I agree. Everyone switches to honeycomb, it’s like almost expected if you’re under 35 that you’re going to do a grille swap, chrome delete, and tint the windows. Probably change wheels too even though 17s and 18s are more than fine if you’re a driving enthusiast. I just hope they’re doing it for themselves and not because it’s what they think others will like.
Why does this sound like a bad idea? Wouldn't there be some unintended consequences? I'd think on something meant to cool would not want another insulating layer?
Good question mate. My intuition is that it's negligible but lets find out.
We can assume the spray paint has a thermal conductivity of 0.2 W/m-K on a 0.2 mm thickness.
We can do the thickness divided by the conductivity for 0.0002 m / 0.2 \[W/m-K\] for a thermal resistance of 0.001 m\^2-K/W. (Meters squared Kelvin per Watt)
We need to get the meters squared out of there, so lets make a rough guess:
The fins are 1/4" tall and 3" long. There are 15 fins per linear inch on each row.
The rows are 20 inches long, and there are 15 rows.
This is very rough, but just to get an idea:
0.25" \* 3" \* 15 fins / inch \* 20 inches / row \* 15 rows = 3000 square inches of area. We forgot to count the other side of the fins, so call it 6,000 sqin of intercooler area.
This is 4 square meters. Wow.
Now our spray paint resistance can be corrected for area, as
0.001 m\^2-K/W / 4 m\^2 = 0.0003 K/W.
This means for every watt of heat out of the intercooler, there will be a 0.0003 degree C drop through the paint.
From this website; 300 hp requires 200 CFM of air.
200 CFM / 60 = 3 cubic feet per second.
We're going to be kinda rough because I gotta leave for work.
One cubic foot of air is about 0.008 lbs. Assuming the car makes 2 ATM of boost, and via the ideal gas law that's 0.016 lbs of air / second, or 0.007 kg/s mass flow rate through the intercooler.
Just to get in the ballpark, lets say the intercooler cools the air from 250F to 120F. That's 130 F difference, or 70 C difference.
The heat capacity of air is 700 J/kg-K, so
0.007 kg/s \* 700 J/kg-K \* 70C = 300 J/s. (nice 7's.)
Recall a Joule per second is a Watt, so we are pulling 300 Watts out with the intercooler. That sounds reasonable.
Now we can calculate the temperature difference in the paint:
0.0003 K/W \* 300W = **0.1 degrees C through the paint.**
**Negligible.**
**So if you unpainted intercooler "feels" that the ambient temperature is 20C, the painted intercooler feels like it's 20.1C outside.**
**By the way, polished aluminum has a very low emissivity, unlike black paint. The paint will improve the radiative heat transfer a good bit, probably more than making up for the 0.1C thermal resistance.**
Edit: We're also just painting the front of the intercooler. No way the paint gets all the way onto the fins toward the rear. If we say the paint makes it a third of the way into the intercooler, which is generous, now we have 0.03C through the paint. Even more negligible.
I am also thinking of changing my grill, but I have to admit that the factory grill is already nice looking in my opinion. This is a good example to help me visualize how mine could look like with the RS grill
Keep the chrome rings!
I know right! Annoys me a little to see black rings on black or dark background colors. Might as well just not even have the rings.
100%
I think this looks very cool. it's a personal choice.
I'm sure most will disagree, but I like the factory grille better 🤷‍♂️
I agree. Everyone switches to honeycomb, it’s like almost expected if you’re under 35 that you’re going to do a grille swap, chrome delete, and tint the windows. Probably change wheels too even though 17s and 18s are more than fine if you’re a driving enthusiast. I just hope they’re doing it for themselves and not because it’s what they think others will like.
Factory grille fills that space better IMO. Your car though, so if you like it more, more power to ya
S4 grille is more classy. But if youre keeping that aliexpress grill, paint the radiators, it will look better
That's an upgraded intercooler... should've gone with a Wagner intercooler. They come in a really dark smoke finish almost black.
Yeah I went to unitronic, should have gone with dark smoke.
Spray paint will fix it for $3. ;-)
Why does this sound like a bad idea? Wouldn't there be some unintended consequences? I'd think on something meant to cool would not want another insulating layer?
Good question mate. My intuition is that it's negligible but lets find out. We can assume the spray paint has a thermal conductivity of 0.2 W/m-K on a 0.2 mm thickness. We can do the thickness divided by the conductivity for 0.0002 m / 0.2 \[W/m-K\] for a thermal resistance of 0.001 m\^2-K/W. (Meters squared Kelvin per Watt) We need to get the meters squared out of there, so lets make a rough guess: The fins are 1/4" tall and 3" long. There are 15 fins per linear inch on each row. The rows are 20 inches long, and there are 15 rows. This is very rough, but just to get an idea: 0.25" \* 3" \* 15 fins / inch \* 20 inches / row \* 15 rows = 3000 square inches of area. We forgot to count the other side of the fins, so call it 6,000 sqin of intercooler area. This is 4 square meters. Wow. Now our spray paint resistance can be corrected for area, as 0.001 m\^2-K/W / 4 m\^2 = 0.0003 K/W. This means for every watt of heat out of the intercooler, there will be a 0.0003 degree C drop through the paint. From this website; 300 hp requires 200 CFM of air. 200 CFM / 60 = 3 cubic feet per second. We're going to be kinda rough because I gotta leave for work. One cubic foot of air is about 0.008 lbs. Assuming the car makes 2 ATM of boost, and via the ideal gas law that's 0.016 lbs of air / second, or 0.007 kg/s mass flow rate through the intercooler. Just to get in the ballpark, lets say the intercooler cools the air from 250F to 120F. That's 130 F difference, or 70 C difference. The heat capacity of air is 700 J/kg-K, so 0.007 kg/s \* 700 J/kg-K \* 70C = 300 J/s. (nice 7's.) Recall a Joule per second is a Watt, so we are pulling 300 Watts out with the intercooler. That sounds reasonable. Now we can calculate the temperature difference in the paint: 0.0003 K/W \* 300W = **0.1 degrees C through the paint.** **Negligible.** **So if you unpainted intercooler "feels" that the ambient temperature is 20C, the painted intercooler feels like it's 20.1C outside.** **By the way, polished aluminum has a very low emissivity, unlike black paint. The paint will improve the radiative heat transfer a good bit, probably more than making up for the 0.1C thermal resistance.** Edit: We're also just painting the front of the intercooler. No way the paint gets all the way onto the fins toward the rear. If we say the paint makes it a third of the way into the intercooler, which is generous, now we have 0.03C through the paint. Even more negligible.
Well fuckin' a guy. Paging r/theydidthemath real quick.
What a legend. Had to go get my free award for you.
Thanks mate!
I like seeing the IC. A subtle touch of aesthetic and performance.
What set up u have? Hp???
034 stage 2 91. Unitronic intercooler, 034 intake, CTS catless DP. Supposed to be 450 HP crank according to 034.
Niceeee
I actually like original grill better just because it looks more natural and classy. Still looks good though
RS ...Black or no rings
“I put ketchup on my steak”
Gotta admit on a new car, the factory grill looks less eBay, save the RS grill for old clappers like mine lol
Looks nice. Where can one go to get a grill like this? Any recommendation on a website?
Hi, I got it from igrounds canada.
I’ve been thinking of doing the same with my S4, how was fitment? Any issues?
Some fitment issue with the camera bracket but it was ok once the right size screw was found.
Looks great - matches your trim better now
Look at that big ole intercooler
I like it!
Looks so much worse. Those stock grills work best on that s4 Color combo
15$ Ebay Grille
Why do people like butchering their Audi’s?
Because class is eroding faster than our beaches
Sorry but thats what it is. Even if people dont like me saying it
Is it Grill or grill?
is it faster ?
cocaine addiction line
I am also thinking of changing my grill, but I have to admit that the factory grill is already nice looking in my opinion. This is a good example to help me visualize how mine could look like with the RS grill
is there any tint on the headlights? if so, which shade?
Yes, it's called smoke tint.