Exhaust Manifold Temperature And Turbo Efficiency

[saliya]

There is another way. You can take an infra red photgraph of the exhaust manifold section that has been coated. If (& only if) the coating works you will see a significantly lower temperature on the exhaust manifold section that is coated. If it doesn't work you won;t see any real difference between the coated & uncoated sections. Do a search - you should find it.

Hi,

Are you talking about this pic?

I think that the deduction from the pic - "it isn't noticeably cooler where the coating is, therefore the coating is

ineffective" - is hard to justify; you don't know what temps were_before_ the coating. What's the big lump?

To show a change in surface temps that is attributable (or not) to a coating, you need to measure

the surface temps on the object before the coating is applied; then repeat the measurement post-coating

while making no other changes in conditions. Unfortunately, that hasn't been done here.

Then you have to say "OK, I measured the surface temps, but what does this mean for HP?"

The only way to measure the HP difference attributable to a ceramic-coated manifold is to

actually measure the HP, then add the coating, and then re-measure.

Regards,

Saliya

Edited June 1, 2006 by saliya

[xRHETTx]

From having a good look at that pic it seems the guyt that comment has got it wrong. The outer edge of the pipe on both sections is at about the same temperature, but the decrease in air temp within the coated section is much slower than that in the uncoated section. (The gradients in the graph are different, the gradient in the coated section is lower therefore less temp drop than the uncoated section with a larger gradient).

Conclusion: That coating keeps more heat in the exhaust air than with uncoated mild steel.

[xRHETTx]

And there's no way they are "surface" temps - if they were you expect purple colour all the way across - its more like a cross section or a sum of all the heat from that part of the pipe.

[djr81]

At the risk of starting WW3....

The 'guy" in question is a mate of mine, a bloke that I happened to sit next to for four years whilst studying mechanical engineering at uni. I say this only to pre-empt any claims that the photo is some random down load from the net.

The photo shows the dump pipe on a turbo charged 12A rotary.

The photo is of the surface of the pipe.

The discontinuity is the flange on the exhaust.

The section downstream of the flange is uncoated.

The comment attached to the photo is correct, ie the coating, if working, should substantially lower the surface temperature of the pipe on the sections that have been coated. Clearly it hasn't and it follows that the coating is not having any measureable effect.

Edited June 2, 2006 by djr81

[saliya]

At the risk of starting WW3....

Hi,

Boom!!! (that's tongue-in-cheek, by the way )

The 'guy" in question is a mate of mine, a bloke that I happened to sit next to for four years whilst studying mechanical engineering at uni. I say this only to pre-empt any claims that the photo is some random down load from the net.

The photo shows the dump pipe on a turbo charged 12A rotary.

The photo is of the surface of the pipe.

The discontinuity is the flange on the exhaust.

The section downstream of the flange is uncoated.

Thanks for the clarification; it's not apparent from the photo.

The comment attached to the photo is correct, ie the coating, if working, should substantially lower the surface temperature of the pipe on the sections that have been coated. Clearly it hasn't and it follows that the coating is not having any measureable effect.

This logic is erroneous. It can't be asserted that the 'after' is no different to the 'before' without a 'before'

This is because you don't know what the surface temp of the coated surface would have been without the

coating (under the same conditions)... the surface temps of those sections might be dramatically lowered

by the coat. Maybe they were 5000deg higher Is this very unlikely? Of course. Is it impossible? No.

The hypothesis relies on the assumption that the temperature drop on the surface will be the same

right-to-left without the coat. And that therefore, as the temperature drop is similar to the assumed

conditions with the coat, the coat is useless. This could very well be true - but it also might not be.

Without a 'before' pic, we don't know this.

Please bear in mind, I'm not saying that coatings work (or that they don't). I'm saying that without the control

it's unfair to draw any conclusion (positive or negative).

Regards,

Saliya

[djr81]

Hi,

Boom!!! (that's tongue-in-cheek, by the way )

Thanks for the clarification; it's not apparent from the photo.

This logic is erroneous. It can't be asserted that the 'after' is no different to the 'before' without a 'before'

This is because you don't know what the surface temp of the coated surface would have been without the

coating (under the same conditions)... the surface temps of those sections might be dramatically lowered

by the coat. Maybe they were 5000deg higher Is this very unlikely? Of course. Is it impossible? No.

The hypothesis relies on the assumption that the temperature drop on the surface will be the same

right-to-left without the coat. And that therefore, as the temperature drop is similar to the assumed

conditions with the coat, the coat is useless. This could very well be true - but it also might not be.

Without a 'before' pic, we don't know this.

Please bear in mind, I'm not saying that coatings work (or that they don't). I'm saying that without the control

it's unfair to draw any conclusion (positive or negative).

Regards,

Saliya

Well I am saying that the coating applied in this case didn't work.

I think you are getting a little bit confused between the temperature gradient on the photo and the percieved difference in a like for like test with a coated and an uncoated dump pipe.

What the (Linear) gradient demonstates is that the same amount of heat is being lost per unit length of pipe in both the coated and uncoated sections. That being so the only conclusion is that the ceramic coating is having no effect on the heat loss from the pipe ie it is not working as an effective insulator. You don't actually need a before and after test to prove the point....

[saliya]

Well I am saying that the coating applied in this case didn't work.

What the (Linear) gradient demonstates is that the same amount of heat is being lost per unit length of pipe in both the coated and uncoated sections. That being so the only conclusion is that the ceramic coating is having no effect on the heat loss from the pipe ie it is not working as an effective insulator. You don't actually need a before and after test to prove the point....

Like I said, the logic (therefore, the conclusion) is erroneous.

The actual gradient (it's not linear, there's a much faster fall in temps after the coated section, but I digress)

is not as relevant as whether it is the same or different at the same reference points pre/post coating.

If the very RHS of the now-coated pipe was actually 40deg hotter before the coating was applied, would you not

agree that the coating was effective? Without a 'pre' picture, can you say that it wasn't? No.

Regards,

Saliya

[djr81]

The logic is fine.

The gradient is slightly different at the LHS because the pipe is not straight (it is an exhaust pipe after all) What you see in the photo in terms of the slight difference is merely a result of a different (larger) amount of pipe being projected onto the same amount of graph x-axis. Perhaps I should have made this clearer rather than allow people to misinterpret the photo.

For the coating to have any real effect the gradient needs to be SUBSTANTIALLY different, ie much flatter. Which it isn't.

There are two things to consider:

1. To take your example of the pipe being hotter by 40 degrees at the RHS and the same temp at the LHS. An effective insulator would have the high temperature at the motor end maintained across the length of the exhaust pipe and show up as a flat gradient.

2. An effective insulator (applied internally to the pipe as in this case) will reduce the outside temperature of the pipe. You would then expect a step change in external pipe temperature in areas where the coating is not present, ie a hot spot. We get these at work when refractory fails on some of our pressure vessels & reactors (Not nuclear so calm down). Clearly the photo shows it not happening here.

You don't need a before and after photo (although you could do it that way if you didn't mind the tedium). You just need to properly interpret what you have.

[Sydneykid]

I have seen a power increase from thermo wrapping exhaust pipes, more than once

I can also most certainly measure the external heat difference in hundreds of degrees between a wrapped and an unwrapped exhaust pipe.

This test shows that ceramic coating an exhaust makes no difference

Hence wrapping the exhaust pipes is infinitely better than ceramic coating them?

Have I got it right?

cheers

Edited June 2, 2006 by Sydneykid

[djr81]

Absolutely. The image shows the ceramic coating makes next to no difference. Thermo wrap tape is actually effective. Ugly, messy, but effective.

[Guest Mashrock]

interesting.

in a less technical form

ceramic coating does not hold heat in, or really stop heat comming out?

but that thermo wrap does wonders. and i would dare say the turbo wraps that are also avaliable, which i cant remember who makes them or whatever would be affective also in this aspect?

[dangerous_daveo]

interesting.

in a less technical form

ceramic coating does not hold heat in, or really stop heat comming out?

but that thermo wrap does wonders. and i would dare say the turbo wraps that are also avaliable, which i cant remember who makes them or whatever would be affective also in this aspect?

Considering they are like 20x the thickness of heat wrap, and made of basically the same stuff I dare say they do. That and I have seen the gains on my mates car

But didnt two06l get some of this ceramic type treatment done? I know they got some type of coating done and apparently it worked very effectivly. I had a quick look for the thread but havent found it yet.

[saliya]

Absolutely. The image shows the ceramic coating makes next to no difference. Thermo wrap tape is actually effective. Ugly, messy, but effective.

Plainly, we're going to have to agree to disagree (about the image). If anybody asks, I'm invoking Godwin's Law first

Regards,

Saliya

Edited June 2, 2006 by saliya

[Color_Of_Green]

Here are my thoughts:

1) You cannot draw conclusions from one image. It must be reproducable a number of times under the same conditions.

2) You need to compare the images of a coated / uncoated exhaust since the argument is with vs. without and not half vs other half.

3) You would need to conduct the tests using ceramic coatings from different vendors so as do not introduce bias.

4) and not only that, you would need to test whether coating thickness, or multiple coats makes a difference.

Consider this:

- Insulating pipes to keep heat in has been done effectively for millenia.

- Ceramic has excellent heat insulation properties

I think it really comes down to the different ceramic coatings available, and the thickness at which they become effective. I'm sure there are many inferior products out there and equally as many functional products.

Look for a supplier who can provide scientific facts, not just marketing mumbo jumbo.

Edited June 2, 2006 by Color_Of_Green

[daydreamer]

thermo wrap definitly works , it works too well ,in racing cars we have used it on the extractors only last 12 months at best , and exhaust shops round here dont offer any waranty on systems if it is used ,i think it works by creating a buffer of hot air around the out side of the pipe which decreases the amount of temp lost to the engine bay .

To me the flange is creating a restriction before entering a larger pipe which will by nature increase the temp substantually on the right hand side of pic so before i can draw any conclusions i would like to see a before pic . Djr81 you may be correct but with the evidence before us it is unconclusive.

Just my 2 cents . interesting discusion ,thanks.

[djr81]

1) You cannot draw conclusions from one image. It must be reproducable a number of times under the same conditions.

How many would you like? Five, ten, fifty, a hundred? The stuff claims to be a good insulator. The degree of temperature difference over the short length of pipe shows that the coating doesn't work.

2) You need to compare the images of a coated / uncoated exhaust since the argument is with vs. without and not half vs other half.

Why? The claim for the coating is that it is a good insulator. Dumping that amount of heat in that short a pipe shows that it is not effective.

3) You would need to conduct the tests using ceramic coatings from different vendors so as do not introduce bias.

Why? The reason the stuff doesn't work is because of the thickness applied, not because of the properties of the ceramic.

4) and not only that, you would need to test whether coating thickness, or multiple coats makes a difference.

Assuming the coating is homogeneous (If it isn't it will delaminate & fall off) the number of coats is irrelevant.

Ofcourse insulating thickness plays a part. We use 100, 150 & 200mm in heat insulating refractory bricks & castable refractory on pressure vessels & tanks etc. If we could just spray on a few thousand microns of ceramic that is what we would do - & save huge sums of money in the process.

Consider this:

- Insulating pipes to keep heat in has been done effectively for millenia.

- Ceramic has excellent heat insulation properties

Consider this:

Motherhood has been around for even longer.

Motherhood has excellent child rearing benefits.

I raise the two points because they are about as relevant...

I think it really comes down to the different ceramic coatings available, and the thickness at which they become effective. I'm sure there are many inferior products out there and equally as many functional products.

Look for a supplier who can provide scientific facts, not just marketing mumbo jumbo.

Good luck finding a supplier of this stuff that can provide good scientific facts, or any for that matter. You might want to ask what the coefficient of thermal conductivity is. Glass fibre is about 0.035W/mK. This ceramic stuff would have to be orders of magnitude better to work as advertised.

[predator]

What I would like to to see is a quantifiable difference between the $300+ HPC type coatings, as opposed to your $60 heat wrap roll arrangement... heat *wrap* definitely works.

[R33S2]

Heat wrap adds another stage in the heat transfer process by creating a layer through which the engergy must pass, ceramic coating is attached to the first stage molecularly and as such must repel the heat by its own physical properties.

[sky30]

I have seen a power increase from thermo wrapping exhaust pipes, more than once

I can also most certainly measure the external heat difference in hundreds of degrees between a wrapped and an unwrapped exhaust pipe.

This test shows that ceramic coating an exhaust makes no difference

Hence wrapping the exhaust pipes is infinitely better than ceramic coating them?

Have I got it right?

cheers

Gary,

Which parts of the exhaust system do you wrap?

When you wrap a steampipe manifold, does it shorten the life odf the manifold much due to keeping the heat in?

[Color_Of_Green]

How many would you like? Five, ten, fifty, a hundred? The stuff claims to be a good insulator. The degree of temperature difference over the short length of pipe shows that the coating doesn't work.

Why? The claim for the coating is that it is a good insulator. Dumping that amount of heat in that short a pipe shows that it is not effective.

Why? The reason the stuff doesn't work is because of the thickness applied, not because of the properties of the ceramic.

Assuming the coating is homogeneous (If it isn't it will delaminate & fall off) the number of coats is irrelevant.

Ofcourse insulating thickness plays a part. We use 100, 150 & 200mm in heat insulating refractory bricks & castable refractory on pressure vessels & tanks etc. If we could just spray on a few thousand microns of ceramic that is what we would do - & save huge sums of money in the process.

Consider this:

Motherhood has been around for even longer.

Motherhood has excellent child rearing benefits.

I raise the two points because they are about as relevant...

Good luck finding a supplier of this stuff that can provide good scientific facts, or any for that matter. You might want to ask what the coefficient of thermal conductivity is. Glass fibre is about 0.035W/mK. This ceramic stuff would have to be orders of magnitude better to work as advertised.

The only thing you have proven is that the particular coating that you tested was not effective, not ceramic coating in general.

If a ceramic coating is only rated to 500oC and your gas flow has a temp of 800oC then obviously you wont see any difference. Try a coating thats rated to 3000oC.... then you will see a difference, even if you apply it to half your manifold.

Checkout some results at http://www.carcraft.com/techarticles/80038

Enjoy

Edited June 6, 2006 by Color_Of_Green