Having just had work done on my 03 STi which included an oil catch tank, the black breather pipes running along the leading edge of the intercooler have been removed. The finish on the part that was hidden is pretty tatty so, I thought I'd have the intercooler off and give it a bit of a facelift! (and give the back of the engine a bit of a clean!)
I thought I'd give the main body of the intercooler a spray and was wondering how important it is to use the right kind of paint to allow dissipation of heat? I'd refrain from spraying the core and just give that a good clean.
Has anyone got recommendations regarding paint for this application?

JohnD

 

Surely someone's had a go at this?

 

Meh.. I just blew over the fins very lightly with normal paint!

 

BTTT

 

John, I just used a light spray of some black high temp paint I had laying around...no issues experienced and its been running since September.

ian

 

I guess as air is directed through the core, a light spray or thin coat should be ok for the body.
JohnD

 

Dynamix has a painted APS front mount on his Time Attack car. I don't know what paint was used.



Mark

 

The important bit with painting intercoolers is not what kind of paint to use, its not blocking the fins with paints on the core.

I'd recommend as light-a-colour as possible to reflect heat rather than attract it, although, APS FMIC's do look cool in black.

 

Actually its a proven fact that black intercoolers reject more heat than any other colour.

Also Dynamix's cooler came from APS like that. Its black powdercoat.

 

WOW, defying the laws of physics, thats interesting.

 

Now I do know what paint (powder coat) was used. Praise the oracle.

Is that why they wear black robes in the desert to reject heat? Or is it just so you know who the bad guys are?

Mark

 

The black on the cooler absorbs more heat from the charged air. Thats the workings behind it. Remember the RS500 intercooler?

Came in black for that reason.

LOL @ Mark too

 

We are getting into the whole absorption, reflection, radiation, conduction & convection thing here.

I think you'll find that black radiates heat away better.

Despite my bad guy joke black is used quite extensively in hot countries for clothing. Which also goes against the laws of physics.

Mark

 

I can understand painting the inside black helping on that front but if test have been done and it shows that black intercoolers work better than any other colour, it must be right.

Just doesn't seem right

 

It's off to B&Q for some radiator paint - or is that for the central heating?

I've seen silver intercoolers and I've seen black ones (my old 99MY had black!)
Sublime to the ridiculous - now I'm confused
JohnD

 

Thinking about painting my FMIC too, i considered black but then because silver absorbs less heat i decided on silver, now i'm all confused

 

I have two sti top mounts, One in black and one in the original silver. I also measure charge temp at throttle body and theres no difference

 

OK without getting too technical black absorbs the most energy which is true however the energy is transferred, whether it's via convection (air to air as in your intercooler), via conduction (liquid/solid to solid/liquid as in your radiator) or via radiation (electromagnetic waves i.e. radio waves to microwaves).

The idea of a black intercooler means that it will absorb the heat (which is energy) from the air INSIDE it which is likely to be warm having been rudely thrust there by the turbo. This heat is then transferred into the metal work of the intercooler and of course up the cooling fins.

These cooling fins are exposed to the cold air from outside the car made available via the bonnet scoop in a TMIC or grille in FMIC. The cold air will take this heat (energy) off the tips of the cooling fins, thus making them colder than the core.

And if anyone remembers any laws of thermodynamics where entropy always increases overall (all you need to know is the hot ALWAYS goes to cold to balance out - if anyone ever says, "Shut the door your letting the cold in", I will give them a dry slap) they will know that the hot core of the intercooler will always give it's heat out to the cooler fins (even if they are only slightly cooler). This is the reason an intercooler splitter works to reduce charge temperatures so well - as more cold air hits the fins, taking more heat away, making the difference in temps between the fins and core greater, making the core give up more heat, making the air inside it denser [and breathe].

Conversely a silver coloured intercooler will do the same job (silver both reflects and absorbs heat[energy] averagely), though just not to the same extreme as a black will [absorbs the most, but reflects the least].

If anyone wants a more detailed explanation see me after class, and before anyone questions me for the above lecture my MPHYS says so

 

A+ for you my lad.

 

Mmmmm ..not sure which colour to go with now, silver or black?
What do you guys think?

 

Fantastic explanation mate.

See you lot, i wasnt winding you up regarding the black being better

 

Black, for sure. Personally, I don't like the look of an Impreza with a front mount, but with a black core it gives the car a standard look. This was exact reason I chose an APS FMIC when looking around for a front mount, at the time they were the only manufacturer who did black core FMIC's. I believe Perrin have also recently added it to their range.

 

I'm not sure that just painting it a colour is really going to make much of a difference. If the whole thing is black the process I explained in my post above will happen more, the more black (the more absorption) the cooler the inside air.

Don't forget that it you're sitting around in traffic, warm day etc, your black intercooler will be more susceptible to heat soak!!! So you can't have it all. I would think a black one is suited to those with a large volume of cool air passing over it - i.e. track cars or front mounts.

Probably the reason the silver one is used with it's average of absorbing and reflecting. That and the a turbocharged engine is FAR more effective with one (any one) than without.

 

Thanks guys - I knew those 4 years would come in use somewhere

 

I'm still not convinced how something that absorbs heat well (making it warmer), can make something that passes through it cooler than something that doesn't absorb heat very well (making it cooler than the thing that absorb heat well).

The whole idea of the intercooler to start with is to cool the air passing through it by means of air passing through the fin filled tubes/bars in the intercooler. Conductivity isn't it?

If black absorbs heat so well (which it does) then the intercooler fins must be warmer so the air passing past the warmer fins isn't cooling down as much as it would if the fins were cooler like in an intercooler coloured in a not so heat absorbing colour, like silver.

Can somebody point out where I am wrong in the above because I dont understand.

Oh and Arabs wear THIN black loose fitting robes to promote sweating which inturn cools them down. They are thin to allow the breeze (if any) through to cool the sweat on the skin.

 

I will do this tomorrow Nick although see post 23 for an almost answer. I might even draw a diagram

 

Conclusion- Never stand downwind of an Arab in black!

JohnD

 

 

Or an Arab in black's camel.

Mark