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...c&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/ult...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 *** runners, but if you can find the right brush..

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. 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?

 

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.