Thermal Heat retention, Velocity, Flow 4 Turbo mani

[toE]

Does thick or thin material retain heat in a Stainless Steel application when coming to manifold design matter? If so, which does a better job?

My personal view is that thin material is better as the heat dissipitation caused by the conduction of heat thru the material itself would mean that the thinner material is better. If so why is then that the majority of manifold design uses thick side walling? The answer is the false pretense is that the thermal velocity and heat retention in the majority view means that thicker walls should be the best. However, the majority forget to realise in this fact that the material (is this case is Stainless Steel) itself is a transducer for moving heat from the innards of the manifold to the outer, thus the thicker the material the more respondant to head dissipitation is. In simple physics the heat and velocity of the energy (the exhaust gas pulse) is going to best produce an energy which is used to drive the turbine of a turbo (thru the manifold) if the majority of it is retained in the inners. Thus if the material is thick and withdraws such heat and velocity from the inner, this would mean that it is trasducent to the formula to creating better power.

The advantage which is clear in having a thicker material is that the material itself in this case is being used to create a manifold which at the end of the day without a turbo bracing must be used to hold the turbo up and any parts which are correspandant to its use. Thus the thicker and thus the strength of the manifold must be at the thinnest it can be to retain heat and velocity without dissipation yet must also satisfy the counterweight of having the right strength to hold the manifold and collateral parts to the turbo system up from droipping from the complete system.

Just wanted to share :)

[2ds]

Allright you have definately been smoking this time!

-2ds

[Boost]

lol, ok. thanks for sharing that mate. Makes sence. If you weld some fins on the metal you can dissipate more heat away from the source. :)
confucious says:

[poid]

Someone's being doing some research ;)

Yes that's correct, you want to use a thin material to minimise the amount of heat lost through the manifold but you also need to have enough strength in the manifold to be able to hold the turbo without cracking.

Thick material is used both to avoid cracking, and also because there is a misconception that thick material will retain heat better.

Basically you want a thin material with bracing to hold the weight of the turbo so nothing cracks. That way you retain heat and avoid the cracking problem

[_Wing_]

thin material is better as the heat dissipitation caused by the conduction of heat thru the material itself would mean that the thinner material is better.
After reading your first sentence in your "arguement", I was confused. Did you realise that you went around in a circle which does not make sense? I kept reading through the entire post but could not make exactly what you were trying to say.


you want to use a thin material to minimise the amount of heat lost
How does a thinner material compared to a thicker material of the exact same composition retain heat?


there is a misconception that thick material will retain heat better.
Where is the misconception? Can you explain?

[2ds]

Once the material has absorbed enough heat to equalise the heat inside the manifold with the head of the manifold the thickness of the material should be irrelevant shoudln't it ?

This is ofcourse not taking into account that the thicker material will have more outer surface area to disapate heat. I assume that is the reason you are suggesting thin material ?

[pornstar]

lolz, i think he means that the thicker material retains heat in the inside of the manifold better is the misconception. Because as 2ds said, once the material heats up to the temp inside the manifold, it ceases to extract/withdraw heat from the gases inside, therefore a thinner material will reach this point first, and thus keep the heat in the gases to drive the wheel.

hope that helps

[_Wing_]

It wouldn't make a difference, unless you like to gun your car before it is completely warmed up.

[poid]

please explain why it wouldnt make a difference

[_Wing_]

When you car is up to normal operating temps, the manifold will be up to temp also.

If it's cold, it will mean your engine is cold too... thus me saying...


unless you like to gun your car before it is completely warmed up

[2ds]

When you car is up to normal operating temps, the manifold will be up to temp also.

If it's cold, it will mean your engine is cold too... thus me saying...


unless you like to gun your car before it is completely warmed up

the thicker manifold should have a greater external surface area meaning it will disipate more heat. as far as the actual manifold material it's self stealing heat from the exhaust goes, your statement should be correct. the manifold should only take heat from the exhaust until it reaches equilibrium and it may ever inject it if the exhause cools.

-2ds

[_Wing_]

OK, so the thicker manifold has a SLIGHTLY greater surface area, and yes, larger surface area will disipate more heat, I agree.

Think of this; do you think that the [IMO] negliable extra surface area will dissipate heat more than the extra thickness will hold heat in?

[poid]

the extra thickness doesnt hold heat in, heat travels through that thickness quicker than it would in the open air and hence requires more energy to keep it at that warmed-up temperature. Also it doesnt stay the same temp unless you are at at the same throttle level etc all the time. The temperature fluctuates as you go from WOT to partial, and hence the extra thickness sucks that extra heat energy up again.

Metal is a conductor, so extra thickness will extract extra heat. Larger surface area will also dissipate extra heat. So the goal is a manifold with material that doesnt conduct heat well, is thin and also having the air around the manifold as hot as possible from other sources to keep the heat loss to a minimum

[_Wing_]

OK, let's look at this slowly, statement by statement, line by line.


the extra thickness doesnt hold heat in
Yes it does.


heat travels through that thickness quicker than it would in the open air
Yes.


hence requires more energy to keep it at that warmed-up temperature
This conclusion cannot be derived from the speed at which the heat energy moves within different mediums.


Also it doesnt stay the same temp unless you are at at the same throttle level etc all the time
This is true, although the tempreture delta does not change as significantly as you seem to word it in the following sentence:

The temperature fluctuates as you go from WOT to partial


and hence the extra thickness sucks that extra heat energy up again.
This does not happen unless the tempreture change is significant.


Metal is a conductor
A typical use of the word "conductor" is for electrical reasons, not thermal. Regardless, metal IS a conductor of heat, and so are alot of other things, such as air.


so extra thickness will extract extra heat
You cannot come to such a conclusion fom stating the fact that "Metal is a conductor".


Larger surface area will also dissipate extra heat
Yes I agree [as stated above]


the goal is a manifold with material that doesnt conduct heat well
Yes, that is the goal. [notice I have INTENTIONALLY the "So the goal..." out, because the previous arguement does not hold true]


is thin
We are debating this.


and also having the air around the manifold as hot as possible from other sources to keep the heat loss to a minimum
No. You do NOT want this. I disagree.



Do I make sense?

[pornstar]

makes alot of sense wing, but which would u choose then? thick or thin and for what reason?

[toE]

makes alot of sense wing, but which would u choose then? thick or thin and for what reason?

ditto!!

That was just my "opinion". I din say i was right, neither did i say i was wrong. Now...enuff about me tho..let's hear your opinion aye? :)

[poid]

Instead of statements like "yes it does" why dont you actually explain yourself? For example why would there be less heat loss using a thicker material?

How do you know that the temperature changes are not significant?

My point about metal being a conductor of heat is that more heat will be lost through a thickness of metal than though the same "thickness" if you will of air.

You still havent convinced me that greater thickness does not equal greater heat loss, as you havent presented any arguments for it.

And why dont you want the air around the manifold hot? This would create less heat loss from the manifold itself, no?

Its very easy to suggest something is wrong without offering an alternative, so please do so I can see a different argument :)

[_Wing_]

makes alot of sense wing, but which would u choose then? thick or thin and for what reason?

ditto!!

That was just my "opinion". I din say i was right, neither did i say i was wrong. Now...enuff about me tho..let's hear your opinion aye? :)

What would I choose? Would I be able to choose? The only time you'd be able to choose is with a custom fabrication... and since there are plenty of aftermarket manifold on the market, I'd choose one of them instead of having one designed for/by myself... why the headache and the trouble AND the costs when somebody else has already done the hard yards?




Instead of statements like "yes it does" why dont you actually explain yourself? For example why would there be less heat loss using a thicker material?

How do you know that the temperature changes are not significant?

My point about metal being a conductor of heat is that more heat will be lost through a thickness of metal than though the same "thickness" if you will of air.

You still havent convinced me that greater thickness does not equal greater heat loss, as you havent presented any arguments for it.

And why dont you want the air around the manifold hot? This would create less heat loss from the manifold itself, no?

Its very easy to suggest something is wrong without offering an alternative, so please do so I can see a different argument :)

I thought the reasons were quite clear~ that's why I didn't give an explanation for each statement. If you disagree, you are more than welcome to, but it would be easier for me [or anybody else] to answer specific questions instead of explaining it all.
So I'll answer the question posed in your question/example above:

For example why would there be less heat loss using a thicker material?
A thicker material will always be able to hold more heat in simply because of it's density - the more particles in a given volume/mass, the more heat energy it can hold... thus the overall percentage of heat loss over time compared to that of a thinner material will be less.


How do you know that the temperature changes are not significant?
I don't have scientific data to prove this, perhaps you do?


My point about metal being a conductor of heat is that more heat will be lost through a thickness of metal than though the same "thickness" if you will of air.
I don't quite understand what you are saying here. Can you clarify for me please?


You still havent convinced me that greater thickness does not equal greater heat loss, as you havent presented any arguments for it.
See above.


And why dont you want the air around the manifold hot? This would create less heat loss from the manifold itself, no?
Technically, you are right. If the tempreture outside the manifold is as high as possible then the heat loss will be minimised, BUT that statement is quite different to your previous one which includes these critical words:

...from other sources...
THAT I disagree with. This is a car, there are other components around that do not like heat.


Its very easy to suggest something is wrong without offering an alternative, so please do so I can see a different argument
Yes, it is easy to suggest something is wrong without backup, but I have explained myself, have I not?
I didn't actually say "go thin!", or "go thick!"... I am saying that your arguements are invalid due to so and so reason(s) [or I thought it'd be clear why it is without a supporting peice].

And please note, I am not "picking" on anybody in particular, I am not trying to "rock" anybody in particular, I am not being a dick to anybody in particular, I am here to learn and help. :nod:

[poid]

First in reply to your note, i am the same, here to learn and help. Hence why i was asking for some explanations and clarifying what i wrote ;)

OK first up, we agree on the temp outside the manifold bit. The only consideration here is the manifold, not underbonnet temps in general. So i agree with you, other components dont like heat. But for the best for the manifold, we want the air around it to be as hot as possible. "From other sources" means including heat generated by the engine, for example. I wasnt saying you want everything under there as hot as possible, just the air around the manifold.

I'll be interested in reading your reasons why there is less heat loss in a thicker manifold though, thats the main thing i want to know where you are coming from.

You dont understand what i said about the thickness of metal vs 'thickness' (for want of a better word) of air. I stated in an earlier post that more heat will be conducted through a 1m thick piece of metal than the same space of air. The greater thickness of metal will soak up a greater amount of heat is the point.

I dont have scientific data to support my claims, other than looking at EGT gauges and their readings. The difference from partial throttle/cruising to WOT can be something like 25% or higher, i would think that would make a genuine difference to the heat lost through a thicker manifold and would be significant?

Nice dodge on pornstar's question, but which would you choose if you were going custom? ;)

[_Wing_]

OK first up, we agree on the temp outside the manifold bit. The only consideration here is the manifold, not underbonnet temps in general.
As hard as I may try, I cannot ignore other engine components... there is no use designing THE BEST manifold that will not fit inside the engine bay, and there is no use ignoring other bits and pieces affected by the heat emitted by the manifold.



So i agree with you, other components dont like heat. But for the best for the manifold, we want the air around it to be as hot as possible. "From other sources" means including heat generated by the engine, for example. I wasnt saying you want everything under there as hot as possible, just the air around the manifold.

The ONLY heat is generated by the engine [unless we're talking about brakes, tyres, the friction between moving parts outside the egine, etc etc, which we are not] I doubt that you can supplimentarily heat the air around the manifold more than what the manifold is emitting itself.



I'll be interested in reading your reasons why there is less heat loss in a thicker manifold though, thats the main thing i want to know where you are coming from.

Here it is:


A thicker material will always be able to hold more heat in simply because of it's density - the more particles in a given volume/mass, the more heat energy it can hold... thus the overall percentage of heat loss over time compared to that of a thinner material will be less.




You dont understand what i said about the thickness of metal vs 'thickness' (for want of a better word) of air. I stated in an earlier post that more heat will be conducted through a 1m thick piece of metal than the same space of air. The greater thickness of metal will soak up a greater amount of heat is the point.

OK. I understand what you're saying... the metal will soak more heat than air but once it is saturated, it canot get any hotter than that. What does this have to do with thin or thick manifolds?



I dont have scientific data to support my claims, other than looking at EGT gauges and their readings. The difference from partial throttle/cruising to WOT can be something like 25% or higher, i would think that would make a genuine difference to the heat lost through a thicker manifold and would be significant?

25% is significant change in tempreture. Comming from my point of view when racing, I either have my foot planted on the accelerator or brake pedal, not much time is spent at partial throttle - this would mean no significant change in manifold tempreture.
I assume you're talking from a street point of view, you're crusin' the streets and all of a sudden give it a big squirt - perhaps for the honda in the next lane or maybe the chicky crossing the road? LOL :D
So we have that 25% loss in tempreture for the same manifold between partial and WOT, but we are debating weather a thinner or a thicker manifold would have a smaller loss, right? If that is right, I'll put my chips on the thicker manifold for the above quoted reason.



Nice dodge on pornstar's question, but which would you choose if you were going custom? ;)
LOL!! I would seriously just look what's available and choose from that. If I MUST choose, we'll have to set boundaries~ or else we could be talking paper thin and brick wall thick.

Seriously though, this is getting confusing for me. There are too many factors and it takes too much time for me to go through each line and give a counter aguement to what you have said.

If we should continue on, we should set some boundaries or something~ or else we'd end up with a car that has a bonnet longer than a football field, wider than a swimming pool, manifolds as thin as coke cans and as thick as my head. :P