Teflon Coating Intake Runners

The recent thread in coatings got me fired up again. :) During my research I came across Teflon coating of intake runners. I see that Teflon coating is banned in certain forms of racing. Does anyone have any experience in this area?

I'm going to have the bottom side of my intake coated with a thermal barrier. Was doing some research on a themal barrier on the inside of the intake runners and ran across the Teflon idea.

Just looking for ways to keep the intake charge cool as it gets to the heads. The Teflon appears to be a themal barrier and also might increase the flow. Could kill two birds with one stone if it works. ;)

Maybe it eliminates the "barrier layer" and allows just a little more airflow?

A guy over on the Impala forum used an epoxy coating that he was abe to see gains with. I plan on trying it with my intake when it comes off in the near future.

http://www.impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=003155

Troy

Thanks for the post. That is a good read and is exactly what I'm trying to accomplish. The post was from 4 years ago and hopefully there have been some advances and knowledge gained in coatings since then.

If I could pick up say 10-15cfm from the coatings in my intake track and keep my IAT just a couple of degrees above ambient as it enters the head that could be worth maybe 20 horsepower. The cooler air would also help to keep detonation under control.

http://impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=004589;p=2 Another good thread on the ImpalaSS forum regarding coating the intake. By the way I agree with Stonebreakers assessment on the coating issue. ;)

Yes stony knows his crap when it comes to stuff like this...

"Well, if you want to check my work, go here:

Newton's Law of Forced Convection


The rate of heat transfered to the surrounding fluid is proportional to the object's exposed area A, and the difference between the object temperature Tw and the fluid free-stream temperature .
The constant of proportionality h is termed the convection heat-transfer coefficient. Other terms describing h include film coefficient and film conductance.


Look closely at the above formula. There is no time parameter. The amount of heat transferred is dependent on the area of the surface, not how long it's in contact with it. This is just for the film of air next to the walls of the intake, but the heat still gets into the cylinders.

OK, how much heat gets transferred? Well, using data found on the web at MatWeb and Heat Transfer Coefficient Conversion Factors, it turns out that the h factor in the above equation is equal to

h = 2.360850287 W/(in².°F)

The length of the manifold is what, about 22 inches? And the cross-section of the manifold plenum is an irregular hexagram, but close enough to an equilateral triangle so as to not matter. I'm guestimating the interior of the plenum to be roughly 200 square inches, although if you count the runners it's probably quite a bit more.

I would guess the manifold on my car reaches roughly 140 degrees by the end of a drag race - too hot to touch comfortably; and if the incoming air is at, say, 80 degrees, then delta-T is 60 degrees. Halving that to account for the intake being nearly at ambient at the start of the race, then the average delta-T is 30 degrees. So plugging all that into Newton's equation, you come up with roughly 14,000 watts of heat going back into the engine. Divide that by 740 watts per horsepower and you get about 19 horsepower.

So, just doing a rough estimate, there are 19 horsepower being lost, on average, because of air being heated by the intake manifold. Based on my ET and mph improvements, I'd guess I'm recovering roughly 10-12 horsepower by coating the inside of the intake. Somebody who road races would see an even bigger improvement."


Based on this and the thermal protection that he calculated with the epoxy, I think that there may actually be an easy 10 hp with the coating, depending on the application. I'm just not sure I have the time patients to do the inside where he says it is as beneficial, if not more than the underside. Somewhere in those posts I think he says that he has the epoxy built up to almost 1/2" on the underside of the intake!

Troy

PimpSS96 what did you coat the inside of your intake with? The same epoxy that Stoney used? I have a highly modifed TPI that I will be doing this to. I want to coat the inside of plenum. I don't know if its worth it to coat the bottom of the intake as I have the egr and water flowing through it.

I want to coat the inside of the runners on the intake manifold and also the fully siamesed SLP runners. If the coating on the inside of the runners and intake manifold will also help with the air flow that would be an added bonus. I will be talking to some of the local coating places. I have already lined up the local Tech Line place to talk to.

I personally have not done it yet...but will be when the intake is off the car soon...

I plan on trying the same epoxy stone used. He said that he used a bunch of the foam brushes and made sure the epoxy was at least 85* so that it was easier to work with...a TPI may be a bit of a pain with the long ass runners, but if you can find the right brush..:confused:

With the EGR and water flowing through it, I really wonder what gains you will see with any coating though...I think stone did this in conjunction with the EGR delete and TB bypass. I think he even talks about EGR making gains minimal at best, but I am not sure.

Troy

I would think there would still be a gain even with the egr. The egr isn't active at wot and as stated can be deleted for best results. A while ago I was planning on ceramic coating my manifold until I realized it would just turn into a giant heatsoak with the egr hooked up. Without the egr it should work well.

Went by two coating shops today. The first one dealt with Teflon. He could do the job but was not sure on the thermal conductivity of the Teflon outside of the fact it would be a lot better than aluminum. He recommended using Teflon PFA. Cost would be $300 for all the parts. Got to research this some more.

Second shop uses the standard heat barrier coatings we have heard so much of lately. I explained to him what I wanted to do and he immediately understood what I wanted and was talking about and recommended a product that would do the job. He has done the exact same thing for some racing teams. :D What he has done is coat the inside of the runners with the same thermal barrier material that he uses on pistons. So he effectively supported stoney's position. His cost was $400. He also stated that in my case coating the underside of the intake manifold was not that effective.

Here is my thoughts on coating the runners on a TPI intake manifold. With the thermal barrier in place it would be hard for the heated intake manifold to transfer heat to the incomming cool air charge. The themal conductivity would be very low. I agree between runs the air would heat up but once the motor is running the cool air would take over very soon and the heat could not transfer fast enough to warm it up much.

Believe with the modified TPI coating the inside of the plenum will be no problem as the side are opened up between the ports. :) I have also realized that with a TPI system there is a lot of square inches of aluminum to heat things up. Probably double what is on at LT1 intake.

If ya just do the bottom and the gasket surfaces with a thermal dispersant ya won't need to do the inside of the ports.Ya could do it on the outside of the intake also but the coating I use only comes in black. As ya said when it is running the temp will fall back to ambient. Ya need to check the temp of everything from the filter to the TB 'cause all that piping gets HOT."O" did ya forget about the lonely head port that has 160+* water cooling it? Or the valves that get very hot. Ya can get carried away with coatings.

well teflon's flux (basically ability of air to flow across the surface) is going to be better than polished aluminum (polishing is another way to decrease surface area significantly and increase the flux of air over the surface)

so less area = less heat transfer
less flash and less area = higher flux
and a high tech teflon coating is also going to be less porous than aluminum and allow more air to flow over it than aluminum, the same as aluminum is to cast iron.

so basically, if you coat, coat everything, inside the runners it will act as a secondary barrier, and allow extra cfm because like i said, it'll smooth the surface, and the material will raise the flux as well. on the outside it'll act as a barrier to splashing oil. if you can get it in the heads and get some good SS valves even better, but if you atleast get it in the intake, less heated area will come in contact with the intake charge and thus there will be less heat transferred because only so much heat can transfer at a time as pimpss has stated

however i disagree with 1racerdude, heat will still transfer, especially if you're running an aluminum intake, aluminum is one excellent conductor, it's why it's used on electronic heat sinks and in your radiator, but simply being in your engine compartment will transfer heat to the intake, being connected to the alternator will transfer heat. and as well as 1racerdude has noted, since you have 160-180* water running through your intake, the ports are the only place it will matter, inside the coolant runners will keep water heat in the water, and inside the intake ports will keep intake heat out of the air

Present thinking on ports is ya DON'T want smooth runners.

If ya put a heat shield coating on the bottom and a heat dispersant on top there will be NO HEAT TRANSFER.

Epoxy is no heat barrier and will absorb heat like aluminum. The bad part is the difference in expansion and it possibly popping off if not prepared properly.

what's wrong with smooth runners?

what's wrong with smooth runners?

They don't work.... a semi smooth finish is much preferred.

Look at a set of pro ported heads and they DON'T look like a mirror.

.....So plugging all that into Newton's equation, you come up with roughly 14,000 watts of heat going back into the engine. Divide that by 740 watts per horsepower and you get about 19 horsepower.

So, just doing a rough estimate, there are 19 horsepower being lost, on average, because of air being heated by the intake manifold. Based on my ET and mph improvements, I'd guess I'm recovering roughly 10-12 horsepower by coating the inside of the intake. Somebody who road races would see an even bigger improvement."


I'm not sure I understand your logic. Are you saying that the heat transferred from the intake manifold to the air goes into the cylinders and reduces HP? Power is lost because the heat transfered to the air decreases the density of the air = less fuel burned, not because "of heat going back into the engine".

They don't work.... a semi smooth finish is much preferred.

Look at a set of pro ported heads and they DON'T look like a mirror.


I always thought that was due to the sanding materials they use.

I always thought that was due to the sanding materials they use.


It is but they could polish it like a mirror or a set of wheels to be like chrome. That was done back that way in the '60's until it was found out that a rougher surface would make more HP.

I have heard the same thing. It was explained to me that a slightly rougher surface produces a slight amount of turbulence which in turn helps to atomize the fuel a little better.

I have heard the same thing. It was explained to me that a slightly rougher surface produces a slight amount of turbulence which in turn helps to atomize the fuel a little better.

Correct
It strengthens the boundary layer and helps with fuel separation.

That doesn't mean that a smooth surface won't flow better, just that a rough surface will keep fuel in suspension better. That would suggest that if you could wet flow test the intake side of an engine you’d probably find that you only needed rough surfaces in a few areas, and almost nowhere in an FI setup.

That doesn't mean that a smooth surface won't flow better, just that a rough surface will keep fuel in suspension better. That would suggest that if you could wet flow test the intake side of an engine you’d probably find that you only needed rough surfaces in a few areas, and almost nowhere in an FI setup.

NOT correct.

NOT correct.
Agreed.

In a FI car it will push harder against the walls meaning it might want to smooth out more. Just because air is moving faster with more pressure does not mean it will keep the fuel atomized. If anything I would think it will work the other way. Kind of like compressing air in a tank, and you get water droplets. Just my logic, I could be wrong though.

About the intake manifold, I think keeping it cooler would help, but not because energy is being lost into the manifold. It would just help keep the air a little denser until it reached the cylinder.

In this case we are talking about a fuel injection system. So there will only be air and no air/fuel mixture until we reach the heads. So the runners in the heads should remain unpolished to help the fuel suspension. IMHO anything upstream of the heads would help the airflow if it was smooth such as using the Teflon coating.

Couple of thoughts. If the Teflon coating increased the intake air flow by 5 cfm that would be equal to around 10 horsepower. If the Teflon coating turned out to be a good themal barrier that could very well be worth another 10 horsepower. I believe both scenarios are entirely possible so I will have to give it a try.

From my reasearch I have found that teflon PFA as a thermal conductivity of .19 w/mk. If anyone on the forum can shed some light on that number I would appreciate it. Thanks

my head hurts.

From my reasearch I have found that teflon PFA as a thermal conductivity of .19 w/mk. If anyone on the forum can shed some light on that number I would appreciate it. Thanks
According to what I found on the internet that number means the "thermal admittance". For every one degree in temperature change on one side, the other side will see .19 degree change. Hopefully I interpretted wikipedia right.

mirror finish is going to have better airflow characteristics near the walls, less turbulence, higher flux, less area and less heat transfer.

yes most prefer semi smooth because this will aid in mixing the air fuel mixture completely, however if you are looking at cfm alone smooth will do it.

if you account for the fact that extra mixing helps, well, then you're adding in an interesting variable, because at high rpm, the mixture near the walls won't move near as fast as the mixture in the center due to the turbulence along the walls. But when the mixture is moving slower, this turbulence will keep it mixed better until it enters the cylinder, which is an issue as the fuel particles will 'fall out' of solution with the air. So what you need is what you need.

EDIT: w/mk is watts per meter kelvin, and the equations involve area and thickness of material, basically the constant (.19) gets entered into an equation that incorporates the area of material and the thickness, then your time factor gets calculated and you get your change in temperature on the other side

It is popularly held that enlarging the ports to the maximum possible size and applying a mirror finish is what porting is. However that is not so. Some ports may be enlarged to their maximum possible size (in keeping with the highest level of aerodynamic efficiency) but those engines are highly developed very high speed units where the actual size of the ports has become a restriction. Often the size of the port is reduced to increase power. A mirror finish of the port does not provide the increase that intuition would suggest. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means. Exhaust ports may be smooth finished because of the dry gas flow but an optical finish is wasted effort and money.

The reason that polished ports are not advantageous from a flow standpoint is that at the interface between the metal wall and the air, the air speed is ZERO. This is due to the wetting action of the air and indeed all fluids. The first layer of molecules adheres to the wall and does not move significantly. The rest of the flow field must shear past which develops a velocity profile (or gradient) across the duct. In order for surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this.




A common beginning porter’s mistake is to apply a nice, shiny finish to all ported surfaces. If your heads come back this way from a tuner, expect less, not more power!

Thanks guys for all the input. Here is something for comparison. 6061 aluminum has a thermal conductivity of 171 W/mk. The PFA Teflon has a .19 W/mk. So the Teflon is 900 times a better thermal barrier than the aluminum. I think that gives me the information I need. Teflon here I come. Still open to opinions.

Some more on how to do it.


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Coating an Intake Manifold

There are two reasons for coating an intake manifold. The first would be Performance, the second Appearance. Let's discuss Performance first.

In this instance, you are dealing with heat that is generated by the engine. You will also acquire heat from the hot oil that may be tossed up under the underside of the intake manifold. This means we want to apply a thermal barrier ( TLLB, CBC2, CBX, MCX ) to the bottom of the intake manifold, the flange area where it would bolt to the head and also the flange area where the carburetor would bolt to the intake manifold. This will reduce the amount of heat that enters the manifold itself, keeping the manifold cooler. Typically, a normally aspirated engine will see a 1% improvement in power for every 10 degree drop in carb air inlet temperature. A Turbo charged engine will see a 2% increase. Keeping the manifold cooler than normal allows an engine to generate more horse power. In addition to this, you would coat the top of the manifold with a thermal dispersant such as our TLTD. This means that the heat that does get into the intake manifold will be more rapidly dispersed into the air moving over it, thus cooling the intake manifold further. This gives you a greater chance of creating more horse power by reducing the inlet temperature. You can also coat the inside of the runners in an intake manifold. You can use 1 or 2 coatings. A single coating that we recommend would be our dry film ( DFL-1, TLML or CERMA LUBE ). These are known as 'fluid retaining coatings' and the fuel/air mix as it passes through an intake manifold on a carbureted engine is treated like a 'fluid in motion'. The coating will have a tendency to create a small amount of boundary layer turbulence which will reduce fuel drop-out. You may also apply a thermal barrier to the inside of a runner first, then the dry film over it. If you're doing this, we recommend using our TLLB with TLML over the top of it. You not only create the boundary layer turbulence, you further reduce the amount of heat that does enter the fuel/air mix.

On the cosmetic side, while the TLTD is a very nice-looking coating, it is Black. If someone is looking for more show and they like a bright, polished appearance, then Cermakrome, as an example, can be used. Since Cermakrome is a thermal barrier, we recommend that you coat the bottom and the top. In this way, while you're inhibiting the amount of heat that can be dispersed from the top of the manifold because of it being coated, you're reducing the amount of heat that can be absorbed by the manifold because of the same coating on the bottom. Thus, you are at least creating an equilibrium and not dealing with a heat problem. The coating is extremely high temperature resistant, does not blue or discolor like chrome, does not oxidize significantly as a polished aluminized surface will, so you can maintain a very nice, high-polished surface not affected by fuel oils and solvents.

I had my intake manifold coated by Swain Technology ( http://www.swaintech.com/store.asp?pid=10961 ). I used their BBE heat emitting coating on the top and their TBC thermal barrier coating on the bottom surface. I don't have any before and after data to report, but they did do a good job, and the black manifold looks pretty good with the polished fuel rails.

Yep, that was helpful… first you tell me my response is totally wrong, then you repeat it and then make another BS statement…

Nutshell… if there is air/fuel flowing through it, generally some texture helps, usually in the curves and areas where the fuel would drop out of suspension if you didn’t create some boundary layer turbulence, otherwise there is an advantage to a smooth surface. Most turbulence, boundary layer or not causes the ports to act smaller (many significant areas of turbulence might as well be part of the port wall), unless there is some deficiency in the port shape (like it’s cast with a port floor that could really stand some filling) and making part of the port dead would help flow, gm actually did this OEM in some cases where they had crappy port entry angles between the heads and the intake.

Secondly, texture to the port walls allows the a/f charge to pick up more heat, this is especially useful for the MPG freaks out there that have found that exaggerating texture in the intake ports can actually impart enough heat to the a/f charge to have a similar effect on gas mileage as heating your fuel and air mixture (and also a similar effect at higher rpms, counterproductive to our MPG discussion).

As far as getting back shiny ports from a porter… it depends on where and when. The fact is a lot do it when it won’t hurt because the normal customer expects it. And in a lot of cases market expectations result in customer’s porting work looking different then what stays in the shop. I’ve seen things all shined and polished up with dimples formed in sections to prevent a/f separation.

Yep, that was helpful… first you tell me my response is totally wrong, then you repeat it and then make another BS statement…

Nutshell… if there is air/fuel flowing through it, generally some texture helps, usually in the curves and areas where the fuel would drop out of suspension if you didn’t create some boundary layer turbulence, otherwise there is an advantage to a smooth surface. Most turbulence, boundary layer or not causes the ports to act smaller (many significant areas of turbulence might as well be part of the port wall), unless there is some deficiency in the port shape (like it’s cast with a port floor that could really stand some filling) and making part of the port dead would help flow, gm actually did this OEM in some cases where they had crappy port entry angles between the heads and the intake.

Secondly, texture to the port walls allows the a/f charge to pick up more heat, this is especially useful for the MPG freaks out there that have found that exaggerating texture in the intake ports can actually impart enough heat to the a/f charge to have a similar effect on gas mileage as heating your fuel and air mixture (and also a similar effect at higher rpms, counterproductive to our MPG discussion).

As far as getting back shiny ports from a porter… it depends on where and when. The fact is a lot do it when it won’t hurt because the normal customer expects it. And in a lot of cases market expectations result in customer’s porting work looking different then what stays in the shop. I’ve seen things all shined and polished up with dimples formed in sections to prevent a/f separation.


If ya are referring to me then ya are incorrect about mirror polished ports and that is what I call smooth.
I have had more than one set ported and haven't seen mirror polished ports since the '60's.I have had head work done by some of the best too. They don't ask what type of intake ya are running whether it be Hilborns,Carb,EFI or Blower. They port them correctly.
If mirror polishing had ANY advantage there would be a LOT of it being done,which there isn't.
Haven't seen many ports that didn't flow fuel unless ya got a sprint car set up that is direct cyl injected where the injector is next to the spark plug.

I will quote again from the porting article I posted:
"A common beginning porter’s mistake is to apply a nice, shiny finish to all ported surfaces. If your heads come back this way from a tuner, expect less, not more power!"
So there ya have it.;)

So if you have a direct injected motor then mirror finish ports would be acceptable (and potentially superior)?

The way I'm reading this is that portion of the "intake tract" that actually carries an air/fuel mixture should have a rough finish. If that statement is true than that part of the "intake tract" that does not carry an air/fuel mixture but just air would benefit from a smooth finish. That is exactly what I intend to do.

it is not possible (with todays technology) to develop a useable boundry layer on a perfectly smooth surface...DON'T COAT THE INSIDE OF YOUR INTAKE RUNNER!

Just the right amount of heat in the intake runner will aid in vaporization...

it's just not as simple as these coating companies make it sound...

it is not possible (with todays technology) to develop a useable boundry layer on a perfectly smooth surface...DON'T COAT THE INSIDE OF YOUR INTAKE RUNNER!

Just the right amount of heat in the intake runner will aid in vaporization...

it's just not as simple as these coating companies make it sound...



And there ya have it from another expert.;)