70% of the thermal energy inwards, it will still do the same if you put paint on it).

This is my theory.

Either way, i doubt that there is much of a difference.

And as for the black metal of stoves, i believe that has more to do with the carbon content of the iron.

 

[jm_foote]

You guys are getting way to deep.

This is fun! It's not like I have a life anyway:? .

 

[Hoomgar]

So with this theory my black exhaust should cool better than a chrome one?

It does. We both have the same exact exhaust on the same bike with the same engine. Had we thought of it when we took a break we could have checked because the only difference between my chrome exhaust and your chrome exhaust is that mine is silver and yours is black. I guarantee yours cools off quicker than mine.

This conversation is funny. You all talking and wondering about something that the bike manufactures knew back in the 80s. This is not new information guys. :lol:

 

[Jethro]

It's new to me! And interesting. I always knew a dark color absorbed sunlight, but I never knew it affected cooling in anyway.

I'm wondering why very few sportbike engines are black these days. And performace car engines. Maybe they have sophisticated enough cooling systems so they don't need to spend money on paint. Still this thread is interesting.

 

[Hoomgar]

It's new to me! And interesting. I always knew a dark color absorbed sunlight, but I never knew it affected cooling in anyway.

I'm wondering why very few sportbike engines are black these days. And performance car engines. Maybe they have sophisticated enough cooling systems so they don't need to spend money on paint. Still this thread is interesting.

I think it is more how you think of it. The black isn't so much affecting cooling or heating as much as it is affecting heat transfer. It transfers temperature well so if the item is cooler than it's surroundings it will take heat faster from that environment while if the black item is hotter than its surroundings then it will expel the heat into its environment faster. I am guessing that the improvement gained by this is marginal. If it were a really big difference this would be better known and would be a mandatory modification by most manufacturers.

My last comment was only based on the fact that when I was 16 (1983) I asked the sales guy at the Yamaha dealer who was selling me my then brand new 650 turbo that came complete with black chrome pipes and black engine, why in the world they would paint it black when "black attracts heat doesn't it?" This that I said in the last paragraph was the reply I got to that. Maybe this isn't as widely known as I thought it would be but it certainly is not new. Just maybe not as widely published.

I do know that my black pipes always cooled off way faster than silver chrome pipes did. That much I have seen myself.

Most modern sport bike engines are black are they not? I actually haven't noticed but my minds eye is telling me yes?

 

[jm_foote]

Some info on the subject:

http://www.sacskyranch.com/paint.htm

I suspect that parts painted black may appear to cool off quicker because the paint is either polymer or ceramic based. Either of these have significantly lower thermal capacities than metal (aka insulaters). This would cause the painted parts to appear cooler (as the plastic handle on a pot appears to cool down faster than the pot itself, once it is removed from the oven).

 

[dpep]

This does not however, change the fact that a black engine looks really cool!!

Amen. I wasn't pondering radiation or convection when I put the flat black to my old 850's motor. Goes great with yellow.

 

[Guest]

This does not however, change the fact that a black engine looks really cool!!

Black is beautiful!! Extra "cool"ing :-D

 

[Robu]

if black is cooler why don't they paint the Reg/Rec black ? If so would it help ?

 

[Nerobro]

it costs money. our RR's are not unreliable because they're the wrong color, they're unreliable becuase they're freakishly to small for the application.

 

[ZOMBIEEATER]

Ive never had a question answered with so much depth, thanks spchips, reno your exhaust looks friggen awsome, how did you get them looking so good?

 

[Guest]

Ive never had a question answered with so much depth, thanks spchips, reno your exhaust looks friggen awsome, how did you get them looking so good?

Thanks, Zombie! I use S100 Engine Brightner on the motor and exhaust (and everything else that's black).

 

[albertaglen]

black PAINT no good

black PAINT no good

Hi. As a lover of air-cooled two-strokes (and someone naturally curious) the question of surface finish as it relates to cooling is something that I've done a bit of research on. As I understand it:

-paint will act as an insulator; there is virtually no difference in heat loss between a white- and black-painted engine (it's been done)
-a flat black anodized layer may not significantly slow down heat loss (although it does NOT seem to increase cooling either); if you want a surface black, this is the way to go
-a matt, slightly rough-finished (e.g. sand-cast) part is the best option for max. cooling, all things being equal
-polished parts retain heat
-powder coating should NOT be applied to surfaces where heat mgmt is important (as it is just a layer of paint in essence)

 

[Guest]

See:

http://www.egglescliffe.org.uk/physics/astronomy/blackbody/bbody.html

and:

http://en.wikipedia.org/wiki/Black_body

Painting something black has essentially nothing to do with "black body radiation". The "black body" is something that can absorb or emit radiation at any wavelength.

Einstein won his Nobel prize in 1905 for his work on the photoelectric effect, which is closely related.