Adam's powder-coated intake thread reminded me of this: I heard once that powder coating your intake manifold helps REDUCE the temperature of the manifold itself... as it was purported to act like insulation from the hot engine bay. True? False? My initial reaction is false, but then again, I really don't know shit.
Momo, insulation is just that. It's a barrier preventing a TEMPURATURE difference from one side effecting the temperature on the other side. We're worried about heat. So insulation is to stop the transfer of heat. Now look at the sources of heat with respect to the intake. Think of the manifold and heads as sort of a bread box where we want to keep the air inside as cool as possible. We don't want the manifold heating the air inside of it. The heat sources warming the manifold (or possibly cooling it) are the surrounding engine bay air and heat conducted directly from the engine/block. For all practicle purposes we can assume the intake air will always be cooler than the manifold. Sooo... If the heat conducted directly to the manifold from the engine is greater than the heat conducted from the engine bay air then we would want the manifold to RADIATE heat into the engine bay making it cooler than if it didn't. Insulating the manifold in this case would impede that. If the heat conducted from the engine bay is greater then we WOULD benefit from insulating the manifold. The above assumes the thermal barrier is on the outside of the manifold. If you used some sort of phenolic spacer between the manifold and the heads this would provide a thermal barrier between the engine and the manifold. Assuming this is effective, the engine bay heat should become the greater source. So coating the outside of the manifold and using a phenolic spacer should give the most benifit. Depends on how much heat is attributable to each source and how effective the barriers are. If one were to only coat the manifold then coating the INSIDE of the manifold would be most effective. This would reduce the heat from a hot manifold from warming the intake air. Might end up with air flow problems though... So it depends... where is the most heat coming from? What's the application? If you're tracking the car then the heat evacuation from the engine bay will be much greater. If you're waiting to drag race it's probably the other way around. Now consider the discussion of how long it takes a particular bit of air to get from the throttle body into the cylinder. Just how hot does the manifold have to be to change the air temp significantly? If the manifold is not glowing does it make a difference?
holy shit, you have some of the most deep posts i ever read dave....... although this comment: "If you used some sort of phenolic spacer between the manifold and the heads this would provide a thermal barrier between the engine and the manifold. Assuming this is effective, the engine bay heat should become the greater source. So coating the outside of the manifold and using a phenolic spacer should give the most benifit. Depends on how much heat is attributable to each source and how effective the barriers are." is exactly what i am planning to do when the BT spacers finally get perfected (if they have not already) and then powder coating the manifold like the car...... oh yeah, you also forgot the "it makes the engine bay purdy" comments......lol
D, My head hurts just from reading that! I was hoping for a yes or no, but that is for the challenged polk det be me......................... Jason is going to fall asleep before he hits the third paragraph!
Chris you love to use that two sided verbage don't you! Dirty little boy....Now Dave is going to think he is Shaq!
Oh yea, I'd say the primary objective is to keep the ENGINE cool. Obviously the coolant is the predominant mechanism for doing this but heat radiated elsewhere is significant. The intake manifold provides a lot of heat radiant surface. Heat is conducted from the block and radiated from the manifold. Without phenolic spacers I think the manifold will be hotter than the engine bay air as long as you're moving. Maybe all the time. It's probably the case that engine cooling from manifold radiation is very small compared to heat carried away by the coolant... which is transferred to the air coming into the... engine bay. But maybe it's something that should be quantified. When you use phenolic spacers the heat that used to be radiated from the manifold needs to go somewhere. Apparently our coolant system has loads of capacity so a bit more to handle there probably isn't significant, but how much is that?
I've got 2 leads right now. One or both should pan out in the next week or two. Sorry, but they're both short term loaners and not up for sale.
adam - this is all i am looking for as well!!!! :worthy: keep me in mind buddy!!! i just want a loaner while mine is coated!!!
Don't forget this part. Somebody did the calculation but I forgot. Engine displacement = ? The motor displaces that much air every 2 revolutions. At 4K rpm it's displacing 2K x cubic inches every minute. Figure the volume of the intake manifold and I think the air is completely replaced in a fraction of a second. How much can it be heated passing through there in that amount of time with that amount of surface area?
Holy Shit Dave... you're drowning me with knowledge that I could never absorb! Fuq! So, it could help or hurt depending on where the heat is coming from... got that much. So, hopefully Adam can disclose his Top Secret, Compartmentalized information to the masses.
Well, maybe after that comment I shouldn't. I just wanted to check with Cam, who did the testing. I didn't want him to get barraged with PM's and have no idea why. Its called courtesy, look it up. Cam has done a lot of heat transfer testing on our manifolds when he was testing the efficiency of phenolic and billet tech spacers. He has tested on his old mainfold (powder coated) and his new manifold (bare aluminum). His testing showed that the powder coating dropped the temps at the top of the intake by 20 degrees as compared to the bare aluminum. Both were tested with the same spacers in place. So, bare aluminum was the same temp from flange to top of the barrel. The powder coated intake showed that the top of the runner was 20 degrees cooler than the flange. This was not a 100% lab controlled scientific test, which is why it was not written up. So this is anecdotal evidence and you should draw your own conclusions, or do the experiment yourself.
No doubt the outside of the manifold would be cooler. That only means that you have less chance of burning your fingers when you feel to see if it's working. The question is: was there a difference in air tempurature entering the cylinders?
Honestly, I don't know about the air temp entering the cylinder. My thinking is along the lines of heat transfer, like you previously posted. The flange is hot from the block. So I attribute the temp difference between the 2 mainfolds to the powder coating reflecting radiant/ambient heat, I think its especially important on the bottom manifold plate above the valley. If the runner is cooler, the air in it SHOULD (not tested) be cooler too.
I have another question/speculation. I assume the coated manifold is coated on the outside? If so, how do you know that the manifold itself, underneath the coating, is not hotter than it was without the coating (heat trapped inside)?
Haha, think of it like a poptart. Might feel ok on the outside but when you bite into it you burn your tongue on the jelly inside.
Oops, I was assuming a thermal coating. If I remember correctly you are experimenting with powder coating (paint?). Do you think that's an insulator or a conductor? Both might make the outside surface temperature lower.
