What is the concensus on the various coatings.....Internal Heat Coating/Barrier and External Heat Coating/Barrier? Some have said that just the internal coating is worth the $100 or so but the external coating will trap heat and is not worth the $300 to $500 price tag. So let the opinions begin.
well, seeing as i am coating the outside of my intake in black...... i sure hope it works good!!!! hehehehe
There is allot of mis-information out there in regards to coating a manifold. I have seen numerous, "I can hold my hand on the manifold" comments which actually is a bad thing. You want the manifold to be hot to the touch, that means the heat is dissipating out of the manifold, if it is cool to the touch, that just means the coating isnt allowing the heat to transfer out of the manifold. What you want is a thermal block ceramic coating on the bottom and on the flanges, on the sides and top, you want a thermal dispersant to alleviate built up heat inside of the manifold. If your manifold is cool to the touch, you have a problem, if anything, you want the outside to be hotter than it was before. If the outside is cool, that means all the heat is inside the manifold heating up the air coming through. Here is my ideal setup. Extrude Hone Manifold (smoothest possible surface area to increase air speed) Thermal block on bottom plate and flanges Thermal Dispersant up top and on sides to disipate heat The silver header coatings you see are thermal blocks holding heat in, after 5 minutes, they are cooler to the touch than an uncoated header, that doesnt mean the inside is cooler, it just means the coating is holding the heat in. You dont want the manifold to be cooler than stock, if it is, its not dissipating heat. Sorry for the long winded post.
I take it that's using my intake manifold and not an already honed one? How long does it take to do?? (thanx for the info, btw)
There is about a 2 week turn-around. I can do this to one of our cores and send it to you and place a core charge on your credit card that could be refunded once we receive your manifold or we can apply the porting to your manifold itself. This is the best method if you have a new car with a flawless manifold.
Yea, that'd be me, an 06 but only 5K miles on it and I DON'T let the motor get dirty at all (yea, I'm a bit anal, lol!). Thanx for the info, I'll keep it handy for when/if I decide to do this mod!
How does the air flow of an "Extrude Honed" manifold compare to the air flow of a manifold that has been ported and polished? Does the Extrude Hone process do the same as a Port and Polish job? Disregard the coatings for this question. On a side note, how come no one Extrude Hones cylinder heads?
there are companies that sell extrude hone heads, but you dont really want a smooth surface on the cylinder heads as somewhat of a rough surface helps the fuel and air atomize better. An extrude hone manifold is better than porting, because it goes everywhere. It doesnt only port certain sections. Its like enlarging the end of a straw, does that increase the flow? Not really because the rest of the straw is still small. The same thing applies to manifolds. Extrude hone is an abrasive gel that is flowed throughout the entire mannifold to get an even smooth porting surface throughout, not just the areas you can reach. I hope this makes sense as it is late and I may not be making any sense.
This raises an question in my mind, what's your take on phenolic spacers? Are they hurting power in your estimation by not allowing the block to dissipate heat through the manifold?
I just got an extrude honed intake manifold on my 426 build that PPP just did for me last week. Search the site for pics. It's beautiful. Chase
This all assumes that there is heat IN the manifold to begin with right? Here are my thoughts from the last discussion and experimentation which ended when Cam failed to get a temperature probe inside the manifold right at the intake port of the head. First of all I don't think anyone has really quantified the problem itself. At a reasonable rpm the motor will change the air in the manifold in less than a second (maybe a LOT less than a second?). We calculated it last time with a rough estimate of the manifold volume. Not all of that air is coming in contact with or proximity to the inner surface of the manifold. So how hot does the manifold need to be to raise the intake air temperature as it passes through there. Let's say the intake air is 70* and the manifold is 200*. What temperature will the air be when it enters the intake port at the head? at say 4K engine rpm? Think about those shop heaters that look like a jet engine. The heating elements in those things glow at a pretty hot color. The manifold isn't getting anywhere near that hot. It may or may not be significant. Given that let's move on. Once you get to the manifold you're stuck with whatever the intake air temp was entering the throttle body. I think everybody agrees there isn't much hope of cooling the air as it passes through the manifold. What you don't want is for the manifold to heat it up any more. If the manifold is going to heat the intake air it has to be hotter than the intake air. The manifold doesn't generate any heat on it's own so it can only conduct and radiate heat from other sources. Below it you have the engine and above it you have the engine bay air (indirectly heated by the engine - coolant raidator and heat radiating off the headers). I think we can assuming the intake air will be cooler than both of these. So you would want to insulate the intake air from both these sources. If thermal barrier coatings were 100% efficient you would coat the top of the engine in the center, the inside of the manifold and where it contacts the gasket. You wouldn't care if the manifold itself got hot because of the perfect thermal barrier lining the inside. So the barrier and phenolic spacers are not perfect. Some heat will be conducted by the manifold and leak through the inner barrier to warm the intake air. Assuming the manifold gets hotter than the engine bay air you would want it to radiate heat into the engine bay. A heat conductive coating on the outside of the manifold might help somewhat. If the phenolic spacers and/or thermal barrier do a good job the manifold may well be cooler than the engine bay air temperature. In this case you would want a thermal barrier on the outside of the manifold as well. small note here. Polishing the outside of your intake would probably decrease it's ability to conduct heat since there is less surface area on a smooth surface than a rough one. Could be good or bad. see above. So if a thermal barrier on the inner surface of the manifold is fairly efficient it doesn't matter how hot your manifold gets. If it's not then you want the inner surface of the manifold as cool as possible and increasing it's ability to radiate it's heat to the OUTSIDE might help. Note that the manifold does not generate any heat on it's own. If you made the outside temperature of the manifold hotter than it was before by doing something you would have taken a step backwards (by conducting more heat through the manifold from somewhere else). I think ideally you want a thermal barrier inside the manifold (surrounding the intake air) and a radiant coating outside the manifold. See first paragraph, it might be like buying a space shuttle to get your lunch pail to work. We could solve this and most of the problems of the world if someone would just make a head with a temperature probe at the intake port. (P.S. I think this is worth at least $100 casino bucks on post size alone. More if it's not completely wrong)
Sounds like a very educated post and not a sales line. Thanks for the insight on this matter. I too have been looking into a P&P manifold and we share the same thoughts on why the coating is really worth it. I disagree with Extrude honing however. I think we can all agree making these things too big will begin to loose us power.
I didn't say the coating is worth it. I don't know. I think it depends if the problem is significant in the first place. I am fairly sure that if you wanted a coating on the inside it would be a thermal barrier coating. If you wanted a coating on the outside the type would depend if your manifold is hotter or cooler than the engine bay air temp.
(this thread didn't just die did it?) I'm thinking that, at 4K rpm, the intake air only spends about 0.03 seconds in the intake manifold. Is that right? I'm not sure about the volume of the intake manifold. Just eyeballing it looks to be about the same size as 2 or 3 2-liter bottles? So I used 6.1L just for convenience. Probably on the large size? Engine displacement is 6.1L Engine sucks in it's displacement every 2 rotations At 4000 rpm that would be 12,200L per minute 12,200L per minute would be 203.33L per second To get 203.33L per second through a 6.1L container you would have to change the air in there 33.33 times per second That would mean that any bit of air would only spend 0.03 seconds going through the manifold. That sound right? (assuming the manifold has a 6.1L volume)
dave - the thread has not died, it has just put everyone reading it, into information overload!!! btw, where are the pics??? hahahahaha i actually found the information very informative!! for that, i thank you my friend!!!
I'd say no. Without the spacer the manifold would be acting as a radiator and helping cool the engine. With the spacer you should be cutting that off (to some extent) so the heat that was being radiated off the manifold has to go somewhere. That would be easily taken care of by the coolant system. Our coolant systems have loads of capacity.
