exhaust wrap absorbs moisture rumour

[upontheriversky]

i read through lots of forums regarding exhaust thermal wrap and how lots of enthusiasts and mechanics are against it and suggested ceramic coating instead but price difference is really big. They claimed it absorbs moisture and eventually our extractor will weaken and crumble before its time

however, i came across this saying in a website:

"Point to note: It's only a rumour that exhaust wrap absorbs water and can encourage your mild steel headers to crumble away prematurely. If anyone tells you this, they're fearmongering." - car bibles

the full address is here, check out the most bottom part on "exhaust wrap":

http://www.carbibles.com/fuel_engine_bible_pg5.html

ive been searching for similar opinions on the web for extra confirmation but couldn find yet

comment anyone??

 

[wsukun]

First of all, ever "accidentally" touch any of the exhaust piping after long driving of afternoon?
Any clue how hot can it be? Not just absorb moist but will absorb your soul as well if u know what I mean..
Oh ya, those thermal bandage wrap won't be useful in country like Msia where the weather alone enough to moist your underwear.

 

[upontheriversky]

haha moisted underwear is caused by sweating, i dont think applicable to exhaust:D.
but i dont really understand what u trying point out..mind explain more?the "accidentally" touch part...

anyway if the exhaust is always running hot during driving, wont the moisture be vaporized before it can do damage to it?

it would be helpful if got someone who experienced crumbled exhaust before due to wrapping, just want to know whether this problem is certain or just potential only..

 

[BE5RSK]

I'm not a scientist nor had an experienced done this.

But, I just believe by wrapping the exhaust manifold, we can prevent the heat generated by the manifold into the engine bay. Thus, lower down the engine bay temperature. However, where the heat gone? I'm sure the heat was trapped in between the outer layer of the manifold (iron cast/stainless steel, whatever it is) and the wrapper. Subsequently, the heat level received by the manifold was increased further (assumed that it was not wrapped before). For some non high heat-resistant manifold (well, it depends on the material also), it gone crack/crumble time to time due to "higher-than-usual" temperature.

Well, I maybe wrong. It just my opinion on the other possibility why the wrapped exhaust manifold easily going cracked/crumbled, other than caused by moist (as lots of forums mentioned it).

 

[tofu_manic]

i cant say for sure that hotbits headers never crack but i have seen one crack with heatwrapping

 

[D7zul]

I'm not a scientist nor had an experienced done this.

But, I just believe by wrapping the exhaust manifold, we can prevent the heat generated by the manifold into the engine bay. Thus, lower down the engine bay temperature. However, where the heat gone? I'm sure the heat was trapped in between the outer layer of the manifold (iron cast/stainless steel, whatever it is) and the wrapper. Subsequently, the heat level received by the manifold was increased further (assumed that it was not wrapped before). For some non high heat-resistant manifold (well, it depends on the material also), it gone crack/crumble time to time due to "higher-than-usual" temperature.

Well, I maybe wrong. It just my opinion on the other possibility why the wrapped exhaust manifold easily going cracked/crumbled, other than caused by moist (as lots of forums mentioned it).

i agree with BE5RSK..

the heat must go sumwhere.. if not, it will overheat..

and bad things happens when sumthing overheat..

 

[DanzEterna]

ceramic coating for long time investment......
just wondering, do they sell those ceramic coating in a can at hardware stores? maybe can DIY.

 

[Izso]

ceramic coating for long time investment......
just wondering, do they sell those ceramic coating in a can at hardware stores? maybe can DIY.

No kidding! If really got I'd sure like to try!

i read through lots of forums regarding exhaust thermal wrap and how lots of enthusiasts and mechanics are against it and suggested ceramic coating instead but price difference is really big. They claimed it absorbs moisture and eventually our extractor will weaken and crumble before its time

however, i came across this saying in a website:

"Point to note: It's only a rumour that exhaust wrap absorbs water and can encourage your mild steel headers to crumble away prematurely. If anyone tells you this, they're fearmongering." - car bibles

the full address is here, check out the most bottom part on "exhaust wrap":

http://www.carbibles.com/fuel_engine_bible_pg5.html

ive been searching for similar opinions on the web for extra confirmation but couldn find yet

comment anyone??

Technically, it's not "absorbing water" you should worried about. Fibreglass wraps that'll prick the hell out of you (if you don't wear gloves) will not absorb water that readily. It's trapping the moisture in-between the gaps and exposing moisture to that amount of intense heat that you should worry about. Damage isn't from absorbed water, it's trapped moisture that'll kill it. Accelerated rusting or moisture heat/cold exchange (imagine the same pipe some cooled with moisture some dry but super duper hot.. uneven cooling), this will kill the exhaust.

 

[D7zul]

i've heard about ceramic coating.. it's been recommended sumwhere in d net..

the best thing is ceramic coating plus the wrap.. sure sejuk je engine bay tuh.. hehe

kalau fiber tak ok ke? coz fiber ada jual kat hardware shop..

hehe.. tanya jer..

:hmmmm:

 

[DanzEterna]

Izso : im not sure leh...just wondering only, this weekend i go check it out at ACE hardware....c whether got anot.

 

[jswong]

I've never seen those ceramic coating available as DIY cans in Ace Hardware, though I've seen some ad for DIY spray-on ceramic coating in some car mag before.

For those who are worried about excessive heat cooking off the mainfold material, the logic is wrong. Think of it this way - if you boil water in a clay pot and in a stainless steel pot, then pour out the water from both pots, which will cool down first? The answer is the stainless steel pot, because it is a HEAT CONDUCTOR. Ceramic, on the other hand, is a HEAT INSULATOR and tends to retain heat even after you've stopped applying heat to it. That's how those "Magic Pot" devices work - it's a ceramic-insulated plastic container that relies on heat being stored and retained in the ceramic layer to keep the food hot.

Therefore, if you use thermal wrap on the exhaust manifold, there will be less heat radiated away from the manifold because it will be trapped by the heat insulator (fibreglass cloth). The manifold itself, however, continues to function as a heatsink as it is a heat conductor. However, when the engine is turned off and there's no longer hot gases flowing through the manifold, the steel material will tend to dissipate the heat to the ambient air, but it'll cool down slower than an unwrapped manifold because it's insulated.

But you gotta remember that the heat insulation wrapping is not a free energy device, it will not heat up the manifold beyond what's been insulated by it. With the absence of continuous energy input, heat will still be radiated away gradually. The manifold will not be any hotter than it was when the engine was running, only that it cools down slower.

Manifolds cracking depends on many factors. It could be material fatigue at the bent areas (since the steel grains are aligned differently after the application of mechanical strain by the mandrel or crimp bender), it could be rapid heating and cooling e.g. being splashed with water repeatedly when it's hot (such as when driving through puddles), and it can also be due to a bad choice of material (there are many grades of stainless steel, and not all can maintain structural strength at high temperatures. Cheaper low-carbon percentage stainless steels tend to have lower creep strength at high temperatures).

 

[D7zul]

yeah..

my vote is for no wrapping / coating.. period..

 

[upontheriversky]

I've never seen those ceramic coating available as DIY cans in Ace Hardware, though I've seen some ad for DIY spray-on ceramic coating in some car mag before.

For those who are worried about excessive heat cooking off the mainfold material, the logic is wrong. Think of it this way - if you boil water in a clay pot and in a stainless steel pot, then pour out the water from both pots, which will cool down first? The answer is the stainless steel pot, because it is a HEAT CONDUCTOR. Ceramic, on the other hand, is a HEAT INSULATOR and tends to retain heat even after you've stopped applying heat to it. That's how those "Magic Pot" devices work - it's a ceramic-insulated plastic container that relies on heat being stored and retained in the ceramic layer to keep the food hot.

Therefore, if you use thermal wrap on the exhaust manifold, there will be less heat radiated away from the manifold because it will be trapped by the heat insulator (fibreglass cloth). The manifold itself, however, continues to function as a heatsink as it is a heat conductor. However, when the engine is turned off and there's no longer hot gases flowing through the manifold, the steel material will tend to dissipate the heat to the ambient air, but it'll cool down slower than an unwrapped manifold because it's insulated.

But you gotta remember that the heat insulation wrapping is not a free energy device, it will not heat up the manifold beyond what's been insulated by it. With the absence of continuous energy input, heat will still be radiated away gradually. The manifold will not be any hotter than it was when the engine was running, only that it cools down slower.

Manifolds cracking depends on many factors. It could be material fatigue at the bent areas (since the steel grains are aligned differently after the application of mechanical strain by the mandrel or crimp bender), it could be rapid heating and cooling e.g. being splashed with water repeatedly when it's hot (such as when driving through puddles), and it can also be due to a bad choice of material (there are many grades of stainless steel, and not all can maintain structural strength at high temperatures. Cheaper low-carbon percentage stainless steels tend to have lower creep strength at high temperatures).

with these explanation i could not resist myself from asking. are you an engineer?should be either civil or mechanical because you based your explanation a lot on material science:D

anyway, just to share, in my opinion, the main purpose of exhaust coating/wrapping is to keep the heat within the exhaust systems so that the pressure inside will be relatively high for fast gas flow which results in less restriction for better power output.

As the exhaust gas flows from extractor to the muffler, it gets cooler as heat is radiated and flow becomes slower.Then we need a bit more rev just to push the gases out when the rev could be used for more forward force so less efficiency.

plus we get cooler engine bay as side effect which is good. just my 2 cents :D

 

[PocketRocket]

Dude, I learnt it the hard way...don't do it! my hotbits became...EXPENSIVE HOTBITS!

 

[BE5RSK]

arggghhhh....brooo... that's scary man.
What's the diagnosed result? Moist?

 

[upontheriversky]

Dude, I learnt it the hard way...don't do it! my hotbits became...EXPENSIVE HOTBITS!

whoa that is something we can learn about..how long did it take before your hotbits became like that??? and yea as mentioned..whats the result from diagnosis??

 

[jswong]

with these explanation i could not resist myself from asking. are you an engineer?should be either civil or mechanical because you based your explanation a lot on material science:D

anyway, just to share, in my opinion, the main purpose of exhaust coating/wrapping is to keep the heat within the exhaust systems so that the pressure inside will be relatively high for fast gas flow which results in less restriction for better power output.

As the exhaust gas flows from extractor to the muffler, it gets cooler as heat is radiated and flow becomes slower.Then we need a bit more rev just to push the gases out when the rev could be used for more forward force so less efficiency.

plus we get cooler engine bay as side effect which is good. just my 2 cents :D

Yes, exhaust wrap is to maintain the temperature of the exhaust gases within the manifold in order to preserve temperature differential and to maintain the low exhaust gas density.

When we wrap the exhaust header, the exhaust gases that are within the manifold is still pretty close to the high temperature as when it came out from the engine. Hot gases will tend to dissipate into a region of cooler gas, and that's what the exhaust wrapping helps to do - allowing exhaust gases to exit the exhaust manifold and into the exhaust pipe more efficiently. If you want the gases to come out quickly from the engine head only, you should be cooling the manifold, but the hot exhaust gases will hit a bottleneck pretty soon because they'll hit a region of high-density gas (cooler exhaust gas) just a short distance away, before the joint pipes that are meant to scavenge the gas (through the shockwave effect). The thermal wrap allows the gas to remain low-density (and have a high kinetic energy) past the shockwave-interference collector joints of the extractor (i.e. the 4-2-1 or 4-1 joints). Some people have had good experience wrapping the entire center pipe as well to preserve the low gas density and high gas flow.

So, your concept is correct although by Bernoulli's principle, the exhaust gas pressure is actually *LOW* compared to the cooler air elsewhere within the exhaust system due to its higher flow rate. That's why we'd want to preserve the exhaust gas heat as far as possible within the exhaust system, to maintain the same pressure distribution as evenly as possible. The cooler slower air towards the end of the exhaust system presents a region of high pressure and that contributes to a large component of exhaust back-pressure.

 

[PocketRocket]

around 6 mths if not mistaken...drasticly shorten the lifespan...

here are more angles....*sigh*

 

[wsonny]

Today i when to 1 of the exhaust shop in cheras also saw the same thing. The boss said the owner install the wrap not more then 3 months the extractor become like this... wonder who the guys who design this thing

 

[tugauz91]

i've been wrapping my manifold for almost 7 month's .. none of this happen..