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Discussion Starter · #1 ·
Was at the bar the other night talking to some friends about bikes and cars. I'm in Sydney at the moment and a few of them bring up Mighty Car Mods. They went on for awhile about the show and how much they loved it. Figured I'd check it out.

After watching a few of their episodes I came across the black intercooler myth. It was interesting enough to throw up here. Their findings were a surprise. The whole time I was hoping they would test anodizing too but no luck. Looks like black paint on a radiator might help out if anyone is having overheating issues in heavy traffic.

https://www.youtube.com/watch?v=f1QL9veQaNg
 

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I assume the same would apply to an oil cooler, or air cooled engine (fins, crank case)? I always thought black painted air cooled engines looked crummy, but I guess there's a logic to it. Of course, those WOULD be in sunlight (as would most cycle radiators).
 

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I was interested in this subject when I was big in to drag racing (cars). Big HP and trying to go low weight with a tiny cooling system . Water is heavy. TCI ( transmission people) developed a coating they use on all their convertors now. Basically, is a real dark metallic gunmetal. Almost black .Very little gloss.

Theory was the metallic produces a direct path of heat transfer thru the coating without sacrificing corrosion protection. Tests proved it true. Pretty neat stuff.

Anyway, so I skimmed my tiny ally radiator with some metallic gunmetal. Couldn't find any in a flat or a satin, so wiped it with an acetone soaked rag. Looked real trashy, cooled much better. Cool down ( engine off) times dropped by several minutes too, which is paramount when trying to preserve battery power on a non-alternator equipped car.

Smokey Yunick did tons of testing on this topic. Everything he built was flat black.
 

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Man that difference is wild. I used to own a V8 S10 that I had a hell of a time keeping cool over the summer. Wish I would've known this then. Stop and go traffic was hell on that thing.

And what shinyribs pointed out about TCI converters is neat. I didn't know that. I just figured that they decided that semi-gloss black was a cheap, unoffensive coating.
 

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I was interested in this subject when I was big in to drag racing (cars). Big HP and trying to go low weight with a tiny cooling system . Water is heavy. TCI ( transmission people) developed a coating they use on all their convertors now. Basically, is a real dark metallic gunmetal. Almost black .Very little gloss.

Theory was the metallic produces a direct path of heat transfer thru the coating without sacrificing corrosion protection. Tests proved it true. Pretty neat stuff.

Anyway, so I skimmed my tiny ally radiator with some metallic gunmetal. Couldn't find any in a flat or a satin, so wiped it with an acetone soaked rag. Looked real trashy, cooled much better. Cool down ( engine off) times dropped by several minutes too, which is paramount when trying to preserve battery power on a non-alternator equipped car.

Smokey Yunick did tons of testing on this topic. Everything he built was flat black.
I painted the sides of my last bikes radiator but not the fins because I figured the paint would insulate and reduce efficiency. Really interesting though, sounds like it would help a ton when bikes get their hottest idling and putting around in city traffic; may be worthwhile to pull and paint the radiator :cool:
 

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I'm not grasping how that could work and there are so many issues with their test. Why black? For it to be definitive they would have to paint the same style cooler white or another lighter color and see what happens. Did the paint really get all the way into the fins since that is were the majority of the surface area is? Why aren't all OEM coolers black? They have a vested interest in getting the most performance for their dollar. Don't you think they would rather spend a few pennies on some paint or coating rather than adding more metal, more space, and more weight to their various coolers? So their test shows that an intercooler with no airflow dissipates more heat when it is black. That is great for all the times I need max intake air cooling while idling.

I'm wondering if the paint actually added surface area to the polished areas and created micro valleys and peaks. I've read that a rough finish cools better than a polished finish.
 

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Discussion Starter · #9 ·
I had similar concerns. Would of liked to see anodizing tested. If it had the same effect with a uniform coating it would rule out increased surface area.
 

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I'm wondering if the paint actually added surface area to the polished areas and created micro valleys and peaks. I've read that a rough finish cools better than a polished finish.
That was Smokey's take on the idea. And why he used flat versus semi or gloss. Why black? Supposedly, black absorbs heat. Even just radiant heat. The idea ( according to Smokey) is the black would absorb the heat to the surface where it could be dispelled.

He also built an oil pan once. SBC, of course. He brazed a brass rod about every 1/4'' standing straight up. Trimmed them just short enough to clear the rotating assembly. Basically like cooling fins inside the sump of the pan. It drew enough heat out of the oil and directed it thru the rods to the flat black outer surface of the pan that he was able to eliminate external oil coolers and and their plumbing. Which is a TON of weight. Not to mention another source of underhood radiant heat. But, the rods would give up to the vibrations and come loose. Heat dissipation is a weird science.
 

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It's a difference between radiant heat and convection heat. Or stationary vs moving.

The black makes a difference when stationary. It absorbs and releases heat faster. Without airflow, convection heat transfer is low, since the air immediately around the hot part quickly warms up and only moves away by the hot air rising, slowly. So radiant heat is a higher percentage of your heat loss, and black vs polished makes a difference. A rougher surface- like the micro-texture coatings mentioned- increases surface area which helps as well.

When you're moving and air is being forced through the fins, that "hot layer" of air never forms and convection becomes much more efficient, so the effect of black vs polished greatly diminishes.

So it's an interesting concept, but in practice not terrible useful. It makes your radiator or fins more useful when you least need it. It might be a little beneficial to free air cooled motors- the little thumper on my Grom was black from the factory- but aside from that, there's limited applications for such a trick.
 

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when i still had a raw radiator on the gsxr it would get hot quick in stop and go traffic. almost took my motor a the first ff i went to. the overheat ignition shutoff clicked my bike off a few times and would take forever to cool down. perfectly fine while riding though. after painting it black i noticed no difference in riding it but i havnt had it shut off in stop and go traffic yet. it will idle at a red light all day long in 110 degree weather. and you can definitely feel the heat coming off it more. but you can also feel more heat coming off of the alloy frame after i painted it black too.

so basically after painting my radiator black i havnt heat soaked my motor.
 

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It's a difference between radiant heat and convection heat. Or stationary vs moving.

The black makes a difference when stationary. It absorbs and releases heat faster. Without airflow, convection heat transfer is low, since the air immediately around the hot part quickly warms up and only moves away by the hot air rising, slowly. So radiant heat is a higher percentage of your heat loss, and black vs polished makes a difference. A rougher surface- like the micro-texture coatings mentioned- increases surface area which helps as well.

When you're moving and air is being forced through the fins, that "hot layer" of air never forms and convection becomes much more efficient, so the effect of black vs polished greatly diminishes.

So it's an interesting concept, but in practice not terrible useful. It makes your radiator or fins more useful when you least need it. It might be a little beneficial to free air cooled motors- the little thumper on my Grom was black from the factory- but aside from that, there's limited applications for such a trick.
Exactly. It does actually work, but its definitely not a replacement for a properly sized system with adequate air flow. Yet, every little bit helps.
 

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On bikes that run hot without airflow (honda vfr and vtr) this would be brilliant.

my front mount on my vfr was painted black for looks, didn't know it was actually a performance mod.
 

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I might like this show except that one guy. The guy on the right... He's rather annoying. And strikes me as someone who exaggerates things. I wouldn't hang onto every word from these knuckleheads.
 
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